Habitat heterogeneity and mammalian predator-prey interactions

Correlation between mammal track abundance and Forest Landscape Integrity Index validates actual forest ecological integrity

Human disturbance compromises the ecological integrity of forests, negatively affecting associated species. Assessing the impact of forest integrity on biodiversity is complex due to the interplay of various human activities, ecological factors, and their interactions. Current large-scale indices assess forest integrity but often lack a direct connection to the biotic environment. We tested the effectiveness of the global Forest Landscape Integrity Index (FLII) in evaluating aspects of anthropogenic forest degradation on the biotic community. We analyzed the relationship between changes in the ecological integrity of Finnish forests and variations in mammal species abundance, using the number of tracks from 17 different species collected during the winter seasons between 2016 and 2020 in south-central Finland. Beyond the FLII, we analyzed forest and canopy cover to enhance the accuracy of habitat preference assessments. We found that the FLII captures the varying degrees of forest integrity, as reflected by the correlation between the abundance of winter tracks and the FLII for most mammals. Species that were positively associated with forest integrity were all native to the boreal forest, while mammals that adapt well to human-disturbed environments including two invasive species were more common in lower FLII forests. Significant differences in habitat preferences were also observed in relation to forest and canopy cover, revealing additional nuances that the FLII alone did not capture. This study demonstrates that the FLII, when combined with a comprehensive dataset and supplemented with region-specific factors, can assess species' adaptability to human-modified forests, aiding in the development of conservation strategies.

Integration of the landscape of fear concept in grassland management: An experimental study on subtropical monsoon grasslands in Bardia National Park, Nepal

The 'landscape of fear' concept offers valuable insights into wildlife behaviour, yet its practical integration into habitat management for conservation remains underexplored. In this study, conducted in the subtropical monsoon grasslands of Bardia National Park, Nepal, we aimed to bridge this gap through a multi-year, landscape-scale experimental investigation in Bardia National Park, Nepal. The park has the highest density of tigers (with an estimated density of ~7 individuals per 100 km2) in Nepal, allowing us to understand the effect of habitat management on predation risk and resource availability especially for three cervid species: chital (Axis axis), swamp deer (Rucervus duvaucelii) and hog deer (Axis porcinus). We used plots with varying mowing frequency (0-4 times per year), size (ranging from small: 49 m2 to large: 3600 m2) and artificial fertilisation type (none, phosphorus, nitrogen) to assess the trade-offs between probable predation risk and resources for these cervid species, which constitute primary prey for tigers in Nepal. Our results showed distinct responses of these deer to perceived predation risk within grassland habitats. Notably, these deer exhibited heightened use of larger plots, indicative of a perceived sense of safety, as evidenced by the higher occurrence of pellet groups in the larger plots (mean = 0.1 pellet groups m-2 in 3600 m2 plots vs. 0.07 in 400 m2 and 0.05 in 49 m2 plots). Furthermore, the level of use by the deer was significantly higher in larger plots that received mowing and fertilisation treatments compared to smaller plots subjected to similar treatments. Of particular interest is the observation that chital and swamp deer exhibited greater utilisation of the centre (core) areas within the larger plots (mean = 0.21 pellet groups m-2 at the centre vs. 0.13 at the edge) despite the edge (periphery) also provided attractive resources to these deer. In contrast, hog deer did not display any discernible reaction to the experimental treatments, suggesting potential species-specific variations in response to perceived predation risk arising from management interventions. Our findings emphasise the importance of a sense of security as a primary determinant of habitat selection for medium-sized deer within managed grassland environments. These insights carry practical implications for park managers, providing a nuanced understanding of integrating the 'landscape of fear' into habitat management strategies. This study emphasises that the 'landscape of fear' concept can and should be integrated into habitat management to maintain delicate predator-prey dynamics within ecosystems.

Predator-prey interactions across hunting mode, spatial domain size, and habitat complexities

Predator-prey interactions are a fundamental part of community ecology, yet the relative importance of consumptive and nonconsumptive effects (NCEs) (defined as a risk-induced response that alters prey fitness) has not been resolved. Theory suggests that the emergence and subsequent predominance of consumptive or NCEs depend on the given habitat's complexity as well as predator hunting mode and spatial domain sizes of both predator and prey, but their relative influence on the outcome of predator-prey interactions is unknown. We built agent-based models in NetLogo to simulate predator-prey interactions for three hunting modes-sit-and-wait, sit-and-pursue, and active-while concurrently simulating large versus small spatial domain sizes for both predators and prey. We studied (1) how hunting mode and spatial domain size interact to influence the emergence of consumptive or NCEs and (2) how, when NCEs do dominate, hunting mode and spatial domain separately or additively determine prey shifts in time, space, and habitat use. Our results indicate consumptive effects only dominate for active predators when prey habitat domains overlap completely with the predator's spatial domain and when sit-and-wait and sit-and-pursue predators and their prey both have large spatial domains. Prey are most likely to survive when they shift their time but most frequently shift their habitat. Our paper helps to better understand the underlying mechanisms that drive consumptive or NCEs to be most dominant.

