Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Accueil du site → Master → Etats Unis → 2014 → Influence of sympatric livestock grazing on Desert bighorn sheep (Ovis canadensis mexicana) forage resources and foraging behavior

New Mexico State University (2014)

Influence of sympatric livestock grazing on Desert bighorn sheep (Ovis canadensis mexicana) forage resources and foraging behavior

Garrison, Kyle Robert

Titre : Influence of sympatric livestock grazing on Desert bighorn sheep (Ovis canadensis mexicana) forage resources and foraging behavior

Auteur : Garrison, Kyle Robert

Université de soutenance : New Mexico State University

Grade : Master of Science (MS) Wildlife Sciences 2014

Résumé
Sympatric cattle grazing on desert bighorn ranges is frequently proposed as a limiting factor to desert bighorn population growth. However, few studies have measured the effect of cattle grazing on bighorn forage resources and subsequent foraging behavior, factors which have important effects on fitness. I estimated biomass and availability of bighorn forage at two sites, the cattle grazed Caballo and ungrazed San Andres mountains, New Mexico. I expected forage biomass and availability to be lower in the cattle-grazed Caballo site than in the ungrazed San Andres site and lower at cattle-accessible areas within the Caballo, but not the San Andres site. At each site, I recorded foraging bout efficiency of adult ewes by recording foraging time per step while feeding and activity budgets of all age classes (i.e., adult rams, adult ewes, yearlings, and lambs) by documenting behavior (i.e., grazing, browsing, traveling, standing, and bedded) via instantaneous sampling. I also recorded forage characteristics at sites where bighorn were observed foraging. Because forging efficiency is positively associated with forage abundance, I predicted that bighorn would be less efficient foragers in the Caballo site. Groundcover forage biomass and availability was low in both sites throughout the study (June 2012 - November 2013). However, the Caballo site had 82.5% lower browse biomass and 50% lower browse availability versus the San Andres site. Consequently, Caballo bighorn exhibited higher daily travel rates, but lower daily foraging time, to locate areas of higher forage abundance. By selecting areas with high forage abundance, ewes in the Caballo Mountains had foraging bout efficiency levels that were similar to their San Andres counterparts. However, lower daily foraging time may decrease daily intake rates while increased travel increases energetic cost, indicating that Caballo bighorn may be inefficient foragers at larger temporal scales. I did not find a significant reduction in forage recourses at cattle-accessible sites in the Caballo site, contrary to my prediction. The entire Caballo site had little available forage except for the most rugged areas, potentially a result of intensive historic livestock grazing, limiting my ability to detect an effect of current livestock-induced forage reduction.

Sujets : Forage plants— Effect of grazing on— Desert bighorn sheep— Habitat— Browse (Animal food)

Présentation (NMSU Library)

Page publiée le 12 février 2016, mise à jour le 27 décembre 2017