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Community‐level responses of African carnivores to prescribed burning

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Abstract

Fires are common in many ecosystems worldwide, and are frequently used as a management tool. Although the responses of herbivores to fire have been well‐studied, the responses of carnivores to fire remain unclear. In particular, post‐fire habitat changes, and the associated changes in prey availability, might affect the coexistence or competition of carnivore species within the larger carnivore community, but few studies have focused on how fires influence multiple carnivore species simultaneously. Using South African carnivores as our focal community, we explored relative changes in carnivore intensity of use in post‐fire landscapes associated with hypothesized changes in prey availability and top‐down suppression. We monitored carnivore intensity of use in relation to prescribed burning using camera traps, with a Before‐After‐Control‐Impact study design. We analyzed the camera trap data using community N‐mixture models to understand how individual species, as well as the carnivore guild as a whole, respond to burning. Changes in carnivore intensity of use in response to prescribed burns were not uniform; however, no species decreased intensity of use of post‐fire landscapes. The apex predator, the lion (Panthera leo), increased use of prey‐rich burnt areas, but other large carnivore species exhibited neutral responses to fire despite the associated prey increase. Responses of medium‐ and small‐sized carnivores were species‐specific, and included both neutral and positive responses. Positive responses to fire by lions and herbivores were short‐lived, and did not persist a year after burning occurred. Synthesis and Applications: Our results indicate that fire does not promote carnivore coexistence by creating conditions for all carnivores to increase use of burned areas, but that it also likely does not result in spatial avoidance of subordinate predators. Instead, fires might cause a suppression of opportunities for subordinate large carnivores because they need to avoid the apex predator, rather than take advantage of short‐term increased hunting opportunities in recently burned areas. Our results highlight the complexity of understanding species‐specific and community‐level responses of carnivores to fire, and overlooked ecological effects of its use as a management tool.

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... In support of the prey catchability hypothesis, lions Panthera leo (typically an ambush predator) in Tanzania avoided burnt areas, even though their prey were abundant there, probably because lions prefer to hunt in areas with high vegetation cover as this favours their short-range stalk and ambush hunting style (Hopcraft et al., 2005;Eby et al., 2013). However, a more recent study found that lions increased their use of prey-rich burnt areas in southern Africa, possibly because the retention of shrubs after fire facilitated hunting (Gigliotti et al., 2022). In the Appalachian Mountains, USA, bobcats Lynx rufus strongly selected forest edges created by fire and other disturbances, likely because the denser understorey vegetation at the forest edge relative to the interior facilitated their ambush hunting strategy (McNitt et al., 2020). ...
... Intra-guild dynamics can also shape how predators respond to fire (Gigliotti et al., 2022). Several studies have reported that subordinate predators used burnt or unburnt areas as a means of predator avoidance. ...
... For instance, in semi-arid Australia red foxes showed no direct response to fire, but were negatively associated with dingoes Canis dingo which preferred recently burnt (<11 years post-fire) areas (Geary et al., 2018). In South Africa, lions showed a positive response to prey-rich burnt areas, but the subordinate predators (spotted hyena Crocuta crocuta, cheetah Acinonyx jubatus, and leopard Panthera pardus) showed a neutral response, suggesting that fire may suppress hunting opportunities for some species due to apex predator avoidance (Gigliotti et al., 2022). By contrast, San Joaquin kit foxes Vulpes macrotis were more common in burnt areas, possibly because it was easier for them to avoid bobcats and coyotes Canis latrans there (Warrick & Cypher, 1998). ...
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... We used a BACI (before-after-control-impact) study design (Castro et al., 2021;Gigliotti et al., 2022) to examine the effects of mowing on bird and small mammal communities occurring in a high-elevation grassland ecosystem, used mainly for wildlife grazing, in South Africa. The areas neighboring the study site are used for livestock rearing and crop farming. ...
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Prescribed fire is an important management tool in east Africa as a way to improve foraging conditions for herbivores, and to make wildlife easier for tourists to observe and photograph. Although past research has investigated the factors influencing herbivore use of post-fire vegetation, the temporal dynamics of these effects have seldom been documented, and use of burned areas by African carnivores has not been evaluated. Between 2008 and 2011, we studied responses of 8 common herbivores and 8 carnivore species to burns in the Mara-Serengeti ecosystem in southwestern Kenya by monitoring mammal abundance on 4 transects from up to 136 days before burning, and up to 748 days after burning. Among herbivores, zebra, warthog, Thomson's gazelle, Grant's gazelle, and topi, occurred in higher densities in burned than unburned areas. Impala and wildebeest showed trends toward occurring in higher densities in burned areas. These effects lasted up to 120 days for Thomson's gazelle, but we did not observe a specific temporal relationship to burning in the other 5 herbivore species. Both small and large carnivores were more likely to be observed along transects after than before burns; we observed small carnivores including black-backed jackals, side-striped jackals, bat-eared foxes, and banded mongoose in greater numbers up to 365 days after burns but observed large carnivores, including African lions, spotted hyenas, leopards, and cheetahs, in greater numbers only for up to 120 days after burns. Our results indicate that wildlife responses to prescribed fire last ≤1 year in this region. Although burning stimulates vegetation growth and improves wildlife visibility, managers should recognize that wildlife responses might not persist for more than a few months in tropical African savannas like the one monitored here. © 2014 The Wildlife Society.
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In a recent paper, Welsh, Lindenmayer and Donnelly (WLD) question the usefulness of models that estimate species occupancy while accounting for detectability. WLD claim that these models are difficult to fit and argue that disregarding detectability can be better than trying to adjust for it. We think that this conclusion and subsequent recommendations are not well founded and may negatively impact the quality of statistical inference in ecology and related management decisions. Here we respond to WLD's claims, evaluating in detail their arguments, using simulations and/or theory to support our points. In particular, WLD argue that both disregarding and accounting for imperfect detection lead to the same estimator performance regardless of sample size when detectability is a function of abundance. We show that this, the key result of their paper, only holds for cases of extreme heterogeneity like the single scenario they considered. Our results illustrate the dangers of disregarding imperfect detection. When ignored, occupancy and detection are confounded: the same naïve occupancy estimates can be obtained for very different true levels of occupancy so the size of the bias is unknowable. Hierarchical occupancy models separate occupancy and detection, and imprecise estimates simply indicate that more data are required for robust inference about the system in question. As for any statistical method, when underlying assumptions of simple hierarchical models are violated, their reliability is reduced. Resorting in those instances where hierarchical occupancy models do no perform well to the naïve occupancy estimator does not provide a satisfactory solution. The aim should instead be to achieve better estimation, by minimizing the effect of these issues during design, data collection and analysis, ensuring that the right amount of data is collected and model assumptions are met, considering model extensions where appropriate.
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Fire-prone savanna ecosystems in southern African conservation areas are managed by prescribed burning in order to conserve biodiversity. A prescribed burning system designed to maximise the benefits of a diverse fire regime in savanna conservation areas is described. The area burnt per year is a function of the grass fuel load, and the number of fires per year is a function of the percentage area burnt. Fires are point-ignited, under a range of fuel and weather conditions, and allowed to burn out by themselves. The seasonal distribution of planned fires over a year is dependent on the number of fires. Early dry season fires (May–June) tend to be small because fuels have not yet fully cured, while late season fires (August–November) are larger. More fires are ignited in the early dry season, with fewer in the late dry season. The seasonality, area burnt, and fire intensity are spatially and temporally varied across a landscape. This should result in the creation of mosaics, which should vary in extent and existence in time. Envelopes for the accumulated percentage to be burnt per month, over the specified fire season, together with upper and lower buffers to the target area are proposed. The system was formalised after 8 years of development and testing in Pilanesberg National Park, South Africa. The spatial heterogeneity of fire patterns increased over the latter years of implementation. This fire management system is recommended for savanna conservation areas of >20 000 ha in size.
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The Florida panther (Puma concolor coryi) is one of the most endangered mammals in the world, with only 30-50 adults surviving in and around Florida Panther National Wildlife Refuge and the adjacent Big Cypress National Preserve, hlanagers at these areas conduct annual prescribed burns in pine (Pinus sp.) as a cost-effective method of managing wildlife habitat. Our objectives were to determine if temporal and spatial relationships existed between prescribed fire and panther use of pine. To accomplish this, we paired fire-event data from the Refuge and the Preserve with panther radiolocations collected between 1989 and 1998, determined the time that had elapsed since burning had occurred in management units associated with the radiolocations, and generated a frequency distribution based on those times. We then generated an expected frequency distribution, based on random use relative to time since burning. This analysis revealed that panther use of burned pine habitats was greatest during the first year after a management unit was burned. Also, compositional analysis indicated that panthers were more likely to position their home ranges in areas that contained pine. We conclude that prescribed burning is important to panther ecology. We suggest that panthers were attracted to <1-year-old burns because of white-tailed deer (Odocoileus virginianus) and other prey responses to vegetation and structural changes caused by the prescribed fires. The strong selection for stands burned within 1 year is a persuasive indication that it is the bunting in pine, rather than the pine per se, that most influenced habitat use. Before burning rotation lengths are reduced, however, we suggest managers determine effects of shorter burning intervals on vegetation composition and evaluate the landscape-scale changes that would result.
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Recent methodological advances permit the estimation of species richness and occurrences for rare species by linking species-level occurrence models at the community level. The value of such methods is underscored by the ability to examine the influence of landscape heterogeneity on species assemblages at large spatial scales. A salient advantage of community-level approaches is that parameter estimates for data-poor species are more precise as the estimation process "borrows" from data-rich species. However, this analytical benefit raises a question about the degree to which inferences are dependent on the implicit assumption of relatedness among species. Here, we assess the sensitivity of community/group-level metrics, and individual-level species inferences given various classification schemes for grouping species assemblages using multispecies occurrence models. We explore the implications of these groupings on parameter estimates for avian communities in two ecosystems: tropical forests in Puerto Rico and temperate forests in northeastern United States. We report on the classification performance and extent of variability in occurrence probabilities and species richness estimates that can be observed depending on the classification scheme used. We found estimates of species richness to be most precise and to have the best predictive performance when all of the data were grouped at a single community level. Community/group-level parameters appear to be heavily influenced by the grouping criteria, but were not driven strictly by total number of detections for species. We found different grouping schemes can provide an opportunity to identify unique assemblage responses that would not have been found if all of the species were analyzed together. We suggest three guidelines: (1) classification schemes should be determined based on study objectives; (2) model selection should be used to quantitatively compare different classification approaches; and (3) sensitivity of results to different classification approaches should be assessed. These guidelines should help researchers apply hierarchical community models in the most effective manner.
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1. Given the role of fire in shaping ecosystems, especially grasslands and savannahs, it is important to understand its broader impact on these systems. Post-fire stimulation of plant nutrients is thought to benefit grazing mammals and explain their preference for burned areas. However, fire also reduces vegetation height and increases visibility, thereby potentially reducing predation risk. Consequently, fire may be more beneficial to smaller herbivores, with higher nutritional needs and greater risks of predation.2. We tested the impacts of burning on different sized herbivores’ habitat preference in Serengeti National Park, as mediated by burning's effects on vegetation height, live to dead biomass ratio, and leaf nutrients.3. Burning caused a less than four month increase in leaf nitrogen (N), and leaf non-N nutrients (copper (Cu), potassium (K), and magnesium (Mg)), and a decrease in vegetation height and live:dead biomass. During this period, total herbivore counts were higher on burned areas. Generally, smaller herbivores preferred burned areas, more strongly than larger herbivores.4. Unfortunately, it was not possible to determine the vegetation characteristics that explained burned area preference for each of the herbivore species observed. However, total herbivore abundance and impala (Aepyceros melampus) preference for burned areas was due to the increases in non-N nutrients caused by burning.5. These findings suggest that burned area attractiveness to herbivores is mainly driven by changes to forage quality and not potential decreases in predation risk caused by reductions in vegetation height.This article is protected by copyright. All rights reserved.
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Given the budgetary restrictions on scientific research and the increasing need to better inform conservation actions, it is important to identify the patterns and causes of biases in research effort. We combine bibliometric information from a literature review of almost 16,500 peer-reviewed publications on a well-known group of 286 species, the Order Carnivora, with global datasets on species' life history and ecological traits to explore patterns in research effort. Our study explores how species' characteristics influenced the degree to which they were studied (measured as the number of publications). We identified a wide variation in intensity of research effort at both Family and Species levels, with some of the least studied being those which may need protection in future. Our findings hint at the complex role of human perspectives in setting research agendas. We found that better-studied species tended to be large-bodied and have a large geographic range whilst omnivory had a negative relationship with research effort. IUCN threat status did not exhibit a strong relationship with research effort which suggests that the conservation needs of individual species are not major drivers of research interest. This work is the first to use a combination of bibliometric analysis and biological data to quantify and interpret gaps in research knowledge across an entire Order. Our results could be combined with other resources, such as Biodiversity Action Plans, to prioritise and co-ordinate future research effort, whilst our methods can be applied across many scientific disciplines to describe knowledge gaps.
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Fire is a major agent involved in landscape transformation and an indirect cause of changes in species composition. Responses to fire may vary greatly depending on life histories and functional traits of species. We have examined the taxonomic and functional responses to fire of eight taxonomic animal groups displaying a gradient of dietary and mobility patterns: Gastropoda, Heteroptera, Formicidae, Coleoptera, Araneae, Orthoptera, Reptilia and Aves. The fieldwork was conducted in a Mediterranean protected area on 3 sites (one unburnt and two burnt with different postfire management practices) with five replicates per site. We collected information from 4606 specimens from 274 animal species. Similarity in species composition and abundance between areas was measured by the Bray-Curtis index and ANOSIM, and comparisons between animal and plant responses by Mantel tests. We analyze whether groups with the highest percentage of omnivorous species, these species being more generalist in their dietary habits, show weak responses to fire (i.e. more similarity between burnt and unburnt areas), and independent responses to changes in vegetation. We also explore how mobility, i.e. dispersal ability, influences responses to fire. Our results demonstrate that differences in species composition and abundance between burnt and unburnt areas differed among groups. We found a tendency towards presenting lower differences between areas for groups with higher percentages of omnivorous species. Moreover, taxa with a higher percentage of omnivorous species had significantly more independent responses of changes in vegetation. High- (e.g. Aves) and low-mobility (e.g. Gastropoda) groups had the strongest responses to fire (higher R scores of the ANOSIM); however, we failed to find a significant general pattern with all the groups according to their mobility. Our results partially support the idea that functional traits underlie the response of organisms to environmental changes caused by fire.
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Managers of African lions (Panthera leo) on reserves where they have been reintroduced increasingly face challenges associated with ecological regulation,genetic degradation and increased susceptibility to catastrophic events. The Lion Management Forum (LiMF) was formed in 2010 to define these challenges and explore possible solutions with the view to developing appropriate management guidelines. LiMF bases its recommendations on the ecologically sound premise thatmanagers should,as far as possible,mimic natural processes that have broken down in reserves, using proactive rather than reactive methods, i.e. management should focus on causal mechanisms as opposed to reacting to symptoms. Specifically, efforts should be made to reduce population growth and thus reduce the number of excess lions in the system; disease threats should be reduced through testing and vaccination whenever animals are translocated; and genetic integrity should be monitored. The latter is particularly important, as most of these reserves are relatively small (typically <1000 km2). An adaptive management framework is needed to implement the guidelines developed here on reserves across the country, with regional nodes addressing more local genetic issues, within an overall national plan. Ongoing monitoring and scientific assessment of behavioural, population and systemic responses of lion populations and responsive modification of the guidelines, should improve management of lions on small reserves in South Africa. This approach will provide a template for evidence-based conservation management of other threatened species. Ultimately ‘National Norms and Standards’must be established and a ‘National Action Plan’ for lions in South Africa developed.
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An effort to re-establish lions and cheetahs into northern KwaZulu-Natal, South Africa, was studied for 40 months to collect information on the behaviour and ecology of reintroduced felids and to assess the success of such restoration attempts. ‘Soft-release’ methods including a period of captivity prior to release were employed for the release and probably increased project success. All reintroduced lions and cheetahs remained at the release site. Animals generally did not display ‘homing’ behaviour, though three groups of lions and cheetahs showed some evidence of homing for two months following release. Unfamiliar, unrelated animals socialised during the pre-release captivity period often remained together following release for long periods. Reintroduced lions and cheetahs at Phinda established home ranges with similar characteristics and patterns to that observed in other ecosystems. All individuals which survived the early post-release period remained at Phinda and settled in ranges within the reserve which were largely stable for the duration of the study. Lions (of both sexes) and male cheetahs were territorial whereas female cheetahs showed no signs of establishing territories and used (in some cases) the entire reserve as their home range. The long-term nature of some individual’s ranges suggests that lions and cheetahs are able to establish a home-range following translocation, and therefore, that reintroduction may be a viable method for re-establishing resident felids in areas of their former distribution. The greatest cause of mortality to reintroduced felids was as a result of human activity, particularly poaching. Inter and intra-specific conflict with other large carnivores was also a significant factor. Despite mortalities, population characteristics suggested lions and cheetahs are rapid and effective in re-colonising vacant areas. Most lions and cheetahs survived the critical early post-release stage and a minimum of 60% of females of both species survived to reproduce. At least 43 lion cubs and 48 cheetah cubs were born during the study. High rates of cub and sub-adult survival contributed to rapid population growth. Population modelling suggested that low mortality rates for juveniles and sub-adults may be critical for re-establishment. Re-introduced lions and cheetahs foraged successfully and their post-release survival was not affected by characteristics of food resources. Wildebeest, zebras, nyalas and warthogs made up 86% of biomass killed by lions. Wildebeest were clearly the most important species to lions which were killed at three times their availability. Predation pressure on wildebeest resulted in a population decline during the study period, probably due to the lack of predation-free refuges inherent in small, enclosed reserves. Cheetahs preyed upon reedbucks at eight times their availability at Phinda and reedbucks underwent a population decline. Nyalas and impalas were the other two most important prey species to cheetahs, the former constituting almost 50% of biomass killed by cheetahs. This is the first study of cheetah feeding ecology in woodland habitat and the first to demonstrate that cheetahs can specialise on an ungulate species almost twice as heavy as ‘typical’ prey species from other ecosystems. Female cheetahs showed a pattern of hunting larger prey as litters grew, particularly where a high percentage of cubs survived. Aside from evidence that predation affected some ungulate populations, the study demonstrated significant behavioural changes by herbivores in response to felid reintroduction. Wildebeest and impalas underwent a 200% increase in vigilance behaviour in the first five months following the release of lions and cheetahs. Wildebeest and impalas in exclusion areas free of reintroduced felids did not show any change in vigilance. The study suggested that, contrary to most other efforts at large African carnivore translocation, reintroduction may be a viable method for re-population, at least in the short-term. Methodological and management issues which may be important for the longer term success of these types of projects are discussed.
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Small mammals were live-trapped monthly over a three-year period in a subtropical grassland in Swaziland. Seven species of small mammals were recorded from the study grid. There were significant seasonal and inter-annual differences in rodent numbers, breeding intensity and community structure. Mastomys natalensis was numerically dominant throughout most of the study period, but its numbers fluctuated widely and without a seasonal basis. Numbers of Lemniscomys rosalia and Mus minutoides also fluctuated widely, but both species tended to be more numerous in the dry winter months. A large proportion of the adult M. natalensis, L. rosalia and Steatomys pratensis were reproductively active in the first breeding season of the study, but breeding intensity decreased sharply in the second and third breeding seasons. Species richness and diversity also fluctuated widely throughout the study. In general, species richness was highest in winter months, while species diversity increased with decrease in numbers of M. natalensis. Fire had a severe impact on the small mammal community; densities of M. natalensis increased markedly following the fire, while those of other species declined. Total biomass of small mammals increased, but species diversity and evenness declined as the community became dominated by a single species. Few long-term population studies of small mammals have been conducted in southern Africa. In light of the large inter-annual variability potentially present in most small mammal communities of southern Africa, such studies are essential.
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Africa supports Earth's richest assemblage of large predators, which coexist despite a high degree of dietary overlap. This study used reviews of the prey preferences of African wild dog Lycaon pictus, cheetah Acinonyx jubatus, leopard Panthera pardus, lion P. leo, and spotted hyaena Crocuta crocuta to Investigate the degree of dietary overlap and dietary niche breadth amongst the guild. Wild dogs and cheetahs exhibited the greatest dietary overlap and smallest dietary niche breadth, while lions exhibited the least dietary overlap and, with leopards, had the broadest dietary niche breadth. Increased extinction risk within the guild was related to lower dietary niche breadth. The behavioural and morphological specializations of the two most threatened predators (wild dogs and cheetahs) limit the prey available to them, and increases the potential for dietary competition. Conversely, the large body mass and group hunting strategy of lions and the predatory flexibility of leopards and spotted hyaenas minimizes the effects of dietary overlap, assuring a more secure status. This study Intimates reasons why cheetahs and African wild dogs are naturally less common than lions, leopards and spotted hyaenas In unmodified landscapes. The methods used can be applied to all adequately studied faunal guilds and could highlight previously undetected competitors.
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The honey badger, or ratel, Mellivora capensis has not been well studied despite its extensive distribution. As part of the first detailed study, visual observations of nine habituated free-living individuals (five females, four males) were used to investigate seasonal, annual and sexual differences in diet and foraging behaviour. Theory predicts that generalist predators ‘switch’ between alternative prey species depending on which prey species are currently most abundant, and diet breadth expands in response to decreased availability of preferred food types. There were significant seasonal differences in the consumption of eight prey categories related to changes in prey availability but no seasonal differences in food intake per kg of body mass. As predicted, the cold-dry season diet was characterized by low species richness and low foraging yield but high dietary diversity, while the reverse was true in the hot-dry and hot-wet seasons. In accordance with these predictions, results suggest that the honey badger maintains its intake level by food switching and by varying dietary breadth. Despite marked sexual size dimorphism, male and female honey badgers showed no intersexual differences in prey size, digging success, daily food intake per unit body weight or foraging behaviour. Results do not support the hypothesis that size dimorphism is primarily an adaptation to reduce intersexual competition for food.
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A pride of lions (Panthera leo) was studied on a 15 km2 reserve using radio-telemetry. Kills were recorded from direct observations, as well as reserve management records. The prey base was enumerated by an aerial and road count and the standing biomass crop was calculated. The daily food intake per lioness was calculated to range from 4.1 ± 1.3 (S.E.) to 4.6 ± 2.4 (S.E.) kg/day. Two approaches for determining the sustainability of lions were evaluated: a Large Herbivore Biomass (LHB) and b) Maximum Sustained Yield (MSY) of the main prey. The term Lion Feeding Unit (LFU) was introduced to depict the feeding requirements of an adult lioness. It was calculated that the LHB could support 185 LFUs/100 km2, which was clearly not sustainable in the context of prey declines at an LFU density of 50 LFUs/100 km2. The MSY of prey could sustain 6.7 LFUs/100 km2, which would reverse prey declines if prey populations were initially maintained at 1/2 K. This capacity was recommended for savannas receiving between 500 and 700 mm rainfall per annum, and where no other carnivores were present. This capacity was, however, too low for small reserves (<20 km2) where a large group of lions is needed for aesthetic and economic purposes. A trade-off is suggested where a normal pride size (4-10) is prescribed, but with the understanding that prey declines are inevitable and that prey will need to be replenished on an annual basis.
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Lion hunting behaviour was studied in two regions of Queen Elizabeth National Park, Uganda. Six environmental, three prey-related and two lion-related factors were evaluated for their influence on hunting success. Grass and bush cover, hunting group size, prey group size and the presence/absence of the moon (on nocturnal hunts) had significant effect on the outcome of hunts. Interspecific differences in escape methods used by prey are also discussed.Cover, prey availability and prey body size appeared to be the major causes of variation in lion foraging behaviour between study sites. In Mweya, lions hunted opportunistically for small prey species during the day, while at night, the pride actively searched for large prey. In Ishasha, lions foraged most often during moonless nights, when their hunting success was greatest.RésuméLe comportement de chasse du lion fut étudié dans deux régions du Queen Elizabeth National Park en Ouganda. L'influence de six facteurs environnementaux, trois facteurs liés aux proies et deux facteurs liés au lion lui-même furent évalués dans le cadre du succès de la chasse. La couverture des graminées et des buissons, la taille du groupe en chasse, la taille du groupe des proies et la présence/absence de la lune (durant les chasses nocturnes) ont un effet significatif sur la conclusion des chasses. Les différences interspécifiques des méthodes de fuite utilisées par la proie sont aussi discutées.Le couvert végétal, la disponibilité de proies et la taille corporelle de la proie paraissent être les causes majeures de variation du comportement de recherche du lion entre les sites d'étude. A Mweya, des lions chassent de manière opportuniste des espèces de proie de petite taille durant la journée, alors que de nuit, la bande cherche activement des grandes proie. A Ashasha, des lions chassent le plus souvent durant les nuits sans lune, lorsque leurs chances de succès sont les plus élevées.
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Apex predator reintroductions have proliferated across southern Africa, yet their ecological effects and proposed umbrella benefits of associated management lack empirical evaluations. Despite a rich theory on top-down ecosystem regulation via mesopredator suppression, a knowledge gap exists relating to the influence of lions (Panthera leo) over Africa's diverse mesocarnivore (less than 20 kg) communities. We investigate how geographical variation in mesocarnivore community richness and occupancy across South African reserves is associated with the presence of lions. An interesting duality emerged: lion reserves held more mesocarnivore-rich communities, yet mesocarnivore occupancy rates and evenness-weighted diversity were lower in the presence of lions. Human population density in the reserve surroundings had a similarly ubiquitous negative effect on mesocarnivore occupancy. The positive association between species richness and lion presence corroborated the umbrella species concept but translated into small differences in community size. Distributional contractions of mesocarnivore species within lion reserves, and potentially corresponding numerical reductions, suggest within-community mesopredator suppression by lions, probably as a result of lethal encounters and responses to a landscape of fear. Our findings offer empirical support for the theoretical understanding of processes underpinning carnivore community assembly and are of conservation relevance under current large-predator orientated management and conservation paradigms.
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Understanding the link between environmental factors such as disturbance events, land cover, and soil productivity to spatial variation in animal abundance is fundamental to population ecology and wildlife management. The Longleaf pine (Pinus palustris) ecosystem is an archetypal fire-mediated ecosystem, which has seen drastic reductions in land area due to fire suppression. Current restoration utilizes prescribed fire and hardwood removal, but little is known regarding how these restoration efforts influence predator spatial distributions and predator-prey interactions. We conducted a study to investigate how fire, land cover, and soil productivity influence spatial distributions of predators in a fire-mediated ecosystem. We conducted a 34-camera survey across Camp Blanding Joint Training Center, a military installation in northern Florida, and utilized N-mixture models to estimate relative abundances of mammalian predators. To conceptualize our results relative to managed prey species, we categorized predators into white-tailed deer fawn predators [i.e. coyote (Canis la-trans), bobcat (Felis rufus), and Florida black bear (Ursus americanus floridanus)] and nest predators [i.e. raccoon (Procyon lotor), Virginia opossum (Didelphis virginiana), and nine-banded armadillo (Dasypus novemcinctus)]. Coyote (P = < 0.001) and bobcat (P = 0.01), increased relative abundance with decreasing pyrodiversity, the number of unique time since fire values. Raccoon relative abundance increased with distance from recent burns (P = 0.02). Coyote (P = < 0.001) and bobcat (P = < 0.001) relative abundance also increased with proximity to hardwoods, while raccoon relative abundance decreased with proximity to pine (P = 0.02). Interestingly, there was a lack of detections of mesopredators [i.e. red fox (Vulpes Vulpes), grey fox (Urocyon cinereoargenteus), spotted skunk (Mephitis mephitis) and striped skunk (Spilogale putorius)] that were historically considered common throughout the Southeastern United States and longleaf pine ecosystems. Our results indicate that predator space use was altered by fire conditions and distances to pine and hardwood stands, which supports a predator management strategy that utilizes management tools commonly used in restoration and conservation of the LLP ecosystem to indirectly alter predator distributions, which has the potential to positively affect the management of important species within this ecosystem.
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Many terrestrial ecosystems are fire prone, such that their composition and structure are largely due to their fire regime. Regions subject to regular fire have exceptionally high levels of species richness and endemism, and fire has been proposed as a major driver of their diversity, within the context of climate, resource availability and environmental heterogeneity. However, current fire‐management practices rarely take into account the ecological and evolutionary roles of fire in maintaining biodiversity. Here, we focus on the mechanisms that enable fire to act as a major ecological and evolutionary force that promotes and maintains biodiversity over numerous spatiotemporal scales. From an ecological perspective, the vegetation, topography and local weather conditions during a fire generate a landscape with spatial and temporal variation in fire‐related patches (pyrodiversity), and these produce the biotic and environmental heterogeneity that drives biodiversity across local and regional scales. There have been few empirical tests of the proposition that ‘pyrodiversity begets biodiversity’ but we show that biodiversity should peak at moderately high levels of pyrodiversity. Overall species richness is greatest immediately after fire and declines monotonically over time, with postfire successional pathways dictated by animal habitat preferences and varying lifespans among resident plants. Theory and data support the ‘intermediate disturbance hypothesis’ when mean patch species diversity is correlated with mean fire intervals. Postfire persistence, recruitment and immigration allow species with different life histories to coexist. From an evolutionary perspective, fire drives population turnover and diversification by promoting a wide range of adaptive responses to particular fire regimes. Among 39 comparisons, the number of species in 26 fire‐prone lineages is much higher than that in their non‐fire‐prone sister lineages. Fire and its byproducts may have direct mutagenic effects, producing novel genotypes that can lead to trait innovation and even speciation. A paradigm shift aimed at restoring biodiversity‐maintaining fire regimes across broad landscapes is required among the fire research and management communities. This will require ecologists and other professionals to spread the burgeoning fire‐science knowledge beyond scientific publications to the broader public, politicians and media.
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Understanding and quantifying a large carnivores’ feeding behaviour is a key component in determining its functional significance in an ecosystem, both in terms of its top‐down influence on prey species, but also its relationships with sympatric carnivores. Dietary overlap is one of the numerous niche dimensions used to characterize resource partitioning and potential competition within a community. We characterize the diet, potential dietary niche overlap and prey preference of a large African carnivore guild on small fenced protected areas. To quantify the potential inter‐ and intraspecific foraging competition, we analysed 5,128 kills, representing 35 prey species made by African wild dogs Lycaon pictus (n = 553), cheetahs Acinonyx jubatus (1,427), lions Panthera leo (2,648) and leopards P. pardus (500). Our results show that large African carnivores in small protected areas are exposed to considerable overlap in dietary resource utilization. At the interspecific level, African wild dogs and cheetahs displayed the greatest vulnerability to potential dietary competition. Lions exhibited marked differences in prey preference, mass and species utilization compared to the other carnivores. African wild dogs and cheetah females with dependent offspring occupied the greatest potential for dietary competition within the large carnivore guild. Using a case study based on the preferred biomass of prey available, we estimate the sustainable density of large carnivores at a small fenced prospective African wild dog reintroduction site. African wild dogs displayed the lowest mean predicted density compared to all sympatric predators with an expected population size of 7 individuals. Our research highlights the need to assess the influence of competitive forces in structuring and restoring large predators to portions of their historical range by identifying species most vulnerable to a potential reintroduction attempt. In the absence of controlled experiments, elucidating the influences of exploitation competition is challenging, and only through manipulating sympatric species presence and densities can these complex interactions be fully understood. We characterize the diet, potential dietary niche overlap and prey preference of a large African carnivore guild on small fenced protected areas. Our results show that large African carnivores in small protected areas are exposed to considerable overlap in dietary resource utilization. African wild dogs and cheetah females with dependent offspring occupied the greatest potential for dietary competition within the large carnivore guild. Our research highlights the need to assess the influence of competitive forces in structuring and restoring large predators to portions of their historical range by identifying species most vulnerable to a potential reintroduction attempt.
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In areas with diverse herbivore communities such as African savannas, the frequency of disturbance by fire may alter the top–down role of different herbivore species on plant community dynamics. In a seven year experiment in the Kruger National Park, South Africa, we examined the habitat use of nine common herbivore species across annually burned, triennially burned and unburned areas. We also used two types of exclosures (plus open access controls) to examine the impacts of different herbivores on plant community dynamics across fire disturbance regimes. Full exclosures excluded all herbivores >0.5 kg (e.g. elephant, zebra, impala) while partial exclosures allowed access only to animals with shoulder heights ≤0.85 m (e.g. impala, steenbok). Annual burns attracted a diverse suite of herbivores, and exclusion of larger herbivores (e.g. elephant, zebra, wildebeest) increased plant abundance. When smaller species, mainly impala, were also excluded there were declines in plant diversity, likely mediated by a decline in open space available for colonization of uncommon plant species. Unburned areas attracted the least diverse suite of herbivores, dominated by impala. Here, herbivore exclusion, especially of impala, led to strong declines in plant richness and diversity. With no fire disturbance, herbivore exclusion led to competitive exclusion via increases in plant dominance and light limitation. In contrast, on triennial burns, herbivore exclusion had no effect on plant richness or diversity, potentially due to relatively little open space for colonization across exclosure treatments but also little competitive exclusion due to the intermediate fire disturbance. Further, the diverse suite of grazers and browsers on triennial burns may have had a compensating effect of on the diversity of grasses and forbs. Ultimately, our work shows that differential disturbance regimes can result in differential consumer pressure across a landscape and result in heterogeneous patterns in top–down control of community dynamics. This article is protected by copyright. All rights reserved.
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Small mammal populations were studied in five grasslands: Themeda triandra-dominated, Aristida junciformis-dominated, Kikuyu (Pennisetum clandestinum) pastures, disturbed grassland and seasonally-wet vlei grassland. Small mammals were live-trapped monthly for six months, from late summer to mid-winter. Cover and average height of the vegetation were sampled, and rodent snap-trapping was undertaken in summer and winter to determine seasonal changes in diet composition. Species diversity and abundance of small mammals were highest in late autumn-early winter. Species diversity was greatest in disturbed and Aristida grasslands. The striped mouse (Rhabdomys pumilio) and the forest shrew (Myosorex varius) were caught in all habitats sampled. At some sites, small mammal abundances declined to almost zero following unscheduled, mid-winter burns. Stomach content analysis revealed that R. pumilio was primarily granivorous whereas the multimammate mouse Mastomys natalensis preferred green plant foods. Green plants contributed less to the diets of these species during winter when seed intake was increased. The diet of the swamp musk shrew (Crocidura mariquensis) comprised 92% insect material. Disturbed grasslands, owing to their variety of foliage profiles, supported diverse rodent communities.
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Camera trap surveys exclusively targeting features of the landscape that increase the probability of photographing one or several focal species are commonly used to draw inferences on the richness, composition and structure of entire mammal communities. However, these studies ignore expected biases in species detection arising from sampling only a limited set of potential habitat features. In this study, we test the influence of camera trap placement strategy on community-level inferences by carrying out two spatially and temporally concurrent surveys of medium to large terrestrial mammal species within Tanzania's Ruaha National Park, employing either strictly game trail-based or strictly random camera placements. We compared the richness, composition and structure of the two observed communities, and evaluated what makes a species significantly more likely to be caught at trail placements. Observed communities differed marginally in their richness and composition , although differences were more noticeable during the wet season and for low levels of sampling effort. Lognormal models provided the best fit to rank abundance distributions describing the structure of all observed communities, regardless of survey type or season. Despite this, carnivore species were more likely to be detected at trail placements relative to random ones during the dry season, as were larger bodied species during the wet season. Our findings suggest that, given adequate sampling effort (> 1400 camera trap nights), placement strategy is unlikely to affect inferences made at the community level. However, surveys should consider more carefully their choice of placement strategy when targeting specific taxonomic or trophic groups.
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Fire management is an important conservation tool in Canada’s national parks. Fires can benefit some species, while others may be negatively impacted. We used GPS and VHF collar data for 47 wolves from 12 separate packs and 153 caribou from 5 separate herds, and resource selection analysis to model the effects of fire on these species’ habitat and potential interactions. Resource selection modeling showed that wolves select for burned areas and areas close to burns, presumably due to the presence of primary prey (i.e., elk and moose), while caribou avoid burns. Fire reduced the amount of high quality caribou habitat (a direct effect), but also increased the probability of wolf-caribou overlap (an indirect effect). We delineated a spatial index of caribou “safe zones” (areas of low overlap with wolves), and found a positive relationship between the proportion of a herd’s home range represented by “safe zone” in winter and population size (P = 0.10, n=4). While currently-planned prescribed fires in Banff and Jasper reduced the amount of quality caribou habitat by up to 4%, they reduced the area of “safe zones” by up to 7%, varying by herd, location, and season. We suggest that conservation managers should account for the indirect, predator-mediated impacts of fire on caribou in addition to direct effects of habitat loss.
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Predators often have important roles in structuring ecosystems via their effects on each other and on prey populations. However, these effects may be altered in the presence of anthropogenic food resources, fuelling debate about whether the availability of such resources could alter the ecological role of predators. Here, we review the extent to which human-provided foods are utilised by terrestrial mammalian predators (> 1 kg) across the globe. We also assess whether these resources have a direct impact on the ecology and behaviour of predators and an indirect impact on other co-occurring species. Global. Data were derived from searches of the published literature. To summarise the data we grouped studies based on the direct and indirect effects of resource subsidies on predators and co-occurring species. We then compared the types of predators accessing these resources by grouping species taxonomically and into the following categories: (1) domesticated species, (2) mesopredators and (3) top predators. Human-provided foods were reported to be utilised by 36 terrestrial predator species in 34 different countries. In the presence of these resources we found that: (1) predator abundance increased, (2) the dietary preferences of predators altered to include the food subsidy, (3) life-history parameters such as survival, reproduction and sociality shifted to the benefit or detriment of the predator, and (4) predators changed their home ranges, activity and movements. In some instances, these modifications indirectly affected co-occurring species via increased predation or competition. The availability of human-provided food to predators often results in behavioural or population-induced changes to predators and trophic cascades. We conclude that there is an urgent need to reduce the access of predators to food subsidies to minimise human–wildlife conflicts and to preserve the integrity of ecosystem functioning in human-influenced landscapes world-wide.
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Most ecosystems have multiple predator species that not only compete for shared prey, but also pose direct threats to each other. These intraguild interactions are key drivers of carnivore community structure, with ecosystem-wide cascading effects. Yet, behavioral mechanisms for coexistence of multiple carnivore species remain poorly understood. The challenges of studying large, free-ranging carnivores have resulted in mainly coarse-scale examination of behavioral strategies without information about all interacting competitors. We overcame some of these challenges by examining the concurrent fine-scale movement decisions of almost all individuals of four large mammalian carnivore species in a closed terrestrial system. We found that the intensity ofintraguild interactions did not follow a simple hierarchical allometric pattern, because spatial and behavioral tactics of subordinate species changed with threat and resource levels across seasons. Lions (Panthera leo) were generally unrestricted and anchored themselves in areas rich in not only their principal prey, but also, during periods of resource limitation (dry season), rich in the main prey for other carnivores. Because of this, the greatest cost (potential intraguild predation) for subordinate carnivores was spatially coupled with the highest potential benefit of resource acquisition (prey-rich areas), especially in the dry season. Leopard (P. pardus) and cheetah (Acinonyx jubatus) overlapped with the home range of lions but minimized their risk using fine-scaled avoidance behaviors and restricted resource acquisition tactics. The cost of intraguild competition was most apparent for cheetahs, especially during the wet season, as areas with energetically rewarding large prey (wildebeest) were avoided when they overlapped highly with the activity areas of lions. Contrary to expectation, the smallest species (African wild dog, Lycaon pictus) did not avoid only lions, but also used multiple tactics to minimize encountering all other competitors. Intraguild competition thus forced wild dogs into areas with the lowest resource availability year round. Coexistence of multiple carnivore species has typically been explained by dietary niche separation, but our multi-scaled movement results suggest that differences in resource acquisition may instead be a consequence of avoiding intraguild competition. We generate a more realistic representation of hierarchical behavioral interactions that may ultimately drive spatially explicit trophic structures of multi-predator communities.
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Since the 1960s, Japan has become highly dependent on foreign countries for natural resources, and the amount of managed lands (e.g. coppice, grassland, and agricultural field) has declined. Due to infrequent natural and human disturbance, early-successional species are now declining in Japan. Here we surveyed bees, birds, and plants in four human-disturbed open habitats (pasture, meadow, young planted forest, and abandoned clear-cut) and two forest habitats (mature planted forest and natural old-growth). We extended a recently developed multispecies abundance model to accommodate count data, and used the resulting models to estimate species-, functional group-, and community-level state variables (abundance and species richness) at each site, and compared them among the six habitats. Estimated individual-level detection probability was quite low for bee species (mean across species = 0.003; 0.16 for birds). Thirty-two (95% credible interval: 13–64) and one (0–4) bee and bird species, respectively, were suggested to be undetected by the field survey. Although habitats in which community-level abundance and species richness was highest differed among taxa, species richness and abundance of early-successional species were similar in the four disturbed open habitats across taxa except for plants in the pasture habitat which was a good habitat only for several exotic species. Our results suggest that human disturbance, especially the revival of plantation forestry, may contribute to the restoration of early-successional species in Japan.
Article
The effects of fire-grazing interactions on grass communities are difficult to identify because fire and grazing influence each other on a landscape scale. Persistent heavy grazing can prevent the spread of fire by breaking up the grass layer. In contrast, frequent burning might inhibit the persistence of grazed patches by attracting grazers to the post-burn green flush. We explored the effect of burning on grazing activity, and the persistence of grazed patches, in a landscape-level experiment in a South African savanna. We created 17 grazed patches by mowing grass in a 20 m diameter plot, with an adjacent un-mown control. We used dung counts as a measure of grazer visitation, and grass height as a measure of grazing intensity, at each of the sites over a year. Nearly all mowing treatments resulted in a rapid increase in grazing activity relative to controls (on average, 4-6 times more dung was found on mown sites). Subsequent fates of the grazed patches depended on their location with respect to fire. Burned areas drew animals off nearby unburned grazed patches, which then recovered lost biomass. Patches >1.5 km from burns remained grazed short. Frequent large fires might prevent areas of heavy grazing from persisting in the landscape, and thus limit the spread of grazing-adapted grasses. Spatial information on fire frequencies in the park was used to explore the influence that the "magnet effect" of fire can have on grass communities. We mapped the distribution of tall, bunch grasslands and grazing-lawn grasslands using a 1999 Landsat TM satellite image. The extent of grazing lawns was directly related to fire return interval. Areas with a fire return of <4 years had less lawn grass than would be expected from the proportions of lawn grass in the park. A logistic regression analysis, which used various environmental variables known to influence grazing, showed fire history to be an important predictor of grazing-lawn distributions. This work shows that, by influencing where, when, and for how long animals graze a patch, fire can influence the competitive balance between grazing-tolerant, and grazing-intolerant grass species and affect their distributions in the landscape. We discuss the implications of this research for the management of natural grazing systems and rangelands.
Article
This study examined the impacts of different burning regimes (fire frequency and season) and fire history (time since last burn) on invertebrate morphospecies richness and abundance. The study was carried out in the Brotherton experimental plots at Cathedral Peak in the KwaZulu-Natal Drakensberg. Pitfall traps targeting epigaeic invertebrates were set for one week, and soil cores were collected for extraction of hypogaeic invertebrates in 21 plots. A total of 2585 individual specimens from 219 morphospecies were identified. Mean morphospecies richness was consistently highest in blocks burnt in autumn, and higher for biennial burns or two years since last burn for epigaeic, winged and wingless invertebrates, but this was not the case for soil invertebrates which showed little real response to fire. Fire season and frequency significantly influenced epigaeic and winged invertebrate species richness and abundance, with autumn burning and a fire return period of two years favouring richness and abundance. However, the small size of the plots and their proximity and a runaway fire in 2000 could have influenced results and could also result in relatively homogenous communities.
Article
1. Species richness is often used as a tool for prioritizing conservation action. One method for predicting richness and other summaries of community structure is to develop species-specific models of occurrence probability based on habitat or landscape characteristics. However, this approach can be challenging for rare or elusive species for which survey data are often sparse. 2. Recent developments have allowed for improved inference about community structure based on species-specific models of occurrence probability, integrated within a hierarchical modelling framework. This framework offers advantages to inference about species richness over typical approaches by accounting for both species-level effects and the aggregated effects of landscape composition on a community as a whole, thus leading to increased precision in estimates of species richness by improving occupancy estimates for all species, including those that were observed infrequently. 3. We developed a hierarchical model to assess the community response of breeding birds in the Hudson River Valley, New York, to habitat fragmentation and analysed the model using a Bayesian approach. 4. The model was designed to estimate species-specific occurrence and the effects of fragment area and edge (as measured through the perimeter and the perimeter/area ratio, P/A), while accounting for imperfect detection of species. 5. We used the fitted model to make predictions of species richness within forest fragments of variable morphology. The model revealed that species richness of the observed bird community was maximized in small forest fragments with a high P/A. However, the number of forest interior species, a subset of the community with high conservation value, was maximized in large fragments with low P/A. 6. Synthesis and applications. Our results demonstrate the importance of understanding the responses of both individual, and groups of species, to environmental heterogeneity while illustrating the utility of hierarchical models for inference about species richness for conservation. This framework can be used to investigate the impacts of land-use change and fragmentation on species or assemblage richness, and to further understand trade-offs in species-specific occupancy probabilities associated with landscape variability.