Monday, August 30, 2010

Things You Remember Around Ponds

But let’s back up a day.

That Thursday afternoon, after we arrived at the cabin and unloaded the car, AW and I sat out on the beach and relaxed a bit. The cabin sits on the point of an esker which is joined to the “mainland” by a small 1-lane bridge just a short walk away. The sun was out, the air warm, and we gazed across the lake as the Twins played in the water and Bird Whisperer went out to explore. After a short while, he returned.

BW: Hey Dad, there’s a lady fishing on the bridge who says she knew you when you were a kid.

Me: What’s her name?

BW: A-----.

Me: Does she have blond hair?

BW: Yes.

One of the fringe benefits of living 2,500 miles from where you grew up is that there is a whole class of awkward encounters, or more properly re-encounters, to which you are almost never subject. Living in Utah I never unexpectedly run into anyone who ever sentenced me to detention, or with whom I tried unsuccessfully to make out*, or who saw me wearing bell-bottoms, working at the White Hen Pantry or dancing to KC and the Sunshine Band. The people in this category of encounter include former teachers, marching band directors, friends-of-parents, schoolyard bullies, newspaper-route-customers-who-never-tipped, and of course, former girlfriends.

*Barring one awkward early-dating incident with AW.

Bridge Beach Walking toward the bridge I saw a blond-haired woman helping a young boy to fish. Seeing me approach, she stood up and smiled, and I was strangely relieved to see that, more than 2 decades since I’d last seen her, she was instantly recognizable, her form and weight apparently the same. Never before having run into someone 27 years after we’d dated, I wasn’t quite sure of what to say, so I blurted out the first thing to come into my head: “I didn’t know you fished.”

The human body is strange on so many levels. It’s this amazing machine that can do all sorts of things, comprised of all these complex parts. And the weirdest part is probably the brain. Think about it: everything else is in your body is doing something- moving, bearing loads, fighting germs, digesting food, transporting oxygen and nutrients, secreting stuff- all kinds of things. And then there’s the brain. It’s this huge organ you carry around all day up high on this big stalk, encased in this bony shell, which uses an inordinate portion of the calories consumed by the human body, and it doesn’t do anything.

Oh, I know it “does” stuff. But it’s like this giant clump of interconnected cells that are firing electrical signals all over the place, pretty much all day long. For sure, some of these actions make a lot of sense (Hey, my finger is in the spokes, it hurts, I better send a signal to my arm muscle to pull it out…) but others (I’ve always felt that Major Nelson’s eventual marriage to Jeannie was vaguely misogynistic...) seem awfully trivial for the expense and general overhead that the brain requires.

Of all the weird stuff the brain does, I’m not sure any is weirder than memory. If I tell you to think about your mother, an “image” of your mom pretty much instantly “comes into” your “mind.” Probably you “see” her face, maybe you “hear” her voice, or maybe even recall her scent. How’s that? A moment ago you didn’t see her face, and now you do. Where was it? Where and how was it stored and how did your mind suddenly produce it at my suggestion? Isn’t that bizarre?

And I can do the same for lots of other memories. If I ask you to think of the day you graduated high school/college, or the day you started your first job, or the day the Challenger blew up, or 9/11, each of those “commands” will trigger not just a picture, but a “scene.” Chances are you can tell me where you were, what you were doing, and who you were with at the time. And the recall of some/many of those memories may actually change your emotional state, making you happy, sad or wistful. But you weren’t happy, sad or wistful a moment ago. How did that happen? Isn’t that the weirdest thing ever??

A----- and I both laughed and embraced. As we did the side of my face brushed against her hair, and my arms briefly wrapped around her shoulders/upper back. I caught a brief, slight, scent- a perfume, a body wash, a deodorant, a powder?*- I don’t know what, but it was somehow vaguely, reminiscently similar to her scent in the early 1980’s. A scent I hadn’t smelled, remembered or even remembered remembering for more than a quarter-century, and the sudden recollection of it triggered a whole other level of images, memories of actually being with/around her**.

*The myriad products with which women treat, anoint and enscent*** their persons will ever remain a mystery to me.

**I don’t know how I smelled to her. But given that I’d spent 3 ½ hours in the car and then gone for a quick swim, my guess is that if anything it was sort of a low-grade BO doused with pond-water. Which, come to think of it, was probably how I usually smelled most of the time in summers in the early 1980’s.

***Yes, another made-up word. After “aquadynamic”, anything goes.

If memory is weird, then trigger-memories are extra-weird. You may smell or see something, or hear an old song, and then suddenly recall detailed memories you hadn’t thought of in decades. My sister- let’s call her Elizabeth- who has a great memory, will often trigger such memories when we’re together. She’ll say, “Remember that time when we…” and then suddenly I do remember that time, long ago, in vivid detail, even though I hadn’t even thought of it in decades. That memory was sitting somewhere in my brain in many cases for the majority of my life, completely un-recalled, until just now.

The brain is frustrating because although we know a lot about it, we still can’t “put it all together.” We understand the basic elements, and we know a fair amount about the overall structure, but we don’t understand exactly how they fit together to do something like form, store and recall memories*. At a cellular level, researchers understand pretty well how the machinery functions. Your brain is composed overwhelmingly of 2 types of cells: neurons, or “nerve cells”, and ganglia, which support the neurons and handle much of the “care & feeding” of the brain. The neurons are where the action is, connected to each other and transmitting signals from one to the other like crazy

*Brain Researcher David Linden calls this gap “the Middle Thing”.

Neurons connect to one another via long, tendril-like extensions called dendrites and axons. Signals are sent out on axons and received on dendrites. The axon of one neuron is connected to the dendrite of the next by a synapse, which a teeny-weeny gap, about 1/500th the width of a hair*, filled with the saltwater fluid in which the brain is immersed/bathed/inundated.

*Head, not pubic. I mentioned the difference in this post.

The neurons maintain a voltage differential relative to the surrounding saltwater solution of about -70 millivolts, the result of a relative excess of potassium ions inside the neuron and relative excess of sodium ions in the fluid outside. When a signal is generated, ions are rapidly exchanged across the surface of the neuron, generating a voltage spike of about +50 millivolts, which travels rapidly* down the axon toward the next synaptic cleft.

*Well actually not all that rapidly, as we’ll see in a moment…

Neuron Expand-O When the spike reaches the synapse, the end of the axon releases one or more of a series of different chemicals, jointly classified as neurotransmitters, which transmit the signal to the end of the dendrite of the next neuron on the other side of the cleft, and so on and so on. I’m leaving out a bunch of details, but that’s the gist of how signals are transmitted around the brain. This hardware has been around for a long time- at least as long as jellyfish have been around- and it’s how nerve cells work in pretty much every living thing that has a nervous system. So while our brains are certainly more impressive than that of a jellyfish*, they’re constructed out of the same parts, which aren’t particularly impressive. Nerve signals are transmitted at no more (and usually less) than a rather leisurely 120 m/s, and they’re remarkably unreliable in getting to their destination; some significant portion of signals just don’t get through. The brain works because it’s hugely redundantly “over-wired”. Compared with copper wire, neurons are slow and unreliable.

