Smart, Aggressive And Not Always Entirely Honest

Since the new year I’ve been home a bit more often during the day, seeing as… well, I’ll get to that in the next post, which has given me an opportunity to see the comings and goings of various creatures in the yard- mainly birds- during the day. Last week one morning this big Scrub-Jay showed up on our deck.

Tangent: One of the weird things about Winter, assuming you work a full-time job, is that a whole week can pass without you ever seeing your home in the light of day. You leave when it’s dark and come home when it’s dark. Sometimes you’ll wake up on a Saturday morning in January, look out the window, and think, “Oh yeah- this is where I live…”

The Western Scrub-Jay, Aphelocoma californica, is a super-easy bird to ID, as it’s pretty much the only blue bird in Salt Lake Valley in the winter. It has a distinctive call, arguably the harshest of corvid squawks: a razor-sharp, scratchy, climbing note that instantly catches your attention. When it shows up in the yard- never staying more than 5 or 10 minutes- it immediately disrupts the social equilibrium around the feeders*, sending juncos, siskins and finches scattering.

*I described the Winter “regulars” at my feeders 2 years ago in Bird Feeder Week. Man, was that a great week or what?

Scrub-Jays are birds of woodlands. In Utah they’re most often found in either Piñon-Juniper or Scrub Oak. This time of year you’ll almost always come across a couple if you go poking around on any of the foothill trails across the street form the zoo, or up around the Death Climb. Aphelocoma, the Scrub-Jays, includes 5 species, all native to North America, but the only other one* you’re likely to see in the US is the Florida Scrub-Jay, A. coerulescnes, native to, yes that’s right, Florida.

*The Island Scrub Jay, A. insularis, is endemic to Santa Cruz Island off the California coast.

The Western Scrub-Jay is divided up into a whole bunch of subspecies, grouped broadly within 2 clades, (which may in turn get reclassified as 2 distinct species sometime in the near future): one inland and one in California.

Side Note: This might sound similar in some ways to the division between Black-billed and Yellow-billed Magpies; the Sierra Nevada/Great Basin constitute a formidable barrier to migration. But while Magpies came over from Asia some 3-4 million years ago, Scrub-Jays are “New World Jays”, thought to have migrated Northward from Central America.

One of the interesting markers of A. californica subspecies is bill morphology. Subspecies that live in Piñon-Juniper woodlands have straight, thin bills for reaching in between cones scales to grab Piñon seeds, while those that live around Oak woodlands have slightly broader, more hooked beaks (better for working with acorns). Our subspecies here in Northern Utah, A. californica woodhouseii woodhouseii (sometimes called Woodhouse’s Scrub-Jay by bird geeks) has sort of an in-betweeener beak: straight but heavy, with a slight hint of a hook at the tip.

In any case, it’s easy to dismiss Scrub-Jays as somewhat unremarkable in that compared to other “Pine Birds” their capabilities can seem rather unimpressive. Pinyon Jays for example can carry 0.6 oz worth of nuts in their mouth/esophagus. Clark’s Nutcracker- the champion pine bird- can carry over a full ounce- over 20% of its body weight.. Guess how much a Scrub-Jay can carry? 0.05 oz- less than 2% of its body weight. And it barely limps along with that load. A fully-loaded A. californica will fly no more than 1/3 mile to cache nuts, reaching a top speed of no faster than 18 MPH.

The Pinyon Jay carries its load up to 6 miles, at speeds up to 26 MPH, and Clark’s Nutcracker up to 18 miles at up to 29 MPH. Even Stellers Jay- not a nut or acorn specialist- can manage up to 2 miles with a 0.2 oz payload at up to 22 MPH.

Side Note: An interesting corollary to these figures is the role- or rather lack thereof- played by Scrub-Jays in the modern-day distribution of Piñon pines*. Piñon pine has steadily expanded Northward across the Great Basin since the end of the last ice age, only reaching its present range within the last few thousand years. Piñon doesn’t occur on the floors of Great Basin valleys- only on mountain slopes. The principal agent moving it between disjunct ranges was pine birds, who spread the nuts via caching. With such a dismal loaded flight-range, the Scrub-Jay has likely played little role in its expansion to new ranges.

*I’ve covered Piñons extensively in this project, most notably in this post and this post. Man it is like I have a post for everything.

Stellers Jay’s loaded flight range is also pretty modest. It’s a bird of higher altitudes, and an infrequent visitor to Piñon-Juniper Woodland. When it does collect piñon nuts, it most often caches them at higher altitudes, unsuitable to piñon growth. But as temperatures rose following the end of the last ice age, its slightly-too-high seed caches may possibly have helped piñon expand up-slope within ranges where it was already established.

Scrub-Jays’ bills aren’t strong enough to pry apart the scales of unopened piñon cones. Instead they pick seeds from already opened cones, or wait for other, stronger-beaked corvids, such as Pinyon Jays, to open them for them, whereupon they harass them, drive them away, and make off with the goods.

What Scrub-Jays have going for them is their big brains. We covered the high intelligence of corvids when we looked at Magpies last Fall. Scrub Jays aren’t champion tool-makers, aren’t known to recognize themselves in mirrors, and certainly don’t display the phenomenal memory and navigational skills of Clark’s Nutcracker. But they appear to have both strong episodic memory and exceptional social awareness.

Episodic memory is the memory of autobiographical events and context, including time, place and emotion. In experiments Scrub-Jays have been placed in 2 different cages- one in which they were fed, the other in which they weren’t. Later the same jays were given the access to, and the opportunity to cache food items in, both cages. They overwhelmingly cached food in the cage in which they’d been hungry.

Extra Detail: Episodic memory is one of the 2 forms of declarative memory, which I described in this post. The other form of declarative memory is semantic memory, which is information or knowledge independent of personal context or relevance.

Scrub-Jays remember not only events, but others present at those events. When Scrub-Jays cache food items in front of other Scrub-Jays, they’ll frequently return later and move the items multiple times to avoid pilferage. They even appear to be able to keep track of specifically which individual birds saw them cache at which location on which occasion. Clark’s Nutcrackers, on the other hand, as brilliant as they are navigationally, seem to be utterly clueless to potential theft, happily caching away in front of Scrub-Jays and other thieving corvids.

Side Note: Lest this post make Scrub-Jays sounds like scoundrels, I should mention that they exhibit strong pair-bonding and parenting habits. In fact, when Scrub-Jays cache in front of their “spouse”, they only re-cache about as often as if they’d done so unobserved; their spouse is clearly on the same “team.”

Florida Scrub-Jays BTW, seem to take social cooperation even further, with young adults helping parents to cooperatively raise younger siblings. Family members also collaborate to take regular “watches” looking out for hawks, snakes and other predators. Similar cooperative breeding efforts are displayed by Western Scrub-Jays down in Mexico, but not here in the Western US.

But what’s interesting about this re-caching behavior is that it’s exhibited only by Scrub-Jays who have experienced cache-theft directly. By which you probably think I mean that once they’ve been robbed, they figure it out, smarten up and start caching in private or re-caching if they cached while observed by other Scrub-Jays, right? Wrong. What I meant was specifically the opposite: Scrub-Jays don’t re-cache until they themselves have robbed other birds’ caches. The experience of having observed another bird caching, and then they themselves having robbed that cache, clues them in that other Scrub-Jays watching them will likely figure out the same schtick. This learning-process suggests that Scrub-Jays, like us, have evolved a “theory of mind”- the ability to attribute knowledge, intent and desire to others. What does so-and-so know? What is he or she likely to do with that information?