Behavioral responses to predator and heterospecific alarm calls are habitat-specific in Eurasian tree sparrows

Acoustic communication plays a vital role in predator-prey interactions. Although habitat structure has been shown to affect anti-predator tactics, little is known about how animals vary their behaviors in response to predator calls or heterospecific alarm calls in different environments. Here we used sound playbacks to test the responses of Eurasian tree sparrows (Passer montanus) foraging in harvested/unharvested rice paddy and open residential area. In the first experiment, we tested their behavioral responses to dove calls, male common cuckoo (Cuculus canorus) calls, hawk-like calls mimicked by female common cuckoo, sparrowhawk (Accipiter nisus) calls, and human yell calls produced to scare birds (predator signal playbacks). In the second experiment, we tested their behavioral responses to the Japanese tit's (Parus minor) territorial songs and alarm calls (heterospecific alarm signal playbacks). Results showed that the tree sparrows had less fleeing in unharvested ripe rice paddy than in harvested rice paddy and open residential area. In predator signal playbacks, call type affected the escape behavior of sparrows in unharvested rice paddy and open residential area but not harvested rice paddy. In alarm signal playbacks, tit alarm calls evoked more fleeing than territorial songs in harvested rice paddy and open residential area but not unharvested rice paddy. These results suggest that anthropogenic habitat changes may influence avian anti-predator tactics.

Habitat modification destabilizes spatial associations and persistence of Neotropical carnivores

Spatial relationships between sympatric species underpin biotic interactions, structure ecological communities, and maintain ecosystem health. However, the resilience of interspecific spatial associations to human habitat modification remains largely unknown, particularly in tropical regions where anthropogenic impacts are often greatest. We applied multi-state multi-species occurrence models to camera trap data across nine tropical landscapes in Colombia to understand how prominent threats to forest ecosystems influence Neotropical carnivore occurrence and interspecific spatial associations, with implications for biotic interactions. We show that carnivore occurrence represents a delicate balance between local environmental conditions and interspecific interactions that can be compromised in areas of extensive habitat modification. The stability of carnivore spatial associations depends on forest cover to mediate antagonistic encounters with apex predators and structurally intact forests to facilitate coexistence between competing mesocarnivores. Notably, we demonstrate that jaguars play an irreplaceable role in spatially structuring mesocarnivore communities, providing novel evidence on their role as keystone species. With increasing global change, conserving both the extent and quality of tropical forests is imperative to support carnivores and preserve the spatial associations that underpin ecosystem stability and resilience.

Longitudinal multidiversity pattern and the environmental drivers of riparian bird communities along submontane rivers of Changbai Mountains, China

Riparian zones are biodiversity hotspots in montane ecosystems and are of critical conservation concern. However, studies on longitudinal diversity patterns and environmental drivers have been restricted to aquatic fauna, while the animals that rely on both river and riparian resources have been of much less concern. Here, we examined the multifaceted diversity distribution of riparian birds along longitudinal gradients and analyzed the importance of environmental factors in shaping these patterns in the Changbai Mountains. Hump-shaped relationships between elevation and taxonomic, phylogenetic, and functional diversity, as well as with the conservation value index, were evident along each of the classic submontane rivers. Forest cover, vegetation height variation, and land cover patches positively affected the taxonomic diversity indices. In addition to the species richness, fluvial geomorphology variables (river sinuosity and gravel bar) were significantly related to the phylogenetic diversity. However, there was no statistical evidence for a relationship between functional diversity and the environmental variables examined. This study emphasized the necessity of including multiple diversity measures beyond taxonomic diversity and demonstrated the importance of both terrestrial and aquatic components in shaping the multifaceted biodiversity pattern of riparian organisms living in riparian zones. The results suggested that conservation priority should be given to both rivers and banks in the middle reaches and that riparian birds could be good candidate indicators of environmental change in the submontane river-forest ecotone.

Risk perception and terrestriality in primates: A quasi‐experiment through habituation of chacma baboons ( Papio ursinus ) in Gorongosa National Park, Mozambique

Objectives

Habituation is a common pre‐requisite for studying noncaptive primates. Details and quantitative reporting on this process are often overlooked but are useful for measuring human impact on animal behavior, especially when comparing studies across time or sites. During habituation, perceived risk of a stimulus—human observers—is assumed to decline with repeated exposure to that stimulus. We use habituation as a quasi‐experiment to study the landscape of fear, exploring relationships between actual risk, perceived risk, mediating environmental variables, and behavioral correlates.

Materials and Methods

We recorded vocalizations and observer‐directed vigilance as indicators of perceived risk during habituation of two troops of chacma baboons (Papio ursinus) in Gorongosa National Park, Mozambique. Here, we model changes in these variables as a function of habituation time, troop, time of day, and habitat features. We also model the relationship between each of the anti‐predator behaviors and ground‐use, exploring whether they predict greater terrestriality in the baboons.

Results

In both troops, vocalization rates and observer‐directed vigilance declined with cumulative exposure to observers, but were heightened later in the day and in denser habitat types. We found that terrestrial activity was negatively related to levels of both vocalizations and observer‐directed vigilance.

Discussion

This study provides a quantitative assessment of the impact of human observation on primate behavior and highlights environmental variables that influence anti‐predator behaviors, perhaps indicating heightened perception of risk. The relationship between perceived risk and terrestriality is significant for understanding the evolution of this rare trait in primates.