*Which actually has no brain…

A----- and I stood and caught up while her son cast his line from the bridge. After a few minutes the Twins ambled up, curious, and were soon chatting with her son while he showed them how to cast. As I spoke with her I noticed little differences from the A----- I remembered- a few lines near the eyes, and hair that revealed subtle highlights closer up*. I remembered her eyes, and how one day I’d swear they were blue, and then the next they’d be green**. I remembered, way back, mentioning it to her and her laughing it off. I’d wonder sometimes if they somehow caught and flashed back the gleam of the sky or the water, or if they conveyed some mood or secret in her. Or me.

*Because practically no woman has blonde hair after 40, as I mentioned in this post. Yes, I know this is a complete non-news item to female readers, but I never knew it till I was over 40.

**No, she didn’t wear tinted contacts, she just had/has sort of in-betweeny-green/blue eyes. And then some days they’d look kind of gray.

At a macro-level, researchers also know a fair amount about brain function, and most of what they learned they’ve discovered from damage, whether accidental- through a number of fascinating Phineas Gage-type incidents- or deliberate, as in the case of test-subject monkeys and rats. Just as we carry the legacy of our ancestors at a micro/neuron level, we also do so at the macro/structural level. A lizard has a brain that seems sort of simple compared to ours. A rat has a brain that’s more complicated, and can figure out more stuff, but is still structurally simpler than ours. A chimpanzee has a brain that’s even more sophisticated than the rat’s, can do all sorts of cool stuff, and is pretty much like ours, except not as big.

But structurally a rat’s brain is more or less the stuff of a lizard’s brain, plus a bunch of other stuff. Because a rat’s brain wasn’t just designed from scratch, but rather evolved out an earlier, simpler reptilian brain. A chimpanzee’s brain- or our brain- is more or less the lizard stuff, plus the rat stuff, plus some other stuff, and that structural legacy, combined with the crappy jellyfish wiring, makes up the huge, over-wired, high-maintenance brains we have today.

brain-limbic Different portions of the brain (diagram above, not mine) do different things. For example there’s a part in the back of your brain that handles visual processing. We know this because if this area is damaged you can actually be blinded, even though your eyes are just fine. There are other regions which are linked to hearing, or sense of smell, or various subconscious/half-conscious functions (pumping blood, breathing). In the case of memory an important role seems to be played by a small structure on the underside called the hippocampus.

Extra Detail: Strangely, people who suffer from this type of brain-damage-blindness may still “see” after a fashion. Even though they swear they can’t see anything, such persons seem to have a better-than-random chance of locating/picking up objects or ducking/avoiding objects thrown at them. One hypothesis is that in so doing they’re somehow utilizing another more ancient part of the brain that may have been associated with vision in the ancestral/reptilian brain. The visual processing portion of our brains is an area that doesn’t exist in reptiles, but that ancestral reptilian processing hardware might possibly be intact enough in us to provide some basic function.

Tangent: A while back I did a couple of posts on vision in birds. BirdEyeConesDroplets4Later I did a post on the evolution of avian intelligence, where I talked a bit about the structure of bird brains. But I never made the obvious link between the two topics until now. When I previously tried to imagine avian vision, I pictured vision sort of like my own, except with new/ unimaginable colors, greater clarity, binocular-like Bird Brain Schematic2[6]foveal power and perhaps even an overlay of features I couldn’t see at all, such as magnetic fields. But now this image seems almost na├»ve. So much of “vision” happens in the brain, and bird brains have nothing like our visual processing hardware, but probably(?) have a completely different processing center which evolved along a completely different path from reptiles. Avian vision may well be as alien to us as the sonic “vision” of bats.

The hippocampus is the part that allows you to make and store new memories, and the way we know this is because people who experience severe damage to the hippocampus are unable to make new memories, even though they remember old stuff. So while the person remembers their mother or childhood friend or where they were when the Challenger exploded just fine, if they were to meet you today, and then you returned to see them again tomorrow, they’d have no idea who you were.

Extra Detail: Interestingly, this seems to be true for declarative memories, but not for non-declarative memories. Declarative memories are specific facts or events. “Twin A is allergic to eggs…” is a declarative memory. Non-declarative memories are things like skills, such as ice-skating, or playing the ukulele. A person with a trashed hippocampus can be taught to ice-skate (even if they have to be reintroduced to their instructor over and over again…)

But hippocampus damage reveals something else about memories: they move over time. A person with a damaged hippocampus not only is unable to form new memories, but also loses recent memories, where “recent” is anywhere from 1 to 4 years. Memories, like wine, age, and as they do so are moved elsewhere.

So where do they go? I remember way back in junior high school (I think) seeing a film in science class where a researcher is doing some kind of brain surgery on a patient who is conscious. (Do you remember this? No seriously, I’m not messing with you; I think most American kids in public schools at roughly that grade level in the 70’s or early 80’s saw this…) In the film, the researcher touches different parts of the brain- the outer brain, the neocortex- with an electrical probe, and as he does so the patient suddenly recalls specific old memories in incredible vivid detail. The takeaway was that memories are stored, sort of like sensurround movies in specific locations in the neocortex.

That film- like the film in which flat worms learned knew tasks by eating mashed-up flatworms who already knew the task- was largely bogus*. The content behind the brain-surgery-electro-stim-memory film came out of experiments in the 1930’s by a Canadian neurosurgeon named Wilder Penfield**. Penfield’s electro-stim experiments did produce vivid recollections, but only in about 5% of the cases. The rest of the time such stimulation produced various reactions, including hallucinations.

*They were almost certainly following the slime trails of the previous flatworms.

**To be clear, the oversimplified claims of memory-locations were not Penfield’s doing. Penfield’s research made huge accomplishments in mapping the functional areas of the brain.

It’s not known for sure where long-term memories are stored, but the most commonly-accepted idea nowadays is that the components of memories are stored in areas having to do with specific senses. In other words, images are stored in the visual-processing area, smells in the olfactory-processing area, etc. And when you recall a memory, your brain somehow “grabs” these components, which must somehow be linked or “tagged” and brings them to “mind” in a cohesive “scene.” That’s the thinking, anyway.

All About My Neurological Disorder

Extra-Big-Side-Note-Tangent: This one is a bit lengthy, and goes rather far afield, but I hope you’ll indulge me as it has personal significance.

This “tagging” or linking- if that is in fact what is going on- may sometimes manifest itself in odd ways. Some number of people, possibly as many as 1 in 20*, exhibit a pattern in memories which suggests a non-standard linkage, or possible “cross-wiring” of the specific mnemonic elements that comprise a given memory. In the condition known as synesthesia, the recall or triggering of a memory or even a sensory input automatically, consistently and involuntarily triggers another memory, image or sensation. For example, a synesthete may always see the number 6 as green. Or they may smell a particular food when they see a bridge. Or they may feel a tingle in their hand when they hear a particular piece or type of music.

*But possibly far fewer. More on this in a moment.

There are over 60 documented (and probably many, many undocumented) forms of synesthesia. One of best known is most common is Grapheme -> Color Synesthesia, where the subject perceives numbers or letters as having specific, consistent colors. Another common form is Sound -> Color Synesthesia, where the subject associates specific sounds- musical tones, animal sounds, whatever- with specific colors. A much rarer form is Lexical -> Gustatory Synesthesia, in which the subject experiences actual tastes in association with specific spoken words*.

*This one sounds kind of cool. If you knew the triggers for your favorite foods, could you enjoy fat-free delicacies all day long just be listening to a played-back recording of those words?

