Tom Mason

Striking changes in animal physiology could indicate population collapse.

Evidence for human-caused global warming can come in large forms, such as temperature readings that suggest 2014 will be the hottest year yet. Or it can come in small guises, like the shrinking ungulates of the Italian Alps.

Scientists have known for a while that hotter weather often creates smaller animals. Warm-blooded animals can drop body weight because they no longer need the protection from the chill it provides, for example; some cold-blooded creatures have their metabolisms kicked up by heat, requiring them to either eat more or lose mass. And researchers say this thinning process is now happening with stunning speed in populations of Alpine Chamois, a species of goat antelope that really needs that extra muscle, considering (fun fact!) they like to "attack the belly and flanks of their rivals in order to rip it open with the sharp hooked horns."

A team led by Tom Mason at Durham University have studied the animals' weights over three decades, and they say they're shrinking at a clip that's "striking in its speed and magnitude." A juvenile Chamois is a full quarter lighter than it was in the 1980s, a fact likely due to a swell in warm weather in the mountains, they write in Frontiers in Zoology.

A shrunken Italian goat. (Tom Mason)

Some animals drop weight during warm temperatures because of disruptions in their food supply. The Pied Flycatcher is under a threat of extinction, for instance, because the bugs they eat are appearing earlier in the year and out of sync with their migration schedules. That doesn't seem to be happening with the goats, says researcher Stephen Willis. Instead, the animals respond to heat snaps much like a human would: by resting. This cuts down on the time they spend foraging for vegetation, and "may be restricting their size more than the quality of the vegetation they eat," says researcher Stephen Willis.

So why's this matter? Less body mass means the young goats will have a harder time surviving the winter cold. And the startling way these creatures transform under altered weather could illuminate similar changes in other animals, says Mason:

"This study shows the striking, unforeseen impacts that climate change can have on animal populations.

"It is vital that we continue to study how climate change affects species such as Chamois. Changes in body size could act as early-warning systems for worse impacts to come, such as the collapses of populations."

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