Published online by Cambridge University Press: 04 June 2019
CHAPTER 6 deals specifically with fertility control as a possible means of population management of free-ranging African elephants. Because methods that are described here for elephants function by preventing cows from conceiving, fertility control cannot immediately reduce the population. This will only happen once mortality rates exceed birth rates. Considering, however, that elephants given the necessary resources can double their numbers every 15 years, fertility control may have an important role to play in population management.
The first part of the chapter is devoted to the reproductive physiology of elephants in order to provide the reader with information and understanding which relate to fertility control. This is followed by examples of contraceptive methods that have been used in mammals, and a description of past and ongoing research specifically carried out in elephants. Finally guidelines for a contraception programme are provided, followed by a list of key research issues and gaps in our knowledge of elephants pertaining to reproduction and fertility control.
In this chapter we will also attempt to answer the following questions in regard to reproductive control of African elephants:
• Do antibodies to the porcine zona pellucida (pZP) proteins recognise elephant zona pellucida (eZP) proteins or is the vaccine likely to work in African elephant cows?
• Is it possible to implement a contraceptive programme using the pZP vaccine?
• Is it practical to implement such a programme?
• What contraceptive efficacy can one expect?
• Is the method safe, reversible and ethical?
• What effect does the implementation have on the behaviour of a population?
• What are the effects of contraception on behaviour?
• What are the proximate and ultimate effects of contraception?
• Given the current technology, what population sizes can be tackled?
• What are the costs involved?
• Are there alternatives to pZP for contraception of elephants?
• What developments are in the pipeline that could facilitate implementation?
ASPECTS OF ELEPHANT REPRODUCTION THAT RELATE TO REPRODUCTIVE CONTROL
Elephants live in female-dominated herds comprising an old female referred to as the matriarch together with her mature daughters and their offspring, including sexually immature male calves (Owen-Smith, 1988). Female elephants remain in their natal herds their whole lives; male elephants leave their natal groups at approximately 12–14 years or when they reach sexual maturity (Poole, 1996a & b).