Recipient Organization
UNIVERSITY OF MONTANA
COLLEGE OF FORESTRY AND CONSERVATION
MISSOULA,MT 59812
Performing Department
College of Forestry and Conservation
Non Technical Summary
Federally-endangered Sierra Nevada bighorn sheep (Ovis canadensis sierrae; SNBS), the rarest sub-species of North American mountain sheep, are endemic to California and have been a flagship wilderness species for Yosemite National Park (YNP), Sequoia-Kings Canyon National Park (SKNP) and several other public land and wildlife agencies. Unfortunately little is known about the species' historic range; SNBS was largely extirpated prior to coming under scientific scrutiny and persists only as a series of fragmented sub-populations (hereafter 'herd units'). These herd units are wide-ranging and rely on seasonal habitat areas both within and outside park boundaries. While these seasonal ranges and their connectivity are thought to be essential to herd unit viability, the habitat requirements of SNBS are poorly understood. SNBS from different herd units appear to employ different patterns of habitat use. Within a single herd unit, individuals manifest different migratory strategies that may even change year to year. A better understanding of SNBS migration and habitat-use strategies would allow us to quantitatively evaluate: 1) the goals proposed by the SNBS Recovery Plan (U.S. Fish and Wildlife Service [USFWS] 2003); 2) the proposed implementation of these goals (i.e. evaluating unoccupied habitat in order to identify viable unoccupied herd units that are strong candidates for translocation); 3) how shifts in migration may affect population recovery; and 4) how climate change may interact with current habitat to limit future population growth and habitat potential. Thus, the current project examines the interaction of migratory patterns, habitat and population viability and how this interaction may be impacted by a changing climate. We will use a large range-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. We will then use these definitions to construct more accurate models reflecting different strategies of resource selection and variation in resource selection by season. Next, we 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 strategies of native and translocated individuals; and 3) assess changes to SNBS habitat predicted under down-scaled models of climate change. Finally, we will apply the preceding analyses to form specific recommendations that quantitatively evaluate the viability of proposed recovery goals and the management actions required to implement them.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
Federally-endangered Sierra Nevada bighorn sheep (Ovis canadensis sierrae; SNBS), the rarest sub-species of North American mountain sheep, are endemic to California and persists only as a series of fragmented sub-populations (hereafter 'herd units'). The habitat requirements of SNBS are poorly understood. A better understanding of SNBS migration and habitat-use strategies would allow us to quantitatively evaluate: 1) the goals proposed by the SNBS Recovery Plan (U.S. Fish and Wildlife Service [USFWS] 2003); 2) the proposed implementation of these goals (i.e. evaluating unoccupied habitat in order to identify viable unoccupied herd units that are strong candidates for translocation); 3) how shifts in migration may affect population recovery; and 4) how climate change may interact with current habitat to limit future population growth and habitat potential. Thus, the current project examines the interaction of migratory patterns, habitat and population viability and how this interaction may be impacted by a changing climate. Consequently, the goals of this project are to provide: 1) a model developed to characterize seasonal resource selection of suitable habitat for SNBS in the Sierra Nevada Mountains; 2) quantification of seasonal connectivity between home ranges and location of migration routes within herd units; 3) a model of the effects of climate change on habitat suitability for SNBS; and 4) an estimate of the availability of current and future SNBS habitat and evaluation of proposed recovery goals and the potential for successful reintroductions. A final report is due no later than May 1, 2014.
Project Methods
While SNBS are known to be partially migratory (i.e. populations contain individuals of mixed migrant and non-migrant strategies), migration has never been studied in this species. Differences in migratory strategies among individuals have likely confounded previous attempts to evaluate SNBS habitat selection and limited understanding of the species' distribution and potential range. We will collect two types of data: 1) high frequency location data acquired from global positioning system (GPS) collars and 2) demographic data (e.g. survival and lambing rate) collected by monitoring the population of marked radio-collared individuals and surveying the entire population. We will use the GPS data to quantify the timing, duration and distance of migration by applying the methodology of Bunnefeld et al (2011). This will provide a basis for 1) categorizing individuals by migratory strategy (migrant or resident) ; 2) identifying migratory pathways; 3) determining the location and extent of strategy specific seasonal ranges; and 4) quantifying the connectivity between these ranges. We will then develop strategy and season specific resource selection functions (RSFs) to model habitat selection by strategy and season. We will then attempt to relate our estimates of seasonal habitat quality and quantity to demographic data (e.g. survival and lambing rates) in order to test the importance of these variables for population persistence. Next, we will apply this framework to the existing species range in order to identify currently unoccupied areas that have a high likelihood of supporting viable SNBS populations. Finally, we will combine the habitat selection framework we have developed with down-scale climate models for the Sierra Nevada Mountains in order to predict future effects of climate change on the availability of SNBS habitat. All results will presented directly to the Sierra Nevada Bighorns Sheep Recovery Program led by the California Department of Fish and Game. These results will provide a clear quantitative basis for recovery goals and actions that currently depend largely on expert opinion.