Can shrub cover increase predation risk for a desert rodent?

Schooley, Robert L.; Sharpe, Peter B.; Horne, Beatrice Van

doi:10.1139/z96-020

Cited by 101 publications

(83 citation statements)

References 41 publications

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“…2, Table 1). Many lizard and rodent species have lower escape speeds in dense vegetation compared with open areas (Vasquez et al, 2002;Schooley et al, 1996;Goodman, 2009;Vanhooydonck and Van Damme, 2003). Species utilizing bipedal running may be able to exploit habitat types with uneven substrata because of the increases in visual perception and/or by reaching their maximum speed more quickly (Rieder et al, 2010;Djawdan and Garland, 1988;Rocha-Barbosa et al, 2008;Kohlsdorf and Biewener, 2006).…”

Section: Performance and Behavior With Multiple Obstaclesmentioning

confidence: 99%

The effects of multiple obstacles on the locomotor behavior and performance of a terrestrial lizard

Parker

McBrayer

2016

Journal of Experimental Biology

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Negotiation of variable terrain is important for many small terrestrial vertebrates. Variation in the running surface resulting from obstacles (woody debris, vegetation, rocks) can alter escape paths and running performance. The ability to navigate obstacles likely influences survivorship through predator evasion success and other key ecological tasks (finding mates, acquiring food). Earlier work established that running posture and sprint performance are altered when organisms face an obstacle, and yet studies involving multiple obstacles are limited. Indeed, some habitats are cluttered with obstacles, whereas others are not. For many species, obstacle density may be important in predator escape and/or colonization potential by conspecifics. This study examines how multiple obstacles influence running behavior and locomotor posture in lizards. We predict that an increasing number of obstacles will increase the frequency of pausing and decrease sprint velocity. Furthermore, bipedal running over multiple obstacles is predicted to maintain greater mean sprint velocity compared with quadrupedal running, thereby revealing a potential advantage of bipedalism. Lizards were filmed running through a racetrack with zero, one or two obstacles. Bipedal running posture over one obstacle was significantly faster than quadrupedal posture. Bipedal running trials contained fewer total strides than quadrupedal ones. But on addition of a second obstacle, the number of bipedal strides decreased. Increasing obstacle number led to slower and more intermittent locomotion. Bipedalism provided clear advantages for one obstacle, but was not associated with further benefits for an additional obstacle. Hence, bipedalism helps mitigate obstacle negotiation, but not when numerous obstacles are encountered in succession.

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Section: Performance and Behavior With Multiple Obstaclesmentioning

confidence: 99%

The effects of multiple obstacles on the locomotor behavior and performance of a terrestrial lizard

Parker

McBrayer

2016

Journal of Experimental Biology

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“…Studies at the San Joaquin Experimental Range near Fresno, California, showed similar results in that squirrel populations were larger in areas grazed by livestock compared with ungrazed areas (Howard et al 1959;Fitch and Bentley 1949). Other studies have documented higher predation risk for ground squirrels in habitats with high, compared to low, vegetative cover (Schooley et al 1996;Sharpe and Van Horne 1998). Furthermore, the spatial distribution of Arctic ground squirrels (S. parryii plesius Osgood) may be directly linked to predation risk because squirrels tend not to occupy habitats that reduce their ability to perceive predators (Karels and Boonstra 1999).…”

Section: Discussionmentioning

confidence: 63%

The Effects of Livestock on California Ground Squirrels (Spermophilus beecheyii)

