Ecologists have suggested that as a result of global warming, species will shrink in size, as bigger creatures will have more problems losing heat.

Though the effects of the climate change are likely not to be seen for many more years, it is important to consider how to preserve larger species right now.

"Our collective actions are negatively affecting body sizes of many living species," Kaustuv Roy, a biologist at the University of California in San Diego, told New Scientist.

It is well-known that humans tend to hunt or fish larger animals, creating a selective pressure that favours the smaller ones that can reproduce while they are still small.

Several species of cod are smaller as a result of pressures of the fishing industry.

The degradation of natural environments around the world is having the same effect by limiting the amount of food available to animals, meaning smaller animals that need less food have a head start.

But, according to Roy, there is another factor that threatens the world's most impressive animals.

"Global warming may reinforce this trend towards smaller sizes through the temperature-size rule," he said.

The temperature-size rule, also known as Bergmann's rule, says that species size increases with latitude: they tend to be smaller in the tropics, and larger closer to the poles.

Bergmann's rule is debated, but one explanation for it is that larger animals have a lower surface-area-to-volume ratio, allowing them to retain more heat and fare better in cooler climes.