Synesthesia has fascinated me since I first heard of it a few years back, because while I never considered myself a synesthete, I’ve always knew that I had an unusually visual way of thinking of numbers and dates. It wasn’t until researching this post that I realized that I am in fact synesthetic. The specific form of synesthesia from which I “suffer”(!) is another common form, Number -> Form Synesthesia.

In Number -> Form Synesthesia, a visual “map” of numbers comes to mind whenever that person thinks of numbers. For as long as I can remember, this is exactly what happens with me, though I’ve always thought of the numbers as having a “path” more than a “map”. Here’s how I “see” the numbers 1 through 20:

NF 1-20 You’ll note the obvious clock influence between 6 and 12. I see this when I count, when I perform arithmetic, and when I learn/recite numbers in a foreign language. Interestingly, I don’t think of the hours of the day in this form, but in accordance with a standard 12-hour clock. When I extend the path/map up to 100, it looks like this:

NF 1-100 The 0 – 100 path/map maintains its form at higher orders of magnitude. 0- 1000 follows the same map. When I think of numbers in the thousands- say income for example- I think of the same map from 0 to 100,000 and then the same map again from 0 to 1,000,000 when thinking of income in the low to mid six figures. Negative numbers follow a similar path/map, but with the direction, aspect and flow a bit different. I also see this path/map- especially with the negative number component- when thinking about time in terms (specifically) of years. Here’s how I see recorded Western history:

NF Western History Here’s how I see biological/geological history:

NF Life on Earth Here’s my temporally “in-between” path/map of human history over the last 200,000 years:

NF Human 200K cut Interestingly, I don’t see the months of the year, nor the days of the month, along this map. But I see them along another path/map. Here’s what the months of the year look like to me:

NF Months of Year cut The days in this map are on the same path/map; I see days of (specifically) the month as “zooms”. But I see the days of the week on a different path/map, specifically like this:

NF Days of Week cut This one, like the clock part of my number path/map, I suspect has a clear origin. I have a memory (quite possibly wrong) of seeing a days-of-the-week chart similar to this path/map on the TV show “Romper Room” when I was around 5 years old, with Saturday and Sunday both bigger and “higher”, just as in my path/map.

I emphasize here that these aren’t just typical Watcher-graphics I cooked up for this post. I’ve always seen numbers and dates on these paths, for as long as I can remember. In many cases Number ->Form synesthetes report color associations with map-elements, but that’s not the case with me; my path/maps have no connection with color.

Numbers around synesthesia are way squishy. Estimates have ranged from 1 in 20 to 1 in 200,000 people. Older research indicated a much higher prevalence among women (6-to-1!) but more recent studies suggest that perhaps the female participants in earlier surveys were simply more forthcoming. A similar, maybe-possible correlation has been suggested for left-handedness.* For a while it was suspected that synesthesia was linked to the X chromosome, but this idea seems to have fallen by the wayside of late. More recent research hints at a possible link to chromosome #2 in an area associated with autism and epilepsy.

*I am right-handed.

plobe1 Getting back to me, it’s been hypothesized that Number -> Form Synesthesia is the result of some kind of cross-wiring in an area of the brain called the parietal lobe (diagram left, not mine), a region that handles both numeric and spatial processing. N->F Synesthesia is interesting because it hints at spatial-numeric links that be unconsciously present in everyone, but which are unusually “visible” in N->F synesthetes.

A----- and I caught up on the happenings of old friends around the lake: who did what, lived where, etc. Over the years we’d been kept somewhat abreast of each other’s lives through our parents. She knew that I bike-raced; I knew that she’d recently been divorced. When the conversation came around to families, I made what seemed the obligatory consolatory remark, mentioning that I’d heard she and her husband had split up, and was sorry to hear it.

“Don’t be,” she answered, a bit too quickly. “It’s a good thing.” Her swift response hinted at the sting of recent unpleasantness, and we moved on to other subjects..

There’s another part of the brain, just slightly below/in front of the hippocampus, called the amygdala (see the first diagram). This component, which seems to be part of the ancient reptilian core structure, appears to be associated with some of the most “primitive”, basic emotions, such as fear and anger, and is suspected to be involved with the retention of important memories. When an event happens to us that’s particular painful or fearful or otherwise traumatic, the amygdala seems to be triggered, as if it’s somehow “stamping” the event, or underlining it, marking it as important. This may be why we all remember where we were and what were doing on September 11, 2001, and yet likely have no idea what we were doing on October 4, 2002. Because on September 11 we were afraid, we were angry and our memory of that day was “stamped” by the amygdala.

Tangent: We all know how the “sting” of bad memories such as a death or a break-up seems to fade a bit after time. Bad memories are still bad, but many, many years later they just don’t, well, “hurt” quite as much as they did when they were fresh*. I wonder if somehow, as memories are transferred from the hippocampus to their eventual homes in the neocortex, if not quite all of the amygdala-“stamping” is included in the transfer…

*My own divorce probably falls into this category. Part of that is probably because my life turned so, well, great**. But memories of those times seem somehow muted, or removed, and when I think back on those days, it’s almost like thinking about some stuff that happened to somebody else. (Which, in a strict materialistic sense, maybe it was.)

**That sounds cocky, but it’s not meant to be. If you have a loving family, good health, good friends, enough money to get along decently and live in a beautiful place to boot, well I call that a great life. The rest is up to you.

In a previous post I blogged a bit about the mystery of self. If we are the stuff that comprises our brains, and over a period of years that stuff is gradually replaced by new stuff, then ultimately, are any of our long-term neocortical memories really “ours”? Maybe old memories seem distant and strange in a way because they’re not really ours, but rather a storybook of sorts, a tale of our past, ever-changing selves, which shaped and made possible the self we are today.

Maybe, as A----- and I talked on the bridge, it was two strangers speaking. Strangers who each carried around a storybook of tales in their heads, and whose storybooks overlapped for a while and shared a chapter many years ago. Like new acquaintances who discover they’ve enjoyed the same book, it was fun to reminisce and catch up.

We think of the people closest to us- our siblings, our spouses, our parents, as somehow always being the same age they were when we got to know them. AW will always be around 30, Brother Phil will always be a brainy 10 or 11 year-old, and my father will always be in his late 30’s, as he was when together we camped up by the lake the summer he built the cabin. But with old acquaintances we once knew well though haven’t seen in years, there’s a sort of disconnect between the “them” we remember and the “them” we see now. As I talked with A----- on the bridge, I saw two people before me- the 45 year old woman, and the 18 year-old girl, different and yet the same, somehow overlaid together as both a person and a memory at the same time. Looking at her, I caught a glimpse of her storybook, and mine, in her green eyes. I mean blue.

Note About Sources: My primary source for this post was David Linden’s The Accidental Mind, which was one of my 2 very enjoyable vacation reads*. Additional info on synesthesia came from Wikipedia, as well as this helpful site. Additional info on neurons and their electrochemical function came from this site and this site.

*The other was Nathaniel Philbrick’s The Last Stand: Custer, Sitting Bull and the Battle of Little Bighorn. It was an outstanding, well-researched read, although for sheer telling of the tale, it’s hard to beat Evan Connell’s Son of the Morningstar.

Tuesday, August 24, 2010

Things That Grow Around Ponds

I have 2 more posts I want to do about Maine- this one on aquatic freshwater plants* and then one on memory. It’s been tough to crank them out this week as I’m down in Brazil on business. If I get time this week I may do a completely off-topic random- observations-about-this-place-type-post, but in the meantime I’ll just share this one snippet of Sao Paulo street life. If any Portuguese-speaking reader can tell me what this guy’s saying**, they get a WatcherSTICKER.

