Animal accomplishments that have caused my students to break into applause

I’m teaching an Animal Behavior course this semester. The lectures are 80 minutes long and exactly during the sleepiest time of the afternoon; I enjoy the challenge of getting a reaction from the students under these circumstances. Videos of baby animals in peril always get attention (some good ones: marine iguana, barnacle goose, water buffalo), but they’re so reliable it almost feels like cheating.

My students have actually broken into applause during lecture three times so far. One of these will not be discussed in detail (it involved the recitation of poetry), but the other two were in response to two quite different animal accomplishments, which I thought I would share.

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Why is a bird like a violin?

Don’t worry: this isn’t Lewis Carroll’s maddeningly unanswered riddle “Why is a raven like a writing desk?” (Although, if you’re interested, it turns out that has been answered.) There is an answer to this one—two answers, in fact.

Answer 1: They both make sounds by vibrating strings.

Well, strings, feathers—they’re all the same, right? This Club-winged Manakin produces its courtship song by vibrating its wing feathers: they strike each other about 107 times per second.

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Niche partitioning by the bay

DSC_6511The sun dips low over the bay, its fading rays gilding the avocets as they swish their heads through the water. The egrets eye their own reflections as if in profound self-contemplation. A willet flashes past, its black-and-white wings an exclamation in the dusk.

DSC_7921Faced with such beauty, two words come irrepressibly to mind: niche partitioning.

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Finding the tiny dinosaurs in hummingbirds

Hummingbirds wear a public image of fragile, ethereal beauty: tiny jewels whirring through the air, occasionally pausing to drink daintily from a flower. Their unusual appearance supports this: the iridescent feathers, the long dainty bill, the near-invisible feet all make them seem quite apart from the everyday world of animals who don’t shimmer in the sun and do have feet.

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80% gemstone, 15% fairy from a storybook, only maybe 5% actual bird. He doesn’t even have feet! (Yes he does.)

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But hummingbirds, like all birds, evolved from dinosaurs. Hidden under that glimmering exterior is a tiny, fierce raptorial dinosaur.

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It’s all connected: birds, introduced trout, and talking trees

We all know about food webs—or we think we do. Herbivores eat plants, then predators eat herbivores, and if one part of the web is affected, other parts are impacted too. Seems pretty simple—except that the threads in those webs sometimes connect things you would never expect.

For example: trout and a songbird, the Gray-crowned Rosy-Finch, in an alpine habitat. The fish are in the water and the birds are on land—how connected can they be? If the birds were Bald Eagles or Ospreys or Great Blue Herons, sure, they would be connected because the birds eat the fish. If the birds were ducks, maybe the trout would be an occasional threat to the ducklings. But this is a Gray-crowned Rosy-Finch:

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Photo by Blake Matheson*

They’re not going to be eating fish, and their babies definitely don’t float about on the water.

The reason that we need to worry about what threads on the food web those trout might be tugging at is that the trout are introduced, nonnative species. Alpine lakes often don’t have any fish in them naturally. In the Sierra Nevada and many other mountain habitats, however, people have stocked these lakes with fish so that people can come and fish them for fun. This has been a problem for aquatic species such as frogs, which get gobbled up quite happily by the new fish, but nobody was particularly worried about the effects on songbirds.

It turns out that we should have been.

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Poison frogs are excellent parents

 

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Ranitomeya imitator giving his tadpole a piggy-back ride. Photo by John Clare*

You can find poison frogs at zoos, aquaria, and some museums now: tiny and colorful, often hard to see in the vegetation-rich tank until— oh! all those little blue things, that’s them! They’re so pretty! You watch for a while, and they sit on their leaves unmoving, doing accurate impressions of the plastic toy frogs being sold in the gift shop, until you get bored and move on to the next exhibit.

They have a secret: they have rich lives full of interesting behaviors. They just aren’t interested in doing those behaviors in front of you.

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Hidden worlds: whale falls

I like to read science fiction. I particularly enjoy a good alien world, like Neal Asher’s world of hyper-aggressive invertebrates or Lois Bujold’s planet of radially symmetric beasts. Still better than these, however, are the alien worlds right here on Earth, hidden in plain sight. (Well… if “on the same planet” counts as “in plain sight.”) The hidden world I’d like to talk about today is that of whale falls.

A “whale fall” is just a nice way of saying a dead whale: when a whale dies in the ocean, it sinks—falls—to the bottom, and you have a whale fall. Whale falls are different from other dead animals in two big ways. First, they are, well, big. No other living animal gets as big as our biggest whales. When one of those dies, that’s a lot of dead whale.

Also, whale falls are pretty cool in their pre-fall form.

Also, whale falls are pretty cool in their pre-fall form.

Second, when they fall to the ocean floor, they change the environment on the ocean floor dramatically. A dead animal in a forest or jungle or lake is a piece of dead meat in a habitat already full of other kinds of food: leaves, berries, insects, fish, etc. Some animals in these habitats will scavenge on the dead meat, but many other animals will ignore it. The deep ocean floor is not like a jungle. It is barren, with no sunlight to support plants or plankton, which are generally the food sources that the rest of a food chain depends on. The only organic food sources near the deep sea floor are the dead things that fall down from the water column above, picturesquely named “marine snow;” and that water column is filled with creatures trying to eat anything they can find, so not a lot makes it all the way to the bottom. When a dead whale lands on the ocean floor, it is the equivalent of an enormous banquet being dropped into the middle of a desert.

When a whale falls, it gives rise to an entire ecosystem by itself.

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Advice from whales and elephants: listen to Grandma

Grandmothers are an evolutionary mystery.

Well, not grandmothers exactly: rather, women who have passed menopause. Human men can sire children as long as they live, but human women can’t have children after they go through menopause. But why do we have menopause at all—why stop having babies? Isn’t it always better, evolutionarily, to have more babies?

I don't know, this might be too many babies...

I don’t know, this might be too many babies…

The mystery is far from solved, but we have some good clues.

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Why do animals lick their fur?

Furry animals can spend a lot of time licking their own fur. Here, a mother sea otter demonstrates:

The simple explanation—that these animals lick their fur to keep it clean—is more or less true, but not nearly the whole story: animals get a lot more out of licking their fur than a stain-free coat.

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