BACKGROUND : Androgen-related aggressive behaviour and musth cause serious problems in
captive African elephant bulls and often lead to human and animal injuries, and damage to
OBJECTIVES : To review the work carried out with anti-gonadotropin-releasing hormone (GnRH)
vaccines to control androgen-related behaviour and fertility in captive and free-ranging
elephant bulls and the induction of anoestrus in elephant cows.
METHOD : In the first study, an anti-GnRH vaccine from Pepscan was tested in six bulls (four
captive and two free-ranging). Once the vaccine Improvac® became available, the effect on
behaviour, the reproductive organs and semen quality was tested. Improvac® was also used
to attempt induction of anoestrus in elephant cows.
RESULTS : The first study proved that aggressive behaviours are significantly associated with
increased faecal androgen concentrations. Musth (n = 1) and aggressive behaviour (n = 2) were
down regulated and correlated with a decline in faecal androgen concentrations. Aggression and
musth could be controlled with Improvac® (600 μg), but were more consistent when the dose
was increased to 1000 μg administered every five to six months. The same dose down regulated
testicular function and bulls (n = 17) were rendered infertile within 12 months after commencement
of treatment. Initial attempts to induce anoestrous with 600 μg in free-ranging elephant cows
gave inconclusive results, but 1000 μg in captive cows delivered five-monthly was successful.
CONCLUSION : The treatment of elephant bulls with Improvac® resulted in the successful downregulation
of androgen-related behaviour and sperm production in captive and wild elephant
bulls of various ages (≤ 34 years). Preliminary studies to induce anoestrus in cows with
Improvac® appear to be successful.