The influence of familiarity on socially monogamous behavior of red-backed salamanders

Previous research suggests that some individuals of the red-backed salamander (Plethodom cinereus) ill Virginia form socially monogamous relationships. We investigated if living together for 9 d is sifficient to establish such) it relatiollshill. In our. first laboratory experiment, we tested two hypotheses: that increased familiarity, behween territorial males and female intrudcrs would lead to (1) reduced aggression and (2) increased touching (conciliation) 1)), the males, as expected ill social monogamy. We posed the same two hypotheses ill our second experiment for territorial females responding to male intruders. When]tell residents and intruders first met, residents ill both experiments spent more time in threat postures than they (fill 9 d latcr. Thus, fainiliarity led to decreased aggression toward intruders of the opposite sex. We then removed the]now familiar first intruders and replaced then with unfamiliar second intruders. Aggression by residents in both experiments increased, suggesting that male and female, residents call distinguish between it familiar and an imfamiliar intruder of the opposite sex. When we shortly thereafter removed the second intruders and, 2 d later, reintroduced the original first intruders, in botii experiments residents maintained low levels of aggression. This suggests that they could remember the first intruders after 2(1 of separation, even with the intervention of an unfamiliar member of the opposite sex. We found no difference ill touching beliavior for residents ill either experiment. Thus, our first hypotlicsis (Concerning reduced aggression) was supported while our. second hypothesis (concerning increased touching) was not. Therefore, the formation of socially monogamous relationships may), require longer than 9 d of living together an(d/or it 'choice' of partners, which would be possible ill the natural habitat but was randomized ill our experiments.