"It is an interesting approach to ensure survival," said Darrel Frost, curator in the department of herpetology at the American Museum of Natural History in New York.
Tales of these "frog transport events" have been reported from Papua New Guinea, but neither the sex nor the species were documented.
Bickford discovered this unusual form of parental care via daily surveys of the rain forest floor during a four-year stay in the Chimbu Province of Papua New Guinea, where he trained the local Pawaia people as research assistants. Here he combed plots of damp leaf litter on his hands and knees searching for frogs. When he discovered a vigilant frog father hugging his clutch, he marked the area and returned at night when the frogs are most active. But things became most interesting when the eggs hatched and the father began to "transport."
A couple of hours before sunset, Bickford or a colleague would return and mount a "24/7 vigil." Remaining about ten feet (three meters) behind, the researcher would follow the father by candlelight or with a dim red flashlight, noting how far he traveled each night and when each froglet leapt to independence.
"It was really tough, frustrating work," said Bickford. "We lost a lot of frogs with our do-not-disturb attitude."
Male Parental Care Is Rare
The world of frogs harbors a wide spectrum of parental care.
There are some species of poisonous frogs in South America where the males transport tadpoles, says Caldwell. "The males crouch down in the leaf litter next to the hatching eggs and the tadpoles wriggle up onto the father's back and he transports them to water."
Mothers of the Jamaican cave frog speciesEleutherodactylus cundallicarry their froglets from the cave into the rain forest. It is the only known example of female froglet transport.
Male parental care is rare. There are isolated examples in nature: the American burying beetle watches its larvae, and male fish do the majority of egg guarding and cleaning. Male seahorses take parental care to an extreme, assuming all responsibility for the pregnancy and actually carrying the eggs around in a chemically controlled pouch until they hatch.
Bickford anticipates that weighing the costs and benefits of such varied parenting styles will reveal exactly how such systems evolved.
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