Fehmi¹,

Russo²,

Bartolome³

2005

REM

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Understanding the impacts of livestock grazing on wildlands is important for making appropriate ecosystem management decisions. Using livestock exclosures, we examined the effects of moderate cattle grazing on the abundance of California ground squirrels (Spermophilus beecheyii Richardson) and the spatial distribution of active burrows within their colonies in grassland and blue oak (Quercus douglasii Hook. & Arn.) savanna habitats in the coastal range of California over a 3-year period (1991)(1992)(1993)(1994). Overall, relative population densities of California ground squirrels declined significantly throughout the experiment, but did not differ between grazed and ungrazed colonies or between habitats. There was also no significant interaction between these 2 factors. The spatial distribution of burrows, as measured by the mean nearest neighbor distance of active entrances within a colony, did not differ significantly between grazed and ungrazed colonies or between habitats, nor was the interaction significant. Thus, low to moderate levels of cattle grazing did not appear to have a strong effect on the population dynamics of California ground squirrels, and grazing may be compatible with maintenance of ground squirrel populations. Based on multivariate analysis of variance of 1994 data, live plant cover, native plant cover, and standing biomass were lower where the number of burrows was higher on grazed colonies but were little affected on ungrazed colonies. Ground squirrels may increase the impact of livestock grazing and thus reduce the capacity of the land to support other activities. However, it is clear that the effects of livestock grazing are complex and that detailed studies of potential mechanisms by which grazing impacts California ground squirrel populations are necessary. ResumenEntender el impacto del apacentamiento del ganado en tierras silvestres es importante para tomar decisiones apropiadas sobre el manejo de los ecosistemas. Durante un periodo de tres añ os (1991-1994) y usando exclusiones de ganado, examinamos los efectos del apacentamiento moderado en la abundancia de ardillas terrestres de California (Spermophilus beecheyii) y la distribució n espacial de madrigueras activas dentro de sus colonias en há bitats de pastizal y ''Blue oak'' (Quercus douglasii) en la regió n costera de California, USA. En general, las densidades relativaas de la població n de ardillas declinó significativamente durante el experimento, pero no hubo diferencia entre colonias con apacentamiento pastoreo y sin apacentamiento, ni entre habitats. Tampoco hubo interacció n significativa entre estos dos factores. La distribució n espacial de madrigueras, medida por la distancia promedio del vecino más cercano de entradas activas dentro de una colonia, no difirio significativamente entre las colonias apacentadas y no apacentadas ni entre habitats, ni la interacció n fue significativa. Así, niveles de apacentamiento bajos a moderados no parecieron tener un efecto fuerte sobre las diná micas de la població n de a...

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“…In addition to forage, we framed our habitat selection analyses specifically around the concept of cover, which is an important structural element of the habitat as it modifies interactions with conspecifics or predators due to reduced visual detection rates or hindrances in escaping (Schooley et al 1996, Heithaus et al 2009, Camp et al 2013. Moreover, cover affects food availability and abiotic factors such as temperature, wind speed, humidity, snow depth and precipitation (Mysterud and Østbye 1999).…”

Section: Als Improves Understanding Of Habitat Selectionmentioning

confidence: 99%

Improving broad scale forage mapping and habitat selection analyses with airborne laser scanning: the case of moose

et al. 2014

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Abstract. Determining the spatial distribution of large herbivores is a key challenge in ecology and management. However, our ability to accurately predict this is often hampered by inadequate data on available forage and structural cover. Airborne laser scanning (ALS) can give direct and detailed measurements of vegetation structure. We assessed the effectiveness of ALS data to predict (1) the distribution of browse forage resources and (2) moose (Alces alces) habitat selection in southern Norway. Using ground reference data from 153 sampled forest stands, we predicted available browse biomass with predictor variables from ALS and/or forest inventory. Browse models based on both ALS and forest inventory variables performed better than either alone. Dominant tree species and development class of the forest stand remained important predictor variables and were not replaced by the ALS variables. The increased explanatory power from including ALS came from detection of canopy cover (negatively correlated with forage biomass) and understory density (positively correlated with forage biomass). Improved forage estimates resulted in improved predictive ability of moose resource selection functions (RSFs) at the landscape scale, but not at the home range scale. However, when also including ALS cover variables (understory cover density and canopy cover density) directly into the RSFs, we obtained the highest predictive ability, at both the landscape and home range scales. Generally, moose selected for high browse biomass, low amount of understory vegetation and for low or intermediate canopy cover depending on the time of day, season and scale of analyses. The auxiliary information on vegetation structure from ALS improved the prediction of browse moderately, but greatly improved the analysis of habitat selection, as it captured important functional gradients in the habitat apart from forage. We conclude that ALS is an effective and valuable tool for wildlife managers and ecologists to estimate the distribution of large herbivores.

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Can shrub cover increase predation risk for a desert rodent?

Cited by 101 publications

References 41 publications

The effects of multiple obstacles on the locomotor behavior and performance of a terrestrial lizard

The effects of multiple obstacles on the locomotor behavior and performance of a terrestrial lizard

The Effects of Livestock on California Ground Squirrels (Spermophilus beecheyii)

Improving broad scale forage mapping and habitat selection analyses with airborne laser scanning: the case of moose

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