Evaluation Of Melengestrol Acetate And GnRH Agonist Implants In Controlling Aggression In Captive Ungulates
Abstract
In many species, such as the Scimitar-horned oryx (Oryx dammah) , high levels of inter-male aggression plague attempts to-maintain bachelor herds in captivity. At Fossil Rim Wildlife Center, two groups of 5 male oryx were treated with hormonal implants in an attempt to reduce aggression, with one receiving melengestrol acetate (MGA) and the other a GnRH agonist. At 1-yr post-implantation, the following aspects were examined: (1) the effectiveness of the implants in controlling aggression, (2) the relationship among plasma testosterone, dominance, and aggression, and (3) influences such as the presence of female-typical hormones (progestins) in males, shortened horns in the MGA-implanted group, and possible depressant effects of MGA on inter-group differences in aggression. At 1-yr post-implantation, three types of behavioral data were collected: (1) frequency of social actions using an all-occurrences recording technique; (2) activity state using scan sampling with instantaneous recording at 15-min intervals, and (3) association in terms of subgroup size at 15-min intervals. Within all categories of agonistic behavior, the mean number of acts was significantly lower in the MGA-implanted group than in the GnRH agonist-implanted group (p=0.0001). Between groups, there was no significant difference in plasma testosterone concentrations at 1-yr post-implantation (p=0.1172). Over all individuals, there was no significant correlation between plasma testosterone and frequency of ritualized threats (p=0.93) or non-ritualized aggression (p=0.86). The MGA-implanted group displayed significantly lower levels of all social behaviors (p=0.0001), a significantly lower index of association (p=0.0001), and a significantly higher index of resting (p=0.0001). At 1-yr post-implantation, the MGA implants were more effective in controlling aggression, but the lower levels of aggression could not be attributed solely to depressed plasma testosterone, a "feminizing" effect of MGA, or shortened horns in the MGA-implanted group. The MGA appeared to reduce the frequency of all social behavior, including aggression, and general activity.
Description
Program year: 1992/1993Digitized from print original stored in HDR
Subject
Scimitar-horned oryxinter-male aggression
melengestrol acetate implant
testosterone concentrations
social behaviors
Citation
Spoon, Tracey (1993). Evaluation Of Melengestrol Acetate And GnRH Agonist Implants In Controlling Aggression In Captive Ungulates. University Undergraduate Fellow. Available electronically from https : / /hdl .handle .net /1969 .1 /CAPSTONE -SpoonT _1993.