Unlocking reproductive success in the Eastern black rhino: exploring Chester Zoo’s ‘Conservation Toolbox’

The zoo population today is growing well, however historically; although self-sustaining, the EEP had lower annual population growth rates of 1-2%, compared to the managed in-situ population, which had rates of 6-8%.

Using studbook data, keeper surveys, and endocrine monitoring, Chester Zoo Conservation Scholar Alumn, Dr. Katie Edwards, in collaboration with the University of Manchester, tried to uncover which factors may have been limiting breeding success in EAZA black rhinos. The research team took holistic approach to tackle this challenge; by evaluating the link between reproductive physiology, individual body condition score, enclosure design, and animal personality to reproductive success, the team were able evaluate each animal in the European study population on an individual-basis.
After analysing over 11,000 faecal samples from 90% of the European population of black rhino, the research team were able to identify individual trends in reproductive physiology– from females with abnormal oestrus cycles to understanding how previous reproductive success associated with trends in progesterone, testosterone, or cortisol fluctuations. Moreover, the team identified how higher body condition and a more unpredictable temperament was linked to lower reproductive success in females. Factors such as enclosure design and social management did not appear to link to reproductive success.

To this day, many zoos around Europe continue to send the Chester Zoo endocrine laboratory faecal samples for routine monitoring, and the EAZA population is growing strong The EAZA black rhino population boom has even allowed for the reintroduction of five captive-born Eastern black rhinos to the Akagera National Park in Rwanda at the end of 2019. These rhinos hold important genetic diversity for the sub-species, which is likely no longer found in in situ populations. This reintroduction is supported by research undertaken by current Chester Zoo Conservation Scholar, Frankie Elsner, who, in partnership with the University of Manchester, is comparing genetic markers between the in situ and the EAZA population of Eastern black rhinos.

As for Katie, following a five-year stint at the Smithsonian Conservation Biology Institute as a post-doctoral researcher, Katie is back at Chester Zoo as a Lead Conservation Scientist, focusing on the development and research of biomarkers for animal health, well-being, and reproduction. Moreover, in conjunction with the Manchester Metropolitan University, she is also helping to train a new generation of scientists, both in and out of the field.

Alongside Dr. Sue Walker, Head of Science at Chester Zoo, and Rebecca Mogey, Chester Zoo’s Laboratory Coordinator, and the Kenya Wildlife Service, Katie is helping to establish Kenya’s first wildlife endocrinology laboratory at the Lewa Wildlife Conservancy. Among other projects, this lab will be monitoring the in-situ rhino population, looking for factors that contribute to healthy reproduction in wild populations.

References:
Edwards, K.L., Pilgrim, M., Brown, J.L. and Walker, S.L., 2020. Irregular ovarian cyclicity is associated with adrenal activity in female eastern black rhinoceros (Diceros bicornis michaeli). General and Comparative Endocrinology, 289, p.113376.

Edwards, K.L., Walker, S.L., Dunham, A.E., Pilgrim, M., Okita-Ouma, B. and Shultz, S., 2015. Low birth rates and reproductive skew limit the viability of Europe’s captive eastern black rhinoceros, Diceros bicornis michaeli. Biodiversity and conservation, 24(11), pp.2831-2852.

Edwards, K.L., Shultz, S., Pilgrim, M. and Walker, S.L., 2015. Irregular ovarian activity, body condition and behavioural differences are associated with reproductive success in female eastern black rhinoceros (Diceros bicornis michaeli). General and comparative endocrinology, 214, pp.186-194.

Edwards, K.L., Shultz, S., Pilgrim, M. and Walker, S.L., 2015. Male reproductive success is correlated with testosterone in the eastern black rhinoceros (Diceros bicornis michaeli). General and comparative endocrinology, 213, pp.40-49.