Testosterone, aggression, and territoriality in male Western Screech-owls (Otus kennicottii): results from preliminary experiments

Abstract

Using a hormone implant protocol, we created treatment groups in which circulating levels of testosterone (T) were increased, decreased, or maintained at normal levels (controls) in male Western Screech-owls (Otus kennicottii). Owls were exposed to tape-recorded vocalizations of a conspecific, to which territory holders responded with aggression. Several measures of the intensity of aggression (e.g., approach and vocal behavior) provided the basis for comparisons among treatment groups. Exogenous T elicited increased aggression during the breeding and nonbreeding seasons. Although male owls remained sensitive to exogenous T during the nonbreeding season, aggression also occurred in the absence of circulating T at this time.

Parent Publication

• Biology and conservation of owls of the Northern Hemisphere: 2nd International symposium

Citation

Herting, Brian L.; Belthoff, James R. 1997. Testosterone, aggression, and territoriality in male Western Screech-owls (Otus kennicottii): results from preliminary experiments. In: Duncan, James R.; Johnson, David H.; Nicholls, Thomas H., eds. Biology and conservation of owls of the Northern Hemisphere: 2nd International symposium. Gen. Tech. Rep. NC-190. St. Paul, MN: U.S. Dept. of Agriculture, Forest Service, North Central Forest Experiment Station. 213-217.