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Postponing Breeding May Make Good Evolutionary Sense

A mystery that has puzzled evolutionary biologists for years -- why some animals postpone breeding in order to stay home and help their families -- may actually make good evolutionary sense.

Cornell University biologist Paul Sherman figured young human animals would be intrigued, too, so he drew on the latest research about the phenomenon of cooperative breeding -- including some of his own groundbreaking studies -- to co-author a new children's book, Animal Baby Sitters (Franklin Watts, September 2001).

"People seem to expect animals to look out only for themselves. When we see what looks like unselfish, altruistic behavior -- animals that postpone starting their own families to help care for others -- we become extremely curious," says Sherman. A professor of neurobiology and behavior, Sherman wrote the new book with his next-door neighbor, children's book author Gail Jarrow.

"It took repeated studies of cooperative breeding in different species, plus a theoretical breakthrough known as kin selection, to figure out the puzzle of reproductive altruism," Sherman continues. "It now appears that when opportunities to disperse and breed independently are limited, individuals stay at home. This is how extended families form. By assisting their parents in raising little siblings, animal baby sitters are helping perpetuate their own genes at a time in their lives when they would be unable to rear their own offspring. They also may be learning parenting skills that will come in handy when their turn to breed finally comes."

The scientific data in Animal Baby Sitters come straight from investigators doing field and laboratory research, Sherman and Jarrow emphasize -- experts like Glen Woolfenden, who has studied Florida scrub jays for 30 years to learn, among other things, why scrub jay parents get most of the baby-sitting help from their older sons; and John Hoogland, a leading specialist on the prairie dogs of South Dakota, where a "kiss" is the identifying password for members of closely related coteries and relatives cooperatively attack and chase away intruders.

Cornell-based research figures prominently in the book's examples of family cooperation. Kevin McGowan, a research associate in the Cornell Lab of Ornithology, contributed findings from his research with the American crow. According to McGowan, crow offspring in some areas stick around the home nest for one or more breeding seasons to help their parents feed the next generation and ward off predators. But in other places, breeding pairs of crows get no help from their kids.

"No one is sure why these differences exist, although they probably involve conditions such as food and territory availability," the authors write, hinting at a potentially exciting research project for the next generation of scientists.

Sherman's 20 years of research with naked mole-rats was groundbreaking in more ways than one. Only after moving colonies of the nearly sightless and hairless creatures -- from subterranean tunnels in northeastern Africa to laboratories at Cornell -- could he study at close range an animal society where all the "helpers" are physically able to breed, but most never will.

"For a juvenile naked mole-rat, sticking around the natal burrow can pay off," Sherman and Jarrow observe. "It may eventually get the chance to produce its own young if one of the breeders dies. Waiting for this opportunity and helping its queen mother rear little brothers and sisters is its safest bet."

Writing for children is a bit "outside the box" for most active scientists, but Sherman and Jarrow find making the excitement of behavioral ecology accessible to the next generation to be both challenging and rewarding. Together they have written about a dozen articles for children's magazines and have authored two previous books: The Naked Mole-Rat Mystery (Lerner Publishing Group, 1996) and Naked Mole-Rats (CarolRhoda Books, 1996). The authors are betting that some of their young readers will be intrigued by animal stories about behaviors that pose many questions and offer some -- but not all -- of the answers.

"It's never too early," Sherman says, "to get children hooked on the magic and mysteries of behavioral biology." - By Roger Segelken

Related website:

Cornell Dept. of Neurobiology and Behavior

[Contact: Roger Segelken]

13-Nov-2001

 

 

 

 

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