Humans seem to develop a theory of mind around age 4. Before this time, children fail “false belief” tasks. For example, a child is told a story with 2 characters. Character A puts something- a toy, a ball, whatever- in a basket, then leaves the room. Character B moves the object from the basket to someplace else- say a box. Character A returns, and the child is asked where Character A will look for the object. Up until about age 4, most kids get the answer wrong. So in other words, the Scrub-Jay is- in at least some ways- smarter than a 3 year-old kid.

Side Note: Autistic kids over age 4 usually still fail this test, which backs up my previously-expressed Half-Baked Theory that Clark’s Nutcracker is essentially an autistic corvid.

This social intelligence makes possible all sorts of deception. Scrub-Jays and other corvids, such as crows and ravens, routinely move caches, make false caches, and cache inedible items to throw off would-be thieves and competitors. In other words, they-deliberately and with forethought- lie. How “human” is that?

You may object that simply misleading is not lying, that a lie is a specific statement of falsehood, and corvids lack the level of language to be able to explicitly state such falsehoods. But I disagree; I’ve always felt that the nature of a lie is in intent, not words. Most of us are uncomfortable directly stating a falsehood, but we all “tell” little partial lies of omission all the time. When we host a party, we don’t call or email our friends whom we’re not inviting to tell them of the event. In business we don’t notify our competitors before calling on their clients, and we don’t usually tell our bosses before interviewing for another job. Often these lies of omission are harmless. Sometimes, as in the case of the uninvited guest, we tell ourselves it’s for the benefit of the person to whom we are “lying” (although the real reason is just as likely to be our own cowardice or conflict-avoidance…) Then there are lies of omission that might- or might not- cause harm, such as when your new boss fails to volunteer why the 2 people to hold your job before you quit, or when a manufacturer fails to disclose certain product information…

Part of being an intelligent social animal with a well-developed “theory of mind” is constantly deciding what information to share when with which individuals. To simply describe this information we share as “truths” or “lies”, while comforting, doesn’t always describe things the way they really are.

All of which brings me, in a rambling and roundabout way, to my point, which is this: there’s a piece of information, an aspect of this project, which, while I haven’t misstated or misrepresented, I haven’t been entirely forthright with you about, and it is this “lie of omission” about which I will come clean in the next post.

Next Up: ABC in Perseus.

Note About Sources: Thanks to my friend and fellow nature-blogger KB for help accessing several of the sources for this post. Scrub-Jay caching, pilfering and memory info came from Food Caching Western Scrub-Jays Keep Track of Who Was Watching When, Joanna Dally et al, Social cognition by food-caching corvids: the western scrub-jay as a natural psychologist, Nicola S. Clayton et al, The Mentality of Crows, Convergent Evolution of Intelligence in Corvids and Apes, Nathan J. Emery et al, and The rationality of animal memory: Complex caching strategies of western scrub jays, Nicola S. Clayton et al. General info on Scrub-Jays came from Kaufman Field Guide to Birds of North America, the Cornell University Lab of Ornithology All About Birds website and Wikipedia. Info on episodic memory and theory of mind (including the example story) came from Wikipedia. Figures on flight loads, speeds and ranges of various pine birds came from Made For Each Other: A Symbiosis of Birds and Pines, Ronald M. Lanner, and info on the historic range expansion of Piñon pine came from The Desert’s Past: A Natural Prehistory of the Great Basin, Donald K. Grayson.

Birds, Hearing and Ears

Note: This is my 400^th post. It’s just a number, but kind of a big number, and certainly far more posts than I ever intended this project to include. This post is around 3,800 words. If I guesstimate that the average post is ~3,000 words long, that’s ~1.2 million words*, which is roughly 10-15X the length of an average novel.

*Probably around half of which are tangents.

The other night I woke up with a start in the middle of the night* and had a heck of a time falling back to sleep. It was still early enough (2:30AM) that it wasn’t worth getting up, and so I tossed and turned for a while. As I did so I noticed that I’m always hearing things. Winter nights in our neighborhood are super-quiet- no birds, no crickets, windows shut tight, but it seems like I’m always hearing stuff: Awesome Wife’s breath, the click of the thermostat, the air moving through the heating vents, even my own pulse as my head lies sideways on the pillow. You can close your eyes, but you really can’t ever “close” your ears.

*Yes, like many middle-agers, I often awake at odd times. But this was different: it was “dream shock”. You know, when you’re so startled or alarmed or scared in a dream that you wake yourself up.

Oh, you want to know what the dream was? OK, I’ll tell, even though it’s kind of personal and embarrassing and borderline TMI, because that’s just the kind of blog this is. It was a Pee Dream. You know, one of those dreams where you have to pee real bad and you’re looking for a place to go, but can’t manage to find a bathroom? I dreamt I was waiting my turn to start in a race. The race was- I am not making this up- a Night Snowblade Race. Remember snowblades? They were like these super-short mini-skis that were briefly popular in the late 90’s, and you could ski downhill on them or skate along on the flats. (I tried a friend’s once- total blast.) Anyway, racers were heading out on these things, with headlamps, one after another at regular intervals, like some kind of night-time-trial. I looked up on this open, snow-covered hillside (the race was somewhere up around Kimball Junction), and saw little dots of headlamps moving downward on the descent. My turn was coming up, and I realized I had to pee, so I thought I’d just step a ways off in the bushes (it was dark, you know) and pee real quick. But I stepped away, and was still in view, so stepped a little further away, and then a little further, and all of a sudden I was standing along someone’s driveway. But the house was dark, and I thought, “I’ll just pee in their bushes real quick…” and I was just getting ready to go and then all of a sudden the garage door started opening and a car pulled into the driveway and someone was yelling at me and I was like all panicked and that’s when I woke up.

Visually-oriented as we are, we’re always hearing, but mostly half-consciously. We tend to think about our own hearing when we hear something significant- music, birdsong, waves crashing- but largely ignore it otherwise. But if you stop and listen, say right now- in your home, office, wherever- hearing is really remarkable. You’re constantly receiving all sorts of information- machines running, people passing, cars outside, planes overhead. We get all sorts of cool details about these things- presence, direction, speed, distance- all the time, without even looking, without focusing, without even having to turn our heads. We’ve all seen shows or read stories about psychics, telepaths, or people with special powers who can somehow sense or detect things that can’t be seen. But with hearing, all of us have a sense that’s far more real, more precise and more powerful than any Yuri Geller trick.

Over the course of this project I’ve kept bumping into hearing, but never really gave ears much thought. But the research I did for the All About Heights post got me curious about them, and then the Owl post got me wondering (again) about birds’ ears, and so I started reading and one thing lead to another, and, well it turns out that ears are not just way cool, but have an absolutely amazing story.

In a side note to the heights post I wondered about balance in birds, and whether the ear played a similar role in birds- specifically a vestibular sense- as it does in mammals. The short answer is yes, but the story behind it is a bit more complicated. But first, to tell the story, we have to know just a bit about the human ear.

All About Ears

You’ve probably heard that the ear has 3 major chunks: the Inner, Middle and Outer Ears. The outer ear is the only part you see, and consists of the pinna and the ear canal. The pinna is the part on the outside that your junior high school girlfriend/ boyfriend stuck their tongue inside when they gave you a Wet Willie*. The pinna is strictly a mammal thing; birds, reptiles and amphibians don’t have them.

