The more closely knit an animal society is, and the more interdependent its members, the higher the rate of taxation. Among bell miner birds of Australia, for example, pairs of breeding adults are assisted at the nest by several youthful helpers, usually male. The helpers provision the couple’s fledglings with a steady supply of lerp, sugary casings secreted by plant-sucking insects. And though some scientists had wondered whether lerp wasn’t basically a junk food, offered up to the young bell miners as much for show as for substance, researchers report in the March issue of Animal Behaviour that lerp is, in fact, as important to the fledglings’ growth as is the meatier arthropod prey supplied by their parents. By all evidence, the helper birds are honestly “paying to stay,” trading a valuable currency for the right to remain within the aggressively guarded precincts of a bell miner breeding colony, with the hope of better times and personal propagation opportunities ahead.

Or at least of averting personal injury. Among another Australian species of cooperatively breeding birds, the superb fairy-wren, dominant males notice when their helpers are less than superb about paying their taxes. Should a helper fail to feed and groom the dominant’s nestlings, or to give an alarm call on seeing intruders enter the territory, the dominant male will angrily chase, harass and peck at the helper, for up to 26 hours at a time. In the case of the highly social cichlid fish, fear of punishment inspires delinquent helper fish to ostentatiously redouble their contributions to the communal nest, their digging in the sand, their cleaning and fanning of the eggs  rather like politicians who suddenly pony up three years of back taxes for themselves, the nanny and the gardener. “If they don’t pay their bill, there will be punishment,” said Michael Taborsky of the University of Bern, “so they try to pre-emptively appease the dominant individuals in the group.”

If hope and fear don’t guarantee compliance, there’s always embarrassment. Vampire bats are famous for their willingness to regurgitate a blood meal to feed fellow bats that are down on their luck. In fact, hiding one’s wealth is a problem. A fully fed vampire bat is as bloated as a fraternity water balloon, and the bats appear to rub bellies to see who is in a position to share. “It’s hard to cheat when your stomach is obviously distended,” Dr. Santos said.

It’s also hard to cheat when you live in a small band of big-brained, sharp-eyed individuals, as humans did for vast stretches of our past, which may help explain why we are so easily taxed. “There’s not a human society in the world that doesn’t redistribute food to nonrelatives,” said Samuel Bowles, director of the behavioral sciences program at the Santa Fe Institute. “Whether it’s through the state, or the chief, or a rural collective, or some other mechanism, food sharing of large nutritional packages is quite extensive and has been going on for at least 100,000 years of human history.” In hunting and foraging cultures, the proportional tax rate is so high, said Dr. Bowles, that “even the Swedes would be impressed.”

Take the case of the Ache tribe of Paraguay. Hunters bring their bounty back to a common pot. “The majority of calories are redistributed,” he said. “It ends up being something like a 60 percent income tax.”