FEMALE COMPETITION AND THE ROLE OF TESTOSTERONE IN A POLYGYNOUS SYSTEM

Testosterone plays an important role in male competitive ability, and it may play a similar function in females. Female-female competition for resources is often associated with high testosterone, both within females and in comparison to males. Positive associations between testosterone and competition are most likely to be seen in systems with high female-female competition. Resource defense polygyny may be one such system since females congregate on high-quality nutrient sources, leading to substantial opportunities for interference competition. I studied female Grant’s gazelle (Nanger granti), a classic resource defense polygynous species, to investigate female competition and its relationship to testosterone. I found substantial evidence for competition between females. Females frequently engaged in agonistic behavior, on average initiating over two agonistic bouts per hour, and higher-ranking females initiated more agonism than lower-ranking females. Testosterone appeared to play an important role in competitive ability. Immunoreactive fecal testosterone metabolites (fT) were strongly positively correlated to both dominance rank and number of agonistic bouts initiated per hour, but only agonism was associated with fT when dominance and agonism were accounted for simultaneously. Females had similar fT concentrations as males. fT was positively associated with immunoreactive fecal glucocorticoid metabolites (fGCM), and this relationship was not due to associations between dominance and fGCM. Month also influenced testosterone physiology. Females had lower fT during a drought than after rains had begun. In addition, fT increased more from August to November in high-ranking females than in low-ranking females. My results suggest that female-female competition may be substantial in resource defense polygynous systems. Testosterone might play an important role in mediating competitive ability in females, but it was also associated with higher glucocorticoid secretion. Future studies on females would be well served to investigate the consequences of testosterone secretion and how they relate to female competition

CORE ZONES, LIVESTOCK AND POPULATION ECOLOGY OF ARGALI IN MONGOLIA’S GOBI STEPPE

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