| The purpose of these studies was to examine the effects of corticosterone (B) on the reproductive biology of the side-blotched lizard, Uta stansburiana. B, testosterone (T), and saline (S) implants were used in both laboratory and field studies to assess the effect that steroids, particularly B, have on aggression, activity, home-range size, and survival. Male-male encounters in the laboratory revealed that B inhibits aggression regardless of whether T levels decrease. Field studies supported these findings in that both B-implanted and B+T-implanted males had decreased activity and reduced home-range size. However, the effect on home-range size was eliminated if all males on an outcrop were implanted with B. Together, these results suggest that B inhibits aggression, putting males at a competitive disadvantage, and, thus, preventing males from maintaining adequate home-ranges. The hypothesis that the changes in home-range size result from competition with other males is supported by the response of cohort S-implanted males on the outcrops. When a steroidal manipulation decreased home-range size (such as with B or B+T implants), S-implanted counterparts increased their home-range size, and when the steroidal manipulation increased home-range size (such as with T implantation), the S-implanted counterparts showed a decrease in home-range size. The inhibitory effects of B on territorial behavior may be an adaptive response in that it presumably conserves energy, a feature which may be critical during adverse times. The activity and home-range size of females, which are less territorial than males, were not affected by B implantation. However, B implantation appeared to increase relative clutch mass. Overall, these studies provide insight into the multiple effects of steroids on territorial and reproductive behavior of lizards and their ecological relevance. |
