Adrian M Shrader - Academia.edu (original) (raw)

Papers by Adrian M Shrader

Research paper thumbnail of Olfactory misinformation provides refuge to palatable plants from mammalian browsing

Research Square (Research Square), Sep 20, 2023

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Research paper thumbnail of White rhinos and other herbivores decrease visitations and increase vigilance in response to human vocalizations

Journal of Mammalogy

Harnessing the fear animals have of humans has the potential to aid in the conservation of wildli... more Harnessing the fear animals have of humans has the potential to aid in the conservation of wildlife. Most vertebrates perceive humans as “super predators.” While predator cues are an important nonlethal management tool, the use of human cues for management has rarely been implemented or experimentally tested. Extensive poaching is threatening the persistence of white rhinos (Ceratotherium simum simum), and there is a need to deter them from areas with elevated poaching risks. To investigate the feasibility of harnessing the fear white rhinos have of humans to aid in their conservation, we conducted playback experiments at rhino middens. We broadcasted repeated human (treatment) and bird (control) vocalizations, and measured changes in visitations and antipredator responses. We found that overall rhino visitations did not change in response to controls but decreased by 46% in response to human vocalizations. This pattern appears to be driven by the response of females, who decreased ...

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Research paper thumbnail of The first report of urine overmarking of pro-oestrus female dung by a male white rhino

African Zoology, Sep 5, 2019

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Research paper thumbnail of Ritualised Dung Kicking by White Rhino Males Amplifies Olfactory Signals but Reduces Odour Duration

Journal of Chemical Ecology, Jul 16, 2018

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Research paper thumbnail of Evaluating Oribi Translocations for Conservation: The Importance of Translocation Guidelines

African Journal of Wildlife Research, 2021

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Research paper thumbnail of Browser Population–Woody Vegetation Relationships in Savannas

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Research paper thumbnail of Does the removal of finder's share influence the scrounging decisions of herbivores?

Animal Behaviour, Nov 1, 2017

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Research paper thumbnail of Increases in food availability can tempt oribi antelope into taking greater risks at both large and small spatial scales

Animal Behaviour, Oct 1, 2015

Differences in food availability and predation risk can influence how herbivores use landscapes. ... more Differences in food availability and predation risk can influence how herbivores use landscapes. As a result, trade-offs between costs and benefits can influence habitat and patch selection. To determine how oribi antelope, Ourebia ourebi, weigh up costs and benefits when making habitat and patch level foraging decisions, we measured giving-up densities in artificial patches. First, we determined large-scale habitat use, and then explored how different variables explained patch use within habitats. When the availability of food within patches across the different habitats was equal, oribi preferred to feed in short and tall grasslands and avoided woodlands. Furthermore, the avoidance of woodlands extended into the surrounding grasslands, resulting in oribi feeding less intensively in grassland areas within 15 m of the woodlands. Within the safe grassland habitats, oribi preferred to feed in patches close to tall grass (i.e. escape cover), and where they could see beyond 2 m. These results suggest that oribi select habitats and patches in relation to perceived predation risk (i.e. predation costs outweigh potential food intake benefits). However, when we increased food availability within woodlands, oribi increased their large-scale risk-taking behaviour and fed in these woodlands. Furthermore, this increased risk taking extended to small-scale foraging decisions whereby an increase in food availability within woodlands caused oribi to increase their relative usage of patches that had sight lines as well as patches that were closer to potential ambush sites. Ultimately, these results highlight how changes in food availability can determine the degree to which herbivores are willing to increase their risk-taking behaviour, and how these changes can affect overall landscape use.

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Research paper thumbnail of Is Hand Plucking an Accurate Method of Estimating Bite Mass and Instantaneous Intake of Grazing Herbivores?

Rangeland Ecology & Management, Jul 1, 2011

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Research paper thumbnail of Forest or the trees: At what scale do elephants make foraging decisions?

Acta Oecologica-international Journal of Ecology, Jul 1, 2012

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Research paper thumbnail of Density-dependent habitat selection varies between male and female African elephants

Biological Conservation, Dec 1, 2022

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Research paper thumbnail of Alarm calls or predator calls: which elicit stronger responses in ungulate communities living with and without lions?

