Some Carnivores Are Better Than Others at Unlocking Dinner
Spotted hyenas are the animals that got Sarah Benson-Amram thinking about how smart carnivores are and in what ways.
Dr. Benson-Amram, a researcher at the University of Wyoming in Laramie, did research for her dissertation on hyenas in the wild under Kay E. Holekamp of Michigan State University.
Benson-Amram博士是拉勒米市怀俄明州立大学的一名研究人员，在密歇根州立大学生物博士Kay E. Holekamp的带领下，她在野外调查鬣狗以完成她的学位论文。
Hyenas have very complicated social structures and they require intelligence to function in their clans, or groups. But the researchers also tested the animals on a kind of intelligence very different from figuring out who ranks the highest: They put out metal boxes that the animals had to open by sliding a bolt in order to get at meat inside.
Only 15 percent of the hyenas solved the problem in the wild, but in captivity, the animals showed a success rate of 80 percent.
Dr. Benson-Amram and Dr. Holekamp decided to test other carnivores, comparing species and families. They and other researchers presented animals in several different zoos with a metal puzzle box with a treat inside and recorded the animals’ efforts.
Benson-Amram博士和Kay E. Holekamp博士决定对其他种类科目的肉食动物进行对比试验。研究团队在多个动物园中进行了相同的试验——给动物装有食物的金属箱，并记录下了它们的行为表现。
They tested 140 animals in 39 species that were part of nine families. They reported their findings on Monday in the Proceedings of the National Academy of Sciences.
They compared the success rates of different families with absolute brain size, relative brain size, and the size of the social groups that the species form in the wild.
Just having a bigger brain did not make difference, but the relative size of the brain, compared with the size of the body, was the best indication of which animals were able to solve the problem of opening the box.
Bears did the best, followed by the family that includes raccoons and coatimundis, results that any homeowner who has garbage cans out in the yard might expect. The family that includes weasels and otters came in third.
The researchers expected that result, but they were surprised by another finding. Animals that lived in complex social groups did not do particularly well.
Sadly, for any fan of “Meerkat Manor,” the family Herpestidae, which includes meerkats and mongooses, was the least successful at solving the puzzles.
Dr. Holekamp said that the result did not support an idea called the social brain hypothesis that living in complex social groups leads to increased relative brain size and problem solving ability. But Robin Dunbar at the University of Oxford, the anthropologist and evolutionary psychologist who proposed the hypothesis, said it was already known that it did not apply to carnivores.
Dr. Holekamp said the findings add to evidence that intelligence is not one quality, and that different tasks depend on different parts of the brain and different abilities. Keeping track of a social hierarchy is one thing, whereas solving a physical puzzle is something else entirely.