"You'd think it would be hard for them to pass up a meal," Matheson said.
Males in many fish species play an active role in caring for eggs, the University of Tampa's Masonjones said. But for a bird, the emperor penguin has a bit of an alternative lifestyle. In this species, fathers care for and hatch the eggs, while female penguins head out to sea to feed.
The males spend more than two months incubating their eggs during Antarctica's harsh winter, huddling together with other males to conserve heat and energy. To prepare for the task, the male bulks up before the breeding season to 40 kilograms (88 pounds). He'll lose half of this weight during his two-month egg-sitting fast.
"They are animals of extreme limits," said Paul Ponganis, a research physiologist at Scripps Institution of Oceanography in La Jolla, California. Emperor penguins, besides having extensive parenting duties, are the best divers in the bird world, dropping down to 500 meters (1,640 feet). "In addition," Ponganis said, "they are beautiful animals."
Among mammals, the South American marmoset may win the prize for most-involved dad. The marmoset mother starts pulling away from her twins a few weeks after they're born. Then "the male steps up," said Jeff French, a primatologist at the University of Nebraska in Omaha.
The male carries, feeds, and grooms the infantswith help from their older siblingsand may even act as a midwife during birth, grooming and licking the newborn marmosets.
One reason for the marmoset father's high involvement may be the high cost of birth for the mother, whose twin babies make up 25 percent of her body weight. "It's like a 120-pound (55-kilogram) woman giving birth to a 30-pound (14-kilogram) baby," French said.
"And on top of that, two weeks later, she's pregnant again," French said. Unlike other speciesin which nursing can provide a kind of temporary birth control for new momsmarmoset mothers can get pregnant right away.
French has been looking at the relationship of hormones to the marmoset male's parental aptitude.
By analyzing the levels of testosterone in male urine, French said, he's found that after a female conceives, the male's testosterone drops by half. The effort a marmoset father puts into his offspring may also be influenced by his testosterone levels, French says.
While none of these animal fathers likely have a tie to show for their efforts, they may be able to pass along a few sets of genes.
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