Meeting Abstract
Behavioral plasticity, which is an important component of life-history trade-offs, is measured by comparing individual behavior across contexts to produce a reaction norm. Plasticity in aggression in the presence or absence of a predator can be critical to the trade-off between survival and reproduction. To date, only a handful of studies have measured aggression in the face of predation risk or addressed the mechanisms that might mediate this critical trade-off. We have previously shown in captive Dark-eyed Juncos (a songbird) that presence of a predator significantly increases plasma levels of corticosterone (CORT). Here we measured plasticity in territorial behavior by comparing behavior of wild male juncos during simulated territorial intrusions (STIs) that were or were not preceded by exposure to a predator. We asked whether CORT or other physiological measures (breathing rate) predicted plasticity in aggression. Birds in the study received two treatments in a random order. In one treatment we simulated the presence of a predator on a male’s territory by displaying a hawk mount and playing heterospecific alarm calls for 5 minutes. After the predator was removed, we simulated a territorial intrusion by playing back conspecific male songs and measured aggressive behavior. In the control treatment, we presented a non-threatening object and played heterospecific songs, followed by an STI. Preliminary trials comparing birds across treatments revealed lower levels of territorial behavior after seeing the hawk mount and hearing alarm calls. However, individuals differed considerably in their plasticity and mean behavior. We will report how the slope and elevation of individual reaction norms in aggressive behavior relate to CORT and other physiological measures.
