If you’ve spent any amount of time boating, fishing, or bird-watching at lakes and rivers, you have most likely seen fishes jumping out of the water. I have seen it many times. Certainly, fishes will exit water in desperate attempts to escape enemies. Dolphins take advantage of the behavior, forming a circle and catching the frightened fishes in midair. But just as we may run fast from fun or from fear, different emotions might motivate fishes to jump.

Mobula rays（蝠鲼）aren’t motivated by fear when they throw their impressive bodies—up to a seventeen-foot wingspan (the distance from the end of one wing to the end of the other) and a ton in weight—skyward in leap（跳跃）of up to ten feet. They do it in schools（鱼群）of hundreds. They usually land on their bellies, but sometimes they land on their backs. Some scientists think it might be a way of removing parasites（寄生虫）. But I think that the rays are enjoying themselves.

In the clear waters of Florida’s Chassahowitzka National Wildlife Refuge, I watched several schools of fifty or more mullets（鲻鱼）moving in beautiful formation. Their well-built bodies were most evident when they leaped from the water. Most of the time I saw one or two leaps by a fish, but one made a series of seven. They usually land on their sides. Each jump was about a foot clear of the water and two to three feet in length.

Nobody knows for sure why the fish leaps. One idea is that they do it to take in oxygen. The idea is supported by the fact that mullets leap more when the water is lower in oxygen, but is challenged by the likelihood that jumping costs more energy than is gained by breathing air. It is hard to imagine they will feel any fresher when back in water.

Might these fishes also be leaping for fun? There is some new evidence. Gordon M. Burghardt recently published accounts of a dozen types of fishes leaping repeatedly, sometimes over floating objects—sticks, plants, sunning turtle—for no clear reason other than entertainment.

Imagine that an alien species landed on Earth and, through their mere presence, those aliens caused our art to fade, our music to standardize, and our technological know-how to disappear. Actually, that is what humans have been doing to our closest relatives — chimps (大猩猩).

Back in 1999, a team of scientists led by Andrew Whiten showed that chimps from different parts of Africa be have very differently from one another. Some groups would get each other’s attention by tapping branches with their knuckles (指关节), while others did it by loudly tearing leaves with their teeth. The team identified 39 of these traditions that are practiced by some communities but not others — a pattern that, at the time, hadn’t been seen in any animal except humans. It was evident, the team said, that chimps have their own cultures.

It took a long time to convince unbelievers that such cultures exist, but now we have plenty of examples of animals learning local traditions from one another. However, when many scientists have come to accept the existence of animal cultures, many of those cultures might disappear. Ammie Kalan and her colleagues have shown, through years of intensive field work, that the very presence of humans has gradually reduced the diversity of chimp behavior. Where we grow, their cultures weaken. It is a bitterly ironic thing to learn on the 20th anniversary of Whiten’s classic study.

“It’s amazing to think that just 60 years ago, we knew next to nothing of the behavior of our sister species in the wild,” Whiten says. “But now, just as we are truly getting to know our primate (灵长类) cousins, the actions of humans are closing the window on all we have discovered.”

No one knows whether the destruction of chimp culture is getting worse. Obviously, conservationists need to think about saving species in a completely new way — by preserving animal traditions as well as bodies and genes. “Instead of focusing only on the conservation of genetically based beings like species, we now need to also consider culturally based ones,” says Andrew Whiten.

When it comes to cooling the planet, forests have more than one trick upon their trees. A new study finds tropical (热带的) forests help cool the average global temperature by more than 1℃. “The effect is largely from forests’ ability to stockpile CO₂. But around one third of that tropical cooling effect comes from several other processes, such as the letting-out of water vapor (水蒸气),” researchers reported on March 24 in Frontiers in Forests and Global Change.

“We tend to focus on CO₂ and other greenhouse gases, but forests can not only keep CO₂,” said Deborah Lawrence, an environmental scientist at the University of Virginia. “It’s time to think about what else forests are doing for us besides keeping CO₂.”

“Researchers already know that forests influence their local climates through various chemical processes. Trees let out water vapor through their leaves and, like human sweating, this cools the trees and the things around them. But on a global scale, it isn’t clear how the other cooling works compared with the cooling provided by forests’ ability of keeping CO₂,” Lawrence said.

So she and her colleagues studied how over-cutting would affect global temperatures, using data gathered from other studies. For example, the researchers used data to decide how much the letting-out of CO2 stored by those forests would warm the global temperature. They then compared those results with other studies’ results of how much the loss of other aspects of forests.

The researchers found that in forests at latitudes (纬度) from around 50°S of the equator to 50°N, the primary way that forests influenced the global average temperature was through CO₂ store. But other cooling factors still played large roles.