Predator Guild Research Articles

Niche Partitioning in a Guild of Invasive Mammalian Predators

Niche Partitioning in a Guild of Invasive Mammalian Predators

Ecological Infrastructures May Enhance Lepidopterans Predation in Irrigated Mediterranean Farmland, Depending on Their Typology and the Predator Guild

Ecological infrastructures (EIs) are considered relevant components in agricultural landscapes to support biodiversity and ecosystem services. We used the predatory attacks on lepidopteran dummies as a proxy to assess predation rates in the agricultural matrix and different EIs types according to their location and vegetation structure. We aimed at comparing the effect of different types of EI on the predation intensity in two intensively irrigated agricultural areas located in the Sorraia and Tagus river valleys in central Portugal. We hypothesized that: (1) the predation rate would be higher near EIs compared with the agricultural matrix, (2) the positive effect of EIs on predation rate would differ with their typologies, and (3) the EIs’ proximity and proportion in the surrounding landscape would have a positive effect on the predation rate in agricultural fields. The EI typologies influenced differently the predator groups and the overall predation rate. Major differences were observed for bird predation, being higher in woody EIs. A positive correlation between predation rate and EIs area of the surrounding landscape, as well as a negative correlation with the distance to the nearest riparian and woody EIs, was observed for birds. The observed dissimilarities in the predators’ response may be related to habitat differences and its functional connectivity. The overall monthly low predation rates are possibly related to the intensive agricultural system and the small area occupied by EIs.

Niche partitioning in a guild of invasive mammalian predators.

Predators compete aggressively for resources, establishing trophic hierarchies that influence ecosystem structure. Competitive interactions are particularly important in invaded ecosystems where introduced predators can suppress native prey species. We investigated whether niche partitioning exists within a guild of invasive mammalian predators and determined the consequences for native species. Over 4405 camera‐trap days, we assessed interactions among three invasive predators: two apex predators (feral cats Felis catus and ferrets Mustela furo) and a mesopredator (stoats Mustela erminea), in relation to their primary prey (lagomorphs, rodents and birds) and habitat use. Further, we tested for mesopredator release by selectively removing cats and ferrets in a pulse perturbation experiment. We found compelling evidence of niche partitioning; spatiotemporal activity of apex predators maximized access to abundant invasive prey, with ferrets targeting lagomorphs and cats targeting rodents. Mesopredators adjusted their behavior to reduce the risk of interference competition, thereby restricting access to abundant prey but increasing predation pressure on diurnal native birds. Stoats were only recorded at the treatment site after both larger predators were removed, becoming the most frequently detected predator at 6 months post‐perturbation. We suggest there is spatial and resource partitioning within the invasive predator guild, but that this is incomplete, and avoidance is achieved by temporal partitioning within overlapping areas. Niche partitioning among invasive predators facilitates coexistence, but simultaneously intensifies predation pressure on vulnerable native species.

Polymorphism promotes edge utilization by marsh crabs.

Understanding how habitat edges affect ecological processes is crucial given widespread and increasing modifications to natural landscapes. Resource specialization is a key factor affecting among-species edge responses, but we know little about how intraspecific resource use variation mediates edge utilization. Here, we integrate stomach content analysis, geometric morphometrics and feeding experiments to explore the role of resource polymorphism in mediating marsh crab (Panopeus obesus) foraging within the marsh-oyster reef boundary. Stomachs of edge individuals contained a greater proportion of morphologically defended edge prey (bivalves) compared to core marsh individuals, and edge individuals possessed relatively tall and robust claw morphology for manipulating such prey. We further show experimentally that phenotypic changes of edge P. obesus are associated with enhanced feeding efficiency on small, but not large edge prey. Morphological and ecological traits of edge P. obesus overlapped with the edge-occurring congener, P. herbstii, suggesting some degree of functional convergence despite the potential for interspecific competition within edges. Though this polymorphism is likely plastic, the success of P. obesus along edges could subsidize predator production within marshes and alter top-down pressure across mosaic estuarine landscapes. More generally, our study reveals polymorphism as a driver of edge utilization, while yielding new insight into the processes that maintain or erode spatial niche differentiation within predator guilds.

