Parental responses of hispid cotton rats (Sigmodon hispidus) to intrusion by red imported fire ants (Solenopsis invicta) into simulated nests

Abstract

modon hispidus were observed in simulated nests at 24, 72, and 120 hours of offspring age in the presence (5 different litters observed at each age, n = 15) and absence (6 unique litters observed at each age, n = 6) of fire ants (Solenopsis Lnvicta). No cases of infanticide or nest abandonment were observed during the experiments. In the absence of fire ants, females spent on average 86% of their time with the pups, and still spent 52% of their time in the nest attending the pups on day 5. When fire ants were present, two maternal strategies were observed: (1) 87% (13/15) of the females removed their offspring from the nest box and (2) 13% (2/15) remained in the nest box with their offspring. In both strategies, females removed fire ants from the pups and ate fire ants off all the surfaces of the nest box. Paternal assistance was rare both in the presence and absence of fire ants. Cotton rat success in dealing with fire ant intrusion resulted from effective maternal care and the precocial nature of the offspring.