Costa Rica Part 1: Sloths, Monkeys and Vampire Bats

So here’s how this blog usually works: I’m out and about biking or hiking or skiing, and I see something interesting. I get curious about it, do a little reading/research, and then think Hey, this would make a great post, and then I deep-dive into it, come up with some lame graphics and do a post.

Sometimes I go away for a weekend- maybe to the desert or someplace- and see a whole bunch of interesting things, and then it’s a little bit trickier, because I have to pick which specific thing or couple of things I’ll blog about (because I actually do have a life with a family and job and stuff and can’t spend like 20 hours/day on this blog.)

But right now I am floored. Because last week, on our Costa Rica trip I saw dozens and dozens and dozens of cool things, any one of which would make for an awesome post. We’re talking mammals, reptiles, amphibians, bugs, birds, trees, flowers, ferns, mosses, clubmosses, lichens, fish- you name it. Seriously, I could do a different post on some cool critter or plant that we saw last week, every day for at least a month, and not run out of material.

But I can’t do that, because this blog is all about Watching the World Wake Up, and with the Equinox gone by while I was away, that whole deal is right around the corner, so what I’m going to try to do is this: 3 posts this week- one on mammals, one on birds, one on plants. Each will be sort of an overview of the cool creatures we saw last week, with “shallow dives” (if I can resist doing a “deep dive”) into 2 or 3 each day. And then, if I get through all that and still have time/energy/focus, maybe I’ll do a Bonus Post on all the creepy-crawly-slithery things we saw. Sound good? Here we go:

Best. Vacation. Ever.

So here’s why Costa Rica is such a great vacation place spot for our family:

1- Beaches. Kids love beaches. Especially land-locked Utah kids. And also land-locked Utah grown-ups. (pic above = Twin A walking down to water at amazing, deserted beach we reached after 45 minute drive through Palm plantations. Beach stretched for miles in both directions, no one in sight but us.)

2- Animals. I recently shared my stunning insight that Kids Love Animals. CR’s got ‘em like you would not believe.

3- Country. CR is the safest, most 1^st-worldy country in Central America. Easy & safe to travel and explore with young children, and spouses who like clean sheets.

4- Plants. Yes, we all know I am a complete Tree Nut. CR takes plants to a whole other level of utter variety and coolness.

5- Language. I love speaking Spanish. The Costa Rican accent is the clearest and easiest to understand of any Spanish-speaking country I’ve visited. (Hardest = Spanish spoken by the guys at the Hertz rental car return at the Guadalajara airport 3 years ago. I have no idea WTF those guys were speaking*)

*Adding insult to injury: after asking one of the guys to repeat something for like the 3^rd time, he puts down his pen, looks at me quizzically, and says (in Spanish), “You don’t speak much Spanish, do you?”

Some Cool Costa Rican Mammals

We spent the first half of the week down on the Pacific Coast by Parque Nacional Manuel Antonio, and the second half up in the Monteverde cloud forest. Our first day in Manuel Antonio, we saw several of these guys: the Three-Toed Sloth, Bradypus variegatus.(pic next paragraph, right) 3T-Sloths live up in trees, doing pretty much a whole lot of nothing.

Tangent: Our hotel outside Quepos was a Total Home Run, and I strongly recommend it. The Blue Banyan Inn, about 20 minutes outside of town, has 3 cabinas (ours pictured right), beautiful grounds, setting, views, pool, (fabulous) breakfast included (for 5 of us) for- get this- $100/night. The owners, Jim & Barb, are a wonderful Canadian-American couple who maintain a preserve for injured/orphaned monkeys and have several, non-barky, super-kid-friendly dogs. The place is a home run (view from our cabin’s porch, left.) If you reserve, make sure it’s at the Blue Banyan, and not at the sister hotel, the Mono Azul, which is completely different.

Their diet consists of leaves, a low-energy foodstuff that encourages energy conservation and a minimum of action. They’re notoriously slow-movers, averaging something like 1/6 of one mile per hour as they move through the trees, and they can barely move on the ground. (They can’t walk at all on level ground, but have to sort of pull themselves along.) They sleep, eat, mate and give birth in the trees, most of the time upside-down.

The one thing they do descend to do- about once a week- is defecate, which they do in a whole at the base of a tree, then cover up. Why they descend to poop isn’t clear, but might be some sort of territory-marking behavior.

Here’s a cool thing about the 3T-Sloth: remember back in the Lichen post when I mused on why animals never “lichenized”? The 3T-Sloth is a step in the right direction; in the summer months its coat hairs can acquire a greenish tinge, the result of cyanobacteria growing on its fur, which may actually help to camouflage the Sloth.

There are 4 species of Bradypus, all occurring in Central or South America. B. variegatus is the only one found in CR, but another, more distantly related sloth, the Two-Toed Sloth, Choloepus didactylus, also is native to CR. 2T-Sloths are in many ways similar to 3Ts, but they enjoy a slightly more varied diet, and they’re far more vicious. While 3Ts will often hang off an arm when approached/picked up, a 2T will immediately slash out at anyone so bold as to attempt contact.

Sloths belong to an order of placental mammals called Xenarthra, which evolved in South America, and includes Armadillos and New World Anteaters. (Speaking of Anteaters, we saw those too. Here’s one we saw the same day up in a Palm.) About 80 million years ago, the Sloths split off from the Armadillos/Anteaters. 3 million or so years ago, following the Great American Interchange, all three groups migrated into Central/North America. The Tree Sloths only made it as far North as Mexico, but their cousins the Giant Ground Sloths made it clear up into the US. (We talked about them last Spring when I blogged about Joshua trees, whose leaves have been found in their fossilized dung.)

