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Accueil du site → Master → Etats Unis → 2012 → Seasonal effects of forage quantity, quality and dietary composition of pronghorn (Antilocapra americana) in a semi-arid environment

New Mexico State University (2012)

Seasonal effects of forage quantity, quality and dietary composition of pronghorn (Antilocapra americana) in a semi-arid environment

Avery, Mindi Marie

Titre : Seasonal effects of forage quantity, quality and dietary composition of pronghorn (Antilocapra americana) in a semi-arid environment

Auteur : Avery, Mindi Marie

Université de soutenance : New Mexico State University

Grade : Master of Sciences (MS) Wildlife Sciences 2012

Résumé
Pronghorn (Antilocapra americana) populations throughout the arid southwest have declined as a result of environmental pressures associated with human-induced and climate-related stressors. A population of pronghorn on White Sands Missile Range (WSMR) has declined since 1980 despite little to no hunting pressure or competition for forage with livestock. While this decreasing trend coincided with intermittent periods of severe drought, the exotic South African gemsbok (Oryx gazella) is presumed to be contributing to the pronghorn decline. Less is known regarding the effects that precipitation has on quantity and quality of forage selected by pronghorn. Thus the goal of this study was to characterize seasonal changes in forage quantity and quality in areas where pronghorn were observed foraging on WSMR and relate these seasonal changes to diet composition and dietary quality of available forage in both pronghorn and gemsbok. Diet composition using microhistological methodology revealed forbs, comprised over half the pronghorn diet in the warm-wet (55%), and warm-dry (68%) seasons of 2010. Diet composition of pronghorn and gemsbok overlapped 17% in the warm-dry season of 2010 and 31% during the drought of the warm-dry season of 2011. I quantified above-ground biomass in pronghorn habitat across three seasons to determine forage availability and to compare biomass with seasonal trends in precipitation. The majority of the annual precipitation (12.6 cm) coincided with above-ground biomass in the warm-wet season (89.8 g/m2 ) compared to the warm-dry (63.9 g/m2 ) and cool-dry (68.9 g/m2 ) seasons which received 3.7 cm and 0.5 cm precipitation, respectively. Across all three seasons, the majority of above-ground biomass consisted of grasses (47.6 g/m2 ) followed by shrubs (14.6 g/m2 ), and forbs (12.1 g/m2 ). Fecal nitrogen (FN) and fecal 2,6-diamonphelic acid (DAPA) were assessed as indices of diet quality. Dietary quality in the pronghorn population on WSMR was affected by seasonal differences in forage as well as severe drought as indicated by a low FN (1.44 %) and FDAPA (0.32 mg/g) in the warm-dry season of 2011. Fecal nitrogen and FDAPA did not differ for gemsbok between warm-dry seasons of 2010 and 2011 reflecting negligible effects of drought on the dietary quality of gemsbok.

Sujets  : Pronghorn—Food—New Mexico—White Sands Missile Range.

Annonce (NMSU Library)

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