Effects of Fertility-Limiting Hormones Quinestrol and Levonorgestrel on Bait Intake and Reproductive Performance of the Nile Grass Rat (Arvicanthis niloticus Rüppel, 1842), a Major Agricultural Rodent Pest in Africa

Rodent species belonging to the Arvicanthis genus cause substantial field and postharvest losses in many African countries, where management still relies mainly on lethal control methods. Hormonal fertility control may provide a complementary strategy for reducing rodent population growth. We investigated the antifertility effects of bait containing quinestrol, a synthetic estrogen, levonorgestrel, a synthetic progestogen, and their combination at 10, 50, and 100 ppm in the Nile grass rat (Arvicanthis niloticus). These compounds suppress fertility by disrupting normal reproductive endocrine function. Adult male and female animals were exposed to treated bait under laboratory conditions, and reproductive responses were evaluated through measurements of bait intake, body weight change, reproductive organ weights, sperm count, sperm motility, pregnancy rate, and litter size. Quinestrol and combined treatments significantly reduced male reproductive organ weights and impaired sperm quality. Female reproductive organ weights were generally unaffected, although uterine edema occurred at higher concentrations. Quinestrol at 50 ppm completely inhibited pregnancy in treated females, regardless of the male mating partner. In addition, untreated females paired with treated males exhibited lower pregnancy rates and reduced litter sizes. Our findings demonstrate the potential of hormonal fertility control as a complementary strategy for sustainable rodent pest management in Africa. Future studies should focus on improving bait intake, field evaluation, and determining the duration and reversibility of contraceptive effects.