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BMC Ecology via Wikimedia Commons // CC BY 2.0
BMC Ecology via Wikimedia Commons // CC BY 2.0

This Crab's Secret to a Happy Relationship Is a Turtle's Butt

BMC Ecology via Wikimedia Commons // CC BY 2.0
BMC Ecology via Wikimedia Commons // CC BY 2.0

Columbus crabs (Planes minutus) are tiny and can’t swim very far, but they manage to get around—in more ways than one. They make their homes on anything that floats—logs, ship hulls, plastic junk, and even sea turtles—and ride the waves around. On many of these mobile “islands,” the crabs are plentiful and have an “inclusive” mating system, say biologists Joseph Pfaller and Michael Gil. Sometimes, the crabs like to play the field, readily switching among multiple mating partners. At other times, though, they have more monogamous love lives, sharing their territory with just one other crab, with whom they form a mating pair. The difference? The size of the place where they shack up, say the researchers. They recently published their findings on the crabs' love life in Biology Letters.

Pfaller and Gil were curious about what made the crabs switch between these two mating styles. What was it about a particular turtle or piece of debris that pushed them toward swinging, or into settling down? For many crustaceans that live on or in other animals, it’s the size of the host that dictates how many critters call it home and how they mate. The biologists wondered if the same was true for Columbus crabs, who thrive in both living and non-living “hosts.”

To find out, they took a boat out into the North Pacific Subtropical Gyre—site of the Great Pacific Garbage Patch—and collected dozens of pieces of plastic debris, from soda bottles to boat bumpers. Back in the lab, they measured the size of the debris and recorded the number of crabs, and each crab’s life stage (adult or juvenile) and sex. To get data on sea turtles, they dove into scientific journals instead of the ocean, reading through 270 records of sea turtle–Columbus crab associations, and recording the same information they did with the debris.

Pfaller and Gil found that even though Columbus crabs can travel far and wide on a hunk of plastic or a sea turtle, they still seek out the cozy confines of a burrow-like refuge on their floating homes. On pieces of debris, they usually take up residence in stalks of barnacles. On sea turtles, the crabs tuck themselves into the supracaudal space—the small area between a turtle’s tail and shell. The researchers say that it’s the size of these refuges, and not the overall size of the host, that matters most when it comes to the size and demographics of a crab community—and thus how they mate.

Bigger refuges, of course, support more crabs. A bigger space with more neighbors makes it harder for any one crab to defend a chunk of real estate or a mate, so they opt for a more open and free mating system. A smaller refuge, on the other hand, can only hold so many crabs and is easier to monopolize, leading the crabs to form monogamous pairs and fend off rivals. This was almost always the case for crabs living on sea turtles, where Pfaller and Gil found lone male–female pairs far more frequently than expected by chance. Because a typical turtle’s supracaudal space is the perfect size for two crabs, the researchers say, “sea turtle symbiosis specifically promotes social monogamy.” Who would have thought that living on a turtle’s tush could provide the key to a happy, stable relationship?

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Pigeons Are Secretly Brilliant Birds That Understand Space and Time, Study Finds
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Of all the birds in the world, the pigeon draws the most ire. Despite their reputation as brainless “rats with wings,” though, they’re actually pretty brilliant (and beautiful) animals. A new study adds more evidence that the family of birds known as pigeons are some of the smartest birds around, as Quartz alerts us.

In addition to being able to distinguish English vocabulary from nonsense words, spot cancer, and tell a Monet from a Picasso, pigeons can understand abstract concepts like space and time, according to the new study published in Current Biology. Their brains just do it in a slightly different way than humans’ do.

Researchers at the University of Iowa set up an experiment where they showed pigeons a computer screen featuring a static horizontal line. The birds were supposed to evaluate the length of the line (either 6 centimeters or 24 centimeters) or the amount of time they saw it (either 2 or 8 seconds). The birds perceived "the longer lines to have longer duration, and lines longer in duration to also be longer in length," according to a press release. This suggests that the concepts are processed in the same region of the brain—as they are in the brains of humans and other primates.

But that abstract thinking doesn’t occur in the same way in bird brains as it does in ours. In humans, perceiving space and time is linked to a region of the brain called the parietal cortex, which the pigeon brains lack entirely. So their brains have to have some other way of processing the concepts.

The study didn’t determine how, exactly, pigeons achieve this cognitive feat, but it’s clear that some other aspect of the central nervous system must be controlling it. That also opens up the possibility that other non-mammal animals can perceive space and time, too, expanding how we think of other animals’ cognitive capabilities.

[h/t Quartz]

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The Queen's Racing Pigeons Are in Danger, Due to an Increase in Peregrine Falcons
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Queen Elizabeth is famous for her love of corgis and horses, but her pet pigeons don't get as much press. The monarch owns nearly 200 racing pigeons, which she houses in a luxury loft at her country estate, Sandringham House, in Norfolk, England. But thanks to a recent boom in the region’s peregrine falcon population, the Queen’s swift birds may no longer be able to safely soar around the countryside, according to The Telegraph.

Once endangered, recent conservation efforts have boosted the peregrine falcon’s numbers. In certain parts of England, like Norfolk and the city of Salisbury in Wiltshire, the creatures can even find shelter inside boxes installed at local churches and cathedrals, which are designed to protect potential eggs.

There’s just one problem: Peregrine falcons are birds of prey, and local pigeon racers claim these nesting nooks are located along racing routes. Due to this unfortunate coincidence, some pigeons are failing to return to their owners.

Pigeon racing enthusiasts are upset, but Richard Salt of Salisbury Cathedral says it's simply a case of nature taking its course. "It's all just part of the natural process,” Salt told The Telegraph. "The peregrines came here on their own account—we didn't put a sign out saying 'room for peregrines to let.' Obviously we feel quite sorry for the pigeons, but the peregrines would be there anyway."

In the meantime, the Queen might want to keep a close eye on her birds (or hire someone who will), or consider taking advantage of Sandringham House's vast open spaces for a little indoor fly-time.

[h/t The Telegraph]

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