A role for selective contraception of individuals in conservation

Abstract

Contraception has an established role in managing overabundant populations and preventing undesirable breeding in zoos. We propose that it can also be used strategically and selectively in conservation to increase the genetic and behavioral quality of the animals. In captive breeding programs, it is becoming increasingly important to maximize the retention of genetic diversity by managing the reproductive contribution of each individual and preventing genetically suboptimal breeding through the use of selective contraception. Reproductive suppression of selected individuals in conservation programs has further benefits of allowing animals to be housed as a group in extensive enclosures without interfering with breeding recommendations, which reduces adaptation to captivity and facilitates the expression of wild behaviors and social structures. Before selective contraception can be incorporated into a breeding program, the most suitable method of fertility control must be selected, and this can be influenced by factors such as species life history, age, ease of treatment, potential for reversibility, and desired management outcome for the individual or population. Contraception should then be implemented in the population following a step-by-step process. In this way, it can provide crucial, flexible control over breeding to promote the physical and genetic health and sustainability of a conservation dependent species held in captivity. For Tasmanian devils (Sarcophilus harrisii), black-flanked rock wallabies (Petrogale lateralis), and burrowing bettongs (Bettongia lesueur), contraception can benefit their conservation by maximizing genetic diversity and behavioral integrity in the captive breeding program, or, in the case of the wallabies and bettongs, by reducing populations to a sustainable size when they become locally overabundant. In these examples, contraceptive duration relative to reproductive life, reversibility, and predictability of the contraceptive agent being used are important to ensure the potential for individuals to reproduce following cessation of contraception, as exemplified by the wallabies when their population crashed and needed females to resume breeding.

Opportunities and Limitations for Reproductive Science in Species Conservation

“…Limiting the size of animal populations, whether in zoos or in nature, also falls within the domain of reproductive science. It may sometimes be necessary to develop and administer contraceptive techniques if, for example, zoo populations are expanding too quickly for the available housing (4,5). In this instance, it may be desirable to avoid irreversible methods, so that population control can be achieved for a limited period and halted later.…”

How much is enough? Sampling intensity influences estimates of reproductive variance in an introduced population

“…2020) and/or contraception (e.g., Cope et al. 2018) of over‐represented breeders. However, pedigree completeness and accuracy is dependent on sampling completeness (Pemberton 2008), and the operational costs of trapping and sampling animals are considerable (McCarthy 2012).…”

“…Indeed, molecular pedigree reconstructions have greatly expanded our ability to infer important population process including identifying over-represented individuals or lineages. With a reconstructed pedigree, individual contributions can be balanced by removal (e.g., Hogg et al 2020) and/or contraception (e.g., Cope et al 2018) of over-represented breeders. However, pedigree completeness and accuracy is dependent on sampling completeness (Pemberton 2008), and the operational costs of trapping and sampling animals are considerable (McCarthy 2012).…”