LACK OF SPATIAL AND BEHAVIORAL RESPONSES TO IMMUNOCONTRACEPTION APPLICATION IN AFRICAN ELEPHANTS (LOXODONTA AFRICANA)

Abstract

Opinions are divided as to whether human intervention to control elephant (Loxodonta africana) population growth is desirable, partly because of elephant welfare concerns. Female contraception through immunization with porcine zona pellucida (PZP) proteins is viable. The effects of sustained use and application of the PZP vaccine on elephant behavioral and spatial responses were examined by evaluating herd ranging, fission-fusion dynamics, association patterns, and reproductive and sexual behaviors. Minimal change was anticipated as a result of long calf dependence on and association with cows, a reduced but not indefinite 0% growth rate and the known mechanism of action of PZP vaccines, and minimal expected change in resource requirements necessitating behavioral or spatial use adaptations. Although behavioral effects identified in previous hormonal contraceptive trials were evident, it was demonstrated that immunocontraception caused no prolonged behavioral, social, or spatial changes over the 11-yr study period. Individually identified elephants were monitored from 1999 to 2011. Minimal, short-term social disruption, with temporary changes to the herds' core ranges, was observed during the annual treatment events, particularly in the first three treatment years, when vaccinations were conducted exclusively from the ground. Thereafter, when vaccinations were conducted aerially, minor disruptions were confined to the morning of administration only. Despite sustained treatments resulting in demographic changes of fewer calves being born, treatments did not alter spatial range use, and no adverse interherd-intraherd relations were observed. Similarly, resource requirements did not change as calving still occurred, although in fewer numbers. It was concluded that PZP immunocontraception has no detectable behavioral or social consequences in elephants over the course of 11 yr, providing a convincing argument for the use of sustained immunocontraception in the medium to long term as an important tool for elephant management. Behavioral consequences of alternative management approaches should all receive similar scrutiny to enable managers to make informed decisions when weighing management interventions.

Zoo elephant research: contributions to conservation of captive and free‐ranging species

“…Ovarian and testicular function are under hormonal control; thus, methods that alter hypothalamic-pituitary-gonadal activity can be used to manipulate reproduction. Under certain managed situations, there is sometimes the need for cessation of breeding to prevent overpopulation in restricted areas without disrupting herd dynamics (Delsink et al, 2002). For example, in well-managed private South African nature reserves and national parks, elephant populations increase about 3-6% annually.…”

“…The most widely applied contraceptive agent in elephants is an immunogenic preparation of porcine zona pellucida (pZP) harvested from pig ovaries (Fayrer-Hosken et al, 1999;Delsink et al, 2002Delsink et al, , 2006. Antibodies block sperm binding on the ZP surrounding the oocyte.…”

Fecal 20-oxo-pregnane concentrations in free-ranging African elephants (Loxodonta africana) treated with porcine zona pellucida vaccine

“…In this regard, the use of the porcine zona pellucida (pZP) vaccine for immunocontraception of African elephant cows is a fairly recent development. The method has shown promise as an effective and acceptable means for management [12,13]. Zona pellucida glycoproteins isolated from pig ovaries have been shown to be homologous to those of the African elephant [1,14].…”

Use of gonadotrophin releasing hormone (GnRH) vaccines for behavioural and reproductive control in managed Asian elephantElephas maximusand African elephantLoxodonta africanapopulations

“…Long-term studies on the use of porcine zona pellucida (pZP) vaccine in wild African elephant females with continued cycle activity have shown a lack of behavioural modifications or change to herd structure (Delsink et al, 2013).…”

“…In southern Africa, female elephant contraception is widely and successfully achieved by the use of the immunocontraceptive pZP vaccine (Fayrer-Hosken et al, 2000;Delsink et al, 2001). Annual boosters seem to be sufficient to sustain the contraceptive properties (Delsink et al, 2013). A long-acting formulation of this pZP vaccine (SpayVac) has been trialled, leading to high titres of up to 7 years in two captive African elephant females (Bechert & Fraker, 2016).…”