The role of the pinna is twofold: to amplify the sound delivered to the middle ear, and to provide information about the direction of sound. Many mammals of course have really big pinnae (in relation to their head/body size) which play an important role in detecting prey, predators or (in the case of bats) the physical world around them. Human pinnae are proportionally much, much smaller and for a long time it was assumed that they were vestigial, playing no real role in our modern-day hearing.

*Over the years, I’ve come to believe that there are 3 categories of human sexual foreplay. The first is things you used to do when you were in high school, and still do with your spouse/partner 20+ years later. The second is things you used to do when you were in high school, and now no longer do, but kinda-sorta-sometimes wish you still did. The third is things you used to do when you were in high school, no longer do now, and can’t for the life of you remember why you ever would have wanted to do such a thing. For me, Wet Willies are firmly in the third category.**

**Along with hickies.

But it turns out that our pinnae do help our hearing. Between 1.5KHz and 7KHz, the pinna and ear canal amplify sound by between 5 and 20dB. Above 6KHz, the pinna plays a significant role is helping to determine the direction of sound.

Extra Detail: As we saw in the bat post, human hearing ranges from about 20 Hz to 20 KHz. Human speech generally runs between 80 and 400 Hz. Middle C is 261 Hz. The highest note on a piano is a little over 4KHz, which is BTW roughly the same frequency as a chainsaw or fingernails on a chalkboard*.

*Unfortunately, I was unable to find out the frequency of a chainsaw slicing through a chalkboard. But man that’s gotta hurt.

Side Note: But there is a part of the human pinna that is vestigial, and which appears in about 10% of humans, including- yes, that’s right- me!* It’s called Darwin’s tubercule, and is a slight thickening/protuberance of the rim of the pinna, about 2/3 of the way up (2 o’clock on the left ear, 10 o’clock on the right.) it corresponds to the point of pointy-eared mammals, and is believe to be a vestigial remnant of our presumably pointy-eared ancestry. Sometimes it’s more of a bump or protuberance pointed away from the ear canal, creating an almost Spock-like effect.

*I have it on the right ear only.

Birds also have an outer ear (pic left, not mine), which also has an ear canal, but does not have a pinna. Instead birds have evolved special feathers, called auricular feathers, which protect the canal opening, as well as direct and amplify sound into it. Reptiles don’t really have an outer ear. In those with external ears (many reptile ears are internal-only) the tympanic membrane, which marks the beginning of the middle ear, is often visible on the side of the head.

At the opposite end of the ear-assemblage is the inner ear, set inside the skull, and constructed out of the hardest bone in the human body (diagram left, not mine). It has separate sections for hearing and balance. The hearing section is the cochlea, which consist of 3 fluid-filed chambers lined with specialized hair cells. The motion of this fluid is directed by vibrations received by the outer ear and transmitted to the cochlea via the middle ear- which we will get to momentarily- and detected by the hair cells, which then transmit this information, via the cochlear nerve, to the brain, where it is interpreted as noises.*

*Or perhaps images, if you are a bat.

The balance section is a fluid-filled chamber called the vestibule, which branches off into 3 semi-circular canals. The canals, which are also fluid-filled and lined with current-detecting hairs, are orthogonal to one another, so as to detect motion and position in 3 dimensions, which is transmitted to the brain via the vestibular nerve.

All amniotes* have this same basic inner ear structure, which we apparently inherited from a common amphibian ancestor. All amniotes use the inner ear not only for hearing but for balance. It’s suspected- but not agreed**- that the amphibian ear may have evolved out of a sense organ called the lateral line in fish, which consists of a line of pressure receptors- called neuromasts- than run along each side of the fish. The lateral line enables fish to detect small disturbances in the water, and is why large schools of fish are able to maneuver elegantly en masse in close quarters without bumping into each other.

*Amniotes = “Reptiles on up”, or reptiles, birds and mammals, but not amphibians. Technically they’re tetrapod vertebrates with land-adapted eggs. The egg can be external, or internal- like the amniotic sac of a mammalian fetus.

**An alternative hypothesis is that the neuromast and the inner ear evolved out of the same ancestral structure, which might-could-maybe have been some sort of statocyst-like thing. A statocyst is a balance organ found in some aquatic invertebrates, including various little plankton-y things and, our old friends, the echinoderms. It’s a little fluid-filled sac lined with sensing-hairs and with a little mineralized sand-grain inside called a statolith. Kind of like a teensy 1-flake snowglobe. Statocysts BTW are the reason that Brittlestars and Seastars (which I blogged about in this post)- which do not have brains- can tell when they’re upside-down (which they want to avoid, so as to deny predators an open shot at their soft juicy undersides…)

Extra Detail: Just because we all share the same basic inner ear structure doesn’t mean it’s stopped evolving. Our cochlea for example is coiled up like a little snail shell, very much unlike that of birds or reptiles. The coiling- which may be an adaptation to support longer sensing hairs- occurred sometime after our ancestors split from monotremes, but before we split from marsupials. Kangaroos have it, platypuses don’t. Another evolved feature is the presence of both tall hairs and short hairs inside the inner ear, something both mammals and birds- but not reptiles- came up with. In our ears the short hairs have “lost” their wiring, and don’t transmit information neurally. Instead they function by moving in response to current in the fluid, setting up motions that are in turn detected by the tall hairs. In birds short hairs perform a similar mechanical function, but also still transmit information neurally themselves as well.

OK, stick with me- we’re almost to the good part. The middle ear begins with a thin membrane- the ear drum- blocking the end of the ear canal. Vibrations received on this membrane are transmitted by a series of 3 connecting, successively smaller bones- the malleus, incus and stapes- through the air-filled chamber of the middle ear to the inner ear.

These bones- together called ossicles- get successively smaller going from outermost (malleus) to innermost (stapes) such that the “footplate” of the stapes has a surface area only a small fraction that of the eardrum. The ossicles are arranged in a lever-like formation, the action of which serves to significantly concentrate and amplify the sound delivered to the inner ear.

The middle ear of a bird or a reptile is set up more or less the same way, with one glaring exception: their ears have but one ossicle- the stapes-equivalent- which is called the columella. Because of this difference, mammalian ears are capable of detecting much higher frequencies than bird or reptile ears. (Finally, something we do better than birds!)

So why don’t bird and reptile ears have 3 ossicles? Did they lose them or something? Actually they still have them, but they serve their original, reptilian function, that of lower jawbones.

Fish don’t have middle ears. The stapes/columella- in all amniotes- is a modified bone from a fish’s upper jaw. Fish have several bones in their lower jaws which in amniotes have fused together in different ways. In birds and reptiles, most of these bones have fused together into what is called the mandible. In mammals, some of the these same bones have been fused together into our modern lower jawbone, but 2 of them have moved back and shrunk until they were tiny little things set way back in our heads- the 2 additional ossicles (malleus and incus).

Extra Detail: In some reptiles the mandible is not completely fused, and the extra bones make possible a double-jointing of the lower jaw, as is the case with many snakes. (Snakes don’t actually “unhinge” their jaws; they just have a joint that we don’t.)

Side Note: There’s kind of a cool corollary here. When a bird opens its mouth, the hinge of its jaw is in a fundamentally different place in its skeleton- located where we would think of as the middle of our middle ear. What does it feel like when a bird opens its mouth? Does it feel like it feels to us when we open our mouths? Or does it feel more akin to popping our ears?