Predator movements in relation to habitat features reveal vulnerability of duck nests to predation

Nest predation is the main cause of nest failure for ducks. Understanding how habitat features influence predator movements may facilitate management of upland and wetland breeding habitats that reduces predator encounter rates with duck nests and increases nest survival rates. For 1618 duck nests, nest survival increased with distance to phragmites (Phragmites australis), shrubs, telephone poles, human structures, and canals, but not for four other habitat features. Using GPS collars, we tracked 25 raccoons (Procyon lotor) and 16 striped skunks (Mephitis mephitis) over 4 years during waterfowl breeding and found marked differences in how these predators were located relative to specific habitat features; moreover, the probability of duck nests being encountered by predators differed by species. Specifically, proximity to canals, wetlands, trees, levees/roads, human structures, shrubs, and telephone poles increased the likelihood of a nest being encountered by collared raccoons. For collared skunks, nests were more likely to be encountered if they were closer to canals, trees, and shrubs, and farther from wetlands and human structures. Most predator encounters with duck nests were attributable to a few individuals; 29.2% of raccoons and 38.5% of skunks were responsible for 95.6% of total nest encounters. During the central span of duck nesting (April 17-June 14: 58 nights), these seven raccoons and five skunks encountered >1 nest on 50.8 ± 29.2% (mean ± SD) and 41.5 ± 28.3% of nights, respectively, and of those nights individual raccoons and skunks averaged 2.60 ± 1.28 and 2.50 ± 1.09 nest encounters/night, respectively. For collared predators that encountered >1 nest, a higher proportion of nests encountered by skunks had evidence of predation (51.9 ± 26.6%) compared to nests encountered by raccoons (22.3 ± 17.1%). Because duck eggs were most likely consumed as raccoons and skunks opportunistically discovered nests, managing the habitat features those predators most strongly associated with could potentially reduce rates of egg predation.

Home Range and Movement Patterns of Reintroduced White Lions (Panthera leo melanochaita) in the Kruger to Canyons Biosphere Reserve, South Africa

White lions are a colour variant of the African lion Panthera leo melanochaita and disappeared from the wild due to anthropogenic factors until their reintroduction to the Greater Kruger Park Region of South Africa in 2006. Natural home range behaviour is an index of reintroduction success. Therefore, the home range and movement of a pride of reintroduced white lions and a constructed pride consisting of reintroduced white lions and translocated wild tawny lionesses in small, fenced reserves was assessed. GPS data from collared adults were collected for the white lion pride between 2010-2011 and 2018-2020 for the constructed pride. Home ranges were estimated using kernel density estimation and minimum convex polygon, with minimum daily distance tested for differences between sex, season, and pride. Home ranges were small and average daily movements restricted for both prides (white lion pride: 5.41 km2 and 10.44 ± 4.82 km; constructed pride: 5.50 km2, 11.37 ± 4.72 km) due to the small reserve size of 7 km2. There was no difference between prides for annual and seasonal home range size, male and female home ranges, minimum daily distance travelled, or habitat selection. White lions from both prides established territories and displayed natural home ranging behaviour, suggesting that their reintroduction was successful, in the absence of anthropogenic threats.

Standardizing protocols for determining the cause of mortality in wildlife studies

Mortality site investigations of telemetered wildlife are important for cause-specific survival analyses and understanding underlying causes of observed population dynamics. Yet, eroding ecoliteracy and a lack of quality control in data collection can lead researchers to make incorrect conclusions, which may negatively impact management decisions for wildlife populations. We reviewed a random sample of 50 peer-reviewed studies published between 2000 and 2019 on survival and cause-specific mortality of ungulates monitored with telemetry devices. This concise review revealed extensive variation in reporting of field procedures, with many studies omitting critical information for the cause of mortality inference. Field protocols used to investigate mortality sites and ascertain the cause of mortality are often minimally described and frequently fail to address how investigators dealt with uncertainty. We outline a step-by-step procedure for mortality site investigations of telemetered ungulates, including evidence that should be documented in the field. Specifically, we highlight data that can be useful to differentiate predation from scavenging and more conclusively identify the predator species that killed the ungulate. We also outline how uncertainty in identifying the cause of mortality could be acknowledged and reported. We demonstrate the importance of rigorous protocols and prompt site investigations using data from our 5-year study on survival and cause-specific mortality of telemetered mule deer (Odocoileus hemionus) in northern California. Over the course of our study, we visited mortality sites of neonates (n = 91) and adults (n = 23) to ascertain the cause of mortality. Rapid site visitations significantly improved the successful identification of the cause of mortality and confidence levels for neonates. We discuss the need for rigorous and standardized protocols that include measures of confidence for mortality site investigations. We invite reviewers and journal editors to encourage authors to provide supportive information associated with the identification of causes of mortality, including uncertainty.

Pathwalker: A New Individual-Based Movement Model for Conservation Science and Connectivity Modelling

Understanding organism movement is at the heart of many ecological disciplines. The study of landscape connectivity—the extent to which a landscape facilitates organism movement—has grown to become a central focus of spatial ecology and conservation science. Several computational algorithms have been developed to model connectivity; however, the major models in use today are limited by their lack of flexibility and simplistic assumptions of movement behaviour. In this paper, we introduce a new spatially-explicit, individual- and process-based model called Pathwalker, which simulates organism movement and connectivity through heterogeneous landscapes as a function of landscape resistance, the energetic cost of movement, mortality risk, autocorrelation, and directional bias towards a destination, all at multiple spatial scales. We describe the model’s structure and parameters and present statistical evaluations to demonstrate the influence of these parameters on the resulting movement patterns. Written in Python 3, Pathwalker works for any version of Python 3 and is freely available to download online. Pathwalker models movement and connectivity with greater flexibility compared with the dominant connectivity algorithms currently available in conservation science, thereby, enabling more detailed predictions for conservation practice and management. Moreover, Pathwalker provides a highly capable simulation framework for exploring theoretical and methodological questions that cannot be addressed with empirical data alone.

