Monday, August 23, 2010

Ball 12. The Truthiness of Animal Signals

Another one from the bird files:

The natural world has no equivalent of the Federal Trade Commission to monitor truth in advertising. Boasts about reproductive fitness—elaborate plumage, antlers and other ornaments—must be sincere because the physical costs of producing gaudy displays are so high. Animals with the most impressive finery have the physical robustness necessary to develop the flourish while fighting environmental threats like predators and infections.

Biologist Gary Bortolotti, of the University of Saskatchewan, says:

Signals have to be honest or cheat-proof and it is their cost that prevents cheating. Peahens like peacocks with big trains. Only the best quality males can pay the price and grow a big train. If it were cheap every male would grow one.
(See Ball 11. Begging to Differ)

As intuitive as it seems, however, proving the honesty of ornamentation is tricky. But Bortolotti and his colleagues have found compelling new evidence that, at least for one species of game bird, the cocks of the walk really strut the talk

The study found that the size (and, presumably, the attractiveness to females) of decorative combs above the eyes of red grouse depend largely on how much recent environmental pressure the birds endured. In particular, the researchers showed that levels in the birds’ feathers of the stress hormone corticosterone were linked to the height of their crimson courtship tufts. What’s more, the study also found that infecting the grouse with parasites diminished the size of the ornamental plumage—consistent with the idea that the wage of cultivating displays is reduced immunity.

We all know too well the important role of stress is in our own lives. How well an animal copes with the many, often concurrent, challenges in the environment may be one of the more meaningful, if not the best, overall measure of its ‘quality’ and fitness potential.

The researchers reported their findings in PLoS ONE.

Thursday, August 12, 2010

Ball 11: Begging to Differ — New research challenges conventional wisdom about why animal babies grovel for food

Begging may be distasteful in polite society, but it’s a routine means of communication between animal offspring and their parents. Bird experts have assumed for two decades that they understood why chicks beg for food. But a group of scientists say the accepted theory is almost certainly wrong.

The prevailing view, solidly in place since the early 1990s, is that babies beg “to indicate how pathetic and needy they are,” says Douglas Mock, a behavioral ecologist at the University of Oklahoma. Their pleas signal parents to their most pressing desires—hunger to be sated—triggering a care-giving response that nature can’t ignore.

That theory resonated with our own cultural values,” Mock says. “We claim to love all of our children equally, we try to get everybody through by giving extra to the ones that need the most.

The problem, Mock says, is that the evidence doesn’t support the hypothesis.

I’ve been doing field work since 1970s and I seldom see it working the way these happy faced thoughts seem to be taking us.

Virtually any life form that features progressive provisioning of dependent offspring from birds to mammals, even insects and probably a lot more plants than anybody has contemplated, Mock adds

Researchers can’t measure true need in animals. After all, one more grub in the gullet is unlikely to improve a baby indigo bunting's prospects to a detectable degree, Mock notes. But the basic message that the chick is ready for another gulp is easy to test. And scientists can observe the way adult birds respond to the signals of their chicks.

Mock says:

If the signal of need idea is correct, then parents should do whatever they need to do to get food to the runts, but it turns out that parents more often than not bias deliveries of food to the bigger chicks.

Instead, Mock and his colleagues believe the true impetus for begging could be the opposite of a signal of need. Or, they say, it may be nothing more than a reporting of desire, like a child's letter to Santa.

In other words, he says, perhaps the only thing a begging baby bird communicates is the fact that it’s hungry. Yet the parents look at which baby is doing well and ask themselves, Is this a season that the family budget can support everyone, so I should shunt food to the runt, or is this a typical lean season when feeding the runt is a mistake?

Mock’s group, who presented its argument at a recent meeting of the Animal Behavior Society, takes another whack at the conventional wisdom about begging.

For a signal to be honest, the energy required to produce it can’t outweigh the potential upside. Consider the peacock, whose gaudy tail feathers boast of genetic fitness—yet serve as an “eat here” sign to predators.

Only a really strong male can carry around the drag queen paraphernalia. In effect, he's demonstrating that he can escape from predators even with the outrageous plumage. And that may indicate that his offspring will escape predators as well, Mock says.

For peacocks, the prospect of more frequent mating is worth the risks of ostentation, Mock says. But what’s the upside of a chick that so obviously advertises its need, in this case, hunger? Not much, he says.

The chick is supposedly announcing that it is weak and imperiled. It's giving a supposedly costly signal that it can ill afford to give, because it's so weak, but hoping to reap a disproportionate windfall.

Mock, who has spent his career studying siblicidal herons and egrets—sib-killing is also found in various hawks, owls, cranes, boobies and laughing kookaburras—says that for certain bird species, displays of weakness in the nest are death sentences.

If nothing else, one wonders why [a begging chick’s] stronger nest mates are suppressing their own, easily affordable signals, thereby stealing the spotlight and the meal. Sibling altruism certainly can evolve, but that cannot be assumed.

Wednesday, August 4, 2010

Ball 11. How Large is the trade in illegal wildlife?

One smuggler was caught with a single, scaly clam, another with three live iguanas in his artificial leg. Some thieves had larger ambitions—1.05 million queen conch, fat from 100,000 frogs, 68,000 kilograms of pangolin meat.

These grim statistics come from a new, comprehensive look at the illicit global trade in wildlife—a sub rosa industry estimated to be worth as much as $20 billion each year, second only the market for illegal drugs. Beyond the economic cost, researchers said, the stream of trafficked animals, from Southeast Asia in particular, poses a potential source of emerging or yet-unseen viruses that could make the jump to people with lethal consequences.

“From 1996 to 2008, more than 191,934 live animals were traded illegally from ‘disease hotspots’ in Southeast Asia,” said Gail Rosen, a Brown University graduate student and co-author of the study. “With no quarantines or certification systems, there is no way to know what diseases these animals may carry.

The study, reported in the journal EcoHealth, reviewed 12 years of seizure records, spanning the period 1996 to 2008, compiled by Traffic, an international wildlife monitoring program. In all, researchers identified 967 seizures involving everything from tiger pelts to live birds.

Mammals and products from these animals were the targets of choice for wildlife smugglers, accounting for 51% of all seizures. The bulk of those involved skins from big cats and elephant ivory. Among live animals, however, reptiles made up nearly 70% of seizures. Customs officials seized more than 72,000 live turtles and tortoises—more than enough to fill every seat in the Louisiana Superdome, Rosen noted.

“If we can understand the dynamics and scale of the trade, then we can improve legal enforcement,” Rosen says. “This knowledge can also help us anticipate problems like species invasions before they happen, so that we can work to prevent them.”

Tuesday, August 3, 2010

Retractions R Us

The estimable Dr. Ivan Oransky, executive editor of Reuters Health and founder of Embargo Watch, and I have launched a new blog: Retraction Watch.