Humans aren't the only mammals with a sweet tooth. Omnivores from beagles to grizzlies can detect a wide range of flavors and enjoy the taste of sugar. But other mammals with narrow carnivorous diets have been subjected to evolution's "use it or lose it" decree. These meat-eaters are genetic mutants without working taste receptors for sweets. Not only do they not want your cupcake, but they can't even taste it.
Researchers led by Peihua Jiang at Monell Chemical Senses Center in Philadelphia wanted to know how often evolution has removed tastes from animals' repertoires. Omnivores such as humans can detect five basic tastes: sweet, sour, bitter, salty, and umami (a meaty flavor). Previous studies had shown that cats, though, are indifferent to sweetness. Cats were also known to have a mutation in the gene for the sweet taste receptor, rendering it nonfunctional. Had other carnivores' sweet receptors met the same fate?
For 12 carnivore species, the authors sequenced the genome section containing the sweet taste receptor. In just 5 of these species, the gene was intact. These included the aardwolf, Canadian otter, spectacled bear, raccoon, and red wolf.
It was presumably not practical to round up all these animals and give them tests to confirm that they like sugar. But the authors were able to test four spectacled bears, a charismatic South American species. When given a choice between a bowl of plain water and a bowl of sugar water, the bears strongly preferred the sugar water. They even enjoyed some artificial sweeteners (Splenda, for instance, but not NutraSweet).