Functional Responses Shape Node and Network Level Properties of a Simplified Boreal Food Web

Ecological communities are fundamentally connected through a network of trophic interactions that are often complex and difficult to model. Substantial variation exists in the nature and magnitude of these interactions across various predators and prey and through time. However, the empirical data needed to characterize these relationships are difficult to obtain in natural systems, even for relatively simple food webs. Consequently, prey-dependent relationships and specifically the hyperbolic form (Holling’s Type II), in which prey consumption increases with prey density but ultimately becomes saturated or limited by the time spent handling prey, are most widely used albeit often without knowledge of their appropriateness. Here, we investigate the sensitivity of a simplified food web model for a natural, boreal system in the Kluane region of the Yukon, Canada to the type of functional response used. Intensive study of this community has permitted best-fit functional response relationships to be determined, which comprise linear (type I), hyperbolic (type II), sigmoidal (type III), prey- and ratio-dependent relationships, and inverse relationships where kill rates of alternate prey are driven by densities of the focal prey. We compare node- and network-level properties for a food web where interaction strengths are estimated using best-fit functional responses to one where interaction strengths are estimated exclusively using prey-dependent hyperbolic functional responses. We show that hyperbolic functional responses alone fail to capture important ecological interactions such as prey switching, surplus killing and caching, and predator interference, that in turn affect estimates of cumulative kill rates, vulnerability of prey, generality of predators, and connectance. Exclusive use of hyperbolic functional responses also affected trends observed in these metrics over time and underestimated annual variation in several metrics, which is important given that interaction strengths are typically estimated over relatively short time periods. Our findings highlight the need for more comprehensive research aimed at characterizing functional response relationships when modeling predator-prey interactions and food web structure and function, as we work toward a mechanistic understanding linking food web structure and community dynamics in natural systems.

Spatiotemporal co-occurrence of predators and prey in a neotropical mammal community in southern Mexico

Predator-prey interactions are one of the central themes in ecology due to their importance as a key mechanism in structuring biotic communities. In the predator-prey systems, the behaviours of persecution and avoidance impact on the ecosystem dynamics as much as the trophic interactions. We aimed to analyse the spatiotemporal co-occurrences between prey and predators in a community of medium- and large-sized mammals in southern Mexico. We predict prey will avoid sites where a predator previously passed. Contrarily, we expect a search behaviour by predators and a synchronization in activity patterns among them. We found prey does not occur either in time or space where predators have passed, suggesting an avoidance behaviour. Contrary to our expectations, we did not find significant search behaviours from predators to prey. Synchronization in the daily temporal overlap between predators was higher (Δ = 0.77–0.82) than with their prey (Δ = 0.43 – 0.81). The results suggest prey perceives the risk of predation and displays avoidance behaviour both spatially and temporally, which is consistent with the fear theory. This study provides a complementary approach to understanding the behaviour mechanism between predators and prey through camera-trapping or similar data of spatiotemporal co-occurrences.

A rodent herbivore reduces its predation risk through ecosystem engineering

Predator-prey interactions are ubiquitous and powerful forces that structure ecological communities.^1-3 Habitat complexity has been shown to be particularly important in regulating the strength of predator-prey interactions.^4-6 While it is well established that changes in habitat structure can alter the efficacy of predatory and anti-predatory behaviors,^7-9 little is known about the consequences of engineering activity by prey species who modify the external environment to reduce their own predation risk. Using field surveys and manipulative experiments, we evaluated how habitat modification by Brandt's voles (Lasiopodomys brandtii) influences predation risk from a principal avian predator (shrike; Lanius spp.) in a steppe grassland, located in Inner Mongolia, China. We found that voles actively modify habitat structure by cutting down a large, unpalatable bunchgrass species (Achnatherum splendens) in the presence of shrikes, a behavior that disappeared when these avian predators were excluded experimentally. The damage activities of these voless dramatically decreased the volume of unpalatable grasses, which in turn reduced visitations by shrikes and thus mortality rates. Our study shows that herbivorous prey that act as ecosystem engineers can directly reduce their own predation risk by modifying habitat structure. Given the ubiquity of predation risks faced by consumers, and the likely ability of many consumers to alter the habitat structure in which they live, the interplay between predation risk and ecosystem engineering may be an important but unappreciated mechanism at play in natural communities.

Influence of multiple predators decreases body condition and fecundity of European hares

We assessed the hypothesized negative correlation between the influence of multiple predators and body condition and fecundity of the European hare, from 13 areas in the Netherlands.Year-round abundance of predators was estimated by hunters. We quantified predator influence as the sum of their field metabolic rates, as this sum reflects the daily food requirements of multiple individuals. We determined the ratio between body mass and hindfoot length of hares as an index of body condition and the weight of their adrenal gland as a measure of chronic exposure to stress, and we counted the number of placental scars to estimate fecundity of hares.As hypothesized, we found that the sum of field metabolic rate of predators was negatively correlated with body condition and the number of placental scars, whereas it was positively related to the weight of the adrenal glands. In contrast to the sum of the field metabolic rate, the total number of predators did not or weakly affect the investigated risk responses.The sum of the field metabolic rate can be a useful proxy for the influence of multiple predators and takes into account predator abundance, type, body weight, and food requirements of multiple predators.With our findings, our paper contributes to a better understanding of the risk effects of multiple predators on prey fitness. Additionally, we identify a potential contributor to the decline of European hare populations.

The Winner Takes it All: Risk Factors and Bayesian Modelling of the Probability of Success in Escaping from Big Cat Predation

Simple Summary

Predation is a complex behavioural interaction that is conditioned by biotic and abiotic factors. In their struggle for survival, the agents participating in the hunt interaction adapt their strategies seeking an opposite interest which leads to the same outcome, success in surviving. Predator/prey interaction data was obtained from on-line posted videos. The examination of records suggested that the species and age range of the predator, its status at the end of the hunt, the time elapsed between the sighting of its prey and the physical contact with it, the species of the prey and the relief of the land were determined success of escape of the prey in case of attack. The present study sheds light on the multietiological nature of predatory abilities and the strategies to fend off anti-predation strategies of the prey in big cats. The theoretical and empirical contents derived from this work will allow the design of environmental enrichment programs in captivity to be substantially improved by providing preys and enough space for them to express big cats predating strategies. The extrapolation of these results to domestic contexts may enable approaching selection strategies from two perspectives, with the aim to boost predating ability of domestic felids for pest control or to enhance defence in domestic ruminant prey from big cats.

Abstract

The individuals engaged in predation interactions modify their adaptation strategies to improve their efficiency to reach success in the fight for survival. This success is linked to either capturing prey (predator) or escaping (prey). Based on the graphic material available on digital platforms both of public and private access, this research aimed to evaluate the influence of those animal- and environment-dependent factors affecting the probability of successful escape of prey species in case of attack by big cats. Bayesian predictive analysis was performed to evaluate the outcomes derived from such factor combinations on the probability of successful escape. Predator species, age, status at the end of the hunting act, time lapse between first attention towards potential prey and first physical contact, prey species and the relief of the terrain, significantly conditioned (p < 0.05) escape success. Social cooperation in hunting may be more important in certain settings and for certain prey species than others. The most parsimonious model explained 36.5% of the variability in escaping success. These results can be useful to design translatable selective strategies not only seeking to boost predation abilities of domestic felids for pest control, but also, biological antipredator defence in potential domestic prey of big cats.

Small Prey Animal Habitat Use in Landscapes of Fear: Effects of Predator Presence and Human Activity Along an Urban Disturbance Gradient

Human activity can impose additional stressors to wildlife, both directly and indirectly, including through the introduction of predators and influences on native predators. As urban and adjacent environments are becoming increasingly valuable habitat for wildlife, it is important to understand how susceptible taxa, like small prey animals, persist in urban environments under such additional stressors. Here, in order to determine how small prey animals’ foraging patterns change in response to habitat components and distances to predators and human disturbances, we used filmed giving-up density (GUD) trials under natural conditions along an urban disturbance gradient. We then ran further GUD trials with the addition of experimentally introduced stressors of: the odors of domestic cat (Felis catus)/red fox (Vulpes vulpes) as predator cues, light and sound as human disturbance cues, and their combinations. Small mammals were mostly observed foraging in the GUD trials, and to a lesser degree birds. Animals responded to proximity to predators and human disturbances when foraging under natural conditions, and used habitat components differently based on these distances. Along the urban disturbance gradient situation-specific responses were evident and differed under natural conditions compared to additional stressor conditions. The combined predator with human disturbance treatments resulted in responses of higher perceived risk at environments further from houses. Animals at the urban-edge environment foraged more across the whole site under the additional stressor conditions, but under natural conditions perceived less risk when foraging near predators and further from human disturbance (houses). Contrastingly, at the environments further from houses, foraging near human disturbance (paths/roads) when close to a predator was perceived as lower risk, but when foraging under introduced stressor conditions these disturbances were perceived as high risk. We propose that sensory and behavioral mechanisms, and stress exposure best explain our findings. Our results indicate that habitat components could be managed to reduce the impacts of high predation pressure and human activity in disturbed environments.

Fear of large carnivores is tied to ungulate habitat use: evidence from a bifactorial experiment

The fear large carnivores inspire in large ungulates has been argued to have cascading effects down food webs. However, a direct link between ungulate habitat use and their fear of large carnivores has not been experimentally tested. To fill this critical gap, we conducted a bi-factorial experiment in an African savanna. We removed shrub cover and broadcast large carnivore vocalizations (leopard, hyena, dog) or non-threatening control vocalizations in both experimentally cleared and shrubby control sites. We recorded the proactive (frequency of visitation) and reactive (fleeing or vigilance) responses of multiple prey (impala, warthog, nyala and bushbuck). Critically, we found a significant proactive-reactive interaction. Ungulates were 47% more likely to run after hearing a predator vocalization in shrubby control sites than experimental clearings, demonstrating that ungulates perceived less fear from large carnivores in open habitat (clearings). Consistent with this finding, ungulates visited clearings 2.4 times more often than shrubby control sites and visited shrubby control sites less often at night, when large carnivores are most active. Combined with results from previous experiments demonstrating that the disproportionate use of available habitats by large ungulates can alter ecosystem properties, our experiment provides critical evidence that the fear large carnivores inspire in large ungulates can cause trophic cascades.

Does Habitat Diversity Modify the Dietary and Reproductive Response to Prey Fluctuations in a Generalist Raptor Predator, the Eurasian Buzzard Buteo buteo?

Predators can modify their diet and demography in response to changes in food availability and habitat quality. I tested the prediction that some species can change their predation pattern, between specialist type and generalist type, depending on the complexity of habitat structure. It was hypothesized that their dietary response is stronger in diversified habitats than in simplified ones, but the opposite tendency occurs in the case of reproductive response. The nestling diet and breeding success of the Eurasian Buzzard Buteo buteo, the abundance of its main prey (the common vole Microtus arvalis), and that of the most important alternative prey group (passerines) were estimated over ten years in two types of agricultural habitat in western Poland, i.e., in the diversified habitat of small fields and the simplified habitat of large fields. The vole abundance was higher in large fields, but the abundance of passerines was greater in small fields. The frequency of voles in the Eurasian Buzzard nestling diet was higher in large fields than in small fields and increased with the abundance of this prey in crop fields. However, no difference in the relationship between the vole frequency in the diet of Eurasian Buzzards and the abundance of voles was found between the two habitat types. The breeding success of Eurasian Buzzards was dependent on the vole abundance, but this relationship did not differ between the two field types. It seems that the pattern of dietary and reproductive response of Eurasian Buzzards depends on the actual availability of individual prey species, which can be modified by habitat quality, rather than on relative prey abundance.

Peninsular effect on species richness in Italian small mammals and bats

Peninsular effect is an anomalous gradient in plant and animal species richness from base to tip of a given peninsula. This pattern has been studied intensely on various taxonomic groups, but with scarce attention for using standardized data. Here, using presence-absence data normalized by the field effort, the peninsular effect on the species richness of some mammalian groups (Eulipotyphla [i.e. Soricomorpha + Erinaceomorpha], Rodentia, and Chiroptera) was analyzed along the Italian peninsula. Specifically, species richness at each 30′-wide latitudinal band and the normalized species richness were compared, and generalized linear models (GLM) were used to assess whether habitat diversity, altitudinal range and area of each latitudinal band were the main predictors in explaining the peninsular effects in each of the three mammalian orders. In both Rodentia and Chiroptera, species richness was better predicted by habitat heterogeneity and by the interaction term habitat heterogeneity × field effort. For Eulipotyphla, GLM models gave no significant results. Our study highlighted the importance of taking into account the sampling effort in order to proper evaluate the peninsular effects on species richness in animals.

The context dependence of non-consumptive predator effects

Non-consumptive predator effects (NCEs) are now widely recognised for their capacity to shape ecosystem structure and function. Yet, forecasting the propagation of these predator-induced trait changes through particular communities remains a challenge. Accordingly, focusing on plasticity in prey anti-predator behaviours, we conceptualise the multi-stage process by which predators trigger direct and indirect NCEs, review and distil potential drivers of contingencies into three key categories (properties of the prey, predator and setting), and then provide a general framework for predicting both the nature and strength of direct NCEs. Our review underscores the myriad factors that can generate NCE contingencies while guiding how research might better anticipate and account for them. Moreover, our synthesis highlights the value of mapping both habitat domains and prey-specific patterns of evasion success ('evasion landscapes') as the basis for predicting how direct NCEs are likely to manifest in any particular community. Looking ahead, we highlight two key knowledge gaps that continue to impede a comprehensive understanding of non-consumptive predator-prey interactions and their ecosystem consequences; namely, insufficient empirical exploration of (1) context-dependent indirect NCEs and (2) the ways in which direct and indirect NCEs are shaped interactively by multiple drivers of context dependence.

Landscape predictors of human-leopard conflicts within multi-use areas of the Himalayan region

Conflict with humans is a significant source of mortality for large carnivores globally. With rapid loss of forest cover and anthropogenic impacts on their habitats, large carnivores are forced to occupy multi-use landscapes outside protected areas. We investigated 857 attacks on livestock in eastern Himalaya and 375 attacks in western Himalaya by leopards between 2015 and 2018. Multivariate analyses were conducted to identify the landscape features which increased the probability of livestock depredation by leopards. The risk of a leopard killing livestock increased within a heterogeneous landscape matrix comprising of both closed and open habitats (very dense forests, moderate dense forests, open forests, scrubland and non-forests). We used the results to map potential human-leopard conflict hotspots across parts of the Indian Himalayan region. Our spatial risk maps indicate pockets in the eastern, central and western part of eastern Himalaya and the central, northern part of western Himalaya as hotspots of human-leopard conflicts. Most of the attacks occurred when livestock were grazing freely within multi-use areas without supervision of a herder. Our results suggest that awareness about high risk areas, supervised grazing, and removing vegetation cover around human settlements should be initiated to reduce predation by leopards.

The impact of human land use and landscape productivity on population dynamics of red fox in southeastern Norway

In the boreal forest, the red fox (Vulpes vulpes) is a key species due to its many strong food web linkages and its exploitation of niches that form in the wake of human activities. Recent altitudinal range expansion and a perceived population increase have become topics of concern in Scandinavia, primarily due to the potential impacts of red foxes on both prey and competitor species. However, despite it being a common species, there is still surprisingly little knowledge about the temporal and spatial characteristics of its population dynamics. In this study, we synthesized 12 years of snow-track transect data covering a 27,000-km2 study area to identify factors associated with red fox distribution and population dynamics. Using Bayesian hierarchical regression models, we evaluated the relationships of landscape productivity and climate gradients as well as anthropogenic subsidies with an index of red fox population size and growth rates. We found that landscapes with high human settlement density and large amounts of gut piles from moose (Alces alces) hunting were associated with higher red fox abundances. Population dynamics were characterized by direct density-dependent growth, and the structure of density dependence was best explained by the amount of agricultural land in the landscape. Population equilibrium levels increased, and populations were more stable, in areas with a higher presence of agricultural lands, whereas density-dependent population growth was more prominent in areas of low agricultural presence. We conclude that human land use is a dominant driver of red fox population dynamics in the boreal forest. We encourage further research focusing on contrasting effects of anthropogenic subsidization on predator population carrying capacities and temporal stability, and potential impacts on prey dynamics.

