Will climate change bring huge spiders, tiny horses and giant snakes?

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Could climate change bring huge spiders and snakes, or shrunken mountain goats? Apparently, there’s some science behind the wacky news headlines.

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Carbon Brief

Rising temperatures have caused mountain goats in the Alps to ‘shrink’ by up to 25 per cent, according to new research. The news follows on from recent stories of how climate change could bring us  huge spiderstiny horses and  giant snakes.

Despite the slightly ridiculous headlines such research prompts, there is actually some science behind it all.

Behavioural change

So, first things first; rising temperatures haven’t actually caused any goats to shrink per se. Rather the research, published in the journal Frontiers in Zoology, finds that young goats aren’t as big as they were 30 years ago.

Scientists analysed records of the Alpine Chamois goat in the Italian Alps and found they were as much as 25 per cent smaller than goats of the same age in the 1980s.

Two things are surprising about their smaller size, the researchers say: that the change has happened so quickly, and that it wasn’t caused by a lack of food.

Spring and summer maximum temperatures increased by as much as 4 degrees in the region during that time, but the study found the change in climate had no impact on food availability.

The reason they suggest the goats have got smaller is that in hot temperatures the goats prefer to lounge in the shade rather than searching for food. The researchers think that’s the reason they’re not putting on as much weight.

The size of the goats is important because they need to build up sufficient reserves to survive the harsh winters.

Bergmann’s Rule

So is it just goats that need to be concerned? Well, research suggests that most mammals follow ‘ Bergmann’s Rule‘, which states that the body size of mammals decreases as temperatures rise.

This is because smaller animals have a larger surface area of skin compared to their overall size, making it easier to lose heat when temperatures are high.

Fossil records have shown that horses, for example, became around 30 per cent smaller during a period of around 6 degrees of warming about 55 million years ago.

But evidence of mammals changing size as a result of recent warming is currently thin on the ground. A study of 52 populations of meat-eating mammals around the world found only a few had shown any significant reduction in body size, and this couldn’t be linked directly to rising temperatures.

Fossil records

What about creatures that aren’t mammals? During the same period of warming that gave the world tiny horses, fossils records have revealed that huge reptiles stalked and slithered their way across the Earth.

One example was a giant plant-eating lizard, which was up to six feet long and weighed up to 60 pounds. The warm temperatures allowed these mega-lizards to thrive, providing them with an abundance of food to eat, the researchers say, although it was also an absence of predators also allowed them to grow so large.

A similar, if much much smaller, effect has been seen in the UK this year. Reports of larger-than-average spiders this summer have also been linked to temperatures. Warmer summers has meant there is more food available for spiders, and fewer have been killed off by cold.

So while there are examples of species being affected by a changing climate, you probably shouldn’t worry quite yet about fighting off huge snakes like Jon Voight in Anaconda, as the Daily Mail previously intimated.

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Jon Voight in the film Anaconda. Fangoria.

Mason et al. (2014) Environmental change and long-term body mass declines in an alpine mammal, Frontiers in Zoology, doi:10.1186/s12983-014-0069-6

This article was originally published on Carbon Brief

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