The sperm whale is an astonishing creature. It’s longer than a semi-truck, weighs more than 90, 000 pounds and is the largest member of the toothed whale family. It’s known to dive 6, 500 feet in search of food, and to stay down there for longer than an hour at a time.

Perhaps most fantastically, the sperm whale’s brain weighs as much as 20 pounds-the biggest of any species on Earth. But when it comes to brains, is size all that matters? There’s a lot we don’t know about the sperm whale’s intelligence because it’s difficult to carry out neurological (神经的) testing on such a huge marine mammal. But some clues point to sperm whales being much smarter than we give them credit for.

A 2021 study published in Biology Letters, for example, looked back to 19th-century historical logbooks from whalers. Researchers found that sperm whales were at first easy to catch-but almost immediately, the whales learned how to evade hunters and whaling success dropped by 60 percent. The study suggests that the whales passed information to one another through soundwaves to avoid being caught.

Animals that have big brains usually have a few things in common. They usually live long lives; for example, sperm whales can live for 70 years or longer. Additionally, they’re capable of complex behaviors and they tend to be more socia1. Whales may work together to hunt or communicate in a language all their own.

What’s more, humans, whales and dolphins all have spindle neurons in their brains. These nerve cells make us capable of deeper thought, such as reasoning skills, memory, communication and adaptive thinking. And like humans, whales have emotional intelligence- meaning they＇re capable of empathy, grief and sadness. Still, in proportion to (与…成比例)our body size, the human brain is bigger than that of the sperm whale.

Yet there’s still so much we don’t know about how smart sperm whales really are. And just like the whalers of a century ago, we have likely been underestimating marine mammals, whether large or small, for as long as we’ve known of their existence.

Scientists have provided new evidence to help solve one of the world’s oldest mysteries---zebras stripes. Researchers recently described experiments showing that horse flies have a difficult time landing on zebras while easily landing on horses of a single color.

In one experiment, the researchers put blankets with stripes on horses and saw that fewer flies landed on them. "They fly past them or hit them and bounce off, "said Tim Caro of the University of California-Davis. He was the lead writer of a report on the study. The report was published in the journal PLOS ONE.

Closely related to horses, the world’s three zebra species are known for their black-and-white striped bodies. Zebras are native to Africas savannas, or grasslands. The appearance of the stripes is different from one zebra to the next.

There have been four main theories about the reasons why zebras developed stripes. The first theory is to avoid attacks by meat-eating animals. Another is that zebras have an easier time recognizing other zebras. a third idea is thermoregulation, which is the ability of a creature to control its body temperature, even when the surrounding temperature is different. The fourth theory is to prevent attacks by biting flies.

Only the last stands up, Caro said. "Most biologists involved in research on mammal coloration accept that this is the reason why zebras have stripes. University of Bristol biologist Martin How worked with Caro on the study. He said stripes may confuse flies when they get too close to zebras. African horse flies carry diseases, such as trypanosomiasis. The sickness can cause weakness and be deadly.

“In addition to stripes that prevent controlled landings by horse flies, zebras are always moving their tail and may frighten off the horse flies if they do land successfully, "Martin How said. He added that zebras are also using behavioral means to prevent flies from biting them

In many big cities, a lot of old people keep birds, cats, dogs and other animals in their houses. These animals are friendly to the old people and never leave them. So the old people love them and see them as their good friends or families.

It’s not difficult to keep these lovely animals at home. But you have to take them to animal hospitals to give them needles (注射), so they won’t get ill or they will make people ill. Now there are lots of animal food stores here and there. People can buy good animal food for their animals there. Old people can buy animal food on the phone or on the Internet. But it’s a little more expensive.

Sometimes it’s kind of dirty and dangerous to keep animals. They sometimes look dirty and smell terrible and can be dangerous. For example, an old woman in Shanghai lost her life on the street for her pet dog.

Maybe old people in big cities have many reasons to keep these nice and clever animals. They may feel lonely when their children leave. And these pets can be their great helpers. They are their good friends and help them in many things.