Aggression control in a bachelor herd of fringe‐eared oryx (Oryx gazella callotis), with melengestrol acetate: Behavioral and endocrine observations

Abstract

Aggression control is becoming an important component in the management of animals in captivity, but rigorous quantification of aggressive behavior has heretofore been lacking. This study was done to assess the ability of melengestrol acetate (MGA) given with feed (1.54 mg/kg) to control aggression in a bachelor group of fringe-eared oryx (Oryx gazella callotis). Systematic behavioral observations were conducted and fecal androgen content was measured for 42 and 90 days, respectively, before treatment, and during the 42 days of treatment. There was a significant reduction in concentrations of fecal androgen from 153 ± 6.0 to 95 ± 4.5 ng/g (T 66 = 7, P < 0.0001). This reduction in androgen excretion was apparent after the first week of treatment. There was measurable MGA excreted in the feces during treatment. Although treatment did not arrest all aggressive behaviors among animals, the decline in androgens and increase in MGA was accompanied by a significant reduction in several measures of agonistic behavior. Posturing, aggressive contact, pursuit, and submission occurred significantly less frequently after treatment, and there was also a reduction in fighting-intention movements. Thus, both ritualized and nonritualized aspects of aggression were affected. Reductions in hormones and aggressive behaviors coincided temporally, suggestive of a potential causal relationship. Consistent with this hypothesis is a strong positive correlation between fecal androgen and total aggressive acts. This effect was not the result of a single behavioral element but occurred across several categories of agonistic behavior. Zoo Biol 20:375-388, 2001. INTRODUCTIONIn male ungulates, it has been suggested that there is a causal link between aggressive behavior and androgens [Bouissou, 1983]. A synthetic progestogen, melengestrol acetate (MGA), originally developed as an orally active contraceptive [Kirk et al., 1962], has been reported to decrease aggression in three ungulate species. Silastic implants containing MGA reduced intraspecific aggression in bachelor herds of scimitar-horned oryx, Oryx dammah [Blumer et al., 1992]. Male muntjacs (Muntiacus reevesi) fed MGA had significantly decreased sperm numbers, and anecdotal reports of behavior indicated reduced aggression [Stover et al., 1987]. Orally administered MGA reduced aggression during the early rut in farmed fallow bucks (Dama dama) [Wilson et al., 2000]. None of these studies, however, systematically quantified aggression before and after MGA administration, leaving the question of efficacy unresolved.The fringe-eared oryx (Oryx gazella callotis), an east African subspecies of the gemsbok (Oryx gazella), is a horselike antelope that lives in the harsh arid environments of east Africa. This species has no particular breeding season. Most frequently, territorial males breed females in their postpartum estrus. Herds of bachelor males are seldom found [Price, 1986;Wacher, 1988]. In captivity, however, it is sometimes necessary to hold males in all-male groups. Elevated aggres...

Maintenance of female dominance in blue‐eyed black lemurs (Eulemur macaco flavifrons) and gray bamboo lemurs (Hapalemur griseus griseus) under semi‐free‐ranging and captive conditions

“…However, most research on how each of the two contraceptives used at the DLC affects behavior suggests that each contraceptive lowers rates of aggressive behavior in the subject. For example, in various macaque species Depo Provera is shown to reduce the frequency of aggressive acts [Michael and Zumpe, 1993], and studies of fringe-eared oryx (Oryx gazella callotis), golden-headed lion tamarins (Leontopithecus chrysomelas), Rodrigues fruit bats (Pteropus rodricensis), and Hamadryas baboons (Papio hamadryas) have all shown that melengestrol acetate (MGA) results in either no significant change or a significant decrease in aggressive behavior [Portugal, 1995;Hayes, 1996;De Vleeschouwer et al, 2000;Patton et al, 2001]. If the contraceptives affect the two species in the study similarly, the data presented in this study may actually underestimate the degree of aggressive behavior typically displayed by females.…”

Declining and low fecal corticoids are associated with distress, not acclimation to stress, during the translocation of African rhinoceros

“…Inter-assay coefficient of variation was o6%. The protocols and performance of radioimmunoassays to measure progestin and androgen metabolite concentrations in the same samples of feces are described in Patton et al (1999Patton et al ( , 2001, respectively.…”

Case studies in antelope aggression control using a GnRH agonist

“…Castration of domestic animals can reduce aggressive interactions between conspecifics and humans [Martin and Lindsay, 1998]. However, although manipulating testosterone concentrations has modified aggressive behavior in some species [Martin and Lindsay, 1998;Norton et al, 2000], including fringe-eared oryx [Patton et al, 2001], the influence of testosterone on aggressive behavior is not fully understood.…”