1 . Any schoolchild knows that a whale breathes through its blowhole. Fewer know that a blowhole is a nostril (鼻孔) slightly changed by evolution into a form more useful for a mammal that spends its life at sea. And only a dedicated expert would know that while toothed whales, such as sperm whales, have one hole, baleen (鲸须) whales, such as humpback and Rice whales, have two.

Even among the baleen whales, the placing of those nostrils differs. In some species they are close together. In others, they are much further apart. In a paper published in Biology Letters Conor Ryan, a marine biologist at the Scottish Association for Marine Science, suggests why that might be. Having two nostrils, he argues, helps whales smell in stereo (立体空间).

Many types of baleen whales eat tiny animals known as zooplankton (浮游动物), which they catch by filtering (过滤) them from seawater using the sheets of fibrous baleen that have replaced teeth in their mouths. But to eat something you first have to find it. Toothed whales do not hunt by scent. In fact, the olfactory bulb—the part of the brain that processes smell—is absent in such creatures. But baleen whales still have olfactory bulbs, which suggests smell remains important. And scent can indeed give zooplankton away. Zooplankton like to eat other tiny creatures called phytoplankton (浮游植物). When these are under attack, they release a special gas called dimethyl sulphide, which in turn attracts baleen whales.

Most animals have stereoscopic senses. Having two eyes, for instance, allows an animal to compare the images from each in order to perceive depth. Having two ears lets them locate the direction from which a sound is coming. Dr Ryan theorized that paired blowholes might bring baleen whales the same sorts of benefits.

The farther apart the sensory organs are, the more information can be extracted by the animal that bears them. The researchers used drones to photograph the nostrils of 143 whales belonging to 14 different species. Sure enough, baleen whales that often eat zooplankton, such as the North Atlantic right whale, have nostrils that are farther apart than do those, such as humpback whales, that eat zooplankton occasionally. Besides allowing them to breathe, it seems that some whales use their blowholes to determine in which direction dinner lies.

3 . It can be a bit of a puzzle for bird lovers. If you feed birds, will that make them unwilling to search for food elsewhere? Each year, millions of people feed birds, driving a $4 billion industry based on bird food, feeders, etc. Bird feeding is especially popular in northern countries during winter, when cold, stormy weather and minimal daylight reduce the time that birds have for locating natural foods.

Bird feeding has positive effects, such as enhanced body conditions and increased reproductive output of birds. On the negative side, it can facilitate disease transmission and change bird migration. A recent mysterious illness, for example, has been blinding and killing birds in several states.

According to Rivers, a scholar of wildlife ecology, not much is known about whether birds become reliant on the feeders. “The only experiment to test that, using the black-capped chickadee (黑冠山雀), was 30 years ago,” he said. “It found no reduction in apparent survival after the removal of bird feeders that had provided extra food for 25 years, leading to the conclusion that bird feeding did not promote feeder dependency.”

Rivers studied the bird feeder using habits of 67 black-capped chickadees subjected to one of three flight-feather-clipping (翼羽修剪) treatments: heavy clipping, light clipping, or no clipping. The birds were tagged with RFID chips (射频识别芯片), and 21 bird feeders along a 3.2-km riverside zone were filled with sunflower seeds and equipped with chip readers to measure feeder visits by the tagged birds.

It turned out that the feather-clipped chickadees did not increase their rates of visits to the feeders. Instead, the feather-clipped birds actually decreased their feeder use for a couple of weeks, possibly to reduce exposure to being hunted. But after that they used the feeders to the extent similar to the unclipped birds’. The findings suggested that foods in the environment were sufficiently available to allow birds to cut back on feeder use.

“Many people are concerned that if we don’t fill our feeders up before big storms, birds can be in trouble. I don’t think so,” Rivers says. “We’re not going to be harming birds and birds aren’t going to starve just because we don’t fill up our feeders. Besides, this can prevent diseases spreading among them.”

5 . Wildlife experts are reporting increasing numbers of Atlantic blue fin tuna(蓝鳍金枪鱼)in the Atlantic Ocean. Atlantic blue fins are highly prized by the fishing industry. The fish can weigh up to 454 kilograms. Its meat is often used in sushi products sold at Japanese restaurants.

But the Atlantic blue fin has been a concern for wildlife experts. The species was listed as endangered by the International Union for Conservation of Nature.

Improved law enforcement appears to be helping the Atlantic blue fin recover after years of overfishing. The popular fish all but disappeared from the Gulf of Maine about 10 years ago. This year, fishers set a record by catching 30 Atlantic blue fins. One of the fish weighed 363 kilograms.

International regulators have eased the catch limits for U. S. fishermen this year, increasing the quotas (限额)by more than 180,000 kilograms. But environmental groups warn increasing the new limits will undo years of wildlife protection efforts.

Scientists have been unable to determine whether or not the Atlantic blue fin population has recovered, so any decrease in the population now is bad for fishermen in the long term.

Blue fin has been at the center of a long battle between the fishing industry and environmentalists. Fishermen can make large amounts of money from a single fish. Environmentalists seek to protect the Atlantic blue fin. Yet many consumers are willing to pay high prices to eat them.

Walt Golet, a professor of marine biology at the University of Maine, says “Probably no other fish has been more politicized than the Atlantic blue fin tuna. From an environmental point of view it's always … Let's try to back off a little bit and make sure that we always have enough fish, and on the other side, we have individuals and organizations that they're making a living out of that fish and that's kind of where the assessment and management come into play. It's kind of balancing all of those opinions and viewpoints.”