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.
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.
Not too long ago, the generally-accepted answer to this question would have been: “Not really—a few birds do, but most don’t.” This was largely based on the observation that most birds have very small olfactory bulbs in their brain relative to their overall brain size. As we observe bird behavior, however, we are are increasingly realizing that most birds can and do use smell regularly, often for very important things.
Let’s begin with the birds that have been known for a long time to use smell. Kiwi birds are unique in having their nostrils on the end of their bills, rather than close to the base of the bill like all other birds. Kiwis stick that long bill into the soil and use their nostrils to sniff for insects and worms.
Brown Kiwi chick.
Photo by Smithsonian’s National Zoo*
It makes a lot of sense that kiwis have a good sense of smell, even if you think that birds in general don’t, because kiwis seem to have evolved to be the avian version of a small fuzzy mammal. Kiwis evolved on the islands of New Zealand, where the only mammals were bats. The small-brown-fuzzy-nocturnal-snuffling-in-the-dirt-for-worms niche was open for the taking, and kiwis—flightless, nocturnal, and covered in long thin feathers that are highly reminiscent of hair—took it. A good sense of smell goes with that niche.
There is a thing that happens a lot in biology, especially in animal behavior: one set of researchers finds an interesting relationship, like, say, “Birds prefer to eat bugs off of cows with lots of spots, and don’t like to eat bugs off of cows with no spots.” (This is a made-up example.)
Blackbirds flying near a cow, Pt Reyes, CA.
Then, some other researchers do a study and say, “Hey, our birds prefer to eat bugs off of cows with no spots! That’s the opposite!”
Then still different researchers do another study and say, “Our birds don’t care at all about the number of spots, they just care whether the spots make a shape like a smiley face. You guys must all have made a mistake. The Smiley Face Rule is the new Lek Paradox! #nobelplease”
To put it less ridiculously: scientists get different results sometimes, and it can be hard to figure out why. Did someone make a mistake? Who is right? Today’s featured paper takes an example of this confusing scientific disagreement and elegantly makes sense of everything, with the help of this handsome little bird:
Common Yellowthroat (male).
Photo by Dan Pancamo*
More than fifty years ago, Russian scientists began an experiment in domestication. At that time, silver foxes had been raised for fur for about 100 years already, so their care and breeding was well known. The scientists began their project like this: they would approach the cage of a silver fox and note its response. The fox would crouch, ears flattened, snarling in fear, or else back away as far as it could until its body was vertical against the back wall of the cage. All of the foxes were frightened of the humans—but some less than others. The scientists chose the foxes that showed the least fear of humans, and bred them. Then they did the same with the pups, raising up and breeding the least-frightened of them; and so on and so on.
Young wild silver fox. Photo by Matt Knoth*
The original foxes were as close to wild animals as anything can be after being bred for fur for a century. Their descendants, after many generations of selection for just one thing—tameness, a liking of humans—look and act like dogs. They seek out humans, they whine and lick your face, they wag their tails. They even look like dogs—mostly, like border collies.
Fox kit showing the white markings characteristic of domestication. Photo by Luz Rovira*