*Yes I know, not the most exciting topic for the non-plant-lover. But as I’ve mentioned before, I have a list of things I feel I need to cover in this project, and watery weeds are on it.

**Is it just me, or does he seem tense? I feel as though he could use a stiff drink, a massage, or perhaps some aromatherapy. Maybe all 3.

The Post

This post is about ponds and plants, but first let’s talk about something else: snorkeling.

I love snorkeling. When I go on tropical vacations, it’s one of my favorite things to do. You put on a mask, look down and see this whole other world below you. With a good breath of air and a few strong kicks, you’re down 10 or 15 feet below the surface, peeking at fish, echinoderms and all sorts of cool creatures hidden among the rocks and coral. I also enjoy scuba, and certainly the world opened up by scuba is even more fantastic than that sampled by the casual snorkeler. But snorkeling has a relaxed, low-risk casualness about it that somehow captures the essence of vacation: Start and stop when you want, do it with friends or alone, minimal gear, hassle and safety checks, and if you’ve had a beer or two already, well, no big deal.

IMG_6737 So a few years back, as we were getting ready for a Maine vacation, I thought, “I like snorkeling, and I’ve always wondered what’s down on the bottom of the lake below the drop-off*. Why don’t I bring snorkel and fins along to Maine?”

*The “drop-off” is sort of the generic term we use for “when the water gets over your head.” In many parts of the 5 Kezar Ponds there is a distinct true drop-off: the lake depth goes from about 2 feet to >10 feet in a horizontal span of only ~6 feet. But in front of our cabin there no true drop-off, just a gradual, steady deepening till you can’t touch.

So our first day at the cabin, I donned snorkel and fins and waded in. I kicked out to about 15 feet of depth and dove down to the bottom. I did so about a dozen more times, moving a few hundred feet along the shore then swam back, walked out of the water, and left the snorkel & fins indoors for the rest of the vacation. There was pretty much nothing to see. Hold that thought.

IMG_6699 A few weeks ago I posted about Lily Pads up in Idaho, which led to my learning about Floating Pondweed. Canoeing around the ponds this year I kept an eye out for it and quickly located it in plenty (pic right). But in doing so I finally paid attention to something I’d mostly ignored over close to 4 decades of canoeing, sailing and swimming in the ponds- the stuff that grows in them.

When I was younger I found weeds and pads and such growing in the water sort of icky, and always favored sandier areas, or shorelines of exposed granite, where pond-plants didn’t grow. What I didn’t realize then is that these areas are the “deserts” of ponds, relatively poor in life (including fish). Aquatic plants are a sign of a healthy lake or pond, and their presence helps to keep the pond cleaner.

Tangent: When I was a teenager, acid rain was a big worry in the Northeast. One of the side effects of acid rain is to make it difficult for freshwater aquatic plants to live, leaving “bare” lakes and shorelines. At the time, being pretty much enviro-clueless, I actually thought, “Hey that doesn’t sound so bad…” I’m even more embarrassed to admit that around that same time I first heard the idea of global warming, and thought, “Oh that sounds nice, these New England winters kind of suck…”

How Ponds Are Like Mountains

On land, the types of plants that grow are largely determined by altitude. Here in the Wasatch as you move up from ~5,000 to 11,000 feet, you pass through Sagebrush and Rabbitbrush, to Scrub Oak and Maple, to Aspen and Douglas Fir, to Subalpine Fir and Engelman Spruce, clear up to alpine tundra. What’s cool about plants in ponds is that they work sort of the same way, but in reverse, and on a way smaller scale.

Water depth impacts aquatic plants in a few ways, probably the most important of which is that it blocks sunlight from reaching the bottom. When the amount of sunlight reaching the bottom of the pond gets down to around 1% of that at the surface, plants can no longer photosynthesize effectively. The depth at which this occurs varies depends on the lake in question and the clarity of its water, but in most lakes and ponds in Western Maine it’s probably somewhere around 12 or 15 feet.

IMG_6579 Extra Detail: Parts of Lake Superior near Duluth are clear enough to support photosynthetic algae down at over 80 feet deep. Lake Tahoe supposedly used to claim the same down to over 300(!) feet, though shoreline erosion and other human-induce factors have decreased that depth over the past half-century.

The zone between the water’s edge and this 1%-of sunlight-at-the-bottom cutoff is called the Littoral Zone, and that’s why you see things like lily pads around the edges of ponds, but not out in the middle, unless the pond is really shallow. Within the Littoral Zone are 3 distinct plant “sub-zones”, which are pretty easy to pick out from a canoe.

Tangent: I’ve been mentioning canoes a lot, because that’s how I usually poke around on the ponds. Canoes are quiet and aquadynamic*, cutting through the water gently and easily, which is nice not only because it makes paddling easier, but it creates minimal water disturbance, which is good for looking down at stuff underwater, like weeds and fish and turtles.

*Is that a word? Because if it isn’t, it totally should be.

Nested Tangent: One of my pet peeves BTW is people who can’t paddle a canoe. You know, they do 2 or 3 strokes on the left, then 2 or 3 on the right, over and over again to keep the thing going in a straight line. What’s up with that? Paddling a canoe correctly- via the J-stroke- requires about as much coordination as buttering a piece of toast. You twist the paddle away from the hull of the canoe at the end of each stroke. (Oddly, paddling a canoe is the only thing I do left-handed.)

Kayaks are even better for poking around, as they’re even more aquadynamic plus you sit lower to the water. But my favorite way to get around on the ponds is by sailing. My parents keep an old (30+ years) Sears Roebuck sunfish-type clone up at the cabin that only I ever break out. Winds on small ponds are gusty and fickle, and sailing them requires a sort weird sort of patience. You have to be willing to inch along, Island nest becalmed or with the slightest of breezes, lazing back with a sort of Zen-like calm. But when a gust kicks up, you have to snap to life, aggressively tacking upwind to get into hard-to-reach spots. Middle Pond is my favorite- long and narrow, with prevailing length-wise winds and an island* in the middle to mix it up. On a good day I can sail clear upwind to the falls, tacking at the end every 15 or 20 feet. I love it.

*Where the Loons nest.

The most amazing, counterintuitive thing about sailing is that you can sail into the wind. Doesn’t that seem like it shouldn’t work? Like you’re cheating somehow? I think the lateen sail is one of my all-time favorite human inventions. Not just because it changed the course of history*, but because it was an innovation of such significance that required no advancements in materials science or other enabling technologies; they just starting cutting sails differently, Makes you wonder what other “lateen”-type ideas are sitting right in front of us, waiting to be discovered…

*It arguably did, enabling the European age of worldwide exploration, expansion and dominance.

The Plants, Already

IMG_6729 The first plant sub-zone is the Emergent Plants sub-zone. Here plants are typically rooted on the lake bottom, but grow up and flower above the water’s surface. An example right on our beach is Rushes. I explained the differences between Grasses, Sedges and Rushes last month up in Idaho, and as you can see, Rushes are Round these rushes are round in cross-section. I think these may be Common Rush, Juncus effusus, which is widespread across North America. They grow just above or just below the shoreline; their bases don’t have to be underwater, but the soil/sand they grow in has to be nearly water-logged.

