Researchers recently discovered some unusual behavior in chimps living in the forests of West Africa. An adult male in the wild would pick up a rock, throw it at a tree while yelling and then run away. Although researchers aren't certain why, they make a guess: The chimps seem to prefer trees that create longer-lasting sounds when struck.

A team of researchers from Germany first discovered this behavior three years ago. Because the actions appeared to be localized, the researchers suggested the purpose was a local tradition and was likely part of some sort of ritual(仪式), Phys. org reports. But they weren't sure what purpose the ritual served.

So the group desired to carry out more experiments to determine why the chimps were so interested in throwing rocks at trees. This time around, they went to the same areas but set up microphones to capture(捕捉) the sounds of the stones as they were thrown.

Researchers analyzed all the recordings and found that the chimps tended to prefer throwing rocks at trees that made lower, longer-lasting sounds. Often these were trees that had exposed roots.

In their findings, published in Biology Letters, the researchers write that “low-frequency sounds travel further in the environment and are better suited for long-distance communication”.

If chimps tried to communicate. it would be more effective for them to strike the trees or choose the ones that made the loudest noises when struck. Because the researchers saw chimps stick to the same trees and never choose new ones, the location could be a factor. Researcher Ammie Kalan tells Science that maybe the locations of the trees have something to do with nearby resources like food and water, and that the sound is a signal to others where to find them.

Animals in Odd Places

Tree Goats

These goats will do a lot for their favorite snacks-including climbing to the top of a 9-m-tall tree! Every summer the argan trees in southwest Morocco produce bitter-tasting fruit that the local goats can’t resist. And these peckish goats are doing us humans a favour — when they spit (for sometimes poo!) out the indigestible nut inside the argan fruit, the nuts can be collected to make an oil that’s used in hair products and food!

City Whales

They’re not visiting the Empire State Building — they’re on the lookout for food! Humpback whales are swimming back in the waters off the coast of New York City in the USA. Why? Years of cleanup efforts in the Hudson River — a tidal estuary where fresh and salt water meet — have brought back algae, zooplankton and fish. And the humpbacks, which are the ultimate foodie tourists, weren’t far behind! So far this year there have been an incredible 377 sightings.

Forest Penguins

Fiordland crested penguins prefer the warm waters and misty rainforest of southwest New Zealand to the icy Antarctic! With smaller bodies than many cold-weather penguins (such as emperors), the flightless birds live in balmy 21℃. And their eggs stay toasty in this warmer habitat, too, tucked away in caves, bushes and tree stumps where males sit on the nests.

Ocean Sloths

Pygmy three-toed sloths might be slow climbers, but when they get into the water, they’re powerful paddlers! These special sloths, which only live in the mangroves of a tiny island off the coast of Panama in Central America, plop into the sea when they want to move to a new tree. Their tummies are often filled with gas due to their leafy diet, so they stay afloat easily-and they can move three times faster in the water than they can on the ground. But since we’re talking about sloths, that’s really saying much!

Scientists have made an amazing discovery: large quantities of species of frog and salamander (火蜥蜴) glow under certain types of light.

Jennifer Lamb and Matthew Davis, at St Cloud State University in Minnesota, in the US, studied 32 different species of amphibians (两栖动物), mostly frogs and salamanders. Lamb and Davis shone blue torchlight on a frog that they were studying and were surprised to see it glow green. They wondered how many others would do the same, so they went to an aquarium (水族馆) in Chicago, US, and shone lights on all the amphibians.

They found that most of the animals lit up green, an effect that showed more clearly when seen through a yellow filter (指示灯). The team say their results have surprised them and they don’t yet know why the amphibians glow like this, but plan to do more research. This glow-in-the-dark ability is known as biofluorescence (生物荧光), and many animals, such as chameleons (变色龙), jellyfish (水母), sharks and sea turtles, can do it. Scorpions (蝎子) glow a bright blue under ultraviolet light (a type of light that causes sunburn).

Biofluorescence is caused by substances (物质) in the body that can absorb one colour of light and then give it out as a different colour. Usually animals absorb blue light and give off green, red or orange light. The bright green might warn off predators (捕食性动物) or help animals like the amphibians signal to each other, or it might even identify individuals, a bit like a call or smell that others can recognise.

“There is still a lot out there that we don’t know, ” Lamb told The New York Times newspaper. “This opens up a whole window into the possibility that organisms can see fluorescence (荧光) — their world may look a lot different from ours.”