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Accueil du site → Projets de développement → Projets de recherche pour le Développement → 2001 → GLOBAL WARMING AND SURVIVAL OF DESERT BIGHORN SHEEP

United States Department of Agriculture (USDA) 2001


Global Warming Desert Bighorn

United States Department of Agriculture (USDA) Research, Education & Economics Information System (REEIS)


Identification : CA-B*-ECO-6535-H

Pays : Etats Unis

Durée : Oct 1, 2001 à Sep 30, 2004

Domaine : Aquatic and Terrestrial Wildlife ; Wild animals ;


Our objectives are to characterize and model the current status and future prospects for survival of desert bighorn sheep in southeastern California. Bighorns exhibit a metapopulation-like distributed, inhabiting about 50 isolated mountain ranges in the California deserts. Their habitat occurs on mountaintops so global warming may cause their habitat to contract upwards with eventual extinction. We assembled a GIS model including the most important environmental variables, and on the basis of 27 previous extinctions, modeled and predicted bighorn vulnerability to climate changes projected by global climate models. Lower elevation, drier, and more isolated ranges are most vulnerable. We also used existing software (a population viability analysis model) to estimate error in our extinction in model. There may be cascading effects because the overall bighorn metapopulation is composed of smaller metapopulation clusters. Consequently, loss of certain populations effects the viability of the metapopulation cluster by loss of sources of dispersal necessary for recolonize following extinction. Although we continue to refine our data sets for the GIS model, this phase of the project is mostly complete. The next phase involves (1) using molecular genetics to establish genetic structuring of the metapopulation, (2) refine predictions of the GIS model, and (3) establishing baseline parameters on vegetation by which future changes due to climate can be monitored. Sequences of mtDNA, inherited only through the female line, will indicate the degree or mixing or isolation from dispersal of the various mountain ranges. From radio-telemetry studies, we know that males commonly move between mountain ranges in search of reproductive females. Females are much less likely to move (i. e., philopatric), but persistence of local populations in the metapopulation are dependent on dispersal of females, the reproductive unit in this species in which males do not participate in rearing of young. If females seldom reach isolated ranges, there should be a pattern in the distribution of haplotypes (mtDNA sequences) that reflects the past history of movement of females. If dispersal by females was prevalent in the past, the distribution of haplotypes should be uniform. Baseline monitoring of vegetation or other environmental variables into the future is necessary because the desert is highly stochastic. The climatic pattern is complex, being driven by two weather systems-western winter precipitation pattern and the southern summer monsoonal pattern-each largely independent in its effects. Thus, different regions of the California desert may follow different climate trends. This accounts for the very different vegetation in different parts of the desert because season, timing, and amount of precipitation have substantially different biological and ecological consequences for bighorn sheep.

Présentation : USDA

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