Reporting tomorrow (Dec. 22, 1998) in the Proceedings of the Royal Society of London Series, Cornell University biologists Stephen T. Emlen and Peter H. Wrege, and Michael S. Webster of the University of Buffalo explain the costs and benefits behind one of the animal kingdom's most extreme examples of sex-role reversal and cuckoldry.
The scientists observed wattled jacanas (scientific name Jacana jacana) over a six-year period on Panama's Chagres River, witnessing more than 1,400 noisy copulations between dominant females and much smaller males. The males were left for weeks to incubate eggs and then, as single parents, to raise chicks of uncertain paternity for two more months.
The females, meanwhile, were copulating with other males. Jacanas are practically unique among vertebrate animals, in that females pair simultaneously with a harem of males (a mating system called polyandry) and the males perform essentially all of the care of the young.
The biologists made DNA fingerprints of 465 adult and juvenile birds. Genetic fingerprinting told the scientists which jacana chicks were carrying the nesting males' genes. Specifically:
-- More than 40 percent of jacana broods that males were tending included chicks
from a different male, in cases where other males were available in the harem.
Those nonrelated chi
Contact: Roger Segelken
Cornell University News Service