This might be why full moons are spooky

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Photo by Patrick Emerson*

The full moon is pregnant with foreboding interpretations, from the legendary werewolves who are supposed to transform under its malevolently shining face to a recent article about November’s upcoming full “supermoon” that faux-reassures, “despite all the rumors… there is no evidence linking supermoons to natural disasters.”

If you look at a full moon and shiver, you aren’t alone—but you are a bit of a mystery. In humanity’s past, the full moon should have been the safest time of the month, since our nocturnal predators tend to attack most on dark nights. The new moon should be spooky, as your hindbrain—unaware that you no longer live on the African savannah (unless you do!)—looks out for predators slinking in the shadows. This is presumably why the fear of darkness is such a common and instinctual one. But the full moon is bright: it should be comforting.

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The very confused wren and the birdwatcher who noticed

In the spring of 2015, a male House Wren and his mate built their nest inside a nestbox near a honeysuckle. His mate laid her eggs and dutifully incubated them. Then, one morning— cheep! cheep! High-pitched calls and gaping red mouths cried hungry, daddy! and the male wren was off in a paternal tizzy, collecting bugs and delivering them to his new offspring.

It was, maybe, odd that his new offspring weren’t in the nest that he had built. It was, maybe, odd that other, larger birds were also feeding his babies. It might even have been called odd that his mate was still sitting in their nest, atop whole and silent eggs. But— cheep! No time for that! The chicks were hungry!

What this male House Wren was doing, no doubt to the profound irritation of his mate, was feeding the offspring of a pair of Northern Cardinals who had nested in the honeysuckle near his nestbox.

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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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An egret nesting colony is a nursery, a neighborhood, and a battleground all in one

Egrets are beautiful, especially in their breeding plumage, when they sport long curved plumes and dramatically colored faces.

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Great Egret displaying breeding plumes and a green face.

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Snowy Egret with similar plumes and a red face.

Those breeding plumes are so beautiful that demand for them—for decorating women’s hats—almost drove egrets to extinction, and concern for the heavily persecuted egrets is what gave rise to the bird conservation movement in the early 20th century.

Egrets earn those luscious plumes. Before they get to be adults in breeding plumage, egrets must survive a cutthroat childhood in considerably less impressive dress.

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Yikes, THAT’S what our chicks look like??

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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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Birds as friendly faces

A birder’s brain responds to photos of familiar bird species in a way that is, neurologically, “strikingly similar” to the way that anyone’s brain responds to photos of familiar human faces (Tanaka & Curran 2001): birders seem to use a similar strategy to recognize birds as everyone uses to recognize people they know. If you are a birder, this probably isn’t surprising; certainly, to me, recognizing a bird species feels similar to recognizing a friend. And it isn’t only birders: the study also looked at “dog experts”—which I did not know existed before I read this—and found the same pattern when those experts looked at photos of dogs. If you are passionate about models of cars or architectural styles or garden flowers, I wouldn’t be surprised if you experience the same thing.

(Bafflingly, the study reports that the photos it showed to the birders included “the robin, sparrow… oriole… [and] hawk,” none of which are actually individual species. Which sparrow, guys? Didn’t you talk to your birders at all while you were studying their brains?)

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The sparrow, obviously. (Rufous-collared Sparrow, San Jose, Costa Rica.)

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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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