Climate change, not human hunting, may have destroyed the thylacine(袋狼) , according to a new study based on DNA from thylacine bones.

The meat-eating marsupials (有袋动物) died out on mainland Australia a few thousand years ago, but survived in Tasmania, an island of southeast Australia separated from the mainland, until the 1930s. Until now, scientists have believed the cause of this mainland extinction was increased activity from native Australians and dingoes (Australian wild dogs).

Scientists behind the University of Adelaide study, which was published in the Journal of Biogeography on Thursday, collected 51 new thylacine DNA samples from fossil bones and museum skins. The paper concluded that climate change starting about 4,000 years ago was likely the main cause of the mainland extinction.

The ancient DNA showed that the mainland extinction of thylacines was rapid, and not the result of loss of genetic diversity. There was also evidence of a population crash in thylacines in Tasmania at the same period of time, reducing their numbers and genetic diversity.

Professor Jeremy Austin said Tasmania would have been protected from mainland Australia’s warmer, drier climate due to its higher rainfall. He argued that climate change was “the only thing that could have caused, or at least started, an extinction on the mainland and caused a population crash in Tasmania.”

“They both occurred at about the same time, and the other two things that have been talked about in the past that may have driven thylacines to extinction on the mainland were dingoes and humans. So the only explanation that’s left is climate change. And because that population collapse happened at the same time that the species went extinct on the mainland, our argument is there’s a common theme there and the only common theme is that there is this change in climate.”

About a billion birds die from flying into buildings each year in North America. Suspicions have been that birds may regard the open areas behind glass as safe passageways. Or they may mistake the reflected trees for the real thing.

Researchers would like to reduce collisions, which requires a solid understanding about what makes a bird more or less likely to die by crashing into a building in the first place.

“There was relatively little known at a broad scale. Previous studies were at one small study site.'' Jared Elmore, a graduate student in natural resource ecology and management at Oklahoma State University. So he and his colleagues used a previously created data set of building collisions for birds at 40 sites throughout Mexico, Canada and the U.S.

The first finding was obvious: bigger buildings with more glass kill more birds. But the details were more remarkable. "We found that life history predicted collisions. Migrants(候鸟), insect-eaters and woodland-inhabiting species collided more than their counterparts(同类).”

Most migratory species travel at night, when lights near buildings can distract or disorient(使迷失方向)them. And Elmore thinks that insect-eating birds might be attracted to buildings because their insect prey(猎物)is attracted to the lights. He suspects that woodland species get tooled by the reflections of trees and bushes in the windows. The results are in the journal Conservation Biology.

By understanding which birds are more likely to collide with buildings, researchers can perhaps determine the best way to adapt buildings, or their lighting, to help prevent such accidents. And by knowing risks, along with migration timing and behavior, building managers can better predict when birds are at their greatest danger - and improve lighting strategics accordingly.

Elmore's next project will use radar to help predict bird migrations. " I think that would maybe go a long way in terms of providing information to people, to the public, to building managers, on when they can get the most benefit in terms of lights-out policies."