Oecologia, Mar 27, 2019

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Research paper thumbnail of Herbivores employ a suite of antipredator behaviours to minimize risk from ambush and cursorial predators

Animal Behaviour, May 1, 2017

Prey species may adjust their use of antipredator behaviours to counter the hunting strategies (e... more Prey species may adjust their use of antipredator behaviours to counter the hunting strategies (e.g. ambush versus cursorial) and the level of risk imposed by different predators. Studies of suites of behaviours across well-defined contrasts of predation risk and type are rare, however. Here we explored the degree to which six herbivore species adjusted their antipredator behaviours to two predator treatments (lion, Panthera leo, versus cheetah, Acinonyx jubatus, and wild dogs, Lycaon pictus). We focused on prey behaviour (vigilance, grouping, temporal use) at waterholes. We predicted that if the hunting strategy of the predator was the key driver of antipredator behaviour, ambushing lions would elicit a greater response than cursorial cheetah and wild dogs. Alternatively, if predator preference was the main driver, then we expected prey species to adjust their antipredator behaviours in response to the predators that specifically target them (i.e. preferred prey of the different predators). Overall, we found that the herbivores maintained greater vigilance, generally moved in larger groups and used waterholes less at dawn, at dusk or at night (when lions are active) when exposed to the potential threat of ambushing lions. However, some species within the accessible prey range of cheetah and/or wild dogs (i.e. red hartebeest, warthog, gemsbok) moved in larger groups when exposed to these predators. Yet, the magnitude of the differences in group size for these herbivores were small. Thus, we suggest that, overall, the potential threat of ambushing lions was the main driver of antipredator behaviour around waterholes, probably determined by prey weight preference and the possibility of being ambushed.

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Research paper thumbnail of The role of companionship in the dispersal of white rhinoceroses ( Ceratotherium simum )

Behavioral Ecology and Sociobiology, Aug 1, 2002

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Research paper thumbnail of Can intrinsic foraging efficiency explain dominance status? A test with functional response experiments

Oecologia, Nov 15, 2018

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Research paper thumbnail of Soil fertility on granite and sedimentary soils is associated with seasonal differences in foraging by elephants

Plant and Soil, Oct 18, 2016

Background and aimsIt is generally assumed that very large herbivores, such as elephants, make fo... more Background and aimsIt is generally assumed that very large herbivores, such as elephants, make foraging decisions at large spatial scales, but the extent to which seasonal foraging decisions are driven by soil quality, and its link to plant nutrient levels, is uncertain.MethodsWe studied the diet selection of African elephants Loxodonta africana in Ithala Game Reserve in northern KwaZulu-Natal, South Africa, using data on elephant feeding preferences and spatial distributions from a published paper. Elephants were present in the eastern half with granite soils in the wet season, and in the western half with sedimentary soils in the dry season. The quality of these two soil types and of seven key tree species for elephants was assessed in both seasons.ResultsSoil quality was higher on the sedimentary soils in terms of total nitrogen, soil respiration, water-holding capacity, organic carbon and pH. Leaf quality was higher on the sedimentary soils in the dry season, while in the wet season there was no significant difference in leaf quality of the seven key tree species growing on the two substrates.ConclusionSoil quality may explain elephants’ foraging decisions in the dry season, but not in the wet season. Elephants preferred trees with higher protein and lower concentrations of fibre on both granite and sedimentary soils.

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Research paper thumbnail of Changes in feeding behavior and patch use by herbivores in response to the introduction of a new predator

Journal of Mammalogy, Dec 30, 2017

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Research paper thumbnail of Shrub cover homogenizes small mammals’ activity and perceived predation risk

Scientific Reports, Nov 14, 2019

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Research paper thumbnail of Is a reduction in the individual vigilance of mothers a key evolutionary driver of group formation in white rhinos?

African Zoology, Apr 1, 2013

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Research paper thumbnail of The biological, social, and political complexity of conserving oribi antelope Ourebia ourebi in South Africa

Endangered Species Research, 2021

The endangered oribi antelope Ourebia ourebi is highly dependent on privately owned lands for its... more The endangered oribi antelope Ourebia ourebi is highly dependent on privately owned lands for its continued survival in South Africa. Despite the fact that conserving oribi may result in costs to farmers in the form of land use restrictions and pressures from illegal hunting, there is evidence that South African farmers are willing to conserve oribi on their lands. However, to date, no research has been conducted to examine farmers’ understanding of how to manage their lands for oribi or their motivations for conserving this species. We conducted 50 in-depth interviews with private landowners in KwaZulu-Natal, South Africa, to investigate why farmers are willing to protect oribi, their perceptions of the threats to the species, and their understanding of how land should be managed to benefit oribi. Respondents’ willingness to conserve oribi was driven primarily by an affinity for the species and wildlife in general. Respondents perceived illegal taxi hunting to be the greatest threa...