Behavioral responses to spatial variation in perceived predation risk and resource availability in an arboreal primate

AbstractPrey species must often face a trade‐off between acquiring resources and minimizing predation risk. The spatial variation in predation risk across a landscape, as perceived by prey across their foraging or home range, creates a “landscape of fear” by which individuals modify their behavior in response to the level of perceived risk. Here, we explored the influence of perceived predation risk, habitat features associated with risk, and fruit availability, on the spatial variation in behavior of the endangered forest‐dwelling samango monkey (Cercopithecus albogularis schwarzi). We collected behavioral and location data on two habituated samango monkey groups in the Soutpansberg Mountains, South Africa, between 2012 and 2016. We further collected location data of the samango monkey's acoustically distinct alarm call, which has an unambiguous association with aerial predators, to spatially map perceived risk across the landscape. Using generalized linear mixed models, we found that perceived risk from eagles significantly influenced the spatial distribution of critical life‐functioning behaviors, with samango monkeys increasing feeding and foraging in high‐risk areas. To mitigate this risk, samangos increased cohesion between group members, which subsequently reduced vigilance levels. Group cohesion further increased in high‐risk areas with abundant fruit, relative to high‐risk, fruit‐poor areas, demonstrating the monkey's foraging/risk trade‐off. Feeding was also reduced in areas of low canopy height, while vigilance decreased with increasing understory visibility and distance from sleep site, showing the influence of landscape features on risk perception from other predator guilds. Thus, for arboreal species foraging in a 3‐D landscape, risk perception may occur at multiple scales and in response to multiple predator guilds. Only moving was influenced by fruit availability, either due to moving between localized food patches or from escaping high‐risk areas following feeding bouts. These findings highlight that risk‐taking in samango monkeys is only associated with behaviors fundamental to survival at a given location and that increased cohesion between neighbors is the main antipredator response in this species.

Status and Management of the Blue Crab Fishery in the Gulf of Mexico

AbstractManagement of the blue crab Callinectes sapidus fishery in the Gulf of Mexico is the responsibility of the individual states under the purview of a regional management plan. States generally follow the “2‐S” system of management, placing emphasis on size and sex. Despite management policies, harvest and juvenile abundances remain in decline. A significant trend toward decreasing harvest began in the early 2000s, with landings below average in 13 of the 20 years from 2000 to 2019. Since 2010, the fishery has maintained a lower but relatively stable harvest. There have been significant decreases in numbers of late‐stage juveniles in fishery‐independent trawl surveys, while numbers of megalopae and early juveniles have not exhibited declines. Postsettlement mortality is potentially driven by climate‐related hydrological processes that structure the biotic community (predator guild) and nearshore habitats. Diversity of predators, few predation‐free refuges, and a lack of seasonality in predation likely contribute to high regional mortality. Factors that influence quality and quantity of available refuge may ultimately control abundance. Although genetics data describe the population as panmictic, geographic differences in coastal climate and hydrological processes may act to structure populations. Separation of stocks according to ecozones may provide a more suitable approach to population delineation. The 2011 stock assessment divided the population into eastern and western regions based on confounding information on genetics, physiographic features that limit larval transport, variations in climate, and migration of female crabs along the west coast of Florida. There is concern that the population is undergoing Gulf of Mexico‐wide changes in biomass associated with regional climate regime shifts that may alter the resiliency of the stock. Whether the shift to a more favorable climate phase would reverse the declining trends is unknown. Changes in population levels could be rapid given the high juvenile mortality and short generation time as well as the importance of climate in structuring habitat.

