The tickbird and the giraffe have a connection relationship that some scientists describe as win-win relationship and some as parasitism (寄生). This interspecies partnership is imbalanced in favor of the giraffe because it can live without the tickbird, while the tickbird is dependent on the giraffe for food resource.

The giraffe is a large mammal that lives in Africa along with other large grass-eaters. All these and many others host the tickbird. This bird has long been thought to remove ticks (扁虱) from its host, to the benefit of both—the bird eats the ticks, and the host is relieved of blood-sucking, disease-carrying insects—but recent studies reveal that this process is less than good. A secondary benefit to a host from the tickbirds’ presence is a sort of early warning system, since the birds make a loud sound if they sight an enemy. This is of less benefit to the giraffe than to other hosts because the giraffe has the advantage of great height and keen eyesight and is fully capable of spotting predators without the bird’s assistance. The tickbird is likely of greater benefit in this capacity to the nearsighted rhino.

They cross through the host’s hair looking for insects as their food. According to the researcher Paul Weeks, reporting in the journal Behavioral Ecology, tickbirds can and do enlarge tick bites and other wounds on their host body to seek for food resource, making the host-tickbird relationship unfair. The host, like the giraffe, however, would have a hard time keeping tickbirds off itself. So they tolerate the birds who cling to their bodies and chow down selectively at the buffet on the giraffe’s body.

For centuries, people thought that fish did not feel pain or emotions. Now research has shown that fish not only have feelings but can also sense others’ moods.

When a human understands and shares the feelings of another person, this is called empathy (共情). Scientists have found that a chemical in the brain called oxytocin (催产素) is involved in our ability to connect with others.

A team of researchers tested zebra fish with a series of experiments. First, they placed the fish in two separate containers and gave one group a material that caused them to act fearful—either freezing or swimming irregularly. Even though the fish in the nearby container had not touched the material, they also began to freeze in fear. “They respond to other individuals being frightened… just like us,” said Ibukun, a co-author of the study. The scientists tried the experiment again with the changed fish whose brains would not produce oxytocin. These fish were much less likely to act anxious when they saw other fish showing fear. If researchers gave them an injection (注射) of oxytocin, their ability to empathize returned.

Finally, researchers played videos of fearful fish on one side of the container and relaxed fish on the other side. Normal fish moved closer to the side that showed the fearful fish, which might have been an attempt to comfort them. The changed fish did not move toward either side.

Looking at the normal fish’s brains, researchers saw activity in an area similar to the one humans and other mammals (哺乳动物) use when empathizing with others. This could mean that the ability to have empathy developed more than 350 million years ago, when fish and mammals shared a common ancestor.

Koalas live in the eucalyptus （枝树）forests of southeastern and eastern Australia. They rely on the eucalyptus tree for both habitat and food. In fact, they seldom leave these trees. When not sleeping, they're usually eating. They can eat more than a pound of eucalyptus leaves a day. Eucalyptus is poisonous, so the koala's digestive （消化的）system has to work hard to digest it, breaking down the poisons and taking in the limited nutrients （营养）.That's why koalas sleep for 18 to 22 hours a day — they get very little energy from their diet.

Koala numbers decreased in the late 19th and early 20th century from hunting for their fur. Now they face serious threats from habitat loss. Land clearing and bush fires-especially the 2019-2020 Australia Bushfire Season-have destroyed much of the forest they live in. Koalas are easy to be affected by climate change. Increasing carbon dioxide in the atmosphere is decreasing the nutritional quality of eucalyptus leaves and causing longer, more serious droughts and wildfires. In response to drought, koalas are forced to stop sleeping and come down from the trees to find water, putting them at a higher risk of being killed.

Koalas have been identified by the Australian government as one of the 113 animals requiring urgent （紧急的）help. Ensuring there's the right kind of forest for them to return to is extremely urgent. State governments should create new koala reserves and persuade landowners not to cut down eucalyptus trees. Meanwhile, getting the public to understand koalas' living habits and their health will throw light on koala biology, which helps to develop plans to better protect the species.