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Research paper thumbnail of Olfactory misinformation provides refuge to palatable plants from mammalian browsing

Research Square (Research Square), Sep 20, 2023

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Research paper thumbnail of White rhinos and other herbivores decrease visitations and increase vigilance in response to human vocalizations

Journal of Mammalogy

Harnessing the fear animals have of humans has the potential to aid in the conservation of wildli... more Harnessing the fear animals have of humans has the potential to aid in the conservation of wildlife. Most vertebrates perceive humans as “super predators.” While predator cues are an important nonlethal management tool, the use of human cues for management has rarely been implemented or experimentally tested. Extensive poaching is threatening the persistence of white rhinos (Ceratotherium simum simum), and there is a need to deter them from areas with elevated poaching risks. To investigate the feasibility of harnessing the fear white rhinos have of humans to aid in their conservation, we conducted playback experiments at rhino middens. We broadcasted repeated human (treatment) and bird (control) vocalizations, and measured changes in visitations and antipredator responses. We found that overall rhino visitations did not change in response to controls but decreased by 46% in response to human vocalizations. This pattern appears to be driven by the response of females, who decreased ...

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Research paper thumbnail of The first report of urine overmarking of pro-oestrus female dung by a male white rhino

African Zoology, Sep 5, 2019

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Research paper thumbnail of Ritualised Dung Kicking by White Rhino Males Amplifies Olfactory Signals but Reduces Odour Duration

Journal of Chemical Ecology, Jul 16, 2018

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Research paper thumbnail of Evaluating Oribi Translocations for Conservation: The Importance of Translocation Guidelines

African Journal of Wildlife Research, 2021

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Research paper thumbnail of Browser Population–Woody Vegetation Relationships in Savannas

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Does the removal of finder's share influence the scrounging decisions of herbivores?

Animal Behaviour, Nov 1, 2017

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Research paper thumbnail of Increases in food availability can tempt oribi antelope into taking greater risks at both large and small spatial scales

Animal Behaviour, Oct 1, 2015

Differences in food availability and predation risk can influence how herbivores use landscapes. ... more Differences in food availability and predation risk can influence how herbivores use landscapes. As a result, trade-offs between costs and benefits can influence habitat and patch selection. To determine how oribi antelope, Ourebia ourebi, weigh up costs and benefits when making habitat and patch level foraging decisions, we measured giving-up densities in artificial patches. First, we determined large-scale habitat use, and then explored how different variables explained patch use within habitats. When the availability of food within patches across the different habitats was equal, oribi preferred to feed in short and tall grasslands and avoided woodlands. Furthermore, the avoidance of woodlands extended into the surrounding grasslands, resulting in oribi feeding less intensively in grassland areas within 15 m of the woodlands. Within the safe grassland habitats, oribi preferred to feed in patches close to tall grass (i.e. escape cover), and where they could see beyond 2 m. These results suggest that oribi select habitats and patches in relation to perceived predation risk (i.e. predation costs outweigh potential food intake benefits). However, when we increased food availability within woodlands, oribi increased their large-scale risk-taking behaviour and fed in these woodlands. Furthermore, this increased risk taking extended to small-scale foraging decisions whereby an increase in food availability within woodlands caused oribi to increase their relative usage of patches that had sight lines as well as patches that were closer to potential ambush sites. Ultimately, these results highlight how changes in food availability can determine the degree to which herbivores are willing to increase their risk-taking behaviour, and how these changes can affect overall landscape use.

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Research paper thumbnail of Is Hand Plucking an Accurate Method of Estimating Bite Mass and Instantaneous Intake of Grazing Herbivores?

Rangeland Ecology & Management, Jul 1, 2011

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Forest or the trees: At what scale do elephants make foraging decisions?

Acta Oecologica-international Journal of Ecology, Jul 1, 2012

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Research paper thumbnail of Density-dependent habitat selection varies between male and female African elephants

Biological Conservation, Dec 1, 2022

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Alarm calls or predator calls: which elicit stronger responses in ungulate communities living with and without lions?

