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Accueil du site → Doctorat → États-Unis → 2016 → Core zones, livestock, and population ecology of argali in Mongolia’s Gobi steppe

University of Montana (2016)

Core zones, livestock, and population ecology of argali in Mongolia’s Gobi steppe

Ekernas, Lars Stefan

Titre : Core zones, livestock, and population ecology of argali in Mongolia’s Gobi steppe

Auteur : Ekernas, Lars Stefan

Etablissement de soutenance : University of Montana

Grade : Doctor of Philosophy (PhD) 2016

Core zones are established to reduce anthropogenic disturbance under the assumption that they protect biodiversity, yet this assumption has rarely been tested. In Central Asia, increasing livestock density threatens 70% of large mammals including in protected areas where livestock often constitute 95% of ungulate biomass. A resulting conundrum is that local pastoralists are both key threats and crucial allies to conservation. Core zones, which reduce disturbance in small areas of important habitat, offer a potential solution to support wildlife and indigenous livelihoods. For my dissertation, I capitalize on a manipulation spanning 12 years to evaluate wild argali sheep (Ovis ammon) responses to reducing livestock density by 40% inside a core zone in Mongolia’s Gobi steppe. I investigate direct and indirect pathways through which pastoralists affect argali ; quantify effects of livestock reduction on argali birth mass, survival, and population growth ; and improve methods for monitoring argali populations throughout Central Asia. Because pastoralists influence plant, herbivore, and predator communities, they can affect argali through diverse pathways. Pastoralists alter predation pressure from both native and introduced carnivores, and their livestock probably compete with argali for food. I found that livestock reduction strongly affected argali, increasing argali birth mass by 18%, increasing juvenile survival from pre-reduction 19% to post-reduction 51%, and increasing argali population growth by 9% annually from 0.91 to 1.00. I found clear signals that argali are resource limited, since livestock reduction plus normalized difference vegetation index (NDVI) explained 97% of the annual variation in cohort lamb survival and explained 90% of the annual variation in asymptotic population growth. My analyses therefore reveal that livestock detrimentally affect argali and simultaneously provide empirical evidence that core zones can mitigate these effects. I also develop methods for monitoring argali populations using lamb:ewe ratios, from which I can infer population trend if adult survival at my study site is incorporated as a ceiling that can be attained but not surpassed at other locations. Lamb:ewe ratios are simple, inexpensive and can engage local communities in conservation efforts. In totality my dissertation advances conservation of argali while broadly yielding insight on a complex ecological process, interspecific competition.


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