北极熊不会使雪雁灭绝-凯发k8官网

as the arctic warms, a new cache of resources—snow goose eggs—may help sustain（维持，支撑） the polar bear population for the foreseeable（可预知的） future. in a new study published in an early online edition of oikos, researchers ¹ with the museum show that even large numbers of hungry bears repeatedly raiding nests over many years would have a difficult time eliminating all of the geese because of a mismatch in the ² of bear arrival on shore and goose egg incubation（孵化，潜伏） . "there have been statements in popular literature indicating that polar bears can ³（灭绝，根除） snow geese quickly once they start to eat eggs," says robert rockwell, a research associate in the division of vertebrate ⁴ at the museum and a professor at the city university of new york. "however, there will always be the occasional mismatch in the ⁵ between the onshore arrival of bears and the incubation period of the geese. even if the bears eat every egg during each year of complete 'match,' our model shows that periodic years of mismatch will provide windows of successful goose reproduction that will ^{6 7} predation（捕食，掠夺） effects."

in the last few years, work along the ⁸ churchill peninsula of western hudson bay by rockwell and colleagues has suggested that polar bears are not as hamstrung（残废） by their environment as many biologists believe. one new ⁹ option for polar bears is the ¹⁰（慷慨，丰富） of goose eggs which had ¹¹ hatched into goslings（小鹅） that were gone by the time bears came ¹². in recent years, 'early' bears have left breaking sea ice to come ashore and consume eggs. in fact, the earlier the bears come ashore, the better: eggs are higher in ¹⁴ when the ¹⁵ is younger.

in the new oikos paper, rockwell and coauthors linda gormezano (also affiliated with the museum) and david koons (a researcher at utah state university in logan) simulated the timing of events during the arctic spring: the break-up of sea ice, the movement of bears onto shore, the ¹⁶ of geese to the north, and the laying of eggs. results from the computer model show that the mismatch of timing is something that both the bears and geese can use to their advantage. the timing of geese migration is primarily based on photoperiod (the amount of light in 24 hours), which will not change as quickly as polar bear movements, which are based on the melting of sea ice.

results show that the advance in mean overlap of the two species gives an advantage to polar bears. but increased variability, also the result of global climate change, leads to an increased mismatch that is good news for snow geese.

"mismatch is often thought to be bad, but in this case periodic mismatch is good because it keeps geese from going extinct and allows polar bears to eat," says rockwell. "are polar bears ¹⁷? of course. this could be a nice stable system. the geese aren't going to go away, and they are a ¹³ resource for the bears."