Now at this point, seeing as mammals evolved from some kind of ancient reptile, you may be wondering how the middle ear could have evolved from 1 to 3 ossicles. How could an intermediate, or transitional form possibly have functioned? The answer is that the middle ear evolved independently in mammals and reptiles. And birds. In fact the middle ear appears to have evolved independently at least 4 times among amniotes, following 4 different basic designs. It evolved once in mammals (or maybe proto-mammals or mammal-like reptiles/synapsids). It evolved separately in archosaurs (superset of dinosaurs) along a design that is present today in birds and crocodilians. It evolved another way in turtles and tuataras*, and a fourth way in lizards and snakes**.

*I didn’t know what they were either. Tuataras, Sphenodon sp., are a genus (2 species) of couple-foot-long lizards native to New Zealand that are, uh, not actually lizards. Meaning that if you or I saw one, we’d say “Hey, that’s a lizard”, but zoologists don’t consider them as such. Their teeth, heart, lungs, brain and mode of walking are all different. They’re sometimes called “living fossils”, as they are the sole survivors of a once-diverse order, and are thought to be anatomically more similar in some respects than other modern reptiles to early amniotes. They have ears, just not external ones.

**It’s actually a little more complicated than this. Turtles and tuataras share a design which probably evolved first, then after the ancestors of lizards and snakes branched off from tuataras, they evolved a significantly different middle ear. The turtle/tuatara middle ear architecture is sort of the stem-reptile default, a structure which they share, even though tuataras are believed to be more closely-related to lizards and snakes than they are to turtles. Got it?

So the middle ear evolved multiple times among amniotes. That’s cool, but it’s really not amazing. At this point in the project we’ve seen countless examples of parallel evolution, from eyes to CAM to C4 to wings to pale skin in humans. But there are 2 cool things about the parallel evolution of the middle ear: a little cool thing, and a Way Freaky Cool thing.

The Little Cool Thing

The little cool thing is the contrast between eyes and ears among amniotes. Think about it. We’ve talked a lot about eyes and vision, and the various differences between bird and mammal vision. But even with all of the remarkable differences between our eyes and bird eyes, the structure of our camera-style eyes is the same basic thing, working on the same principles, and it’s the same basic design we’ve all had since long before our lungfish-y ancestors first flopped up out of the water. But our middle (and outer) ears have evolved completely independently, with significant fundamental structural differences. Imagine if our amphibian ancestors had come up onto land with no eyes, and then the ancestors of birds and mammals evolved them completely independently along fundamentally different structures. Like if birds evolved camera-style eyes and we evolved compound bug-eyes or something. That’s more or less what did happen with the middle ear.

The Way Freaky Cool Thing

But the Way Freaky Cool thing is the timing of the evolution of the middle ear. Middle ears- all four versions- evolved during the Triassic, between 220 – 250 million years ago. That sounds like a huge range of time until you put it into context. Amniotes appeared at least 340 million years ago. Synapsids (mammal-like reptiles) branched off not much later (~324 million years ago) followed later by the archosaurs. And earlier, amphibians were present for maybe 10 or 20 million years before amniotes came about.

So in other words, 4-legged critters were running around on land for something like a hundred million years during which time everyone heard like crap. Then, “suddenly”, over just 30 million years, middle ears evolved independently multiple times amongst different groups of now-way-distantly-related critters. It’s like, for some reason, hearing well- and in particular hearing higher frequencies well- became really important. Why?

Tangent: My wild guess is that once one group of amniotes got decent hearing, it became a huge competitive advantage for both predators and prey. But what’s interesting- if that’s the case- is that that one group to evolve a decent middle ear first didn’t just replace all the other groups relatively promptly, but that the other groups managed to come up with the same gizmo in relatively short order. In any case, it’s weird to think that for like a 100 million years, there were all sorts of animals running around, and none of them ever heard leaves* rustling in the breeze**.

*Well, more like fronds I guess back then.

**Not counting bugs of various sorts, who have a whole different array of “ears” and natural history of hearing.

Just because they don’t hear as high as the highest-hearing mammals doesn’t mean birds don’t have great hearing. The asymmetric supersensitive ears of the Great-Horned Owl are just one example.

Side Note: Now’s a good time to return to a topic that’s bugged me for a while, and which I’ve touched upon a couple of times in previous posts: Why don’t birds rule the skies at night? Or in other words, why don’t they do the bat thing? Maybe it’s the high-frequency hearing limitations of their single-ossicle ear-architecture. There are echolocating birds, but their echolocating frequencies are significantly lower than those of bats. Oilbirds for instance echolocate at frequencies between 1 and 15KHz, swiftlets between 4.5 and 7.5KHz. Using such relatively low frequencies means longer wavelengths, and so neither can effectively echo-detect anything smaller than about 6 cm, which means that they can “see” walls and such, but not flying insects. No bird is known to be able to detect any frequency higher than 29 KHz. Bat-sonar ranges from 11 – 212KHz.

Of course hearing isn’t just in the ears. Just as our brains turn input from our optic nerves into images, they convert input from our cochlear nerve into sounds. And it appears that bird brains may process their input differently than ours do. Birds recognize sounds more quickly than we can. We need to hear a note for at least 1/20^th of a second to recognize it. Birds can do so in just 1/200^th of a second, which means they can hear multiple notes where we might hear just one.

Pitch

Another cool thing about birds and hearing is that they seem to have something like perfect pitch. Perfect pitch is the ability to recognize a specific note at a specific frequency- for example you hear a note on a piano and say (with no other tonal context) Oh yeah, that’s middle C (261 Hz). Or to just sing middle C. Very few people can do this- maybe 1 in 10,000.

Extra Detail: It’s unclear whether there’s a genetic basis for perfect pitch. Early musical instruction and training appear to help. Native speakers of tonal languages, such as Chinese and Vietnamese, seem to be a bit likelier to have the ability.

But birds just seem to nail it, hitting the right note every time. They generate the right notes, and seem to recognize the right notes as well. How do we know that they recognize the right notes? Because they seem, conversely, to lack relative pitch.

Relative pitch is the ability to recognize the relative intervals between different tones, regardless of pitch. Or in other words, a melody. For example, suppose I play Twinkle, Twinkle Little Star* on the piano, starting at middle C. Then let’s say I play it again, starting one octave lower. Or higher. Or maybe I just drop down 2 notes and start the tune at middle A. In all cases, you’ll recognize the tune as the same melody. But a bird won’t; it hears them as different tunes.

*Then again, my own relative pitch leaves something to be desired. I was over 40 before I realized that Twinkle Twinkle Little Star and the Alphabet (ABC…) Song were the same melody. I mentioned this last week to Awesome Wife, who pointed out that it was also the same melody as Bah-Bah Black Sheep…. which I never realized until right then.

Birds do some cool things with hearing. In many species, chicks communicate with their parents before they hatch. Some chicks, such as pelicans, actually complain if too hot or cold while still inside the egg, while others, like quail, chirp to synchronize their hatching. Birds’ ability to discern notes quickly helps them to recognize the calls of parents and chick, which is critical in species that nest in huge, noisy colonies, such as gannets.

So while bird ears and hearing are in many ways similar to ours, they’re also very different. I started this project with only a passing interest in birds, and only gradually became interested in various little things they seemed to do differently- and sometimes better- than we do. But over time I’ve learned that they do all kinds of things differently than we do, having evolved different solutions to so many of the same problems our own ancestors faced. Birds are like the “What if?” version of us, how we might have turned out in a parallel or alternate universe. Except that they did turn out that way, and they’re right here and now, all around us, outside every day. Birds are way cool.