Local environmental context determines the colonisation of leaf shelters by arthropods: an experimental study

Abstract The magnitude of facilitation by shelter-building engineers on community structure is expected to be greater when they increase limited resources in the environment. We evaluated the influence of local environmental context on the colonisation of leaf shelters by arthropods in a Mexican evergreen tropical rainforest. We compared the species richness and abundance of arthropods (total and for different guilds) colonising artificially rolled leaves in habitats differing in understory heterogeneity (forest edge > old-growth forests > living fences). Arthropod abundance of the most representative arthropod taxa (i.e., Araneae, Blattodea, Collembola and Psocoptera) colonising the rolled leaves was greater at forest edge, a trend also observed for average arthropod abundance, and for detritivore and predator guilds. In addition, fewer arthropod species and individuals colonised the rolled leaves in the living fence habitat, a trend also observed for most arthropod guilds. As forest edge is expected to have a greater arthropod diversity and stronger density-dependent interactions, a greater limitation of refuges from competitors or predators may have determined the higher colonisation of the rolled leaves in this habitat. Our results demonstrate that local environment context is an important factor that affects the colonisation of arthropods in leaf shelters.

Insight into the role of cyanobacterial bloom in the trophic link between ciliates and predatory copepods

An important group of protozooplankton, the ciliates, are a crucial component of aquatic food webs. They are the main grazers on bacteria and algae transferring carbon to higher levels of the food web (metazooplankton and fish fry). Changes in the quality and quantity of protozooplankton can modify the quality and quantity of metazooplankton, especially predatory copepods, causing changes in energy transfer and the matter cycle. Observable climate change is one of the most significant factors promoting the increase of cyanobacterial blooms. Therefore, the aim of this study was to find out how cyanobacterial blooms modify relationships between ciliates (prey) and copepods (predator), and to discover possible pathways of changes in freshwater food webs. We analysed the relationship between the biomass of predatory copepods and feeding guilds of ciliates (algivorous, bacterivorous, bacteri-algivorous). The relationship of predators biomass with algivorous and bacteri-algivorous ciliate biomasses, with a simultaneous lack of relationship with bacterivorous ciliate biomass, demonstrates that bacterial fixed carbon may be only partially contributing to the total energy passed through this link. Results demonstrated that the bloom enhanced the relationship between prey and predator. Larger and free-swimming ciliate species appear to play a greater role in energy transfer than smaller sedentary species.

Behavioral effects of wolf presence on moose habitat selection: testing the landscape of fear hypothesis in an anthropogenic landscape

Landscape of fear refers to the spatial variation in prey perception of predation risk, that under certain conditions, may lead to changes in their behavior. Behavioral responses of prey in relation to large carnivore predation risk have mainly been conducted in areas with low anthropogenic impact. We used long-term data on the distribution of moose in different habitat types in a system characterized by intensive management of all three trophic levels (silviculture, harvest of wolves and moose) to study effects on moose habitat selection resulting from the return of an apex predator, the wolf. We assumed that coursing predators such as wolves will cause an increased risk for moose in some habitat types and tested the hypotheses that moose will avoid open or young forest habitats following wolf establishment. After wolf recolonization, moose reduced their use of one type of open habitat (bog) but there was neither change in the use of the other open habitat type (clear-cut), nor in their use of young forest. Wolf establishment did not influence the use of habitat close to dense habitat when being in open habitats. Thus, the effect of wolves varied among habitat types and there was no unidirectional support for a behavioral effect of wolves’ establishment on moose habitat use. Human-driven habitat heterogeneity, concentration of moose forage to certain habitat types, and the effects of a multiple predator guild on moose may all contribute to the results found. We conclude that the landscape of fear is likely to have weak ecological effects on moose in this system.

