Data from: Prairie dogs increase fitness by killing interspecific competitors

Interspecific competition commonly selects for divergence in ecology,
morphology, or physiology, but direct observation of interspecific
competition under natural conditions is difficult. Herbivorous
white-tailed prairie dogs (Cynomys leucurus) employ an unusual strategy to
reduce interspecific competition: they kill, but do not consume,
herbivorous Wyoming ground squirrels (Urocitellus elegans) encountered in
the prairie dog territories. Results from a 6-year study in Colorado USA
revealed that interspecific killing (IK) of ground squirrels by prairie
dogs was common, involving 47 different killers; 19 prairie dogs were
serial killers in the same or consecutive years, and 30% of female prairie
dogs killed at least one ground squirrel over their lifetimes. Females
that killed ground squirrels had significantly higher annual and lifetime
fitness than nonkillers, probably because of decreased interspecific
competition for vegetation. Our results document the first case of IK
among herbivorous mammals in the wild, and show that IK enhances fitness
for animals living under natural conditions.