Note about sources: Evolutionary info on the middle ears of amniotes came from Cochlear mechanisms from a phylogenetic viewpoint*, Geoffrey A. Manley, Your Inner Fish, Neil Shubin, the absolutely awesome blog Evolution of Hearing and the TalkOrigins Archive’s 29+ Evidences for Macroevolution. Info on bird, reptile and other ears came from Winged Wisdom/Pet Bird Magazine, the Earthlife Web website, Melissa Kaplan’s Herp Care Collection and Wikipedia.

*The “Middle Ear Evolution in Amniotes” Awesome Graphic in this post is a re-formatted (WTWWU-ized) version of Figure 1 of this paper.

Suburban Apex Predator, and the F-117 Barn Owl

Note: I had a hard-drive scare yesterday* and, for a couple hours, thought I’d lost the >90% complete draft of this post. I was totally, totally bummed. So I went over to Co-worker Matt’s office to commiserate, and ended up “telling” him the post. After I told him, Matt- who knew pretty much nothing about Owls beforehand- seemed genuinely into my “story-post” and impressed and interested by owls**. And then I realized that I didn’t feel so bad anymore, because at least 1 person had “read” and enjoyed the post. Just then the IT guy came over to Matt’s office looking for me; they’d recovered my drive.

*Yeah, that’s right- I blog on my work laptop. Oh, don’t get all sanctimonious on me; you’re probably reading this post on yours.

**Or maybe he was just yanking my chain to try and make me feel better. Whatever.

The Post

We moved into our current home in the Spring of 2002. When you move into a new neighborhood, you tend to notice all the little things- people out walking, how people maintain their yards, which houses have dogs that bark at you when you walk/run past, etc. One of the first things I noticed in our neighborhood that Spring was all the rabbits.

Our old neighborhood didn’t have rabbits, or if it did, I never noticed them. But here they seemed to be everywhere, and out not just in the early morning, but oftentimes right in the middle of the day. Awesome Wife and I joked that it was because now that we’d moved “uptown”, the neighbors didn’t let their dogs run free., and that if just one dog got out of its yard and roamed free for a weekend, the rabbits would probably disappear.

A few years passed. In early summer of 2005 a neighbor’s kid caught sight of a large owl perched on high up in a tall Blue Spruce next door. We spotted it almost every day for a couple of weeks. Sometimes it would hoot, and once or twice it spread its massive wings and flew off while we watched, probably annoyed by the neighborhood kids hanging out and chattering under its perch. After a couple of weeks it disappeared altogether, and we didn’t see it again. I wondered if all of our attention scared it away.

A few months later, in early Fall 2005, I was pedaling my bike home from a ride. I rolled down the little hill where I regularly used to spot rabbits out on a lawn and realized I hadn’t spotted a single rabbit in the neighborhood in, well, months. In fact I hadn’t seen one, since… that owl showed up.

I didn’t see rabbits again in our neighborhood until this past Spring. Over the Summer I’d see them out now and again, initially just around dawn, but later in the Summer out in the daytime as well. Rabbits aren’t particularly remarkable in a suburban neighborhood, but the kids like wildlife and would point them out to me, each other and their friends. Then last week, a neighbor’s kid* spotted this guy in the Elm** out front, the first one we’d seen in the ‘hood in over 5 years.

*Different kid, different neighbor, but same house. We’ve seen four families in that house- loved the first, didn’t care for second or third, love the fourth. Sort of a cool full circle thing. AW and I are getting all kind of serene and Zen-like with respect to problematic neighbors. We don’t get upset; we just out-wait ‘em. Eventually they all move away or die.

**Which I blogged about in this post. I don’t mean just the species; I mean specifically this tree.

The Great-Horned Owl, Bubo virginianus, is super-easy to ID. If you’re in the Western hemisphere and you see a big owl with ear-tufts, it’s a Great-Horned (GH Owl). And chances are, if you live in a suburban or rural setting anywhere in North America, you’ve already seen one. Its range is huge, from Alaska to Argentina. In fact, everywhere I’ve blogged about in the Western hemisphere- Maine, California, Mexico, Costa Rica, even Brazil- I’ve been within its range. Like many animals with huge ranges, the GH Owl is a generalist, in this case a generalist hunter. GH Owls of course hunt rabbits and mice, but you might be surprised how many other things they eat. Snakes, lizards, squirrels, rats, shrews, bats, moles and other birds. OK, so they eat a lot of different things, so what? Tell me something I don’t know.

OK, here’s something you might-not-maybe didn’t know: If you live anywhere in suburban or rural North America, there’s a good chance that the GH Owl is the single most bad-ass, toughest, fearsome predator that routinely passes through your yard. Don’t believe me? Here we go.

Know what else they eat? Raccoons. That’s a pretty big meal for a predator that only weighs 3-4 lbs, but GH Owls routinely kill prey 2-3 times their mass. What’s that? You’re still not impressed? Get this: GH Owls are more or less the only predator that routinely hunts skunks. That’s not all- they regularly hunt armadillos and even porcupines!* Wait- there’s more! GH Owls regularly hunt other birds, and not just cute little songbirds, but big birds- like ducks, swans and seagulls. That’s not all- GH Owls regularly hunt other birds of prey, including Red-Tailed Hawks and Peregrine Falcons**.

*Sometimes they do so by grabbing the porcupine out of a tree and dropping it to its death. I know that bobcats kill porcupines (on the ground) by going for the face, but don’t know if owls do this as well. I should mention though that in researching this post I learned that hunting/devouring porcupines does not always end well for the GH Owl. I covered porcupines BTW in this post, and bobcats in this one, with (admittedly lame) additional video footage in this post.

**I haven’t done a proper post about Falcons, but covered their hunting prowess and tactics last year during Pigeon Week. Man, it is like I have a post for everything.

In fact, GH Owls regularly hunt other owls, including every other owl species in North America except the (larger) Snowy Owl. GH Owls typically hunt by perching still from a high vantage point, then swooping down onto their prey. Since their eyes don’t move within their sockets, having a neck that can rotate around up to 270 degrees serves them well. But GH Owls can also hunt in other ways, including standing in shallow water to hunt small fish. And GH Owls have a bad rap with chicken farmers, as they’ve been known to actually walk inside coops to kill chickens. Before leaving their roster of prey, it’s worth mentioning that GH Owls also successfully hunt domestic cats and even on occasion small dogs.

Tangent: You can’t help reading about B. virginianus’ range of prey without wondering what it would be like to be attacked by them. Do GH- or any owls- ever attack humans? The answer is yes, though I’m unaware of any doing so fatally*. GH- and other owls- will defend nests vigorously, and may attack visitors, researchers or others who molest them. Then there are the cases where the owls apparently attack people well away from their nests. On Vancouver Island there have been a number of attacks on runners and hikers by Barred Owls, Stix varia**. And a rogue GH Owl attacked several cross-country skiers last year in Bangor, Maine. It’s thought that these owls might be mistaking human head-hair for small mammal prey.

*I came across this claim, which sounds like a stretch.

**The Barred Owl BTW, seems to be a significant threat to the endangered Spotted Owl, whom it typically out-competes for habitat/nesting sites. Interestingly, it also hybridizes with the Spotted.

But would a GH- or any other owl- deliberately hunt a small child? There’s no record of it, and human toddlers exceed the 2-3x body-mass metric. But what about outside of North America?

The closely-related Eurasian Eagle-Owl, Bubo bubo looks a lot like a GH Owl, with ear-tufts and everything. But it’s bigger- up to 9 ½ pounds- and has been known to take deer fawns as big as 22 lbs*. Now we’re approaching toddler territory, though I’m unaware of any such hunting attacks.

