The Dynamics and Scaling of Foraging Velocity and Encounter Rate in Mammalian Herbivores

Shipley, Lisa A.; Spalinger, Donald E.; Gross, John E.; Hobbs, N. Thompson; Wunder, Bruce A.

doi:10.2307/2389848

Cited by 58 publications

(64 citation statements)

References 40 publications

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“…Robbins,unpublished data). Foraging velocities and maximum intake rates observed in captive bears during the board studies were within the range of values reported for herbivores of similar body size (elk, cattle, and horses; Shipley et al 1996).…”

Section: Discussionsupporting

confidence: 80%

Constraints on herbivory by grizzly bears

2001

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Although well known as carnivores and not capable of digesting plant fiber, grizzly bears (Ursus arctos horribilis) consume over 200 species of plants and are entirely vegetarian in some ecosystems. Even in ecosystems with abundant meat resources, green vegetation can be an important seasonal food resource. Therefore, we examined the morphological, physiological, and environmental constraints that determine the nutritional value of herbaceous vegetation to grizzly bears. Short-term, board foraging trials were used with captive grizzly bears to determine constraints on intake rate including bite size, bite rate, bear size, plant species, plant height, and plant distribution. Feeding trials were conducted to determine the effect of protein level (12-35%) and digestible dry matter intake on weight gain. Finally, maximum daily intake, daily foraging time, and weight change were measured for captive bears foraging on highly abundant and nutritious forbs and grasses during 12-day trials. Intake during short-term board trials overestimated the intake of freely foraging bears from two- to seven-fold depending on bear size. Because of their relatively larger bite sizes, smaller absolute energy requirements, and relatively larger intake capacity, smaller bears (<120 kg) made greater weight gains than very large bears on herbaceous vegetation. Smaller bears with ad libitum access to palatable, nutritious forbs gained weight at rates equal to wild bears. However, depending upon plant characteristics, bite sizes and available daily foraging time increasingly prevented large bears (>120 kg) from gaining weight on herbaceous vegetation. Both captive and wild bears select forbs over grasses at similar growth stages because forbs are generally higher in protein and more digestible than grasses. Therefore, the nutritional well-being of wild grizzly bears could be improved in areas where bears are largely herbivorous and, thus, relatively small by purposefully managing for nutritious forbs.

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Section: Discussionsupporting

confidence: 80%

Constraints on herbivory by grizzly bears

2001

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“…Areas near forest roads had more available cover for escape from humans than areas with high human densities near villages. Red deer moved in order to get more nutritional food and at the same time to find suitable sites for bedding to optimize energy balance during late winters (Shipley et al 1996). This led to bedding close to feeding areas (Mysterud and Ostbye 1995).…”

Section: Discussionmentioning

confidence: 99%

Effects of human disturbance on movement, foraging and bed selection in red deerCervus elaphus xanthopygus from the Wandashan Mountains, northeastern China

Jiang

Zhang

2007

Acta Theriol

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Z. 2007. Effects of human disturbance on movement, foraging and bed selection in red deer Cervus elaphus xanthopygus from the Wandashan Mountains, northeastern China. Acta Theriologica 52: 435-446.We characterized 716 sites (including 22 beds, 60 foraging and 604 movement sites) used by red deer Cervus elaphus xanthopygus Milne-Edwards, 1867 in the Wandashan Mountains, northeastern China in the winter period. We used covariates for vegetation, topography, disturbances by other ungulates, and disturbance by humans to develop movement, forage and bed site resource-selection models. We used an information-theoretic approach to select the top 5 models for movement, forage and bed site occurrences respectively. The three most parsimonious autologistic models were good predictors of movement, forage and bed occurrence of this species. Vegetation covariates were important components of all models. We recorded avoidance responses by the behaviours of species to each disturbance type (ie, villages, forest roads and abandoned roads); bed site occurrences were most sensitive to all human disturbances for their lowest odds encountered. Across all parsimonious models, villages have the largest negative effect on movement, foraging and bed occurrences. Movement and bedding behaviours were also affected by other ungulate disturbances. Altitude had slightly negative effect on movement and foraging behaviours. Ridges, topographic aspect and shrub stands were all correlated with bed-site selection. Although different behaviours may be associated with different microhabitat features, behaviours of red deer responded similarly to the same human disturbance on a broad scale. Based on the observations above, we believe that red deer are avoiding human-altered habitat for movement, bedding and foraging because of disturbances during the critical late winter period. Furthermore, various behavioural resource selection models and corresponding graphs of important habitat disturbances can be used to guide and evaluate future development proposals.

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“…Deploying our mobility model in this context, we ask how changes in n affect the rate of transmission of a cultural trait. This research question is analogous to the studies that seek to understand how natural selection shapes the mobility patterns of a species in order to maximize currencies such as mate and prey encounters or predator avoidance (Bartumeus et al, 2008;Charnov, 1976;Gerritsen, 1980;Getty and Pulliam, 1991;Holling, 1959;Lee et al, 2006;Lewis, 2003;Lima and Dill, 1990;Nakajima, 2001;Shipley et al, 1996;Stephens and Krebs, 1986;Visser and Kiørboe, 2006;Viswanathan et al, 1996Viswanathan et al, , 1999. Here we want to understand which part of the forager-collector continuum maximizes the rate at which cultural behaviours are transmitted.…”

Section: Mobility and Cultural Transmissionmentioning

confidence: 99%