Abstract:
Aggressive behaviour and musth are constant problems in captive and sometimes in
free-ranging African elephant bulls. Aggressive bulls are difficult and musth bulls almost
impossible to manage without severely restricting their movement either by leg-chaining
or using tranquillisers. This study investigated the relationship between faecal androgen
metabolites (FAM) and faecal cortisol metabolites (FCM) concentrations and aggressive
behaviour and tested aGnRHvaccine as a means of down-regulating aggressive behaviour
and musth in 1 free-ranging and 5 captive elephant bulls. The bulls were non-aggressive
(n = 3), aggressive (n = 2) or in musth (n = 1) at the onset of the study. The bulls were
injected with a GnRH vaccine-adjuvant combination 3 or 4 times at 3- to 7-week intervals.
Behaviour, FAM and FCM concentrations were measured during every week prior to
vaccination until 4 months after the last vaccination. FAM concentrations were positively
correlated with aggressive behaviour before the 1st vaccination. Androgen production, as
reflected by FAM concentrations, was down-regulated in 3 of the 6 immunised bulls. At
least 2 bulls and possibly a 3rd showed behavioural improvement followingGnRHvaccination
and in all 3 temporal gland secretion ceased. No further aggressive behaviour was
observed until the end of the study in any of the bulls. The results of this 1st GnRH immunisation
study suggest that it could be a useful method to control aggressive behaviour and
musth in African elephant bulls.