Complex spatial patterns delay the discovery and location of food by rodents

Spatial patterns in heterogeneity are generally deemed a central causal factor influencing the physiology and behavior of animals in ecological systems. However, knowledge remains limited about how such patterns influence food discovery by animals. We inferred that spatial heterogeneity plays a key role in animal food discovery and location. To prove this inference, we tested food locating parameters by 2 rodent species, Apodemus agrarius and Lasiopodomys brandtii, in different heterogeneous environments. Our results showed that spatial heterogeneity significantly influenced the food locating time of rodents, with food locating time increasing with increasing spatial heterogeneity. Furthermore, spatial heterogeneity significantly influenced invalid excavations (digging in the wrong place). Finally, spatial heterogeneity significantly influenced the frequency that heterogeneous objects were explored. Supporting our inference, our results indicate that spatial heterogeneity significantly influences the foraging behavior of animals. Consequently, increased spatial heterogeneity will impair the food locating success of rodents. We believe that this work will broaden our understanding of plant-animal interactions.

Lidar Prediction of Small Mammal Diversity in Wisconsin, USA

Vegetation structure is a crucial component of habitat selection for many taxa, and airborne LiDAR (Light Detection and Ranging) technology is increasingly used to measure forest structure. Many studies have examined the relationship between LiDAR-derived structural characteristics and wildlife, but few have examined those characteristics in relation to small mammals, specifically, small mammal diversity. The aim of this study was to determine if LiDAR could predict small mammal diversity in a temperate-mixed forest community in Northern Wisconsin, USA, and which LiDAR-derived structural variables best predict small mammal diversity. We calculated grid metrics from LiDAR point cloud data for 17 plots in three differently managed sites and related the metrics to small mammal diversity calculated from five months of small mammal trapping data. We created linear models, then used model selection and multi-model inference as well as model fit metrics to determine if LiDAR-derived structural variables could predict small mammal diversity. We found that small mammal diversity could be predicted by LiDAR-derived variables including structural diversity, cover, and canopy complexity as well as site (as a proxy for management). Structural diversity and canopy complexity were positively related with small mammal diversity, while cover was negatively related to small mammal diversity. Although this study was conducted in a single habitat type during a single season, it demonstrates that LiDAR can be used to predict small mammal diversity in this location and possibly can be expanded to predict small mammal diversity across larger spatial scales.

Maladaptive nest-site selection by a sagebrush dependent species in a grazing-modified landscape

Animals are expected to select habitats that maximize their fitness over evolutionary time scales. Yet in human-modified landscapes, habitat selection might not always lead to increased fitness because animals undervalue high-quality resources that appear less attractive than those of lower quality. In the American West, agriculture has modified landscapes, yet little is known about whether agricultural changes alter the reliability of the cues animals use to identify habitat quality; ultimately forming maladaptive breeding strategies where behavioral cues are mismatched with survival outcomes. Using the greater sage-grouse, a species highly dependent upon sagebrush landscapes, we (1) evaluated how females select nesting habitats based on sagebrush type, along with livestock grazing related linear and point features, and other biotic, abiotic characteristics, given hypothesized influences on hiding cover, microclimate and predator travel routes and perches, (2) compared habitat selection information with results for nest survival estimates to evaluate if selection appears to be adaptive or not, and (3) used our results to evaluate the most appropriate strategies for this species in a grazing-modified landscape. Nest-site selection for sagebrush type appears to be maladaptive: in the most-preferred sagebrush type, nest survival rate was one-fourth the rate realized by females nesting in the sagebrush type avoided. Nest survival was four times higher for nests placed away from (>100 m), rather than next to (1 m), the nearest fence, and survival was lower within sites with higher cow pie density (a proxy for previous grazing intensity). Live and dead grasses influenced selection and survival in opposing ways such that dead grass was selected for but resulted in reduced survival while live grass was avoided but resulted in increased survival. Results collectively provide the first empirical evidence that a specific type of sagebrush acts as an ecological trap while another sagebrush type is undervalued. These results also suggest that adding more fences to control livestock grazing systems will likely reduce sage-grouse nest survival.

Implications of shared predation for space use in two sympatric leporids

Spatial variation in habitat riskiness has a major influence on the predator-prey space race. However, the outcome of this race can be modulated if prey shares enemies with fellow prey (i.e., another prey species). Sharing of natural enemies may result in apparent competition, and its implications for prey space use remain poorly studied. Our objective was to test how prey species spend time among habitats that differ in riskiness, and how shared predation modulates the space use by prey species. We studied a one-predator, two-prey system in a coastal dune landscape in the Netherlands with the European hare (Lepus europaeus) and European rabbit (Oryctolagus cuniculus) as sympatric prey species and red fox (Vulpes vulpes) as their main predator. The fine-scale space use by each species was quantified using camera traps. We quantified residence time as an index of space use. Hares and rabbits spent time differently among habitats that differ in riskiness. Space use by predators and habitat riskiness affected space use by hares more strongly than space use by rabbits. Residence time of hare was shorter in habitats in which the predator was efficient in searching or capturing prey species. However, hares spent more time in edge habitat when foxes were present, even though foxes are considered ambush predators. Shared predation affected the predator-prey space race for hares positively, and more strongly than the predator-prey space race for rabbits, which were not affected. Shared predation reversed the predator-prey space race between foxes and hares, whereas shared predation possibly also released a negative association and promoted a positive association between our two sympatric prey species. Habitat riskiness, species presence, and prey species' escape mode and foraging mode (i.e., central-place vs. noncentral-place forager) affected the prey space race under shared predation.

