White-tailed prairie dogs -those stand-up, nose-wiggling nibblers of grass - turn out to be routine killers of baby ground squirrels. And the strongest sign of successful white-tailed motherhood could be repeat ground squirrel kills, researchers say. At a Colorado prairie dog colony, females that kill at least two ground squirrels raise almost three times as many offspring during their lives as nonkiller females, says John Hoogland of the University of Maryland Center for Environmental Science in Frostburg. The "serial killers," as he calls repeat-attack females, rarely even nibble at the carcasses and aren't getting much, if any, meat bonus. Instead, the supermom assassins may improve grazing in their territories by reducing competition from grass- j snitching ground squirrels, Hoogland and Charles Brown of the University of Tulsa in Oklahoma propose in the March 30 Proceed- j ings of the Royal Society B.
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