Observations of Potential Avian Predators of Agassiz’s Desert Tortoise (Gopherus agassizii) at the Desert Tortoise Research Natural Area, eastern Kern County, California, in Late Winter and Spring of 1989, 1993, 1997, 2002, and 2012
Dates
Publication Date
2021-08-27
Start Date
1989
End Date
2012
Citation
Berry, K.H., 2021, Demography and habitat of desert tortoises at the Desert Tortoise Research Natural Area, western Mojave Desert, California (1978 - 2014): U.S. Geological Survey data release, https://doi.org/10.5066/P9BY0HVH.
Summary
During the five-survey years at the Desert Tortoise Research Natural Area in the western Mojave Desert of California, 1,645 sightings of 13 species of avian predators were collected. Eleven species occurred both inside and outside the fenced Desert Tortoise Research Natural Area, and two species, the short-eared owl and great horned owl, occurred only inside the fence. The most abundant predator was the common raven with more observations outside the fence than inside the fence in most years. Ravens are hyper-predators of the desert tortoise and, at the Desert Tortoise Research Natural Area, are one of four drivers of population decline. This species also inhibits recovery because of the high numbers (Berry et al. 2020, Wildlife Monographs [...]
Summary
During the five-survey years at the Desert Tortoise Research Natural Area in the western Mojave Desert of California, 1,645 sightings of 13 species of avian predators were collected. Eleven species occurred both inside and outside the fenced Desert Tortoise Research Natural Area, and two species, the short-eared owl and great horned owl, occurred only inside the fence. The most abundant predator was the common raven with more observations outside the fence than inside the fence in most years. Ravens are hyper-predators of the desert tortoise and, at the Desert Tortoise Research Natural Area, are one of four drivers of population decline. This species also inhibits recovery because of the high numbers (Berry et al. 2020, Wildlife Monographs 205:1-53).
References:
Berry, K.H., Yee, J.L., Shields, T.A. and Stockton, L., 2020. The Catastrophic Decline of Tortoises at a Fenced Natural Area. Wildlife Monographs, 205(1), pp.1-53.
Avian predators kill and eat desert tortoises. Desert tortoises are a threatened species under the federal Endangered Species Act and California Endangered Species Act; populations in the western Mojave Desert have been declining for 40 or more years. Knowledge of both relative and actual predation pressure is essential for understanding declines and taking management actions to recover the species. The Common Raven has been identified as a hyper-predator.