By Natalie Angier, The New York Times, May 25, 2015
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| A northern flicker nest |
One of the biggest mistakes my husband made as a new father was to tell me he thought his diaper-changing technique was better than mine. From then on, guess who assumed the lion’s share of diaper patrol in our household?
Or rather, the northern flicker’s share. According to a new report in the journal Animal Behaviour on the sanitation habits of these tawny, 12-inch woodpeckers with downcurving bills, male flickers are more industrious housekeepers than their mates.
Researchers already knew that flickers, like many woodpeckers, are a so-called sex role reversed species, the fathers spending comparatively more time incubating the eggs and feeding the young than do the mothers. Now scientists have found that the males’ parental zeal also extends to the less sentimental realm of nest hygiene: When a chick makes waste, Dad, more readily than Mom, is the one who makes haste, plucking up the unwanted presentation and disposing of it far from home.
“It takes away microbes, removes smells that might alert predators, and makes the whole nest much cleaner,” said Elizabeth Gow, a postdoctoral fellow at the University of British Columbia and an author on the new report. “It’s an important aspect of parental care that we often forget about.”
The new work reflects a growing interest in what might be called animal sanitation studies — the exploration of how, why and under what conditions different species will seek to stay clean, stave off decay and disrepair, and formally dispose of the excreted and expired. Nature may be wild, but that doesn’t mean anything goes anywhere, and many animals follow strict rules for separating metabolic ingress and egress, and avoiding sources of contamination.
Researchers have identified honeybee undertakers that specialize in removing corpses from the hive, and they have located dedicated underground toilet chambers to which African mole rats reliably repair to perform their elaborate ablutions.
Among chimpanzees, hygiene often serves as a major driver of cultural evolution, and primatologists have found that different populations of the ape are marked by distinctive grooming styles. The chimpanzees in the Tai Forest of Ivory Coast, for example, will extract a tick or other parasite from a companion’s fur with their fingers and then squash the offending pest against their own forearms.
Chimpanzees in the Budongo Forest of Uganda prefer to daintily place the fruits of grooming on a leaf for inspection, to decide whether the dislodged bloodsuckers are safe to eat, or should simply be smashed and tossed. Budongo males, those fastidious charmers, will also use leaves as “napkins,” to wipe their penises clean after sex.
Leaves may grow on trees, but serious sanitation work can be costly, as the new study of flickers revealed. Baby woodpeckers, like many nestlings, deposit their waste in the reasonably manageable form of fecal sacs, the mess contained in a gelatinous outer coating “like a water balloon,” Dr. Gow said. “It makes for easier removal from the nest.”
Ah, but what prodigious sac factories the little birds can be. Whereas human parents may change a daunting 50 to 80 diapers a week, flicker parents remove the same number of fecal sacs a day, each time venturing some 100 yards from the nest and risking exposure to predators like hawks.
Dr. Gow determined that father flickers performed about 60 percent of the sanitation runs, spent up to an hour a day on the task, and, in the event of the untimely death of a mate, were happy to let the sacs stack up. “When they’re really strained,” Dr. Gow said, “and the options are, remove fecal sacs or feed the kids, they’ll feed the kids.”
Good hygiene is a matter of context. Luigi Pontieri of the Centre for Social Evolution at Copenhagen University and his colleagues study the pharaoh ant, a tiny, highly successful invasive species that originated in Southeast Asia but in three centuries of piggybacking on human activity has managed to colonize the world.
Unlike most ants, pharaoh ants don’t build structured nests or defend territory. “They’ll live wherever they can, in places other ants avoid,” Dr. Pontieri said. “They’ll live in trash, in layers of old food, in electric plugs, between the pages of books. You can even find a colony inside a mealworm, which they ate their way into.”
Sometimes, Dr. Pontieri said, “it can be really disgusting to work with these ants.”
Delving into the secrets of the ants’ capacity to stay healthy no matter where they roam, the researchers discovered that the insects seemed to resist disease in part through a kind of vaccination program. As the researchers reported in the journal PLOS One, when the ants were given a choice between nesting in clean soil or soil littered with the corpses of pharaoh ants killed by fungal disease, the living ants chose to nest with the fouled fallen.
Uninfected cadavers didn’t hold the same appeal; the pharaoh ants wanted dead comrades with spores.
“We think the ants were actively seeking small doses of the pathogen,” Dr. Pontieri said. “It might be a way of getting immunized against a disease that could kill them.”
Yet stable property can have its benefits. Gene E. Robinson, a professor of neurology and entomology at the University of Illinois, said that when formerly free-living honeybees first “took the show indoors” by constructing thermally controlled hives, they gained the power to coddle their young but faced new challenges of hygiene.
“Dead bees that once dropped harmlessly to the ground could now accumulate in the hive,” Dr. Robinson said. The social insects solved the problem by establishing a tiny corps of undertakers: bees in late middle age and of a particular genotype that has yet to be decoded.
The undertakers tirelessly patrol the honeycomb corridors, lift up any newly deceased bees they encounter, totter off with a payload fourfold heavier than the average pack of pollen, and then dump the bodies some 20 feet from the hive, anywhere from 25 to 100 times a day.
Bees are also careful not to soil the hive with personal droppings, and some species even engage in “cleansing flights.” Hundreds or thousands of hive members swarm out to evacuate en masse — a practice that more than 30 years ago prompted Alexander M. Haig Jr., who was the secretary of state, to mistake the yellow-brown showers in Laos as an act of chemical warfare.
African mole rats, the mammalian equivalent of social insects, cannot risk venturing outdoors to avoid sullying their elaborate underground housing complexes, so they build dedicated lavatories instead. When one toilet chamber is too full, said Chris G. Faulkes of Queen Mary University of London, a leading expert in the evolutionary ecology of African mole rats, the workers will “backfill it, seal it up and make a new one.”
“They keep the burrows very tidy,” he added.
Like its human equivalent, a mole rat toilet chamber is also a place to primp, and a freshly relieved animal will spend time energetically grooming its head, flanks and belly, before marking its recent visit with just a touch of anogenital fluid daubed on the bathroom floor.
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