Modeling Nutritional Carrying Capacity for Translocated Desert Bighorn Sheep in Western Texas

Abstract

Restoration of desert bighorn sheep (Ovis canadensis) is proceeding in several western states. Measurement of nutritional resources (quality and quantity) is not normally conducted to assess future and present translocation sites, although it has been recommended generally for evaluation of ungulate habitat. We estimated nutritional carrying capacity (based on nitrogen in forage species) of three mountain ranges in Trans‐Pecos Texas where desert bighorn sheep have been translocated. We used an explicit nutritional constraint model to estimate carrying capacity on a seasonal basis. Although drought conditions prevailed during the study period, bighorns were not limited by quantity of vegetation. However, forage biomass of high nutritional quality (>1.5% N) was very low (<9 kg/ha in spring; <1 kg/ha in all other seasons). Consequently, there appeared to be inadequate forage of high N content for bighorns to meet reproductive requirements in some seasons. Estimates generated using the explicit nutritional constraint carrying capacity model appeared to be realistic relative to observed densities. Nutritional sampling and modeling can predict potential carrying capacity on areas scheduled for restoration or on ranges already stocked, predict effects of management on carrying capacity, and allow managers to compare among restoration sites. We recommend that desert bighorn managers focus on monitoring the abundance of high‐quality (%N) forage species, especially during periods of drought or higher nutritional requirements (e.g., lactation, post‐weanling growth).

Lack of diet partitioning by sex in reintroduced desert bighorn sheep

“…Bighorns may select forages that, based on trade-offs in forage biomass or nutritional quality, allow them to maintain nitrogen balance (Hobbs et al, 1982). In our study, the nitrogen content of forbs was 2-3 times greater than the nitrogen content of browse (DeYoung et al, 2000). The greater nitrogen of forbs may explain the strong preference for forbs by desert bighorn sheep in western Texas.…”

“…Female bighorns in the Baylor, Beach, and Sierra Diablo mountains of western Texas use primarily higher, more rugged areas during the segregation period, whereas males are evenly distributed among elevations (DeYoung, 1997). Diet composition of males should differ from that of females during the segregation period if reintroduced desert bighorn sheep in western Texas exhibit similar foraging characteristics to desert bighorn sheep in their native habitat.…”

Recognizing the Potential of Sustainable Use of Pasture Resources in South Khorasan Province With Approch of Carrying Capacity

“…In our country, which is the predominant livestock trap of the sheep's pasture, the capacity of sheep is expressed on the basis of sheep's unit, which is equivalent to a non-livestock, indicating the nutritional requirement of a sheep holding 48.73 kg. The metabolic energy for keeping ruminant's changes with age, body weight or body size, food quality, access to forage, land and climate change [8]. The energy required for keeping livestock on rangelands is between 30% and 80% higher than that of livestock fed in closed environments, depending on the grazing forage, the weather conditions, and the level and height of the area [9].…”

COMPOSICIÓN DE LA DIETA Y CAPACIDAD NUTRICIONAL DE CARGA DEL HÁBITAT DEL CONEJO DE LOS VOLCANES (Romerolagus diazi) EN MÉXICO

“…La capacidad de carga se refiere al número de animales que cierta área de hábitat puede sostener durante un periodo o estación determinada, sin que los alimentos presentes y sus nutrientes se vean mermados hasta el punto de deterioro (DeYoung, Hellgren, Fulbright, Robbins, & Humphreys, 2000). La estimación de la capacidad de carga, sobre una base alimenticia, permite comparar el potencial de los hábitats.…”

“…Carrying capacity refers to the number of animals that a certain habitat area can sustain over a given period or season, without the foods present and their nutrients being depleted to the point of deterioration (DeYoung, Hellgren, Fulbright, Robbins, & Humphreys, 2000). Estimating carrying capacity on a food base allows comparing the potential of different habitats.…”