The Rodrigues fruit bat (Pteropus rodricensis) is an endangered species restricted to the island of Rodrigues.1 Bats breed well in captivity and over population can become a problem. Therefore, controlling breeding is required. Reproductive assessment and contraception was carried out on a population of around 240 Rodrigues fruit bats. Bats were assessed for pregnancy by ultrasound using a 16-megahertz probe. If no pregnancy or early pregnancy (uterus <10 mm) was detected the bat was injected with aglepristone (12.1–18.4 mg/kg, twice 24 hours apart) (Alizin® 30 mg/ml, Virbac, UK), then after one week anesthetized with isoflurane and ultrasound was repeated. If no pregnancy was detected the bat was implanted with 34 mg of etonogestrel (Nexplanon®, 68 mg implant, MSD Ltd., UK) subcutaneously in the right brachium and the skin sealed with tissue glue. Contracepted bats were held off show and re-examined six weeks later: 3/34 (8.8%) were found to be in the early stages of pregnancy, and 4/34 (11.8%) had lost their implants and were re implanted. Pregnant bats remained off show until parturition, no issues were seen, and the rest returned to the colony. Nine months later all female bats were assessed again and a further 44 contracepted. 3/43 previously contracepted bats had lost their implants. One of these bats was pregnant. 32 females had confirmed contraception in place, none were pregnant, but two had pups, a possible failure rate of 6%. This suggests that 34 mg of subcutaneous etonogestrel is an effective contraception for Rodrigues fruit bats.
The authors would like to thank the veterinary team, twilight team keepers and registrar team for their assistance in the management of these bats.
1. Tatayah V, Jhangeer-Khan R, Bégué JA, Jones CA. Pteropus rodricensis. The IUCN red list of threatened species. e.T18755A22087057. http://dx.doi.org/10.2305/IUCN.UK.2017-2.RLTS.T18755A22087057.en. 2017. Accessed 27 March 2018.