Enlarge / "That's not my arm": Male serotine bats have such large penises, they can use them as an arm while mating. (credit: Alona Shulenko)

Little is known about the mating habits of the serotine bat ( Eptesicus serotinus ), but the males of the species boast unusually large penises—much larger than the vaginas of the females. The purpose of such an enormous organ has long baffled scientists. But a recent paper published in the journal Current Biology revealed that the males of this bat species use their gigantic members not for penetrating females while mating, but as an arm to push the female's tail sheath aside, thereby improving the odds of successful insemination.

Eurasian serotine bats can be recognized by their long smoky-brown fur (with pale yellow-brown underbelly), large triangular ears, and distinctive flight pattern: bouts of flapping interspersed with brief glides. They typically roost in older buildings like churches that have high gables and cavity walls, or abandoned mines. The male bats are largely solitary until fall mating season arrives, when they seek out females. Females set up maternity colonies around late May in Europe and remain there throughout the breeding season, usually giving birth to a single offspring (pup) in late summer.

Female bats have unusually long cervixes, the better to store sperm. The males have penises that are seven times longer than the females' vaginas, with a heart-shaped head seven times wider than the vaginal opening. “By chance, we had observed that these bats have disproportionately long penises, and we were always wondering, ‘How does that work?’” said co-author Nicolas Fasel of the University of Lausanne. “We thought maybe it's like in the dog where the penis engorges after penetration so that they are locked together, or alternatively maybe they just couldn't put it inside, but that type of copulation hasn’t been reported in mammals until now.”

Enlarge / Gentoo penguins are the world's fastest swimming birds, thanks to the unique shape and structure of their wings. (credit: Priya Venkatesh/CC BY-SA 3.0 )

Gentoo penguins are the world's fastest swimming birds, clocking in at maximum underwater speeds of up to 36 km/h (about 22 mph). That's because their wings have evolved into flippers ideal for moving through water (albeit pretty much useless for flying in the air). Physicists have now used computational modeling of the hydrodynamics of penguin wings to glean additional insight into the forces and flows that those wings create underwater. They concluded that the penguin's ability to change the angle of its wings while swimming is the most important variable for generating thrust, according to a recent paper published in the journal Physics of Fluids.

“Penguins’ superior swimming ability to start/brake, accelerate/decelerate, and turn swiftly is due to their freely waving wings," said co-author Prasert Prapamonthon of King Mongkut‘s Institute of Technology Ladkrabang in Bangkok, Thailand. "They allow penguins to propel and maneuver in the water and maintain balance on land. Our research team is always curious about sophisticated creatures in nature that would be beneficial to mankind.”

Scientists have long been interested in the study of aquatic animals. Such research could lead to new designs that reduce drag on aircraft or helicopters. Or it can help build more efficient bio-inspired robots for exploring and monitoring underwater environments—such as RoboKrill , a small, one-legged, 3D-printed robot designed to mimic the leg movement of krill so it can move smoothly in underwater environments.

Enlarge / Bumblebees can learn to solve puzzles from experienced peers. Honeybees do the same to learn their waggle dances. (credit: Diego Perez-Lopez, PLoS/CC-BY 4.0 )

Social insects like bees demonstrate a remarkable range of behaviors, from working together to build structurally complex nests (complete with built-in climate control) to the pragmatic division of labor within their communities. Biologists have traditionally viewed these behaviors as pre-programmed responses that evolved over generations in response to external factors. But two papers last week reported results indicating that social learning might also play a role.

The first, published in the journal PLoS Biology, demonstrated that bumblebees could learn to solve simple puzzles by watching more experienced peers. The second , published in the journal Science, reported evidence for similar social learning in how honeybees learn to perform their trademark "waggle dance" to tell other bees in their colony where to find food or other resources. Taken together, both studies add to a growing body of evidence of a kind of "culture" among social insects like bees.

"Culture can be broadly defined as behaviors that are acquired through social learning and are maintained in a population over time, and essentially serves as a 'second form of inheritance,' but most studies have been conducted on species with relatively large brains: primates, cetaceans, and passerine birds," said co-author Alice Bridges , a graduate student at Queen Mary University of London who works in the lab of co-author Lars Chittka . "I wanted to study bumblebees in particular because they are perfect models for social learning experiments. They have previously been shown to be able to learn really complex, novel, non-natural behaviors such as string-pulling both individually and socially."

Enlarge / Even hermit crabs have individual patterns of behavior — personalities, if you like. When scientists ignore the effects of such differences, they may produce research that’s flawed. (credit: NurPhoto via Getty Images )

Several years ago, Christian Rutz started to wonder whether he was giving his crows enough credit. Rutz, a biologist at the University of St. Andrews in Scotland, and his team were capturing wild New Caledonian crows and challenging them with puzzles made from natural materials before releasing them again. In one test , birds faced a log drilled with holes that contained hidden food, and could get the food out by bending a plant stem into a hook. If a bird didn’t try within 90 minutes, the researchers removed it from the dataset.

But, Rutz says, he soon began to realize he was not, in fact, studying the skills of New Caledonian crows. He was studying the skills of only a subset of New Caledonian crows that quickly approached a weird log they’d never seen before—maybe because they were especially brave, or reckless.

The team changed its protocol. They began giving the more hesitant birds an extra day or two to get used to their surroundings, then trying the puzzle again. “It turns out that many of these retested birds suddenly start engaging,” Rutz says. “They just needed a little bit of extra time.”

Juvenile snapping shrimp now hold the acceleration record for a repeatable body movement underwater. They can snap their claws at accelerations on par with a bullet shot from a gun. (credit: Harrison and Patek, 2023)

The snapping shrimp , aka the pistol shrimp, is one of the loudest creatures in the ocean, thanks to the snaps produced by its whip-fast claws. And juvenile snapping shrimp are even faster than their fully grown elders, according to a recent paper published in the Journal of Experimental Biology. Juvenile claws accelerate as fast as a bullet shot from a gun when they snap, essentially setting a new acceleration record for a repeated movement performed underwater.

As we've reported previously, the source of that loud snap is an impressive set of asymmetrically sized claws; the larger of the two produces the snap. Each snap also produces a powerful shockwave that can stun or even kill a small fish. That shockwave produces collapsing bubbles that emit a barely visible flash of light—a rare natural example of sonoluminescence .

Scientists believe that the snapping is used for communication, as well as for hunting. A shrimp on the prowl will hide in a burrow or similar obscured spot, extending antennae to detect any passing fish. When it does, the shrimp emerges from its hiding place, pulls back its claw, and lets loose with a powerful snap, producing the deadly shockwave. It can then pull the stunned prey back into the burrow to feed.