Over the years, one of the lingering questions in biology has been why some species, such as humans and dolphins, evolved larger brains relative to their body sizes as opposed to blue whales and hippos with smaller sized brains. Many have thought that bigger brains are connected to intelligence and now a study by researchers at the University of Wyoming supports this theory.

The study uses data gathered from nine different zoos and 140 animals from 39 different mammalian carnivore species including polar bears, tigers and wolves, all of which were presented with a novel problem-solving task. Each animal was given 30 minutes to try and retrieve food from a closed metal box that could only be opened by sliding a bolt latch. Inside of the box was a piece of food that was known to be the favorite of the animal being tested.

The results showed that species with larger brains relative to their body size did better on the task than species with smaller brains in comparison to body size.

"This study offers a rare look at problem solving in carnivores, and the results provide important support for the claim that brain size reflects an animal's problem-solving abilities and enhance our understanding of why larger brains evolved in some species," Sarah Benson-Amram, lead author of the study, said in a press release.

"Overall, 35 percent of animals (49 individuals from 23 species) were successful in solving the problem," added Ben Dantzer, co-author of the study. "The bears were the most successful, solving the problem almost 70 percent of the time. Meerkats and mongooses were the least successful, with no individuals from their species solving the problem."

Ultimately, larger animals were less successful than animals with smaller bodies and manual dexterity was not connected to success at the task.

The study also examined the possibility that species living in larger groups are better at problem solving, a hypothesis called "the social brain hypothesis."

"If the social brain hypothesis is correct, then we would expect that species that live in larger social groups would be more intelligent," said Kay Holekamp, co-author of the study. "However, we did not find any support for the social brain hypothesis in this study. There was no indication that social group size influenced problem-solving abilities."

The findings were published in the Dec. 16 issue of the Proceedings of the National Academy of Sciences.