Littoral1 Moving out just a few feet from shore is a much more prominent emergent plant- Pickerelweed, Pontederia cordata (pic below, left). Like rushes, Pickerelweed is a monocot, and is native throughout the Western hemisphere, IMG_6775ranging from Canada to Argentina. It has thick, waxy leaves and succulent stems. But the easiest way to pick it out is by its stem spike of blue flowers. Blue-flowered plants are unusual in North American lakes, ponds and waterways, so when you see a spike of blue flowers, it’s likely you’re looking at Pickerelweed.

water_hyacinth_01 Side Note: The other common blue-flowered freshwater plant you’ll see, particularly in the Southeast, is Water Hyacinth, Eichornia crassipes, (pic right, not mine) (a member of the same family, Pontederiaceae) which is not native to North America but has been introduced from South America and is a pesky invasive.

The blue flowers are usually busy with Bumblebees, who collect both the pollen and the nectar, and are visited by other bees as IMG_6776 well, including one monolectic species*. P. cordata also grows vegetatively via root-cloning, and so when you see a patch, it’s likely one big clone. Although the individual flowers last for only a couple of days, a given stand/clone will flower throughout most of the summer. Pickerelweed is native, but can be a pest both here in North America and in other parts of the world where it’s been introduced, clogging waterways and crowding out other plants. But it plays an important positive role in keeping lakes and ponds clean, filtering pollutants out of the water.

*Doufourea novangliae.

Extra Detail: Sunfish seem to love Pickerelweed on 5 Kezar Ponds. Algae Cast your line into a stand of the stuff, and a sunfish is the only thing you’re pulling out. Pickerelweed stands also seem to be the favored locale for extensive green algal colonies, probably because the stems help make still waters even stiller, by blocking currents. These colonies always grossed me out as a kid; I swam in constant, low-level dread of sticking a foot in one*. Interestingly, down at a single-celled level, most ponds go through an annual succession of peak-bloom cycles of diatoms, algae and cyanobacteria. Another day, another post.

*Though not as much as I dreaded getting bit by a leech. I never did get bit, though I saw friends and siblings get nailed. Interestingly, Brother Phil noted this year that none of us have spotted a leech for several years. Wonder why that is?

Littoral2 The next sub-zone, starting at ~ 3 or 4 feet deep on our ponds, is the Floating Plant sub-zone, dominated by Waterlilies, and- as I was pleased to notice- Floating Pondweed. The Pondweed leaves are much smaller, which may be part of the reason I never noticed them before.

Pondweed Waterlily Both Waterlilies and Pondweeds use the buoyancy of the water- rather than the support of their stems- to position leaves and blooms on the surface and both- as I mentioned in the Idaho-Lily post, evolved this “Lily-Pad-Schtick” independently. Waterlilies are ultra-“primitive” dicots, having branched off from nearly all the other angiosperms way early in the history of flowering plants, while Pondweeds are monocots, more closely related to the nearby Rushes and Pickerelweeds. 5 Kezar ponds BTW supports both genera of common North American Waterlilies: the white/true-petaled Nympheae and the yellow/sepals-as-petals Nuphar blooms..

Algae Finger As you paddle away from the shore and clear the Waterlilies, if you look down right away, before it gets too deep*, you’ll see other plants below the water. This is the Submersed Plant Sub-Zone, characterized by plants that grow and flower entirely underwater.

*Polarized sunglasses help. But if you buy your cheapie-eyewear at Maverik, using the shadow of a canoe paddle to cut the sun’s glare off the water works fairly well.

There are a number of cool submersed plants growing down in this zone. One of the more interesting is Common Hornwort, Ceratophyllum demersum. Hornworts are entirely submerged, free-floating plants, from 3 to 9 feet in “height”, rooted in mud on the pond-bottom. “Rooted” is a bit of a misnomer; the plants have no real roots, but modified leaves that anchor them to the bottom. They do well in still waters in mud/soil rich in nutrients, and provide shelter to fish-spawn and snails.

Hornwort Hornworts have completely submerged lives. Not only are they “rooted” underwater, but unlike plants of the Emergent and Floating sub-zones, they flower and are pollinated underwater. Hornwort pollination is a weird analog of wind-pollination, pollen grains carried slowly through the waters in the incredible, one-in-a-zillion chance that they’ll wind up at a female Hornwort flower, which of course, a fair number of them manage to do.

Side Note: Plant People will get why this next part is Way Cool. If you’re not a Plant Person*, you may need to go back and read this post and the “Botanical Spotlight” in this post to get it.

*Oh don’t be like that. You know what I’m talking about. You’re rolling your eyes and thinking “boooring.” Let me tell you what: We Plant People see a whole world the rest of you Plant-Blind folk don’t see. Plus we make fun of the rest of you when you’re not around.

IMG_6756 When describing plants in this blog, I usually try to mention what kind of plant it is and give some idea of what it’s related to. When describing flowering plants, part of this includes IDing the plant as dicot or monocot. But I can’t do this with Hornwort because botanists haven’t agreed on what it is. For some time it was though to be a basal offshoot of the angiosperms, similar to Waterlilies. But more recent genetic analyses have suggested that it’s a basal offshoot/sister group of either the monocots or eudicots. IMG_6754 In other words, when the monocots/eudicots branched off from the “primitive” dicots way back over 100 million years ago, and then broke off into monocots and eudicots, Hornworts may have been part of a third branch that subsequently broke off from either the monocot or eudicot line. Today there are tens of thousands of species of both monocots and eudicots, but just 6 species of Hornworts worldwide. Isn’t that freaky? These watery weeds growing out of the muck may be the sole survivors of a 100M+ year-old line of life as ancient as monocots or eudicots.

RCA Phylogeny Tangent: We’ve come across several of these “lone survivors” of ancient lines before, including Mormon Tea, Gingkoes and Cycads. These living fossils are fascinating not just in and of themselves, but because they highlight the common recent ancestry of the vast majority of living species. Think about angiosperms (flowering plants). It’s thought that they evolved once, from a common ancestor*. Today, maybe 150 million years later, they rule the world. And there are similar stories for everything from songbirds (Passerines) to bats to primates. When each of these lines got its start, there were thousands of other living things around whose lines have since dead-ended. A few dozen crucial splits/breaks have defined so much of the history of living things. And if one of those splits/breaks offshoots hadn’t worked out, or if another that almost worked out did work out, well it makes you think about how the world might have turned out. (Or how other worlds maybe did turn out.) The 6 species of Hornwort range worldwide- they’re not in obvious danger of extinction anytime son. Makes you wonder if there the last of their line, or the bridge to some future, diverse order that will dominate the world.

*Because of the pollination-weirdness described in this post.

The Hornworts and other submersed plants seem to give out at somewhere around 10 or 12 feet of depth around the ponds, marking the end of the Sumbersed sub-zone and the entire Littoral Zone. Beyond this is the Limnetic Zone, marked by a lack of higher plants on the lake bottom. But the Limnetic Zone in turn is in turn divided into 2 horizontal zones. The upper waters, extending down to the ~10- 15 foot depth of the end of the Littoral- are mark the Euphotic Sub-Zone, where photosynthesis is still carried out by free-floating algae and cyanobacteria. Below this level is the Benthic Sub-Zone, where no plants grow.