*Wikipedia says up to 37 lbs(!), but every other source said up to 22…

But there used to be even bigger owls. Until around 10,000- and maybe as recently as 8,000- years ago, the Cuban Giant Owl, Ornimegalonyx sp., inhabited that island. Ornimegalonyx stood over 3 ½ feet tall and weighed over 20 pounds. Its wings were small, as was the keel of its sternum, suggesting it either flew only for short distances or not at all, and its legs were longer than a typical owl’s. Ornimegalonyx may have run after prey on the ground, or leapt from treetops. In any case, it was big enough to take a kid. Even though humans were in the New World 8,000 – 10,000 years ago, they don’t appear to have made it to Cuba until more like 5,000 – 6,000 years ago, meaning giant running owls likely never chased Taíno children through tropical jungles. But then again, the mandible of what was apparently a similarly gigantic late Pleistocene owl turned up some years ago in Georgia, so maybe…

The GH Owl’s primary weapon is its talons, which are kind of interesting in that they are semi-zygodactylous. Zygodactylous feet have 2 toes facing forward and 2 backward, in contrast to the standard passerine (perching bird) architecture of 3 forward, 1 backward*. (pic below, not mine)In GH Owls, the fourth toe is reversible, allowing it to shift between a 3 forward- 1 backward, or anisodactylous, to a 2 forward- 2 backward zygodactylous configuration (pic below, not mine**). The 3-1 config is used for perching, but the 2-2, which provides a greater coverage area, for hunting.

*We covered zygodactylous feet last year when we looked at Roadrunners. Seriously, everything.

**Captain Obvious, here…

For most prey, the moment of contact is the moment of death- they never know what hit them. The talons of B. virginianus are incredibly powerful, able to crush bones with a gripping force of up to 500 pound per square inch. For comparison, a human grip generates a maximum force of some 80 psi, the bite of a German Shepherd roughly 250 psi, that of a Rottweiler 325 psi, and a human bite around 150 psi.*

*This is why you can open twist bottle caps with your teeth more easily than you can with your hand. Not that you should ever do so.

Side Note: These figures were surprisingly difficult to obtain* and make sense of, so take them with a grain of salt. Psi is not the same as bite-force; a Rottweiler’s bite has more force than a GH Owl’s grip, but the surface area of the latter’s talons is tiny in comparison. The important point is that, for something that looks rather thin and inconsequential, the talons of a GH Owl are incredibly powerful.

*Which is fair enough, when you think about it. Wouldn’t you hate to be the grad student tasked with getting the wolf or pit bull riled up enough to bite whatever measuring instrument they use with maximum force?

Back to bite-force, wolves and coyotes have much stronger bites than comparatively-sized domestic dogs*, with the exception of special breeds such as a Pit Bull, whose bite is phenomenally powerful. The bites of hyenas, lions and tigers are stronger still, in another category of force altogether.

*So I’m really glad that coyote in Emigration did not manage to connect with my right cheek.

Owls also have exceptional vision. Their eyes (pic left, not mine) are as big as ours*, but many times more powerful- even in full daylight. Most owls can sight a mouse in the grass about 5 times further away than we could make out any object of that size, and in darker conditions the difference is even more dramatic. The eyes of owls are ringed by specialized feathers that reflect/direct light into the pupil, and their retinas are packed with light-sensitive rod cells, enabling them to fly and hunt in what looks to us like near-total darkness.

*Which is proportionally like our having baseball-sized eyes.

But perhaps even more impressive than an owl’s sight is its hearing, which is highly sensitive, particularly in frequencies around that of rustling grass. An owl’s ears are asymmetric; the GH Owl’s right ear is set slightly higher up on its head, and positioned at a slightly different angle. This makes an owl’s hearing more sensitive to position and direction of sounds than ours. Barn Owls in fact can hunt effectively in absolute darkness by sound alone, flying around and landing on prey with accuracies of a fraction of an inch. (I don’t believe GH Owls can quite do this.)

Side Note: BTW, the GH Owls “ear tufts” are nothing of the sort. Though they look like the part of the outer ear that is technically the pinna (the outer, visible part) on a person, dog or cat, birds have no pinnas* (pic right = actual GH Owl ear, not mine). The avian ear does have specialized feathers, called auricular feathers, that serve to direct sound into the ear canal, but GH ear tufts aren’t those either. They’re display feathers, and have nothing at all to do with hearing. We’ll get more into avian ears in the next post.

*Pinnae? Pinnum? I’m never really sure.

Tangent: Let’s pause here for a second. Hopefully by now you’re convinced that the GH Owl- along with many other owls- is a totally Way Badass Predator. It’s for sure more bad-ass than hawks, and maybe even eagles. I didn’t appreciate how bad-ass until researching this post. Oh, I knew they were effective hunters and such, but…porcupines? Armadillos? Cats? And I guess I was surprised because they just don’t look that mean, but rather kind of wise and serene, and well “nice.”* Like, say you were an animal and you lived in a Watership Down**-type universe, where all the animals could talk to each other and you were lost and had to ask another animal for directions. Wouldn’t you be inclined to ask the wise old owl? But no- don’t do it! Because even though he looks so benevolent, he’s really like this hyper-effective, terminator-esque Silent Killing Machine!

*And then there’s “Owl” of the Winnie the Pooh*** gang, and the USFS’s “Woodsy (“Give a hoot, don’t pollute!”) Owl, and even the wise old cheater-Owl (“How many licks does it take…?”) on the old Tootsie-Pop commercials. All of these guys come off as slightly-addled, geriatric, harmless softies. Couldn’t we have just one seriously bad-ass owl in popular culture?

**I love that book.

***Still think that bear should have pants.

I’m not the only guy suckered by the owl’s serene face: think about birds of prey in our culture. The Bald Eagle is our national symbol; it’s on the presidential seal and the quarter, and eagles grace the seals and flags of numerous other countries. We have sports teams named after eagles and hawks. Our military flies the F-15 Eagle and the Blackhawk Helicopter. Know what the much-vaunted F-117 “Stealth Fighter” is officially named? The “Nighthawk”. A Nighthawk- which I’ll mention just below in a moment, and is not at all closely-related to actual hawks- is a cool little bird, but it’s not even really a nocturnal hunter, so much as it is crepuscular, meaning active around dusk/dawn. And you know what it hunts? Bugs. And it’s a little, inconsequential thing; hell, I’ve nearly run over them multiple times night-riding. Our nation’s baddest-ass techno-night-fighter-jet shouldn’t be named after a little birdie that flits around eating bugs. No, it should be the F-117 “Barn Owl”, because the Barn Owl is truly a bad-ass nocturnal predator.

But there’s no fighter-jet, no attack helicopter, no presidential seal, no flag, no heat-seeking missile either named after or with an owl on it. That’s BS. A few years from now, when I found the state of Wasatch*, the GH Owl will be our state symbol.

*I’ll have to cover this one in another tangent in another post, but briefly, it’s for Salt Lake and Summit counties to secede from Utah (West Virginia-style) and form a new state. Economically it’s a total winner for the new state, and would improve everything from class sizes to social justice to open space protection. The constitutional issues involved are thorny, but not insurmountable. I tell you what, I am always cooking up something…

The “faces” of owls are vaguely disk-like in profile, making them almost instantly distinguishable from nearly all other birds. The disk-profile is also thought to direct and optimize sound reception. Speaking of other birds, what are owls related to?