Reexamination of the Purported Rapid Population Decline of Plains Spotted Skunks in the Mid-Twentieth Century

Spilogale putorius interrupta (Plains Spotted Skunk) was once common across its range in the United States from the Mississippi River to the Rocky Mountains, but it is now rare and being considered for protection under the federal Endangered Species Act. Disease and introduction of agricultural chemicals have been suggested as potential causes of an ostensible rapid decline of >90% in Plains Spotted Skunk populations in the 1940s. I examined published scientific literature, agency reports, and other historical accounts to determine if such a decline actually took place and if there is any evidence that these factors could have caused such a decline. I found anecdotal information implying that there were declines in some states, but I found no substantiation of a widespread precipitous decline during the 1940s-1950s. Harvest records of Plains Spotted Skunks, Didelphis virginiana (Virginia Opossum), and Mephitis mephitis (Striped Skunk) from the central United States all demonstrate similar rates of decline and this, along with nationwide information suggest that the fall in Plains Spotted Skunk harvests during this period was due to a crash in demand across the entire fur market. There was an extensive rabies epidemic during this period but little data supportive of it causing a population crash. Similarly, usage of chemicals for agricultural pest and weed control was found throughout the species range, but only on such a small percentage of farms it is unlikely to have had significant impact on their population. The Plains Spotted Skunk most likely experienced a long, gradual decline in population density and scientists should undertake research focused on potential causes of decline relevant to this timescale such as changes in agricultural practices or predator guilds so as to develop testable hypotheses that will lead to effective conservation actions that will benefit the species.

Stronger predation intensity and impact on prey communities in the tropics

The hypothesis that biotic interactions strengthen toward lower latitudes provides a framework for linking community-scale processes with the macroecological scales that define our biosphere. Despite the importance of this hypothesis for understanding community assembly and ecosystem functioning, the extent to which interaction strength varies across latitude and the effects of this variation on natural communities remain unresolved. Predation in particular is central to ecological and evolutionary dynamics across the globe, yet very few studies explore both community-scale causes and outcomes of predation across latitude. Here we expand beyond prior studies to examine two important components of predation strength: intensity of predation (including multiple dimensions of the predator guild) and impact on prey community biomass and structure, providing one of the most comprehensive examinations of predator-prey interactions across latitude. Using standardized experiments, we tested the hypothesis that predation intensity and impact on prey communities were stronger at lower latitudes. We further assessed prey recruitment to evaluate the potential for this process to mediate predation effects. We used sessile marine invertebrate communities and their fish predators in nearshore environments as a model system, with experiments conducted at 12 sites in four regions spanning the tropics to the subarctic. Our results show clear support for an increase in both predation intensity and impact at lower relative to higher latitudes. The predator guild was more diverse at low latitudes, with higher predation rates, longer interaction durations, and larger predator body sizes, suggesting stronger predation intensity in the tropics. Predation also reduced prey biomass and altered prey composition at low latitudes, with no effects at high latitudes. Although recruitment rates were up to three orders of magnitude higher in the tropics than the subarctic, prey replacement through this process was insufficient to dampen completely the strong impacts of predators in the tropics. Our study provides a novel perspective on the biotic interaction hypothesis, suggesting that multiple components of the predator community likely contribute to predation intensity at low latitudes, with important consequences for the structure of prey communities.

Temporal niche partitioning as a novel mechanism promoting co-existence of sympatric predators in marine systems.

Niche partitioning of time, space or resources is considered the key to allowing the coexistence of competitor species, and particularly guilds of predators. However, the extent to which these processes occur in marine systems is poorly understood due to the difficulty in studying fine-scale movements and activity patterns in mobile underwater species. Here, we used acceleration data-loggers to investigate temporal partitioning in a guild of marine predators. Six species of co-occurring large coastal sharks demonstrated distinct diel patterns of activity, providing evidence of strong temporal partitioning of foraging times. This is the first instance of diel temporal niche partitioning described in a marine predator guild, and is probably driven by a combination of physiological constraints in diel timing of activity (e.g. sensory adaptations) and interference competition (hierarchical predation within the guild), which may force less dominant predators to suboptimal foraging times to avoid agonistic interactions. Temporal partitioning is often thought to be rare compared to other partitioning mechanisms, but the occurrence of temporal partitioning here and similar characteristics in many other marine ecosystems (multiple predators simultaneously present in the same space with dietary overlap) introduces the question of whether this is a common mechanism of resource division in marine systems.