Littoral GraphicWhen I snorkeled down to the bottom, I was diving down to the pond equivalent of alpine tundra; the little light that reached there was too meager to support any plants. That’s why the scenery was so uninteresting. On the deep lake bottom, there is life, but it tends to be teeny things- arthropods and such- that work their way through the mud, some feeding on the detritus that falls slowly from the living world above, others on each other. It was also a bit spooky down there- dark, cold and quiet. On the deeper dives I felt out of place and unwelcome, and kept catching myself kicking quickly back up toward the growing light above.

Thursday, August 19, 2010

More Things That Fly Around Ponds

The first morning I awoke at the cabin before everyone else, and stepped out onto the deck to look out on the lake. As I did so, I noticed a large, oval leaf floating in the foot-dip bucket*. Being the kind of guy who’s always interested in leaves, I bent down for a closer look. The “leaf” had fur on it.

*Used to get sand off feet before entering cabin.

I first thought the critter dead, but a gentle prod with a twig produced a healthy response. It wasn’t a leaf and it wasn’t dead; it was a Little Brown Bat, Mysotis lucifugus, and it was stuck.

IMG_6634 We tend to think of bats as somehow unusual or different, but something like a quarter of all species of mammal in the world are bats (over 1,100 species). If a visitor from another planet landed on Earth tomorrow and asked to see a “typical” mammal, the right thing to show him/her/it wouldn’t be a dog, cat, monkey or mouse; it would be a bat. And if that alien landed in North America, it would be a Little Brown Bat (LBB), the most common, widespread bat in North America.

I’ve blogged a bit about bats before, comparing their wings, lungs and senses to those of birds. But as it turns out, a captive bat, especially one stuck in water, is a fabulous opportunity to take a closer look at its wings. Check out this video:

You never see bat-wings opening and closing that slowly in the air. Nor for that matter do you usually get a chance to see them doing so in one place, in broad daylight.

All About Bat Wings

Back in the Spring, in my post on Swifts, I speculated a bit about birds and bats, why bats were overwhelmingly nocturnal, and why they’d evolved echolocation/sonar* more frequently than birds. In passing, I mentioned differences in flight capability, and basically accepted that birds were superior flyers. But subsequently, as alert reader Doug M. brought to my attention, my off-hand assessment of their flight capabilities probably gave short shrift** to bats.

*The more correct term these days seems to be “echolocation.” But I love the word “sonar”, so that’s what I’m generally going to use in this post.

**What’s a “shrift”, anyway?

Tangent: Doug M. is probably the smartest reader of this blog*. Seriously, whoever you are, Doug M. is almost certainly smarter than you, and he’s for sure way smarter than me. If he wrote this blog, it would totally rock. Doug M. frequently emails me comments on posts, with all sorts of great info and insight on everything from geology to bats to the Eocene to arthropod lungs to echinoderms to the ecology of South Florida. If he ever starts a blog, you should read it.

*Tomodactylus may be another contender, though he comments less frequently. And Christopher. Oh, and Sally, when it comes to plants. And Jube when it comes to rocks. And Ted when it comes to bugs. And KanyonKris and SBJ when it comes to bike parts. OK, so most everyone who reads this blog is smarter than the guy who writes it. But I’m OK with that, because although I am often lacking in smarts and facts, I know that my graphics are totally awesome.

Bat wings do indeed produce less thrust and lift than bird wings. (and as I’ve posted previously, their wing-powering musculature is very different than that of birds, and their/our lung architecture is inferior.) But bat wings enable flight that is in many cases more finely-tuned and more maneuverable than bird flight. Although it’s easy to think of bird and bat wings as basically big arms, that’s a bit of an oversimplification. Check out this graphic (not mine, captions/pointers added by me) of the bone structure of bird and bat wings.

bat bird bones captions A bird wing is more or less a big arm, with the “hand” as largely a fused-together extension of that arm. You can imagine flapping as a bit like moving your arms*.

*Though the sensations a bird experiences must be radically different. Birds have no deltoid muscles, so raising a wing must feel nothing like raising an arm, but rather stresses a set of muscles we don’t have.

But much of a bat’s wing is effectively its “hand”. Roughly 1/3 of the wing surface area is the membrane between its forefinger and pinkie-finger. So when a bat flaps, it’s sort of a combo arm-flapping and hand-waving.

Extra Detail: And the motion is fundamentally different from bird-flapping. Bat-flapping is more of a “rowing” motion, almost like a sort of breaststroke. As a bat flaps, its elbows lift out to the side with the fingers extended out, and then the arms and fingers pull forward, down, then up again.

Think about your own hand, and its dexterity, sensitivity and fine motor control compared to that of your forearms and upper arms. That’s probably in line with the sensitivity and dexterity a bat feels in its wings, and it enables maneuvers in flight that are hard to replicate in birds.

When you look close up at the membrane of a bat’s wing, you’ll see it’s covered with tiny bumps. These are called Merkel cells, after Angela Merkel, who before she became Chancellor of Germany was a noted bat researcher in the GDR. Haha- just kidding! No seriously, the Merkel cells, each of which has a tiny hair in the center, are ultra-sensitive touch-receptors, through which the bat actually feels the airflow over its “hands” and (subconsciously) dynamically alters its “hand”-position/wing-shape in response. These guys are in tune with the medium through which they’re traveling at a level hard for us to conceive.

LBB A-Zoom Many bats- including the LBB- have another receptor-type in their wings which is sensitized to the stretching of the wing membrane, and its role is to help the bat catch insects in flight.

About ¾ of bats are insectivores. The LBB for example typically consumes about a third of its bodyweight each night in bugs. I always assumed that bats caught bugs like a Loon catches fish: open the mouth and chomp. But it turns out that while bats do consume smaller bugs (gnats, mosquitoes) mouth-first, most larger insect-prey, such as moths, are caught in the wings and/or tail and then “handed” to the mouth.

Extra Detail: Speaking of moths, there are numerous examples of evolutionary “arms races” between moths and bats. Some moths have a special acoustic organ which, when it detects the ultrasonic peeps pf bat-sonar, automatically sends the moth into evasive maneuvers- a twitchy, erratic flight-path. Other moths emit their own ultrasonic signals in response to bat-sonar. These signals appear to be a form of “sonar-jamming”, but it’s also been suggested that in some cases they may serve as a warning to the bat that they’re poisonous or bad-tasting, similar to how other insects warn off predators with distinctive coloration.

Many of the insects preyed upon by LBBs BTW, are insects that- like mosquitoes- develop in an aquatic stage and so are found near bodies of water. As a result LBBs tend to be common near lakes and ponds.

A bat’s wing isn’t just a lame, bare substitute for a feathered bird wing. It’s a completely different appendage, with different structure and different capabilities.

I don’t know how he/she wound up in the bucket. Bats can “see” the surface of the water effectively with their sonar. IMG_6635Many bats routinely skim the surface of a body of water to drink, and I read that the LBB actually sometimes uses its wings to drink (presumably by scooping up a “handful”- I’m not clear.) Certainly the water in the bucket is a much smaller, and proportionally deeper, body of water than say the lake, but small crevices, puddles and pockets full of water occur all over the place in Maine, and I haven’t heard of bats getting regularly stuck.

My one wild guess- and this is pure speculation- is that somehow the plastic of the bucket (a large Tupperware-style container, actually) threw off his/her spatial “sonar judgment.” Bats routinely recognize rock, wood, living things (prey/bugs, other bats). Maybe the sonic “texture” of plastic is just weird/unknown/different enough that the bat misjudged the dimensions and/or structure of the container, and made a bad landing call, akin to when a Loon lands on a highway.

