Partial Migration as a Basis for Recovery of Endangered Sierra Nevada bighorn sheep

Project Objectives

Bighorn sheep on mountain side - Photo credit: Art LawrenceThe Sierra Nevada bighorn sheep are the rarest ungulate in North America and have been on the endangered species list since 2000. Federally-endangered Sierra Nevada bighorn sheep (Ovis canadensis sierrae; SNBS) is the rarest sub-species of North American mountain sheep, found only in fragmented sub-populations along a single mountain range. The species was largely extirpated from its historic range prior to coming under scientific scrutiny. Estimates of available habitat remain speculative. Recent research has evaluated effects of demographic rates on prospects for SNBS recovery. I propose to further examine recovery goals from a quantitative spatial perspective. I will use a large rage-wide sample of global positioning system (GPS) collars to collect fine scale spatial data that will be combined with existing California Department of Fish and Game (CDFG) datasets to quantitatively define the length and timing of migration. I will then use these definitions to construct more accurate models reflecting different strategies of resource selection and variation in resource selection by season. Finally, I will use the resulting habitat models to: 1) provide an objective basis for defining SNBS habitat and connectivity between seasonal ranges; 2) compare resource selection of native and translocated individuals; and 3) assess changes to SNBS habitat predicted under down-scaled models of climate change. Finally, I will apply the preceding analyses to direct conservation actions.

Sierra Sheep migration

Figure 1. Annual migratory cycle for 2 GPS radiocollared Sierra Sheep in the Mt. Langley herd, CA. 

Lead Researchers

Derek Spitz, PhD Candiate/Wildlife Biology

Tom Stephenson, California Division of Fish and WIldlife Lead Biologist


Heather Johnson, Colorado Divison of Wildlife

Lacey Greene, California Division of Fish and WIldlife

Dr. Scott Mills, Professor, UofMontana


California Department of Fish and Game

Project Duration: 2010 - 2014