biology – Adverbly

Fuzzy green “glacier mice” puzzle scientists

30 May 20203 June 2020 adverbly

“What the heck is this!” was the reaction of one glaciologist when he first encountered glacier mice.¹ Long known to researchers but still not fully understood, glacier mice might best be thought of as bundles of moss that form pearl-like around pebbles or other impurities on glacial surfaces.

Found as far afield as Alaska, Chile, and Norway, glacier mice were first described in 1951 by Icelandic meteorologist Jón Eyþórsson, who referred to them as jökla-mýs (Icelandic for “glacier mice”).²

What’s particularly curious about these “critters,” however, is that they seem to move around much more than any ordinary moss might.

From NPR:

The movement of the moss balls was peculiar. The researchers had expected that the balls would travel around randomly by rolling off their ice pedestals. The reality was different. The balls moved about an average of an inch a day in a kind of choreographed formation — like a flock of birds or a herd of wildebeests.

The researchers considered several possible explanations. The first, and most obvious one, is that they just rolled downhill. But measurements showed that the moss balls weren’t going down a slope.

“We next thought maybe the wind is sort of blowing them in consistent directions,” says Bartholomaus, “and so we measured the dominant direction of the wind.”

That didn’t explain it either, nor did the pattern of the sunlight.

“We still don’t know,” he says. “I’m still kind of baffled.”

You can listen to an 11-minute NPR story about glacier mice here:

Massive superpods of dolphins sighted near South Africa

2 February 20182 February 2018 adverbly

Bottlenose dolphins are social animals. Just as wolves live in packs, dolphins live in pods of generally 10-30 individuals (although groups of 50 or even 60 are not uncommon¹). Researchers studying Indo-Pacific bottlenose dolphins, however, have been documenting substantial increases in pod sizes off the coast of South Africa. From 2008 to 2016, pod size in the area increased from an average of 18 animals per group to an average of 76.² On top of this, some of the largest pods ever reported have been observed in the area — with sightings of as many as 600 dolphins in a single group.

Scientists are unsure as to what might be causing pod size to swell. According to research published in Marine Mammal Science,

“neither season nor behavior had a significant effect on mean group size at both sites. Similarly environmental variables such as the depth and substrate type also had no influence on group size. It remains unclear which ecological drivers, such as predation risk and food availability, are leading to the large groups observed in this area, and further research on abundance and distribution of both predators and prey is necessary.”

Check out some video footage of a superpod, below:

Coconut crabs, which can grow up to 3 feet, now proven to prey on birds

12 November 201712 November 2017 adverbly

Our regular readers will know that I’ve long been fascinated by coconut crabs. The world’s largest

Via wikimedia. — Coconut crabs scale palm trees.

terrestrial arthropod (and thought to represent the upper size limit for land-dwelling creatures supported by exoskeletons), coconut crabs can grow to more than 3 feet in length. They can climb trees and crack coconuts. Their claws are as strong as a lion’s jaws. They can live for up to 60 years. And now, researchers have evidence that their diet isn’t limited to fruits, nuts, and scavenged carrion: they sometimes engage in predation, as well.

It has long been known that the crabs will feed on meat, when they encounter it; in a 2007 experiment, coconut crabs made short work of a small pig carcass, quickly stripping its flesh and scattering the bones. Persistent rumors suggest that a dead or wounded Amelia Earhart may have suffered a similar fate. Researchers now have direct evidence, though, that coconut crabs will not only consume dead animals they come across, they will sometimes go on the hunt themselves.

This Washington Post article describes researchers’ encounters with coconut crabs that have hunted (and fed on) seabirds:

[N]ow, finally, we have video evidence that the crabs — thousands strong on one island — can scale trees and hunt full-grown birds in their nests.

[…] After about a month on the island [in the Chagos archipelago], in February of 2016, [Dartmouth biologist Mark Laidre] investigated a giant crab’s underground lair. “Deep inside the crab’s burrow was the carcass of a nearly full-grown red-footed booby,” he wrote. This was Laidre’s first sign that the stories might be true, that giant crabs really were hunting birds. He had his proof a month later.

“In the middle of the night,” Laidre wrote, “I observed a coconut crab attack and kill an adult red-footed booby.”

You can see some footage from this encounter in the video below.