That’s total conjecture, of course, but it does get you thinking about bat sonar, and how completely amazing it is. We all know the basics of course: bats emit ultrasonic peeps, and then hear those peeps bounced back at them, which lets them know where various things are and enables them to fly around in the dark while not hitting walls and catching bugs. Just like sonar on a submarine, right?

All About Bat-Sonar

Well, not really. Submarine sonar (and accompanying hydrophones) is reasonably good at detecting things like the ocean floor, ships, other submarines, and torpedoes. Bat sonar detects things like moths and gnats, distinguishes them from dozens- or hundreds of other flying things- bugs, other bats, what bat researchers call “clutter”- and enables the bat to make repeated split-second decisions, flight-corrections, attacks and evasive maneuvers. Bat sonar provides bats with a real mental image of the world around them; they “see” the world through sound.

Still, the concept sounds simple enough, but when you scratch your head and think about it, it’s amazing that bats make sonar work. Let’s take a simple example. For bat sonar to work, the emitted peeps need to be LOUD. This makes intuitive sense when you think about it, though chances are you probably never did think too much about it, since bat-sonar-peeps are ultrasonic, too high-pitched for us to hear.

So how loud are bats? Pretty freaking loud. When measured from a distance of 10cm, the sonar-peeps of insect-hunting bats are up to 125 -130 decibels. That’s about the volume of a jackhammer when you’re standing next to it. So here’s this little critter, with these teensy-weensy, ultra-advanced, hypersensitive little ears, which are being blasted by a jackhammer between 10 and 200 times a second. How on Earth does a bat not blow out its own eardrums?

Peep Frequency vs. Sonic Frequency

Before we answer, 2 things worth covering here. “Frequency” is a loaded term with bat-sonar. There’s the sonic frequency of the pitch of the peeps, which generally ranges from ~20kHz to ~60kHz (with extremes from 11kHz to 212 kHz), and then there’s the frequency of the emission the peeps, which usually ranges from ~10Hz to 200Hz. Insect-hunting bats- as I mentioned last year in the post about Vampire Bats- use a lower peep-frequency scanning sonar when cruising along, but switch to a higher peep-frequency “targeting” sonar when closing in on a bug. The higher peep-frequency sonar enables more accurate tracking of the bug, and quicker flight corrections, etc.

Special Side Note for the Scientifically Impaired/Illiterate, Generally Spacy and/or my Mother: 1Hz or “Hertz” is once per second. 1 kHz or “Kilohertz” is 1,000 times per second.

The bat doesn’t use the high-peep-frequency all of the time because LowFreq4a) it presumably requires a lot more energy and b) there’s some evidence that the lower peep frequency may provide a better distance/big picture view of the world. (This may particularly be true for bats that use “chirp sonar”, where each peep starts at a high sonic frequency and then drops. The actual frequency returned may provide additional distance information, and these reflected trailing chirps may be clearer if not packed too closely together.)

The sonic frequencies of bat-sonar are of course ultrasonic to human ears. Our hearing ranges to an alleged maximum of about 20kHz. Given how loud bat sonar is, we should probably be grateful that we can’t hear it, but courtesy to human beings probably wasn’t the evolutionary driver in determining sonar frequencies.

Side Note: I say “alleged” based on my own recent testing. Our own hearing detects higher frequencies best when we’re children, and then deteriorates progressively as we age. While we were back East we visited the (very excellent) Boston Museum of Science. One of the interactive displays on hearing and acoustics was a set of headphones with a user-controlled sound frequency. I (age 46) was able to detect a tone up to about 14.2kHz. Bird Whisperer (age 11) was able to hear up to nearly 17.5kHz.

The reason bat sonar is high frequency is that so many of the things that bats need to “see”- like bugs- are small. HighFreq4 Lower frequency sounds have longer wavelengths, and when the wavelength of a sound wave gets longer than say the wingspan of an insect, it becomes hard to “see” that insect. An analogy with our own vision would be if our eyesight was tuned to the electromagnetic frequencies of radio or TV waves, which range in wavelength from roughly 1 to 10 meters; it would be very hard for us to see much of anything smaller than a piece of furniture.

Tangent: Something occurred to me in doing this bit on frequency. 20kHz – 60kHz is out of range for us humans, but a large portion of that range is easily audible to dogs, whose hearing regularly extends way up over 40kHz. What do dogs hear in the evenings when bats come out? If it’s really that loud, how come they aren’t freaking out? The same is true for most other mammals, BTW. Cat hearing ranges even higher than dogs (up over 60 kHz). Rats and mice hear way higher frequencies than either of them, and even horses and cows can hear pitches up over 30kHz.

Hearing Ranges Yeah, yeah, frequency-schmequency. So what about the blowing out the eardrums thing? Turns out that bats have 2 ways of dealing with this problem. The first is that many species have an organ in their heads that partially mutes their hearing in the exact instance they’re peeping. So if that bat’s peeping 100 times/ second, it’s muting its hearing 100 times/second.

But the second workaround is even more interesting. Many bats peep at slightly lower frequencies than that which their hearing is optimized for. But because the bat is flying forward, the return echoes are received at the slightly higher frequency for which its ears are tuned. This is an example of the Doppler Effect, which is why the siren of an ambulance or the horn of a train sounds slightly higher when it’s coming towards you than when it’s going away from you.

LBB Doppler Sounds cool, but how can this possibly work? A bat flies at all kinds of different speeds, and- as anyone who’s watched a flying bat knows- they change speed and direction all the time? Apparently the bat’s brain is wired to- automatically and subconsciously- modulate the pitch of its own peeps to compensate for changes in flight speed.

A seemingly even thornier problem is how to do all this stuff- peeping, flying, water-scooping, bug-catching, Doppler-adjusting- in the company of dozens or hundreds of other bats. How does the bat keep straight its own echoes from those of other bats, whether of the same or different species?

For a long time these questions were unanswered, and much is still not understood, but research in the last decade has started to make things clearer. First, bats can distinguish peeps of their own species from those of other species. This isn’t surprising. Most bats, including the LBB, are highly social, roost in large groups, and it would be problematic if they routinely confused groups/roost of other species with their own. But the more surprising finding has been that bats can distinguish between specific different/other species, so when they hear an “alien” peep, they don’t just think, “Oh, this is some other kind of bat…” but rather, “This is a type X bat.” This is potentially useful info for a bat. Some species may be more aggressive competitors, other species may favor similar feeding or roosting areas.

Secondly, it seems that bats can recognize “voices” amongst their own kind. For many years researchers have known that if you want to mess up a bat’s ultrasonic “vision”, you can’t do so by just playing recordings of bat-peeps. But you can mess it up by playing back its own recorded, individual peeps. It wasn’t clear why this was, but now it seems that bats recognize their own voices, and that instant recognition is what allows them to sort out the echoes they need to accept to construct a sonic “view”.

Bats not only recognize their own voices, but also those of common associates. So the distinction in a bat’s mind when hearing a voice isn’t just, Me/Other Bat Of My Type, but Me/Bat I Know/Other (Unknown) Bat Of My Type. Interestingly, bats in this research learned to “recognize” specific “new” bats over 2 to 3 weeks of regular exposure/interaction.

