What could boost a cat's ego more than it already is? Probably being told it is better than a dog. Well, as it turns out, in the past that wasn't far from the truth. When members of the felidae family traveled from Asia to North America, their natural hunting prowess decimated the dog family population – with as many as 40 of their species driven to extinction. Interestingly, their arrival played a greater role than climate change in canidae evolution.

When these ferocious kitty cats arrived in North America, their superior predatory ability increased competition for food. Since food resources, or prey, were limited, this meant that not every predator was going to sleep with a full belly. Unfortunately for the canids, they were the ones left struggling for food, and their options were to either adapt or die out. Therefore, the competition to obtain food is inevitably linked with canid evolution. This research comes from the examination of over 2,000 fossils, and can be found in the Proceedings of the National Academy of Sciences.

The scientists remarked that a rate of extinction this significant is more often associated with a dramatic change in climate. "We usually expect climate changes to play an overwhelming role in the evolution of biodiversity. Instead, competition among different carnivore species proved to be even more important for canids," explained lead author Daniele Silvestro from the University of Gothenburg.

Until the unwelcome arrival of felids in the area, canids were doing pretty well in North America. They originated on the continent around 40 million years ago, and were at their most diverse 22 million years ago, boasting more than 30 species. Only nine species remain today.

As felids threatened the survival of canids, they evolved in response – in particular, their body size increased, with some exceeding 30 kilograms (66 pounds). This made them some of the largest carnivores in North America.

Today, several large carnivores face frightening risks of extinction. However, none of the current trends match the pattern of ancient canid extinction. In Africa, for example, canids such as wild dogs are constantly in competition with felids such as lions, rather than being suddenly introduced to them.

^{Central Image: One of the canid skulls studied. Michele Silvestro.}

Correction: We previously, incorrectly, included hyenas with canids. This has been removed.