Owls have been around for something like 60 million years, and became widespread during the Eocene. Today, the owls, order Stirigiformes, include 2 families: the True Owls, Stirigidae, which includes the GH Owl and oodles other interesting species, and the Barn Owls, Tytonidae. For a long time it was unclear where exactly owls fit in the family tree of birds*, but they appear to be most closely-related to the order Caprimulgiformes- the Nightjars, Nighthawks, Frogmouths and Oilbirds.

*One theory was that they were more closely-related to hawks. The owl-like face of the Northern Harrier, Circus cyaneus, seems now to be an example of convergent evolution- not close kinship.

Side Note: Nighthawks, specifically the Common Nighthawk, Chordeiles minor, is on my slightly-embarrassing list of things-I-researched-and-meant-to-blog-about-but-never-got-around-to-doing-so. (Pic right, not mine*). They’re cool little birds which fly around close to the ground at dawn and dusk hunting insects, and are common in the foothills and high rangelands bordering the Wasatch. On several night-rides this Fall I came upon them suddenly, just sitting in the middle of the trail shortly after dark. As I rolled toward them they’d alight, and then fly in my bar-light-beam, staying just 10 or so feet ahead of me for a few seconds as I followed them down the trail. My plan was to get this on helmet-cam for a post, but I was never able to work out a light/cam configuration that captured the action.

*BTW, this is exactly how they look when you come across them in the evening just sitting in the middle of the trail- squat and squint-eyed, almost kind of smug-looking…

I’ve never been able to get decent night-time helmet-cam video. I’ve tried all different light/cam bar/helmet combinations, but the results are always the same- a small circle of white light in a field of blackness:

Believe it or not, that clip was made with both bar and helmet lights going full-blast- I could see fine. Around the same time I experimented with a bar-mount for the cam. Noise was always a problem, as you can hear in this clip:

I was able to partially damp the rattle with multiple rubber-bands, but it was still there. The lower-level video looked faster and better captured the lean-angle of the bike, which was cool, but I found the video quality sort of frenetic and annoying, and switched back to helmet-mount.

Their next closest relatives are the Turacos, order Musophagiae, a funky-looking group of semi-zygodactylous-footed, fruit and bug-eating African birds, and after them, our old friends, Swifts and Hummingbirds.

I mention this not only because I’m always interested in what’s related to what, but also because this roster of the owl’s closest cousins rings a couple of bells from previous posts. Oilbirds and Swifts (specifically some Asian swiftlets) are the only 2 birds known to have accomplished another awesome hearing-feat: echolocation*. Isn’t that interesting.

*Which we looked at last summer in bats. It’s like… Oh yeah, I said that already.

We’ve looked at lots of differences between birds and mammals in how they’ve tackled the same problems, including vision, song, respiration, sex determination, “nursing” and thermoregulation. It’s time to check out their ears.

Next Up: The awesome saga of the middle ear.

Note About Sources: My standard sources for every bird-related post include Kaufman Field Guide to Birds of North America and the Cornell University lab of Ornithology All About Birds website. Additional info came from Phylogeny and Classification of Birds: a Study in Molecular Evolution, Charles G. Sibley & Jon E. Ahlquist, The Origin and Evolution of Birds, Alan Feduccia, Tracking & the Art of Seeing: How to Read Animal Tracks and Sign, Paul Rezendes, the Owl Pages website, the Exploring Nature Educational Resource website, the Colorado Division of Wildlife website, ChaCha (don’t ask), negah28.info, BirdsnWays.com, CubaHeritage.org and Wikipedia. Several of the photos in this post were provided courtesy of Hunky Neighbor.

Thanksgiving Desert Hiking Part 3: Big Footprints

The morning after Thanksgiving we slept in and took our time getting going, lingering over the complimentary hotel breakfast* waiting for the temps to climb over 20F.

*Before I had kids I used to diss those free breakfasts. Now we are all over them- the most cost-effective way to fill the bellies of 3 children around. I only wish our kids were like reptiles- stuff them with half their body-weight in waffles and fruit loops and don’t worry about feeding them again for a week. Unfortunately, no matter how many waffles they eat, they’re hungry again 45 minutes later.

After breakfast we packed up, checked out and headed out of town. Driving North up US191 from Moab is like a drive through time: you cross the Colorado River driving past 290 million year old Honaker Trail rock and by the time you reach I-70 you’re rolling over 80 million year old Mancos Shale.

Side Note: Just a few miles North of the turnoff for Arches, on the way up to the turnoff for Dead Horse Point and Island In The Sky, you pass all these gnarly, convoluted, deep-red cliffs lining the West side of the highway. The shapes looking almost haunting, and sometimes out of the corner of your eye as you’re zipping by at 70 MPH you think you catch a glimpse of a form, or even a face, trapped in the rock. The “face”-glimpses are always convoluted, miserable-looking and vaguely Dante-esque, like those Nazis who looked inside the ark in the first Indiana Jones movie. (Right before they melted.) Anyway, years ago, when I used to do weekend Moab trips from the Denver area and knew absolutely nothing about rocks, I called this section the Wall Of Tortured Souls (WOTS).

The WOTS is actually part of the Cutler Group, which was laid down in Permian times, between 240 and 290 million years ago. Like most of the other main geologic formations around it consists of several distinct sub-units, or members.  The WOTS is composed specifically of the Organ Rock Shale member, which was formed from a series of highly oxidized (hence the reddish color) layers of mud. Organ Rock is always striking, and shows up in some spectacular spots. The sloping bases of the massive buttes in Monument Valley are Organ Rock. When you’re riding the White Rim, and look off the edge and down below into Monument Basin (pic right), those freaky, free-standing “totem pole” pillars are also Organ Rock. It’s a soft stone, eroding quickly and dramatically. The Monument Basin pillars are each capped by a fragment of White Rim Sandstone (stuff you’re riding on), which slows the erosion of the pillar below.

Up and up we drove, past Chinle and Moenkopi, Wingate and Kayenta, Navajo and Entrada. Eventually the rocks melted away and we continued North across the high rolling plain toward I-70 that always seems so dreary after the geo-spectacle that is Moab. But a few miles North of the turnoff for Klondike Bluffs, we turned off the highway and traveled East for a couple of miles over clay roads to the base of a low rocky ridge. We parked, hiked across the rock for 5 minutes, and found what we were looking for.

The rock layer above the Entrada is the Morrison formation. Laid down ~150 million years ago, the formation covers a huge piece of the Western US- from the Dakotas to Arizona. Morrison isn’t particularly spectacular sandstone. Oh, it’s pretty enough in places like Dinosaur National Monument and numerous outcrops just West of Denver, but it’s a cracked, beat-up modest-looking kind of rock. Its outcrops have none of the wow-factor of Wingate cliffs, Navajao dunes or Entrada waves and arches. But what the Morrison does have, and is particularly well-known for, is fossils. Dinosaur fossils.* But we weren’t looking for fossils; we were looking for tracks.

*It’s also rich in uranium.

Unlike fossils, dinosaur tracks- and especially “walkways”, or a procession of tracks- are rare in the Morrison. Copper Ridge North of Moab is one of only two known Morrison formation walkways in Utah. The site contains the tracks of 5 different dinosaurs (though only 3 are really easy to pick out.) Dinosaur tracks are always cool. It’s one thing to look at a rock and know how old it is, and it’s even cooler to come across a fossil of some kind, to see the impression, the remnant of a creature that lived hundreds of millions of years ago, when everything about the world was different- the climate, the geography, even the oxygen content of the atmosphere.

