28th Annual Meeting and Symposium of the
Desert Tortoise Council, February 21-23, 2003
Abstracts

Potential Assets and Liabilities Inherent to Desert Tortoise Hatchery Nurseries

David J. Morafka¹ and April J. Johnson^2
1Research Associate, Department of Herpetology, California Academy of Sciences, San Francisco, California
²Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida

In North America, nursery hatcheries have been established for two tortoise species, Gopherus agassizii and Gopherus flavomarginatus. A hatchery-nursery was established in Mexico in 1983 for G. flavomarginatus. A second hatchery-nursery, the Ft Irwin Study Site (FISS), was established in 1990 at Ft Irwin National Training Center, Ft Irwin, California for G. agassizii, and is still in use. However, certain concerns are associated with their activities, making the hatchery-nurseries to be a topic of controversy.

There are many benefits associated with hatchery nurseries. They provide hatchlings a semi-natural environment with suppressed predation and suppressed contact with diseased adults. It allows for dispersion of neonatal and juvenile desert tortoises into high quality habitats that have suffered prior extirpation. Such programs also provide the settings for long term studies using high numbers of tortoises. Using tortoises of known ages from the same confined area reduces the effects of confounding variables, and allow for studies therein to resolve many unknown issues, such as the causes of morbidity and mortality in the surrounding depleted populations, the identification of genetic variation in populations and the effect of assortive mating.

On the other hand, liabilities may be associated with hatchery nurseries. These liabilities need to be identified and plans made in advance to minimize the negative effects. Predation may be subsidized by releasing a large number of neonates and juveniles at once, or by providing artificial feeding or water to the site. If artificial feeding is not conducted, tortoises may be nutritionally restricted to available food within the enclosure. Inappropriate genetic stock may lead to outbreeding depression. Data collection might be artificially skewed with these semi-wild populations of tortoises from what might naturally be found. High density of animals may lead to altered behavior or increased rates of transmission of disease agents and parasites. Exhaustion of a site and loss of carrying capacity may also occur due to the high density of animals over many years and the increased amount of foot traffic of those managing the site. The site may also be vulnerable to vandalism of equipment and animals.

Certain environmental and demographic conditions do justify construction of a desert tortoise hatchery nursery. There should be a consistent and unambiguous long term trend in declining numbers or a confirmed failure of recruitment. There should be a failure to diagnose causes of morbidity and mortality or the absence of effective alternative mitigations to reverse known causes. Local densities or total numbers should be so low so as to preclude the likelihood of natural recovery, but still sufficient for recruiting local females and eggs for the hatcheries. The hatchery should be in proximity of good habitat with an adequate carrying capacity, and protected to reduce the risk of predation, vandalism and poaching. There needs to be a long term commitment of funding sources and management authorities to ensure that the long term goals of research be met.

In conclusion, although offering many assets to research of the biology of the young desert tortoises, hatchery nurseries have many liabilities that make them such a topic of controversy. As experimental hatchery nurseries are studied, these risks can be identified and addressed in the development of protocols for present and future hatchery nurseries.