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Caribou Food Supply Threatened by Warming

Jessica Marshall, Discovery News

"Overall, this means that the caribou isn't getting the best diet, and isn't able to provide its newborn calf with the best nutrition," he added. "We think that makes it harder for the calves to survive the first few days of life."

"While we were collecting data on plant growth during those seven years, we also made observations on caribou calving, and found that in years when plant growth started almost simultaneously across the landscape, caribou had fewer calves," Post said.

The mismatch arises because caribou use changing day length in spring to cue their reproduction, while plants rely on temperature.

With global warming, "temperatures rise but day length stays exactly the same," said Marcel Visser at the Netherlands Institute of Technology in Heteren.

This is not the first example where climate change has skewed food supply and demand. Visser was the first to discover this relationship in great tits, whose caterpillar prey emerged earlier because of warming, before the birds' eggs hatched.

But "it's the first time people have shown this in mammals," Visser said.

For the animals to adapt, "they need genetic variation in the population that will push back the earliest date for reproducing," he added. "But that is a slow process. One of the worries is that climate change will occur faster than these changes can occur."