Vocalizations of infant brown rats, but not infant house mice, enhance rodent captures in sex pheromone-baited traps

Abstract

Synthetic replica of rat pup, Rattus norvegicus, vocalizations reportedly increase captures of wild rats in traps baited with natural scent of adult female rats. Here we tested the hypotheses (1) that synthetic calls of house mouse pups, Mus musculus, increase captures of wild house mice in traps baited with synthetic sex pheromones of mice, and (2) that synthetic rat pup calls increase captures of wild rats in traps baited with synthetic rat sex pheromones. Analyses of vocalizations from isolated 2- to 4-day-old mouse pups revealed frequency components almost exclusively in the ultrasonic range. In laboratory experiments, playback recordings of these calls, and synthetic replica thereof, each tested versus a silent control or a constant 60-kHz tone, induced phonotactic, arrestment and speaker-contact responses by both “pup-experienced” and “pup-naïve” adult female and adult male mice. In field experiments, synthetic mouse pup calls had no effect on captures of adult and juvenile male mice in female mouse pheromone-baited traps, and reduced captures of juvenile female mice in male mouse pheromone-baited traps. In analogous field experiments with brown rats, traps baited with both synthetic rat pup calls and synthetic rat sex pheromones captured 3.75-times (15 vs 4) more male rats and 2.5-times (15 vs 6) more female rats than traps baited with synthetic sex pheromone alone. We show that synthetic mouse pup vocalizations cannot be exploited as a trap lure to enhance trap captures of mice. Conversely, synthetic rat pup vocalizations enhance the attractiveness of synthetic sex pheromone lures to male and female rats and could become part of integrated brown rat management.