CREW Works to Enhance Fertility in White Rhinos

In September, the Zoo’s Center for Conservation and Research (CREW) was awarded a National Leadership Grant from the Institution of Museum and Library Services in support of a Rhino Assisted Reproduction Enterprise (RARE) initiative for Indian rhinos and African white rhinos. Dr. Monica Stoops will be the Project Director for the grant work and will be working in partnership with Dr. Justine O’Brien from the SeaWorld & Busch Gardens Reproductive Research Center (SWBGRRC), which includes a state-of-the-art sperm sorting and cryopreservation laboratory.  CREW will undertake the project to expand access and build capacity for African and Asian rhino reproductive care within North American zoological facilities. Eight zoos have committed to building a Rhino Assisted Reproduction Enterprise (RARE) in collaboration with CREW.  This project will help 1) contribute to the genetic management and propagation of captive Indian rhinos through artificial insemination (AI); 2) enhance southern white rhino fertility through exogenous hormone administration prior to natural breeding or AI; 3) build upon national rhino gamete rescue centers at CREW and SWBGRRC; and 4) provide collaborating facilities with individualized training and/or support in rhino assisted reproductive technology (exogenous hormone protocols, ultrasonography, endocrine analysis, AI, and sperm collection, sorting and cryopreservation).

One part of the proposed research will be to continue and expand upon a preliminary CREW investigation conducted to develop an exogenous hormone protocol to initiate reproductive activity in previously acyclic southern white rhinos. The African white rhino remains the most popular rhino species held in U.S. zoos (although we do not currently house them here in Cincinnati). Although captive breeding has been successful and a sufficient number of calves are being produced to consistently maintain the population, the proportion of breeding recommendations resulting in offspring is quite low. It is estimated that <30% of all wild born and <20% of captive born African white rhinos have reproduced in captivity. These numbers reflect a major impediment to achieving a sustainable captive breeding program for this species.

A primary reason for the low reproductive rate is that a vast majority of females display long periods of acyclicity. Significant progress has been made in initiating reproductive activity in acyclic white rhinos in Europe using exogenous hormones. However, many drugs used overseas are not commercially available in the United States. Therefore, it became necessary
to develop novel hormone protocols using U.S. drugs to similarly promote a resumption in reproductive activity for acyclic white rhinos.

CREW scientists, in partnership with several North American zoos, embarked on a preliminary exogenous hormone trial in which four acyclic female white rhinos were treated. Females responded by growing preovulatory follicles, but did not stand for breeding by a male and required an additional hormone to ovulate. This initial hormone protocol may be adequate should artificial insemination be performed, but CREW scientists and partner zoos are working to develop an alternative hormone protocol that will result in natural mating so that more individual rhinos and institutions will benefit. By enhancing the fertility of captive African white rhinos, CREW is helping to ensure the sustainability of this rhino population.

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