The approach and proximity behavior of spiny mouse pups (Acomys cahirinus) toward strange neonates: Effects of gender and species of stimulus pup

Abstract

Three experiments were done using male and female spiny mice (Acomys cahirinus) as subjects observed in the presence of both a male and a female newborn stimulus pup. Stimulus pups were either strange spiny mice or Norway rats (Rattus norvegicus). The object of the experiments was to record physical approach and proximity behavior. Individual spiny mouse pups were observed in a small cage with two unfamiliar neonates (one of each sex) as stationary stimuli. Between- subjects variables included the gender and age (1-2 days; 10-11 days) of the spiny pup. The dependent measure used throughout was the duration of time, within a 5-min exposure session, that each subject occupied two proximity zones established around each stimulus pup. In Experiment 1, spiny pups were tested with live newborn rat pups as choice stimuli, and the results indicated that 1- to 2-day-old female spiny pups spent significantly more time positioned near the opposite-sex pup than near the same-sex stimulus rat pup. Experiment 2 was a replication using dead newborn rat pups as choice stimuli to remove any behavioral cues that might have contributed to sex differentiation by female spiny mice. The choice behavior of 1- to 2-day- old female spiny mice was similar to that obtained in Experiment 1. Experiment 3 was a replication with live newborn spiny mice as stimuli; however, no choice preferences were found, suggesting that the sex-differentiation capability observed in Experiment 1 may have been exclusively interspecific. These findings were discussed in terms of sex differences among spiny mouse pups for measures of neophobia and exploratory and predatory behavior and in terms of an odor-based sex-discrimination capability.