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UC Davis Veterinarian Helps Evaluate Reproduction Concerns with Endangered Species

September 17, 2014

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UC Davis’ Dr. Bruce Christensen, right, biopsies the uterus of an African painted dog at the Bronx Zoo.

Every year, as human population increases and natural habitats decrease, more and more animals become endangered throughout the world. With help from the Association of Zoos and Aquariums (AZA) Wildlife Contraception Center (WCC), a veterinarian at the University of California, Davis’ School of Veterinary Medicine is taking measures to do what he can to combat that. Dr. Bruce Christensen, a reproduction specialist, traveled throughout the United States over the past year, assisting zoos and wildlife habitats with fertility problems in several endangered species. Working with veterinary and curatorial colleagues at the local facilities, Dr. Christensen examined several animals, including red and Mexican wolves, African painted dogs, and an African lion.

The first stop on his travel itinerary was Wolf Haven International, a sanctuary in Tenino, Washington. Since 1982, Wolf Haven has been home to more than 170 rescued wolves that are provided lifetime refuge. Over the years, five litters of Mexican gray wolves have been born at Wolf Haven, and 11 adults have been released back into the wild. Not having success recently with some key individuals, Wolf Haven asked for advice from the WCC. The WCC arranged for Dr. Christensen to evaluate their reproduction concerns.

Dr. Christensen was able to biopsy the uterine walls of two red wolves and two Mexican gray wolves, and used the experience as a learning opportunity for UC Davis’ School of Veterinary Medicine DVM student Maureen D’Souza-Anjo, who accompanied him to the sanctuary. The examinations (which were utilized to determine if reproductive failure could be attributed to the females) showed little if any abnormalities, so Wolf Haven was then able to focus more on the males.

A few months later, the Saint Louis Zoo—where the WCC is headquartered—asked Dr. Christensen to train one of their staff veterinarians, Dr. Chris Hanley, in performing the uterine biopsy procedure. The origins of the Saint Louis Zoo go back to 1904, when the World’s Fair in Saint Louis featured a walk-through flight cage commissioned by the Smithsonian Institution. The cage remained in the city following the fair and became a cornerstone for the zoo when it opened nearly a decade later. Big cats have been on the scene since the very beginning, and the zoo has a rich history of caring for the animals. Today, a third of the animals in the zoo’s care, including the big cats, are either threatened or endangered in the wild.

As a participant in the AZA Species Survival Plan, the Saint Louis Zoo is dedicated to working with the AZA to cooperatively manage specific, and typically threatened or endangered, species. This involves matching suitable mates to ensure the sustainability of a healthy, genetically diverse, and demographically varied population. After teaching Dr. Hanley the uterine biopsy procedure on domestic dogs, Dr. Christensen and Dr. Hanley performed the technique for the first time on a species of big cat, an African lion. The lioness had been on chemical contraception for many years and had been exhibiting erratic reproductive cycles. Uterine samples were successfully obtained and later evaluated by Dr. Dalen Agnew, a pathologist at Michigan State University’s College of Veterinary Medicine.

Lastly, Dr. Christensen was asked to travel to New York and share his expertise with the Wildlife Conservation Society’s world-famous Bronx Zoo. First opened in 1899, the Bronx Zoo is the largest urban zoo in America. Long regarded as one of the nation’s preeminent zoos, the Bronx Zoo is home to more than 6,000 animals from species that span the entire globe, especially the continent of Africa, home to the African painted dog.

The Bronx Zoo breeds African painted dogs as part of the AZA Species Survival Plan and is a leader in painted dog husbandry. Having bred and reared 43 pups, the Bronx Zoo’s painted dog program is one of the most successful in the United States. Sometimes called African wild or hunting dogs, these pack animals typically reproduce six to 12 pups per cycle, with some litters reaching as high as 18. Two of the breeding females in the zoo’s current pack—paired with the same males for a number of years—have not successfully produced any litters. The strategy going forward is to try pairing the females with different males. During that process, Dr. Christensen was brought in to determine if the females’ uteri had any problems that were contributing to the reproductive failures. He performed uterine biopsies and cultures on the two females to determine if there are larger issues at hand other than just changing mates. With only an estimated 3,000-6,000 dogs remaining in the wild, it is imperative the zoo explores all avenues in order to carry on its African painted dog pack. 

Dr. Christensen’s work at all three of these locations was organized and funded by the WCC at the Saint Louis Zoo, individual Species Survival Plans, and the local facilities that house the animals. Dr. Christensen serves on the Advisory Board for the WCC, and worked in collaboration on these projects with Dr. Cheryl Asa, director of zoo research and the WCC in Saint Louis, and Dr. Agnew.

Dr. Christensen’s work is one of dozens of initiatives at UC Davis to expand the borders of its veterinary medicine program far beyond its campus walls in Northern California. With activities ranging from continuing education seminars in China and one health initiatives in Nicaragua to the Gorilla Doctors program in Africa and the SeaDoc Society in the Puget Sound, UC Davis is truly embracing its mission of leading veterinary medicine and addressing societal needs.

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To see more photos of Dr. Christensen's visits, please go to: