Herbivores, resources and risks: alternating regulation along primary environmental gradients in savannas

Hopcraft, J. Grant C.; Olff, Han; Sinclair, A. R. E.

doi:10.1016/j.tree.2009.08.001

Cited by 324 publications

(437 citation statements)

References 91 publications

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“…2010). In Nyathi, this size‐dependent vulnerability is less important because lions were the only known resident predator of the prey species investigated and are capable of killing eland and buffalo, the two largest species.…”

Section: Discussionmentioning

confidence: 99%

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Limited spatial response to direct predation risk by African herbivores following predator reintroduction

Davies

Tambling

Kerley

et al. 2016

Ecology and Evolution

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Predators affect ecosystems not only through direct mortality of prey, but also through risk effects on prey behavior, which can exert strong influences on ecosystem function and prey fitness. However, how functionally different prey species respond to predation risk and how prey strategies vary across ecosystems and in response to predator reintroduction are poorly understood. We investigated the spatial distributions of six African herbivores varying in foraging strategy and body size in response to environmental factors and direct predation risk by recently reintroduced lions in the thicket biome of the Addo Elephant National Park, South Africa, using camera trap surveys, GPS telemetry, kill site locations and Light Detection and Ranging. Spatial distributions of all species, apart from buffalo, were driven primarily by environmental factors, with limited responses to direct predation risk. Responses to predation risk were instead indirect, with species distributions driven by environmental factors, and diel patterns being particularly pronounced. Grazers were more responsive to the measured variables than browsers, with more observations in open areas. Terrain ruggedness was a stronger predictor of browser distributions than was vegetation density. Buffalo was the only species to respond to predator encounter risk, avoiding areas with higher lion utilization. Buffalo therefore behaved in similar ways to when lions were absent from the study area. Our results suggest that direct predation risk effects are relatively weak when predator densities are low and the time since reintroduction is short and emphasize the need for robust, long‐term monitoring of predator reintroductions to place such events in the broader context of predation risk effects.

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Section: Discussionmentioning

confidence: 99%

“…2009b; Hopcraft et al. 2010). Moreover, where the ratio of predator to prey density is particularly low, predator regulation of prey populations is weak, and bottom‐up mechanisms are more important (Vucetich et al.…”

Section: Introductionmentioning

confidence: 99%

Limited spatial response to direct predation risk by African herbivores following predator reintroduction

Davies

Tambling

Kerley

et al. 2016

Ecology and Evolution

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“…The prevalence of trophic cascades depends on strong consumer control of the prey community, with a cascading indirect positive effect being generated on the next lower trophic level. There are a number of distinct species traits that determine if species are subjected to consumer control (Duffy and Hay 1990;Coley and Barone 1996;Polis 1999;Hopcraft et al 2010), and the response of the community to changes in predators should ultimately depend on the community composition of each trophic level (Gruner et al 2008). Our results support the concept that the lifestage development of the producer trophic level can be essential for responses to predator declines in the marine benthos, by demonstrating that established larger macroalgae were resource controlled regardless of the composition of the higher trophic levels.…”

Section: Factormentioning

confidence: 99%

“…In addition, the significant effects on food-web structure by predation were apparent only when biomass production was included as an underlying variable in the analyses. This finding emphasizes the need to explore the interdependence between complex ecological interactions, such as joint effects of top-down and bottom-up control, by incorporating environmental conditions and resource availability in food-web analyses (Olff et al 2009;Hopcraft et al 2010). Thus, we cannot understand ecosystem effects of predator exploitation and resource loading by only monitoring standing stocks.…”

Section: Factormentioning

confidence: 99%

“…However, the top-down control of food web dynamics depends on complex interactions between environmental conditions, resource supply, individual species traits, and food web complexity (Polis and Strong 1996;Polis 1999;Menge 2000;Oksanen and Oksanen 2000;Shurin et al 2002;Hopcraft et al 2010). These interactions indicate that predator effects on food web configuration are highly context dependent and that ecosystem-specific properties determine responses to exploitation of higher trophic levels (Strong 1992;Shurin et al 2002;Hopcraft et al 2010). Thus, to further understand the impact of predators on food-web structure and be able to predict effects of predator declines, we need to test predator effects in combination with both abiotic and biotic properties of natural food webs.…”

Section: Introductionmentioning

confidence: 99%

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Cascading predator control interacts with productivity to determine the trophic level of biomass accumulation in a benthic food web

Eriksson¹,

Rubach

Batsleer

et al. 2011

Ecological Research

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Large-scale exploitation of higher trophic levels by humans, together with global-scale nutrient enrichment, highlights the need to explore interactions between predator loss and resource availability. The hypothesis of exploitation ecosystems suggests that topdown and bottom-up control alternate between trophic levels, resulting in a positive relationship between primary production and the abundance of every second trophic level. Specifically, in food webs with three effective trophic levels, primary producers and predators should increase with primary production, while in food webs with two trophic levels, only herbivores should increase. We provided short-term experimental support for these model predictions in a natural benthic community with three effective trophic levels, where the number of algal recruits, but not the biomass of gastropod grazers, increased with algal production. In contrast, when the food web was reduced to two trophic levels by removing larger predators, the number of algal recruits was unchanged while gastropod grazer biomass increased with algal production. Predator removal only affected the consumer-controlled early life-stages of algae, indicating that both the number of trophic levels and the life-stage development of the producer trophic level determine the propagation of trophic cascades in benthic systems. Our results support the hypothesis that predators interact with resource availability to determine food-web structure.

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Population responses of roe deer to the recolonization of the French Vercors by wolves

Randon¹,

Bonenfant

Michallet

et al. 2020

Population Ecology

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In a context of changing carnivore populations worldwide, it is crucial to understand the consequences of these changes for prey populations. The recolonization by wolves of the French Vercors mountain range and the long‐term monitoring (2001–2017) of roe deer in this area provided a unique opportunity to assess the effects of wolves on this prey. Roe deer was the main prey of wolves in the west Vercors mountain range during this recolonization. We compared roe deer abundance and fawn body mass in two contrasted areas of a wolf pack territory: a central area (core of the territory characterized by an intense use by wolves) and a peripheral area (used more occasionally). Roe deer population growth rates were lower in the central area between 2001 and 2006, resulting in a decline in roe deer abundance. Roe deer abundance substantially dropped in the two study areas after an extremely severe winter but the abundance of roe deer in the central area facing with wolves was slower to recover and remained at lower abundance levels for 6 years. Fawn body mass was consistently lower in the central area, varied similarly as roe deer abundance, and was not influenced by weather conditions or red deer population abundance. Altogether, the effects of wolves on roe deer in the central area occurred during a 10‐year period following the establishment of wolves, through the interplay between wolf predation (before wolves started preying on red deer), harsh winter conditions and possibly naivety of prey to this recolonizing predator.

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Herbivores, resources and risks: alternating regulation along primary environmental gradients in savannas

Cited by 324 publications

References 91 publications

Limited spatial response to direct predation risk by African herbivores following predator reintroduction

Limited spatial response to direct predation risk by African herbivores following predator reintroduction

Cascading predator control interacts with productivity to determine the trophic level of biomass accumulation in a benthic food web

Population responses of roe deer to the recolonization of the French Vercors by wolves

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