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Demographic changes were monitored in free-ranging European rabbit (Oryctolagus cuniculus) populations in Australia following the surgical imposition of four levels of female sterility (0%, 40%, 60%, 80%). Rabbit productivity decreased with increasing sterility level, but a greater proportion of offspring were recruited into populations with high levels of sterility. Adult rabbits, particularly sterile females, also survived better in the high sterility populations. Thus we were able to experimentally demonstrate that two density-dependent processes were operating on our rabbit populations: one was acting on juvenile survival, the other on the survival of infertile adult rabbits. However, these compensatory mechanisms were insufficient to overcome the effects of sterility in the high sterility populations and the seasonal abundance of rabbits decreased. Female sterility levels of 60%-80% would benefit rabbit control programs by reducing the peaks of rabbit abundance. This effect is likely to be enhanced if fertility control could be integrated with other pest control strategies. |
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