Tangent: There are 2 interesting corollaries here. The first is that when bats are out hunting, they must recognize the calls of their regular associates. (“Oh, that’s Roy closing on a target off to my right…”) The second is that bats regularly and comfortably do something we’re sort of awkward with: recognizing our own voices. When I’m listening to a recording or a video of family, friends, coworkers, etc., I’m always slightly jarred when hearing my own voice. “That’s what I sound like?” I think. Somehow my own voice, pitch* and even inflection** all seem a bit wrong, like there’s this presumptuous stranger in the midst of my friends/family/team. Why is that? Why can’t I “hear” myself?”

*Always higher than I think.

**Oddly credible, but sometimes slightly affected, like I went to a snooty school or something. Which I did, so I guess that makes sense, but again, I don’t “sound” that way to me when I speak…

This effect is especially unsettling when an “echo” is present in conference calls. (Who is that guy with the irritating voice, and why does he keep repeating everything I just said??)

I’ve touched on just 2 examples, but the point is that there’s far more complexity and sophistication in bat sonar than just shouting at walls; the brains of bats are optimized in all sorts of ways to process acoustic information and translate that data into a working model of the world, much in the way significant portions of our own brain are adapted to processing visual information in creating our model of the world.

It’s interesting to think about how sonar came about. Like vision, we know that it’s evolved multiple times- no one thinks bats and porpoises shared a common sonar-enabled ancestor! But how many times has it evolved in bats? The answer is at least twice, and maybe more.

Bats are generally divided up into 2 types- microbats and megabats. Most microbats, like the LBB, are insectivorous and use sonar, but many- particularly the larger ones- hunt frogs, lizard, fish, scorpions and even birds*. (Vampire Bats BTW are microbats.) Megabats are overwhelmingly fruit and nectar-eaters, have excellent senses of smell, and do not- with one important exception- use sonar. Many megabats are important pollinators and/or seed-dispersal agents.

*Thanks, Doug M.!

Extra Detail: For a long time it was assumed that bats were monophyletic (descended from the same common ancestor species) and that early on they diverged into the micros and megas. But in the late 1980s some researchers suggested an alternate hypothesis: that bats had evolved not once, but twice, and that the similarities between micros and megas were the result of convergent evolution. This would mean that flight- true powered flight- had evolved not just once, but twice independently among mammals. The supporting evidence for this hypothesis included a number of anatomical differences between the 2 groups, but most tantalizingly, the researchers pointed to apparent structural similarities between the brains of the megas and the brains of primates. In other words, maybe the megas were more closely-related to us than they were the micros!

It was one of the coolest, most incredible convergent evolution hypotheses ever. Unfortunately, it was almost certainly wrong. Subsequent DNA research established the monophyly of bats. But that same research did disrupt the traditionally accepted family tree. Bats don’t divide cleanly into megas and micros; instead the megas are just one branch within the (now paraphyletic) micros.

And that branch is overwhelmingly non-echolocating. Whether or not their ancestors were sonar-capable is unclear*; so the megas could be descended from bats that never evolved sonar, or from echolocating bats that subsequently lost the ability.

*Fossil evidence seemed in some cases to indicate bats evolved flight before echolocation, but more recent genetic evidence suggests that the common bat ancestor may have been echolocating. Fossil evidence for bats isn’t all that great BTW, they don’t fossilize that well.

EFB1 That one megabat exception- the species that does use sonar- is Rousettus aegypticus, the Egyptian Fruit Bat (EFB) (pic right, not mine). But its sonar is completely different from microbat-sonar. Echolocating microbats produce sound from the larynx, like us. In effect, an LBB spends its evenings flying around shouting. But the EFB produces its signals by clicking its tongue, something no other bat does.

It used to be thought that the EFB’s sonar was a sort of lame substitute for “real” bat sonar, but more recently it’s been re-assessed as more capable and more comparable to microbat sonar. So clearly sonar has evolved at least twice in bats. More recently, DNA research suggests that traditional, “mainstream”, laryngeal sonar may have evolved twice within microbats (for a minimum of 3 times overall). The question is still unresolved, but bats have a complex and fascinating evolutionary history.

When I come a across an easily or already-captured critter, I often try to show it to the Trifecta, if I think I can do so without excessive harm or trauma to the critter in question. In this instance I was especially motivated to do so, as I wasn’t clear as to when, if ever, they might see another LBB close-up.

As a boy in the 1970s I remember sitting on the beach after dusk, watching dozens of bats flit through the air. We saw bats this trip, but only onesy-twosy. Within the last 5 years, numbers of bats- especially LBBs- have been dying in huge numbers. The dead and dying bats exhibit a white fungus, Geomyces destructans*, growing around their muzzles and wings. Geomyces species do well in cold, dank environments, such as permafrost soils, and, presumably, bat caves. G. destructans seems related to other Geomyces species, though it has an unusual spore morphology.

*Totally bad-ass Latin name.

batface Frustratingly, it’s not known with the fungus is the killer, or an opportunistic infection after the bat has been weakened by some other killing agent. Infected bats are typically emaciated, dehydrated and unable to hibernate. LBBs are social and sleep, mate and hibernate huddled closely together in huge roosts- ideal conditions for communicable pathogens. In less than 5 years since its discovery in upstate New York, it’s spread from Quebec to Oklahoma.

Extra Detail: The fungus is present in Europe, where- presuming it is in fact the killing agent- it doesn’t seem to cause bat die-offs, leading researchers to wonder whether European species are resistant. One of the leading suspects for its spread to North America is humans, and perhaps specifically cavers.

The day we left Boston to drive up to Maine, the New York Times* ran a piece on White-Nose Syndrome. Researchers from Boston University have determined that the probability of LBBs being wiped out completely in the Northeastern US within 20 years is over 99%.

*My parents subscribe to the New York Times, despite living 200 miles from that city. I used to poke fun at them for doing so, but have since desisted, as after several days’ exposure to the Times, my return home to the Salt Lake Tribune makes for a bit of a rough landing.

My LBB’s muzzle looked clean. I gently removed him from the bucket and placed him under another container on the deck.

Side Note: Yes, I was careful to use tongs, and wash everything/hands afterward. You hear a lot about bats and rabies, and it’s true that rabies regularly afflicts many bat species, including the LBB. So how likely is it that a given bat is infected? Typical infection rates are less than 0.5%. But- and this is a big “but”- symptoms of rabies include loss of coordination, which in bats often means loss of flight. So while there’s a small chance that any given bat is rabid, infected bats are probably statistically over-represented amongst those you encounter on the ground in broad daylight.

Last month I made a little extra effort to swim at a Gulf Coast beach, with the thought in the back of my mind that perhaps one day I might not be able to do so. In the same spirit I waited patiently for the Trifecta to awake and check out our visitor.

Maybe someday they’ll tell their kids about it.

Note About Sources: There are tons and tons of great info about bats and echolocation online. My best source was Bat echolocation calls: adaptation and covergent evolution, Gareth Jones and Marc Holdereid. Additional evolutionary and phylogenetic info came from Integrated fossil and molecular data reconstruct bat echolocation, Springer et al. Info on voice recognition in bats came from The Voice of Bats: How Greater Mouse-eared Bats Recognize Individuals Based on Their Echolocation Calls, Yosi Yovel et al. The link to the referenced New York Times article is here. The hearing ranges used in the animal-frequency graphic came from this site. My introduction to bat-sonar some years back came from the excellent description in Richard Dawkins’ The Blind Watchmaker, which though somewhat dated now, is still a wonderful read.