The Worldwide Phenomenon That’s Shrinking Animals

The threat of rising temperatures due to global warming will have serious effects on our tiny blue planet. Warming oceans could kill coral reefs, there might be less fresh water, more disease, less polar bears, more bark beetles, the list goes on. But here is one side effect you may not have heard of…smaller horses. That’s right, warmer temperatures could make some animals shrink. About 50 million years ago, after the dinosaurs died off, the Earth went through a series of warming events called hyperthermals, most likely from an increase of carbon. Most notably was what scientists call the Paleocene-Eocene Thermal Maximum (PETM), when temperatures rose between 5 and 8 degrees celsius, and stayed that way for almost 200,000 years. Now, scientists wanted to know how this global warming event affected the creatures living at the time, so they started studying ancient horse teeth.

And they found that, when global temperatures rose, these horses shrank. During the PETM, one ancient horse species called Sifrhippus (siff-RIP-us), shrunk by 30%. But as the Earth cooled back down, it got 76% bigger. During the less drastic Eocene Thermal Maximum 2, another ancient horse, the Arenahippus shrank by 14%, going from about the size of a dog to about the size of a cat. Yeah, ancient horses were smaller than you might have thought. So, why the shrinkage? Well, one explanation might be Bergmann's rule, which states when the climate gets warmer, mammals get smaller so they can cool off more efficiently. Rising temperatures also see an increase in drought and a decrease in plant growth, which basically mean less food and water for the animals, which could result in smaller and smaller offspring. But this is more than a fun fact, because global temperatures are on the rise again and some shrinking has already been documented in modern day animals, like sheep, goats and reindeer. Now, there are other factors that could have been in play and the same dwarfing may not happen the same way it did over 50 million years ago.

But with some climate scientists predicting the earth’s temperature increasing by up to 6 degrees by the year 2100, there may be a lot to learn from studying these shrinking horses. And if history does indeed repeat itself, more tiny horses could be on the horizon. If you’re tired of talking about the tiny, why don’t you go watch this video on some of the largest creatures to ever walk the Earth, dinosaurs. Scientists have completely rewritten how they are categorized and it’s kinda crazy. Don’t forget to subscribe, share and come back for more on Seeker..