Abstract
Only a few hundred years ago, the California condor (Gymnogyps californianus) ranged from British Columbia, Canada to Baja California, Mexico. As European pioneers settled within its range, this large and impressive species declined dramatically to near extinction in the mid-1980. The main goal of this project is to restore a condor population to the Sierra San Pedro Martir Mountains of Baja California, where this keystone species survived until as recently as 1945. The Sierra San Pedro Martir was selected because of its remoteness and sparse human population. After years of reconnaissance and political negotiations on both sides of the border, the project started with the construction of a condor release pen in early summer of 2002. In August 2002, the first six of 18 condors were transported to the site and were released by October of the same year. We plan to reintroduce five to seven condors per year until the anticipated carrying capacity of 20 pairs is reached; so far, 10 condors fly freely in the Sierra. We anticipate that one day soon these magnificent birds will range along the Pacific coast, over the San Pedro Martir range, to the Gulf of California.
The project field crew is made up of Mexican students and biologists, and the work is managed through the Applied Animal Ecology Division within the Center for Reproduction of Endangered Species (CRES) at the Zoological Society of San Diego. It is carried out in close corporation with our program partners, Centro de Investigation Cientifica y de Educacion Superior de Ensenada (CICESE) and El Instituto Nacional de Ecologia (INE) under the Secretaria de Medio Ambiente y Recursos Naturales (SEMARNAT). The importance of veterinary involvement in the California condor recovery program in the United States has been reported previously.3,4 As is seen in other reintroduction programs, the veterinarian’s role includes monitoring the health status of these endangered birds in the wild and in captivity, as well as providing care to clinically ill or injured birds.5
The medical and pathology support for the California condor release program in Baja California, Mexico is provided by the veterinary department of the San Diego Wild Animal Park (SDWAP) and Department of Pathology of the Zoological Society of San Diego, respectively. Also, a partially funded Mexican wildlife veterinarian has been a valuable component of the healthcare support system since the project started 4 years ago. The professional challenges for the field veterinarians in Baja California are unique when compared to those seen by our veterinary colleagues working with the release programs in the United States. Veterinarians in Baja California also assist as the bridge for communication between different local, state, and federal agencies in Mexico and the U.S. daily bureaucratic challenges are common; situations, if not managed correctly, could cause a breakdown in organizational relationships resulting in decreased participation between different national and international governmental agencies. The California condor represents the first CITES I category species reintroduced into Mexico after complete extirpation; therefore, rules and regulations are new novel for organizations on both sides of the border. Other unique challenges include the accessibility to the remote location of the condor release site in the San Pedro Martir National Park: the roads are primitive and often dangerous; weather conditions vary from extreme heat to freezing temperatures; and there are periods of deep snow due to the high elevation (2400 m/7800 ft). Despite these challenges, the Sierra Mountains create a healthy habitat and unique ecosystem for the future of the condor in Mexico.
International movement of animal and disease is important to both sides of the border. The animal health department of Mexico (SAGARPA), the equivalent of the USDA in the United States, requires that birds that enter the country be negative for Newcastle disease and avian influenza by cloacal and respiratory sampling, respectively. The birds must also be serologically negative for Salmonella pullorum prior to entry. These requirements are based on the government’s concern for the health of the poultry industry. All released condors are vaccinated against West Nile virus using a DNA vaccine6 prior to leaving the U.S., but this vaccine is not required by the Mexican government. Once in Mexico, birds immediately enter a 30-day quarantine period in a holding facility at the release site in the Sierra San Pedro Martir. The condors are then re-tested for Newcastle’s disease and avian influenza by SAGARPA before being released from quarantine. At that time, each condor receives a full health examination, which serves as the last exam prior to release into the wild. Blood samples for complete blood count, biochemistry analysis, chemistries, lead levels and serum banking are obtained during this examination and compared with condor reference values.1 Also at this examination, radio transmitters and identification tags are affixed to the wings of each condor prior to release.
Two deaths have been reported in the Baja Mexico condors since 2002. One mortality was due to predation by a bobcat (Lynx rufus) that entered the aviary through a discrete passage in a pile of adjacent boulders. Repair of the pen and an electric fence perimeter have since made the captive birds more secure. The mountain lion (Felis concolor) population and its potential impact on the condor release program also needs to be addressed. The second death, of a young and newly released condor, remains undetermined; however, it was at least scavenged upon if not predated by a bobcat. Dangerous interactions have been observed in the Baja release program between condors and other predators such as mountain lions and coyotes (Canis latrans) eating from the carcasses offered, and golden eagles (Aquila chrysaetos) with aggressive territorial behavior. All released birds were equipped with radio transmitters, which assisted in the recovery of the carcasses, but management of released condors remains a challenge in this area due to their tendency to fly great distances over rough terrain and the lack of quality roads. Another problem found was that the movement of live birds, carcasses, and bio-samples across both sides of the border is difficult and requires permits that sometimes take days to weeks for clearance approval.
