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.