The diversity of saproxylic beetles’ from the Natural Reserve Voievodeasa forest, North-Eastern Romania

Nature reserves harbor considerable richness and diversity of saproxylic organisms since dead wood is preserved in situ , this being also the case of Voivodeasa beech-spruce-fir forest in North-Eastern Romania, the area investigated under the present research. The employed sampling design consisted in 20 flight interception traps placed in a square grid (100 x 100 m). The beetle content of the traps was collected every two weeks, from May to September. The number of intercepted beetles reached 13,554 individuals, of which 7,174 individuals (assigned to 336 species placed in 217 genera and 58 families) were identified at species level and 6,390 individuals, at genus or family level. The majority of the identified species were obligate saproxylic species (217 species). However, the unexpected high species richness corresponded to an area with modest representation of deadwood due to previous status of commercial forest. The identified beetles were members of different habitat-guilds depending on what type of substrate they colonize: recently dead wood (23%), decomposed dead wood (41%), wood inhabiting fungi (34%) and tree-hollow detritus (2%). According to their trophic position, the identified saproxylic beetles pertained to the following guilds: xylophagous (40%), mycetophagous (39%), predatory (14%), and species relying on other food resources (5%). Non-metric Multidimensional Scaling ordination using Bray-Curtis distance, performed to compare the saproxylic beetles’community at different sampling dates across the vegetation season suggested that species turn-over took place in the time window of one month. The analysis of abundance/dominance structure of the saproxylic beetle community employing classical community indices (abundance, dominance, constancy and Dzuba index) showed that 7% of the species were abundant, and 68% were rare, Fisher’s log series fitting the distribution of abundances. In terms of constancy, 11% were eu-constant and 62% - accidental species. Considering the dominance, only 0.4% represented eu-dominant species while 89% were sub-recedent species. According to Dzuba ecological significance index, four species were characteristic for the saproxylic beetle community: Ptilinus pecticornis, Enicmus rugosus, Cis rugulosus and Taphorychus bicolor , most of the identified species being accessory or accidental (33% and 65%). PCA ordination performed on abundance constancy, dominance and ecological significance scores, showed that all indices were highly correlated with PC1 and further testing using multivariate regression with dominance held as independent variable, showed high correlation among indices. Species ranked according to these indices as rare, accidental or accesory clustered separatelly in the ordination space while dominant and eu-dominant species established another distinct cluster. Species richness estimation based on Chao 1 nonparametric index exceeded the observed richness of saproxylic beetles (estimated number of species = 266.67, observed number of species = 217). Inspection of the individual-based rarefaction curve showed that the number of species did not stabilize after pooling all captured individuals in all samples across the sampling period. The observed richness corresponds to the case of hyperdiverse communities where sampling never leads to the stabilization of species richness under a realistic sampling scheme. Species diversity: The rank-abundance curves constructed on aggregated catches and catches of saproxylic beetles at different sampling dates showed variation in terms of species richness and eveness, with species re-ordering across the sampling period. The diversity profiles constructed on Shannon, Gini-Simpson, Berger-Parker and eveness indices for the pooled sample and for separate samples across the vegetation season indicated the aggregated saproxylic community as highly diverse and also highly uneven, with rich representation of rare species, dominated by few abundant species contrasting the community at the end of the vegetation season characterized by high eveness and few species. Network structure: We assembled four bipartite, unweighted, and undirected networks to approach the temporal changes across the sampling period extended over one vegetation season using the specific metrics derived from the community network analysis: connectance, nestedness, average degree, modularity. The networks corresponded to aggregated community of saproxylic beetles and to xylophagous, mycetophagous and predatory guilds. The topology of beetles’ community and of the three main trophc guilds networks linked to time sequences are characterized by high connectance, high nestedness and modularity, with the exception of the mycetophgous sub-network not displaying significant modularity. The topologies reflect the temporal partition of the ecological niche, with nestedness and modularity relating to species’phenologies during the adult stage. Among the identified species, 13% indicate high degree of naturalness of the Voievodeasa forest: of these, 9 species are old-growth forests relicts. Other 62 species are included in the Red List of European Saproxylic Beetles of which five are near threatened ( Protaetia fieberi, Cucujus cinnaberinus, Crepidophorus mutilatus, Ceruchus chrysomelinus, Prostomis mandibularis ), Ischnodes sanguinolentus is vulnerable and Rhysodes sulcatus is an endangered species. During the study, two Coleoptera species, new for Romanian insect fauna were identified: Denticollis interpositus Roubal, 1941 and Hylis procerulus (Mannerheim 1823).