Oecologia, Mar 27, 2019

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Herbivores employ a suite of antipredator behaviours to minimize risk from ambush and cursorial predators

Animal Behaviour, May 1, 2017

Prey species may adjust their use of antipredator behaviours to counter the hunting strategies (e... more Prey species may adjust their use of antipredator behaviours to counter the hunting strategies (e.g. ambush versus cursorial) and the level of risk imposed by different predators. Studies of suites of behaviours across well-defined contrasts of predation risk and type are rare, however. Here we explored the degree to which six herbivore species adjusted their antipredator behaviours to two predator treatments (lion, Panthera leo, versus cheetah, Acinonyx jubatus, and wild dogs, Lycaon pictus). We focused on prey behaviour (vigilance, grouping, temporal use) at waterholes. We predicted that if the hunting strategy of the predator was the key driver of antipredator behaviour, ambushing lions would elicit a greater response than cursorial cheetah and wild dogs. Alternatively, if predator preference was the main driver, then we expected prey species to adjust their antipredator behaviours in response to the predators that specifically target them (i.e. preferred prey of the different predators). Overall, we found that the herbivores maintained greater vigilance, generally moved in larger groups and used waterholes less at dawn, at dusk or at night (when lions are active) when exposed to the potential threat of ambushing lions. However, some species within the accessible prey range of cheetah and/or wild dogs (i.e. red hartebeest, warthog, gemsbok) moved in larger groups when exposed to these predators. Yet, the magnitude of the differences in group size for these herbivores were small. Thus, we suggest that, overall, the potential threat of ambushing lions was the main driver of antipredator behaviour around waterholes, probably determined by prey weight preference and the possibility of being ambushed.

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Research paper thumbnail of The role of companionship in the dispersal of white rhinoceroses ( Ceratotherium simum )

Behavioral Ecology and Sociobiology, Aug 1, 2002

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Can intrinsic foraging efficiency explain dominance status? A test with functional response experiments

Oecologia, Nov 15, 2018

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Soil fertility on granite and sedimentary soils is associated with seasonal differences in foraging by elephants

Plant and Soil, Oct 18, 2016

Background and aimsIt is generally assumed that very large herbivores, such as elephants, make fo... more Background and aimsIt is generally assumed that very large herbivores, such as elephants, make foraging decisions at large spatial scales, but the extent to which seasonal foraging decisions are driven by soil quality, and its link to plant nutrient levels, is uncertain.MethodsWe studied the diet selection of African elephants Loxodonta africana in Ithala Game Reserve in northern KwaZulu-Natal, South Africa, using data on elephant feeding preferences and spatial distributions from a published paper. Elephants were present in the eastern half with granite soils in the wet season, and in the western half with sedimentary soils in the dry season. The quality of these two soil types and of seven key tree species for elephants was assessed in both seasons.ResultsSoil quality was higher on the sedimentary soils in terms of total nitrogen, soil respiration, water-holding capacity, organic carbon and pH. Leaf quality was higher on the sedimentary soils in the dry season, while in the wet season there was no significant difference in leaf quality of the seven key tree species growing on the two substrates.ConclusionSoil quality may explain elephants’ foraging decisions in the dry season, but not in the wet season. Elephants preferred trees with higher protein and lower concentrations of fibre on both granite and sedimentary soils.

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Research paper thumbnail of Changes in feeding behavior and patch use by herbivores in response to the introduction of a new predator

Journal of Mammalogy, Dec 30, 2017

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Shrub cover homogenizes small mammals’ activity and perceived predation risk

Scientific Reports, Nov 14, 2019

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Is a reduction in the individual vigilance of mothers a key evolutionary driver of group formation in white rhinos?

African Zoology, Apr 1, 2013

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The biological, social, and political complexity of conserving oribi antelope Ourebia ourebi in South Africa

Endangered Species Research, 2021

The endangered oribi antelope Ourebia ourebi is highly dependent on privately owned lands for its... more The endangered oribi antelope Ourebia ourebi is highly dependent on privately owned lands for its continued survival in South Africa. Despite the fact that conserving oribi may result in costs to farmers in the form of land use restrictions and pressures from illegal hunting, there is evidence that South African farmers are willing to conserve oribi on their lands. However, to date, no research has been conducted to examine farmers’ understanding of how to manage their lands for oribi or their motivations for conserving this species. We conducted 50 in-depth interviews with private landowners in KwaZulu-Natal, South Africa, to investigate why farmers are willing to protect oribi, their perceptions of the threats to the species, and their understanding of how land should be managed to benefit oribi. Respondents’ willingness to conserve oribi was driven primarily by an affinity for the species and wildlife in general. Respondents perceived illegal taxi hunting to be the greatest threa...

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