Date: August 31, 2016
Source: Zoological Society of San
Diego
As conservationists work to
recover endangered species populations, taking individuals that are maintained
and protected under human care and reintroducing them into the wild, it becomes
apparent that there is a great deal to learn about the science of species
recovery. In a paper published in the recent edition of the Journal of
Applied Ecology, a team of wildlife experts from San Diego Zoo Global, the U.S.
Geological Survey, the U.S. Fish and Wildlife Service and the University of
Nevada analyzed the effect of habitat quality on the survival and dispersal of
released desert tortoises. Juvenile tortoises used in this study originated
from eggs produced by females housed at the Desert Tortoise Conservation Center
in Las Vegas. Ages ranged from 6 months to 4 years. The tortoises were
translocated and monitored for one year, using radio tracking systems.
"The goals of the study were
to help re-establish populations of this threatened and declining species, and
to understand better what critical resources on the landscape are associated
with the ability of young tortoises to survive and thrive," said Ron
Swaisgood, Ph.D., director of Applied Animal Ecology at San Diego Zoo Global.
Tortoises released in habitat that included appropriate vegetation, rocks and
the presence of animal burrows had lower mortality rates than those released in
areas where land features offered fewer options for predator avoidance.
"Burrows created by small mammals represent critical components of desert
tortoise ecology," said Melia Nafus, Ph.D., a researcher for San Diego Zoo
Global and lead author of the study. "Supporting healthy rodent
populations through habitat management may improve juvenile desert tortoise
survival and recruitment." Another interesting finding of the study was
that tortoises released on rocky ground were less likely to disperse away from
the release site. "This finding probably relates to the tortoise's
dependence on rocky substrate, as camouflage to hide from predators," said
tortoise expert and co-author Todd Esque, Ph.D., from the U.S. Geological
Survey.
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