3-Toed, 2-Toed, whatever. Pretty much the same thing, right? Hardly. 3Ts and 2Ts diverged roughly 35 million years ago, which means that they’re about as closely-related to each other as… you are to this guy: Cebus capucinus, the White-Faced Capuchin Monkey. That’s right- New World Monkeys are the creatures most closely-related to human beings in the Western Hemisphere. They apparently arrived in South America ~35 million years ago as a result of the “rafting event” I described in the Darwin/Days Of Our Lives post and have diverged and evolved into a few dozen species, 4 of which are found in CR. (Click here for video of White-Faced Capuchin stealing Twin A’s hat.)

We saw White-Faced Capuchins all over the place- down in Manuel Antonio as well as up in Monteverde. My favorite sighting was in a Mangrove swamp North of Quepos, where we encountered 2 rival troops threatening and chasing each other (video here.) I first touched on New World Monkeys in passing back in the Color Vision post, where I mentioned that they didn’t share our “Old World Primate” trichromatic vision. The reason is that their ancestors split off from ours before we/they “re-evolved” full color vision. New World primates have kinda-sorta re-evolved color vision on their own, but to different degrees and through different mechanisms. Most of them, including White-Faced Capuchins, have evolved genes for “Blue”, “Green” and “Red” cones, the last 2 of which sit on the X chromosome. But only 1 of the genes- a Red or a Green (but not both)- occurs on any one X chromosome. So all males- who have only 1 X chromosome- are dichromatic, but they’re either Blue-Green, or Blue-Red dichromats- one or the other. Females, who have 2 X chromosomes (just like human females) can have either 2 or all 3 color genes, meaning that roughly ¼ of White-Faced Capuchin females are Blue-Green dichromats, ¼ are Blue-Red dichromats, and ½ are full trichromats. But Howler Monkeys, Alouatta palliate, (pic right = mother w/baby) which we also saw both in Manuel Antonio and up in Monteverde (video here- you gotta hear these guys) have evolved full trichromatic color vision in both males and females, apparently through what appears to have been a chromosomal abnormality (specifically a translocation) which subsequently spread throughout the population, such that the X chromosome of a Howler monkey today contains both a Red and a Green cone gene.

Tangent: It’s fascinating to wonder what other parallel traits New World Primates will or would or could or might evolve in future or alternate conditions. An expanded neocortex? Bipedalism? Tool use?

Nested Tangent: OK see what I mean? We’re only 2 mammals into the vacation and we’re already into all kinds of cool genetics and parallel evolution and such. I am telling you, CR is amazing! Go there!

We also saw Coatis, a Hognosed Skunk, a Kinkajou, and a Common Opposum (the first wild marsupial I’d ever seen) but the last mammal I’ll highlight is this guy- Desmodus rotundus , the Common Vampire Bat. (pic left = D. rotundus hanging from tree branch.)

Tangent: This right here is a reason to hire a guide. I never, ever, ever would’ve noticed these guys on my own, and we walked right under them.

There are 3 species of vampire bat, all native to Central or South America. Though each is monotypic (and therefore in a separate genus) they seem to have evolved from a common blood-sucking ancestor, implying that vampirism (I love that word) evolved but once among bats. Vampire Bats are of course way, way, way, way cool, for several reasons. Pretty much everyone knows they fly around at night, land on horses and cows, bite them and suck their blood. And most (lots?) people know that their saliva contains a mix of anticoagulants to facilitate blood flow. But here are 3 really cool things you probably didn’t know:

First, Vampire Bats have a “minimalist”, low-frequency-only sonar. The bats flying around your neighborhood at night are hunting bugs. As they fly around, they emit a relatively low-frequency sonar to help them “see” the world around them- obstacles, prey, etc. But when they “sight” a bug”, they “lock on” to their target with a more focused/directional, higher-frequency sonar that provides greater definition and clarity of the bug’s position, size, speed and shape, and maintain that high frequency until they catch the bug. In a sense, the high-frequency sonar is the bat’s equivalent of foveal vision in birds. (The high-frequency sonar is a higher-energy effort, so they don’t just blast it all the time…)

But a Vampire Bat has no high-frequency sonar- only low-frequency “scanning” sonar. And this makes sense because the creatures it’s “hunting”- dozing/sleeping horses, cows, goats, etc.- are large, basically motionless objects.

But this brings us to the 2^nd cool thing, which is that Vampire Bats augment their sonar with thermoreceptors on their noses that help them to hone in on veins where blood is flowing close to the skin of their victim. And there’s even an area in the vampire bat brain that looks somewhat similar in anatomy and position to an area of the brains of rattlesnakes which is associated with receiving/processing infrared images.

But the last cool thing is this: Vampire Bats appear to have benefitted greatly from European settlement. Horses and cows in open pastures or barns are far easier targets for a nocturnal blood-sucker than pretty much any native animal in the forest, and as a result it’s thought that Vampire Bat populations are much higher today than in Pre-Columbian times.

Of course there’s another reason why Vampire Bats are so interesting: when you think about them, you can’t help but wonder- do they ever bite humans? Apparently they do, but it’s not common. Our guide, a man in his 40’s who’s lived his whole life in the Quepos area, has never even heard of anyone being bit.

Next Up: Bird Watcher’s Paradise