Assessing the benefits of integrated introduced predator management for recovery of native predators

Increasingly threatened species and their habitats require multiple successful management actions to ensure persistence. Introduced predator exclusion and suppression programs are key conservation actions used to retain or restore Australian ecosystems. Nevertheless, few direct comparisons are made to ascertain the individual and combined efficacy of multiple introduced predator conservation actions to benefit biodiversity. When colocated, both management actions could generate additive conservation benefits that greatly assist the recovery or persistence of threatened native species. Varanid lizards are key functional components in Australian predator guilds and could benefit, via ecological release, when introduced predator management actions are successful. Here we tested the effects of a colocated predator‐exclusion fence and lethal fox baiting on varanid site occupancy in a semiarid protected area. Varanid site occupancy was higher at sites inside (Ψ = 0.90 ± 0.26) compared to sites outside (Ψ = 0.61 ± 0.28) the introduced predator‐proof fenced enclosure. There was only weak evidence of increased varanid site occupancy at fox baited sites (Ψ = 0.037 ± 0.024) compared to nonfox baited (Ψ = 0.00) sites. Overall, colocated introduced predator management actions achieved some additive benefits via possible spillover fencing effects for native mesopredator populations. However, most potential benefits to varanid populations outside of the predator‐proof fenced enclosure were absent due to unsuccessful lethal‐baiting effects on fox populations. The predator‐proof fenced enclosure nevertheless provides important habitat refugia for future source populations for reintroduction once adjacent protected areas become suitable.

Diversity Patterns of Tropical Epigeal Beetle Assemblages Associated with Monoculture and Polyculture Plantations with Big-Leaf Mahogany.

Although commercial forest plantations have experienced a major growth in the tropics over the past decades, little attention has been paid to their role in the conservation of epigeal arthropod communities. We studied diversity patterns of the epigeal beetle community in monoculture and polyculture forest plantations with big-leaf mahogany (Swietenia macrophylla). Likewise, we explored the existence of indicator species of each plantation type. Our findings highlight that each plantation type promotes multiple impacts on diversity patterns. We found that monocultures positively influenced overall beetle species richness and ecological diversity. When broken down by guild, both predator and decomposer species richness were similar between monoculture and polyculture, whereas for beetle diversity we found contrasting responses by guild: decomposer diversity was greater in monoculture whereas predator diversity was higher in polyculture. In addition, species composition differed between monoculture and polyculture, except for the predator guild. Species turnover was the main component explaining beta diversity patterns at all levels, indicating that each plantation type promotes biologically distinct epigeal assemblages. Few superabundant heliophile species dominated the beetle community structure; moreover, monocultures had a composition skewed towards heliophile species whereas polyculture favored umbrophile species. These patterns could be attributed to differences in habitat complexity between plot types, namely differences in tree cover. Additionally, indicator species only were identified in polycultures, reflecting their higher spatial complexity. Monoculture and polyculture plantations with big-leaf mahogany are complementary agroecosystems for preserving diverse epigeal beetle communities and should be considered valuable tools for conservation purposes in the tropics.