No infectious diseases have been detected in any of the condors reintroduced into Baja Mexico. They are routinely screened for END or AI when they arrive to quarantine, but after that only serum is banked for serologic studies if needed. One case of lead poisoning occurred due to ingestion of a bullet fragment in a food item that was donated to the program. An elevated blood lead level was discovered during a routine health examination using a portable blood lead analyzer (LeadCare Analyzer, ESA, Inc., Chelmsford, MA, USA). Fortunately, the bird was asymptomatic and was transported back to the SDWAP. Radiographs confirmed the presence of a metallic density, and endoscopic removal of the bullet was successfully performed. The bird was placed on chelation therapy with Ca-EDTA for 5 weeks. The bird recovered uneventfully and was sent back to the release site after 3 months of hospitalization. Lead poisoning has been reported previously as one of the most common causes of death among the wild and released California condor population.2,3,7
There are no published studies that provide information regarding the health of the environment surrounding the Baja Mexico release site. Specifically, we are interested in determining potential health risks to the release condor population including evaluating the presence of heavy metals, pesticides, insecticides, agricultural fertilizers, rodenticides, and other intoxicants. Other concerns include the risks of predation, poaching, legal hunting (and type of bullets used), and infectious disease agents in the area need to be studied. The California condor appears to be susceptible to West Nile virus infection (a chick died of this infection in Ventura county, CA, last year), and the low surveillance of the disease in the wildlife of México poses an additional problem. The fear or reality of an outbreak of avian influenza H5N1 on either side of the border will undoubtedly affect the potential health of the birds but will also restrict the legal movement of this bird, reducing the chances for emergency medical intervention if needed. An expanding conservation education and outreach program, highlighting the condor release program, has been initiated in an attempt to reach residents in the immediate release area. Involvement of locals will be critical for the success of the program.
Mexico is a country and culture where concern for the environment and conservation issues is still in the process of development. The response of Mexican society to the presence of this magnificent and endangered bird, with all of its conservation issues, has been encouraging but remains uncertain. Direct participation of national and international non-government organizations, local and federal government agencies, universities, and the Zoological Society of San Diego is crucial for the future of the reintroduction program and establishment of a viable California condor population in Baja California, Mexico. Zoo veterinarians can play a major role in conservation programs due to their diverse training in medicine and management of diseases in individuals and populations. But on an international setting, they also need to have the capability of addressing problems related with not only medicine but different ideology, language, and culture.
Literature Cited
1. Dujowich, M., J.K. Mazet, and J.R. Zuba. 2006. Hematologic and biochemical reference ranges for captive California condors (Gymnogyps californianus). J. Zoo Wildl. Med. 36: 590–597.
2. Ensley, P. Medical management of the California condor. 1999. In: Fowler, M.E. and R.E. Miller (eds.). Zoo and Wild Animal Medicine. Current Therapy 4, W.B. Saunders. Philadelphia, Pp. 277–292.
3. Janssen, D.L., J.E. Oosterhuis, J.L. Allen, M.P. Anderson, D.G. Kelts, and S.N. Wiemeyer. 1986. Lead poisoning in free ranging California condors. J. Am. Vet. Med. Assoc. 189: 1115–1117.
4. Oosterhuis, J.E. Veterinary involvement in the California condor recovery program. 1986. Proc. Am. Assoc. Zoo Vet. Pp. 93.
5. Shima, A.L. 1991. Veterinary involvement in the California and Andean condor recovery and release projects. Proc. Am. Assoc. Zoo Vet. Pp. 88–94.
6. Stringfield, C.E., B.S. Davis, and G-J. Chang. 2003. Vaccination of Andean condors (Vultur gryphus) and California condors (Gymnogyps californianus) with a West Nile virus DNA vaccine. Proc. Am. Assoc. Zoo Vet. Pp. 193–194.
7. Stringfield, C.E., A. Wong, M. Wallace, and B. Rideout. 2004. Causes of death in released California condors (Gymnogyps californianus) from 1992–2002. Proc. Am. Assoc. Zoo Vet. Amer. Assoc. Wildl. Vet., and Wildl. Dis. Assoc. Pp. 85–86.