More than 215 pilot whales died after beaching themselves on the Chatham Islands over the weekend. The pilot whales started to become stranded (搁浅的) on the remote islands’ northwest last Friday, according to the Department of Conservation (DoC).

Because of the isolation of the Chatham Islands and an active shark population, it is considered too dangerous to actively refloat stranded whales. Unless they are naturally refloated by the tides, all of them will die.

“We do not actively refloat whales on the Chatham Islands due to the risk of shark attack to both humans and the whales themselves,” DoC said in a statement.

“All the stranded pilot whales are now dead and their bodies will be left to decompose naturally on site.”

A department team was being organized in response to the latest stranding. They will probably be tasked with euthanising (使安乐死) whales that remain stranded.

The Chatham Islands, 840km east of mainland New Zealand, and a resident population of less than 800 people, are “a stranding hotspot, among the top three places for strandings in New Zealand”, according to the conservation department. The islands are the site of the biggest recorded stranding in New Zealand history – an estimated 1,000 pilot whales in 1918.

Pilot whales — which can grow to more than six metres (20 feet) long — are also highly sociable, so they may follow podmates (同伴) who fall into danger.

In New Zealand, about 300 animals beach themselves annually, according to official figures, and it is not unusual for groups of between 20 and 50 pilot whales to run aground.

Why these strandings occurred – and also why they sometimes met with similar strandings in southern Australia – remained a largely unanswered question.

The alligator gar (鳄雀鳝) was a mystery to most people in China, but now it has become famous as a high-risk, invasive fish species.

The fish hit the headlines following the tracking of two alligator gars in a park in Ruzhou, Henan province. Filming of the search, which was live-streamed on Aug 23, attracted about 37 million viewers at its peak. The capture of the fish wasn’t too simple, but they were finally caught on Aug 26.

Gu Dang’en, a scientist associated with a national program on invasive species control, said that the exotic fish was brought into China two to three decades ago for its strange spotted look.

As a predator at the top of its food chain, the alligator gar has already appeared in many places across China. It can eat all the other creatures living in the water, damage local ecosystems and pose risks to humans. A boy in Taizhou Jiangsu, was bitten by an alligator gar on three of his fingers while playing by a community pool on Aug 17. Experts also warn that the alligator gar’s guts and eggs are poisonous.

The Biosecurity Law, which took effect in April 2021, requires that the government must draft a list of invasive species and work out rules for their management. “Authorities have announced a national plan to conduct surveys of 10 invasive species, including the alligator gar, ”said Mu Xidong, a researcher with the Pearl River Fisheries Research Institute at the Chinese Academy of Fishery Sciences.

Ren Dapeng, a professor from China Agricultural University, said that, under the new law, institutions and individuals cannot import, release or abandon exotic species without official approval. If institutions and individuals break the Biosecurity Law, they can face fines of between 10,000 and50,000 yuan. He said that if people no longer want to raise exotic species like the alligator gar, they should send them to the authorities and turn to them for help.

Human activity has shrunk (缩小) the size of wild animals worldwide, and yet recent research has found many mammals (哺乳动物) living near cities have gradually become larger, both in length and in weight. The findings are unexpected. Spreading urban environments can grow much hotter than natural habitats, and warmer temperatures usually benefit mammals that have a smaller, more energy-saving figure—a principle of biology known as Bergmann’s rule.

As the world grows warmer, scientists have worried that mammals living near cities are going to grow smaller, possibly reducing their fitness and the fitness of their predators (捕食者). Even with climate change that might not happen. As it turns out, there is another factor affecting a mammal’s size that might exceed temperature, and that is food. In and around places with dense populations, where high-calorie human foods are more widely available and predators are fewer and farther in between, new research discovered that most of the mammal species studied appear to be growing in size, not shrinking. According to careful measurements of more than 100 species from North America, gathered from museum collections over the past 80 years, the main reason is not a city’s temperature. Instead, the greatest increases in weight and body length appear to lie among those mammals that live near humans, regardless of how hot their surroundings are.

As climate change grows worse, there is, of course, the possibility that that might change, but at least for now, it seems wolves, deer, bats, and other mammals in North America could be affected more by city populations than city climates.

If we want to protect mammals that exist today for the future, it’s important we know how human civilization is influencing their size, behavior, and well-being. In a rapidly changing world, that knowledge could mean the difference between ongoing life and dying out.