Effect of plantation clearcutting on carnivore presence in industrial forest landscapes in south-central Chile

Information on how wildlife is affected by pine plantation clearcutting is relevant for designing management strategies to promote biodiversity conservation in productive systems. By comparing the number of records of carnivores in a mosaic of pine plantations and native forest remnants before and after pine harvesting, we assessed the effect of plantation clearcutting on carnivore presence in ten sampling areas in Central Chile. We also included a number of covariates to account for their potential confounding effects, for example, the distance between each site and the nearesting human settlement and vegetation cover. A total of 10 species were observed, but no negative effect of clearcutting on carnivore presence was detected. Only the culpeo fox (Lycalopex culpaeus) responded positively to the harvesting of pine plantations. The threatened kodkod (Leopardus guigna) was absent in clearcut areas and the number of records increased in forests or plantations with a dense understorey. The domestic dog (Canis lupus familiaris) responded positively to human settlements and seems to prefer more open areas. The number of records for the Puma (Puma concolor) and the domestic cat (Felis silvestris catus) was too few, and hence, we could not make any inference regarding these two species. The other species recorded showed different responses to one or more of the included covariates. Although our results showed that the recording of some species could change in the short term after pine harvesting, future studies should assess the impact of clearcutting at a much higher scale, both in terms of space and time.

Dynamics of predator-prey habitat use and behavioral interactions over diel periods at sub-tropical reefs

The dynamics of fish communities at tropical and sub-tropical rocky reefs are influenced in many cases by predation activity and predator-prey interactions. These processes usually follow specific diel patterns in reef areas with higher rates of these interactions occurring during the crepuscular periods. However, other factors such as habitat complexity and species-specific behavior may alter these patterns, increasing variability in species interactions. A better understanding of the dynamics of these patterns and processes would allow us to manage and monitor fish communities in these productive and vulnerable areas more efficiently. We investigated behavioral changes of predators and prey fish in sub-tropical “live-bottom” (sandstone) reefs at Gray’s Reef National Marine Sanctuary (GRNMS), located 20 nautical miles off the coast of Georgia, USA, using fisheries acoustic methods in association with visual census and direct observation using SCUBA. Changes in co-location and habitat preferences of predators and prey over time throughout the diel cycle were investigated using species distribution models (MAXENT) based on habitat predictors and by means of spatial statistics. The results indicate that predator and prey distribution patterns changed considerably throughout the day. Prey and predator species exhibited complex spatial dynamics and behavior over diel periods, with prey modifying patterns of habitat use and spatial distribution, likely as a response of their interactions with predators. Crepuscular periods were confirmed to be the most active phases in terms of predator-prey interactions and consequently the most variable. The combination of tools and approaches used in this study provided valuable sources of information that support the inferences of predation risk-driven habitat selection of prey in this sub-tropical reef system.

No evidence of handling-induced mortality in Serengeti's African wild dog population

The disappearance of an endangered African wild dog population from Serengeti National Park (SNP) led to international debate centered around one question: were researchers to blame? The "Burrows' hypothesis" postulated that stress induced by research-related immobilization and handling reactivated a latent rabies virus, eliminating the population. Insufficient data inhibited hypothesis testing, but since wild dogs persisted alongside SNP and have been studied since 2005, the hypothesis can be tested 25 years after its proposition. To be supported, wild dog immobilization interventions should have resulted in high mortality rates. However, 87.6% of 121 handled wild dogs (2006-2016) survived >12 months post-handling. Some argued that viral reactivation would necessitate long-term stress. Following immobilization, 67 animals were captured, transported, and held in a translocation enclosure. Despite the longer-term stress, 95.5% survived >12 months. Furthermore, the stable number of wild dog packs in the ecosystem over the past decade, and lack of recolonization of SNP, strongly oppose Burrows' hypothesis. Instead, factors such as heightened levels of interspecific competition are likely to have contributed to the wild dog disappearance and subsequent avoidance of the Serengeti plains. Handling and radio telemetry are invaluable when studying elusive endangered species, yielding information pertinent to their conservation and management, and had no effect on Serengeti wild dog survival.

Home range size, vegetation density, and season influences prey use by coyotes (Canis latrans)

To ensure reproductive success, Canis species establish contiguous mosaics of territories in suitable habitats to partition space and defend limiting resources. Consequently, Canis species can exert strong effects on prey populations locally because of their year-round maintenance of territories. We assessed prey use by coyotes (Canis latrans) by sampling scats from within known territories in southeastern Alabama and the Savannah River area of Georgia and South Carolina. We accounted for the size and habitat composition of coyote home ranges to investigate the influence of space use, vegetation density, and habitat type on coyote diets. Coyote use of prey was influenced by a combination of mean monthly temperature, home range size, vegetation density, and hardwood forests. For example, coyote use of adult white-tailed deer (Odocoileus virginianus) was associated with cooler months and smaller home ranges, whereas use of rabbits (Sylvilagus spp.) was associated with cooler months, larger home ranges, and less vegetation density. Coyotes in our study relied primarily on nutritionally superior mammalian prey and supplemented their diet with fruit when available, as their use of mammalian prey did not appreciably decrease with increasing use of fruit. We suggest that differential use of prey by coyotes is influenced by habitat heterogeneity within their home ranges, and prey-switching behaviors may stabilize local interactions between coyotes and their food resources to permit stable year-round territories. Given that habitat composition affects coyote prey use, future studies should also incorporate effects of habitat composition on coyote distribution and abundance to further identify coyote influences on prey communities.