Researchers studying animal behaviour have recently started noticing something unusual. Some animals were observed to be eating plants that are not part of their normal diet and have no nutritional value. They ate these plants at only some times of the year while other animals in the group did not eat the same plants. What can account for this odd behaviour?

The researchers believe that these animals are giving themselves medicine. These plants can make the animals feel better, kill parasites(寄生虫)or aid in digestion. Many different animals have been observed acting in this way. Some chimps in a nature reserve in Tanzania had parasites which caused them stomach upsets. They were seen chewing and swallowing the leaves containing special medicines. These leaves were rough with sharp spikes sticking out. Scientists think that these rough leaves were eaten to clean out the insides of the chimps’ stomachs so that the parasites would be killed.

Other examples of animals self-medicating include lizards which respond to the bite of a venomous(有毒的)snake by eating a special root that can counter(对抗)the poison, and macaw birds(金刚鹦鹉)that eat clay to aid in digestion and kill bacteria.. Pregnant elephants have been known to eat the leaves of some trees as a way of speeding up the delivery of their babies.

How did animals learn this behaviour? The most obvious answer is that animals learnt by experience. For example, a gorilla once felt ill, ate some leaves and then felt better the next day. It remembered this and passed on this information to the rest of the group and its children. But what about creatures that are less intelligent? Scientists studying the monarch butterfly(黑脉金斑蝶)noticed that some healthy butterflies laid eggs on the milkweed plant which has anti-parasite properties. These eggs produced strong healthy butterflies compared to the ones hatched on plants that do not have such medicinal benefits. Over time the weaker butterflies produced fewer eggs and the healthy butterflies thrived(茁壮成长). This is an example of natural selection.

If we can learn from animals using plants to heal and protect themselves naturally, we too might gain medicinal benefits.

Terns (燕鸥) may change their flight plans based on a sense of coming typhoons, escaping the influence of the storms but still benefiting from feeding opportunities.

Researchers examined information recorded on six terns from Okinawa, Japan, to learn more about the birds’ migrations (迁移) over many years. The terns flew across part of the Philippine Sea’s “typhoon highway” to get to the islands of Borneo and Sulawesi and varied their leaving times—often obviously waiting to leave until a large typhoon was about to cross their projected path.

“They seem to be able to predict (预测) it,” says Jean Baptiste Thiebot, a post doctoral fellow at the National Institute of Polar Research in Japan and lead author of the new study, which was published in June in Marine Biology. The study offers few clues about how terns might do this, but other research suggests some migrating birds notice infrasonic (次声的) weather signals or observe changing clouds.

The terns Thiebot studied typically avoided the typhoons themselves. But these storms can churn (剧烈搅动) food to the ocean surface, so the immediate results may help the hungry travelers. “They might actually use the typhoon to know when to leave for their migrations each year”, Thiebot says. In the unusually quiet 2017 season, with no sign of a strong typhoon, the birds started their journeys later and flew without stops. Thiebot would like to see this pattern confirmed in a larger study. He also worries that increasing typhoon frequency could affect birds’ prediction accuracy (准确), possibly getting them caught in dangerous weather.

Robert Gill, a retired research wildlife biologist, says that although the study’s sample (标本) size is small, it adds to scientists’ overall understanding of migration. “They are able to predict better than the best weather forecasters we have, ” Gill says, “but they’ve also had tens of thousands, if not millions of years to hone that skill.”

Somewhere in the warm, clear waters off the coast of Australia, a mature bottlenose dolphin is swimming with her daughter. It's dinnertime. But, instead of chasing down a fish in open waters like she usually does, mom swims over to a basket sponge (海绵)growing on the ocean floor. In a quick move, she breaks off a piece of the sponge, then fits it closely over her mouth. It's hard not to wonder what that watchful youngster might be thinking about all this. Are you going to eat that sponge? Are we playing?

With the sponge secured on her beak, the older dolphin starts sweeping her head back and forth across the ocean floor. She's looking for fish like the sand perch （沙鲈），which hide themselves on the floor of the sea under the sand. As for the sponge stuck onto her mouth, it allows her to clear away the sand without injuring herself on broken pieces of coral, or maybe even suffering the sting （刺痛）of the scorpion fish. The extra work it takes to catch a fish like the sand perch is worth it because they tend to be fattier. And for a dolphin, fattier means more nutritious.

Sure enough, after a few minutes, a sand perch comes out. The fish dashes off for a few yards and then hesitates, waiting for a moment before burying itself in the sand again. In that brief pause, the elder dolphin shakes off the sponge, surfaces for a breath, and then comes down and catches the sand perch before it can rebury itself. She then passes it to her daughter. And with that, the younger dolphin hasn't just gotten a good meal ； more importantly, she's learned a powerful hunting technique - one that years from now, she'll pass along to her own children.