Gifts of an enemy: scavenging dynamics in the presence of wolves (Canis lupus)

Abstract Carrion represents an important resource for carnivores. Examining competition for carrion in a risk–reward framework allows for a better understanding of how predator guilds compete for and benefit from carrion. We used trail camera data to compare wintertime carrion use and vigilance behavior of four carnivores in Denali National Park and Preserve. We found that carrion use was dominated by wolves (Canis lupus) and wolverines (Gulo gulo), followed by red foxes (Vulpes vulpes) and coyotes (Canis latrans). Wolves and wolverines were twice as likely to visit a carcass as foxes and coyotes, and their visits were longer and more numerous. Our results suggest scavenging animals reduced their risk exposure primarily by reducing their use of carrion, with some evidence of increased vigilance at busy sites. We found that carrion use and behavior at carcass sites were influenced by the mortality type of the carcass, the age of the carcass, and the long-term intensity of wolf use in the area. Our results also suggest that wolves are the “top scavenger,” and indicate that intraguild competition for carrion strongly affects which species benefit from carrion, with larger and more aggressive species dominating.

An omnivorous mesopredator modifies predation of omnivore‐dispersed seeds

AbstractPost‐dispersal seed predation is an important determinant of plant recruitment. Although many plant species are dispersed following consumption by omnivorous vertebrates, the potential for these dispersal agents to indirectly affect seed fate by modifying seed predator behavior is poorly understood. We evaluated the hypothesis that the scat of an omnivorous vertebrate (coyote, Canis latrans), which is also a rodent predator, would reduce seed predation by rodent granivores. We also hypothesized that scat would lead to increased removal by arthropod seed predators by providing a resource that attracts ants and other arthropods. We examined the role of omnivore deposition on seed predation of two animal‐dispersed species that differed in size: Larger Prunus serotina seeds are attacked only by rodents, whereas smaller Rubus allegheniensis seeds are attacked by arthropods and rodents. Using an experiment that manipulated the presence of coyote scat and access by different granivore guilds, we found that scat reduced the total number of seeds removed from full‐access depots by 12%, but it increased the total number of seeds removed from arthropod‐only depots by 43%. Rodent removal of P. serotina seeds was 21% lower in the presence of scat. Scat composition was also important in affecting rodent seed predation, with seed predation 50% lower in the presence of meat‐rich scat compared with mixed or fruit‐rich scat. Arthropod removal of R. allegheniensis seeds was 43% higher in the presence of scat. Prunus serotina seeds were generally removed at greater rates than R. allegheniensis seeds in full‐access trays; however, scat reduced this difference in removal rates from 37% more P. serotina seeds removed to 18% more P. serotina seeds removed. These findings illuminate a new pathway through which omnivores may influence plant populations by modifying post‐dispersal seed predation by arthropods and rodents. Moreover, our results indicate that the ultimate effect of vertebrate omnivores on seed survival in a given region may depend upon omnivore diet, dominant seed predator guilds, and differences in granivore seed preference.

Predation risk and herd position influence the proportional use of antipredator and social vigilance by impala

Vigilance is just one of the many fitness-enhancing activities that animals do each day. However, as vigilance is used for both predator detection and obtaining social information, individuals must decide how to divide their time between these two vigilance types. Yet, it is unclear (1) how prey species living in the centre and edge of groups prioritize their use of these different vigilance types and (2) how this prioritization varies with increasing risk. To explore this, we focused on the degree to which impala, Aepyceros melampus, a herd-living antelope, adjusted their antipredator (looking out from the herd) and social (looking at herd members) vigilance across three sites with different predator guilds and predator densities. We found that as predator types and densities increased, herd size increased, but that impala did not adjust the total time they spent vigilant (antipredator plus social vigilance). Thus, they did not sacrifice other fitness-enhancing activities (e.g. foraging) to increase vigilance. Yet, overall, within the herds, edge individuals displayed greater total vigilance (antipredator plus social) and showed a greater proportional use of antipredator vigilance compared to central individuals. With increasing predator numbers, edge individuals maintained and ultimately increased their proportional use of antipredator vigilance. In contrast, central individuals reduced their use of antipredator vigilance and increased social vigilance. As suggested elsewhere, this adjustment might have been related to these individuals trying to increase foraging efficiency and cohesion benefits. However, they may have also monitored conspecifics to detect threats, while obtaining both short- (e.g. less time spent in a vulnerable head-down position) and long-term (e.g. reduced daily foraging time allowing more time for less vulnerable activities) antipredator benefits. Ultimately, our results highlight that herd position and predator differences can influence overall vigilance levels and how individuals adjust their use of antipredator and social vigilance.