But somehow to see a footprint- better yet a walkway of successive footprints- is cooler still. Here’s evidence of some forgotten creature doing something. These giant prehistoric monsters actually moved, right here, where we’re standing.

All About Dinosaurs

Everybody knows that dinosaurs were the dominant vertebrates on the planet for about 160 million years. At a high level the dinosaur family tree broke out into 2 different groups- Ornithischia and Saurischia. The Ornithischians were all plant-eaters and included dinosaurs like Triceratops, Stegosaurus and Ankylosaurus. Saurischians included both meat-eaters and plant-eaters. The Saurischian plant-eaters, known as sauropods, were long-necked animals that walked on all fours and included the largest dinosaurs. Brachiosaurus, Diplodocus and Apatosaurus* were all sauropods. The meat-eaters, known as theropods (which also included some plant-eaters and omnivores) were 3-toed, and generally- but not always- had shortened forelimbs. Many species were bipedal. T. Rex, Velociraptor, and Allosaurus were theropods.

*Called Brontosaurus when I was a kid.

Extra Detail: The Velociraptors in Jurassic Park were way oversized; an adult would’ve only been about waist-high. The dinosaur used to model them for the movie was a related type, Deinonychus. Utahraptor, though, might’ve been an even better match size-wise.

Theropods are the only dinosaurs not to have become extinct at the end of the Cretaceous. Birds are believed to be a surviving branch of the Coelurosaurs, the group of theropods that included both T. Rex, and the above-mentioned raptor-type dinosaurs. Crocodilians are not dinosaurs, but archosaurs, a group which also includes dinosaurs.

The 5 dinosaurs at Copper Ridge were 4 theropods and 1 sauropod. Paleontologists can’t be sure which species they were, but they have some pretty good suspects, based on the size and shape of the prints, the distance between the prints, and the rock formation (i.e. Morrison is a Jurassic formation, so they have to be Jurassic species.) Sauropod prints are less common that theropod prints*. The sauropod prints here are believed to have been made by Camarasaurus, Apatosaurus or Diplodocus, thought to have been 12 feet high at the hip, and 70 feet long from nose to tail.

*I’ve seen dinosaur prints several other times, but only once stumbled across one by accident. It was a theropod print, about 8 inches long which I came across hiking out of Coyote Buttes. I only noticed it because it was late in the day and the low sun-angle produced a shadow in the print.

Tangent: One of the most remarkable things about dinosaurs to me is the high level of interest in them. Awesome Wife and I discussed a few different possible destinations/ activities for the day after Thanksgiving, and picked Copper Ridge primarily because we knew that dinosaurs are always a hit for kids (especially boys.) Closer to home, the local dinosaur museum is a standard rainy-Saturday backup; we’ve been there probably 30 times. There are countless museums, movies, toys and games related to dinosaurs.

The same holds true by and large for adults. There have been oodles of movies, books and time-travel stories around dinosaurs. I’m hard-pressed to think of a time-travel book/movie in which the protagonists are transported to say the Eocene, or the Carboniferous, or Snowball Earth. Dinosaurs were interesting and important and all, but from a history-of-life standpoint, it’s hard to argue that they were that much more significant or important than many, many other prehistoric life forms. Certainly the evolution of the eukaryotic cell was more significant, complex, world-changing and just head-scratchingly amazing, but proterazoans just don’t make good antagonists. Dinosaurs just have an almost unbeatable level of drama and awesomeness on a scale we can relate to that catches the attention of people- not just paleo-geeks, but regular people who might otherwise not give prehistory another thought.

Nested Tangent: The only other past-time-period-fauna that comes anywhere close is probably the late Pleistocene, which has spawned a fair number of books, toys, games and movies. Part of this could be (or should be) due to its recency, and part of it could be (or should be) due to our own species’ possible role in the demise of these creatures. But I suspect most of it is due to the Wooly Mammoth and Saber-toothed Tiger, the 2 “Ice Age” mammals everyone knows about, which is sort of a shame in that they were just 2 of a cast of dozens and dozens of amazing, recently-extinct, very big mammals.

This everyman-interest in dinosaurs is evident even in the anti-science community. Dinosaur displays are standard fare “creation museums” (pic left, not mine, display of Adam & Eve* in the Creation Museum in Petersburg, KY) where they’re often depicted peacefully coexisting with early humans (presumably within the last 6,000 years.) There are displays of humans riding dinosaurs (pic above, right, not mine either), and vegetarian T. Rexes. But you never see a diorama of a caveman riding an entelodont, or a caveboy feeding an aquarium full of trilobites, or chasing dragonflies with 2-foot wingspans.

*Two things about this display. First, I must note that Adam’s beard looks Way Awesome, and actually not too dissimilar to mine. Second, Eve looks exactly like all my babysitters from the 1970s- pleasant, kind, and disturbingly sort of hot in an I-feel-awkward-to-be-checking-her-out kind of way.

Anyway, I guess the disproportionate attention given dinosaurs is a good thing, in that it provides an approachable and exciting glimpse of paleontology to millions of folks who otherwise wouldn’t give it a second thought.*

*Kind of like geology or botany or hydrology or most of the other things I blog about…

Sauropod Tracks

The sauropod tracks include both front and rear prints. Rear sauropod feet had a fleshy pad toward the back, and so the prints are generally round and amorphous, kind of like an elephant print. Their front feet were very different; they walked sort of like a ballerina on their toes, and the print is more of an arc, or semicircle.

The front prints are often trampled by the rear prints, but I was able to pick out at least 1 front print clearly in the rock. The prints enter the wash at an angle, cross it, and then turn roughly 60 degrees to the right/East, following the wash for a few more steps.

This right here is, to me, the absolutely coolest thing about the Copper Ridge walkway. The dinosaur turned. It changed its mind. The tracks are 150 million year old record in the rock of a living creature actually making a decision in its (admittedly small) brain.

Theropod Tracks

The theropod tracks- though easy to pick out- are trickier to make sense of. 3 of them overlay the sauropod tracks and though it’s not hard to find some, it’s tough to tell who’s who. But the 4^th set of tracks stands alone about 15-20 feet to the West, crossing the wash at about a 45 degree angle. The prints are up to a foot long, suggesting a hip height of ~5 feet. Allosaurus is the top candidate; it stood 15 feet tall and weighed up to 2 tons.

The Allosaurus(?) tracks don’t turn, but they also hint at a story: the gait is irregular. The step of one leg is ~5 feet, the other only ~4 feet. This limp suggests the dinosaur was injured, either recently, or hobbled from an old wound healed imperfectly. Another idea is that maybe it was carrying something heavy- like a hunk of prey in its jaws.

Copper Ridge is a quick stop and a cool site. Having passed by probably close to a hundred times over the past 20 years, I felt silly for not having stopped by sooner. If you’re planning a trip to Moab, or even passing by on I-70- and can spare even 30 minutes, make sure you stop by. And speaking of stops…

Next Up: The Rock Art Extravaganza of Thompson Wash

Note about sources: Most of the info for this post came from Geology Underfoot in Southern Utah, Richard L. Orndoff, Robert W. Wieder and David G. Futey. Additional info came from Canyonlands Geology – A Visual Toolkit, Jerry Shue, Neal Herbert and Barbara Webb, the College of Eastern Utah Prehistoric Museum* in Price, Utah, and the Louisville (Kentucky) Portal website.

*We stopped by, later that day on the drive home, another great stop I’d passed by dozens of times previously without ever having checked out. It’s a perfect 1-hour interruption for a family drive home from Moab.