Artificial nest experiment reveals inter-guild facilitation in duck nest predation

Predation is the most important factor limiting Northern Hemisphere duck nest survival. While most avian nest predators take only eggs, mammalian predators also pose mortality risks to incubating ducks. Partial depredation of duck clutches elevates subsequent nest desertion probability, especially where eggshells provide evidence of the depredation event. Avian predators tend to consume egg contents at the nest, which may not intrinsically pose a risk to hens, but leave egg remains. This begs the question: does primary avian depredation of duck eggs actively facilitate nest visits by secondary mammalian predators, with potential survival consequences for the remaining clutch, but also sitting hens? We created 335 artificial duck nests in Finland and Denmark during 2017–2019 and monitored them for seven days using wildlife cameras to test whether initial avian predators breaking the eggs facilitated visits by secondary mammalian predators in various duck breeding habitats. Visitation rates of mammalian predators likely to take duck hens increased significantly after avian egg depredation events that involved egg breakage, although rates differed between habitats. Most common mammalian nest visitors at nests depredated by avian predators were red fox (Vulpes vulpes), followed by two alien species, raccoon dog (Nyctereutes procyonoides) and American mink (Neovison vison). Although we should be prudent about extrapolating conclusions from artificial experiment to real duck nests, our results strongly suggest inter-guild facilitation between avian and mammalian predators at duck nest sites. We suggest that by breaking the eggs, avian predators may offer olfactory, visual or other cues for secondary predators. Nest visits by mammalian predators could potentially increase egg depredation risk, but also elevate mortality risks for incubating females, dependent upon prevailing predator guilds.

Behavioral strategies during incubation influence nest and female survival of Wild Turkeys.

Females must balance physiological and behavioral demands of producing offspring with associated expenditures, such as resource acquisition and predator avoidance. Nest success is an important parameter underlying avian population dynamics. Galliforms are particularly susceptible to low nest success due to exposure of ground nests to multiple predator guilds, lengthy incubation periods, and substantive reliance on crypsis for survival. Hence, it is plausible that nesting individuals prioritize productivity and survival differently, resulting in a gradient of reproductive strategies. Fine‐scale movement patterns during incubation are not well documented in ground‐nesting birds, and the influence of reproductive movements on survival is largely unknown. Using GPS data collected from female wild turkeys (n = 278) across the southeastern United States, we evaluated the influence of incubation recess behaviors on trade‐offs between nest and female survival. We quantified daily recess behaviors including recess duration, recess frequency, total distance traveled, and incubation range size for each nest attempt as well as covariates for nest concealment, nest attempt, and nest age. Of 374 nests, 91 (24%) hatched and 39 (14%) females were depredated during incubation. Average nest survival during the incubation period was 0.19, whereas average female survival was 0.78. On average, females took 1.6 daily unique recesses (SD = 1.2), spent 2.1 hr off the nest each day (SD = 1.8), and traveled 357.6 m during recesses (SD = 396.6). Average nest concealment was 92.5 cm (SD = 47). We found that females who took longer recess bouts had higher individual survival, but had increased nest loss. Females who recessed more frequently had lower individual survival. Our findings suggest behavioral decisions made during incubation represent life‐history trade‐offs between predation risk and reproductive success on an unpredictable landscape.