Large Prey Research Articles

Foraging Site Selection of the Middle Spotted Woodpecker (Leiopicus medius L.) in Primeval Oak-Lime-Hornbeam Forest of the Białowieża National Park: Comparison of Breeding and Non-Breeding Seasons

The distribution of the Middle Spotted Woodpecker (Leiopicus medius) is restricted to mature deciduous forests with large trees, mainly oaks (Quercus spp.). Intensive forest management resulted in the loss of many suitable habitats, thus resulting in a decline in the population of this species. This study aimed to identify the parameters of foraging sites in the breeding season (April to June) and in the non-breeding season (other months). The research was conducted in the primeval oak-lime-hornbeam forest of the Białowieża National Park, where foraging woodpeckers were observed and detailed parameters of foraging sites were recorded. During the breeding season woodpeckers foraged primarily on European hornbeams (Carpinus betulus L.), but in non-breeding season the use of this tree species decreased by a factor of two, whereas the use of Norway spruces (Picea abies L.) increased more than twice. The most preferred tree species as a foraging site in both seasons was pedunculate oak (Quercus robur L.). In the non-breeding season, woodpeckers foraged at sites located higher, and the foraging session was longer compared with the breeding season. In both seasons, woodpeckers preferred dead and large trees and prey gleaning from the tree surface was their dominant foraging technique. Our results confirmed the key role of oaks and large trees, but also revealed the importance of European hornbeams and Norway spruces as foraging sites for the Middle Spotted Woodpecker.

Strike-Induced Chemosensory Searching in Reptiles: A Review

Chemosensory searching in squamates with specialized tongue–vomeronasal systems is well-documented. By tongue-flicking, these reptiles gather important chemical cues from their environment to guide their feeding behavior. Strike-induced chemosensory searching (SICS) is a specific expression of chemosensory reception that is central to the predatory strategy used by venomous reptiles that strike, release, and relocate their prey. This complex behavioral process consists of multiple sequential steps and has been mainly studied in viperids, particularly rattlesnakes. Although this phenomenon has been extensively researched, there is no comprehensive review of the SICS literature. Here, we provide such a review, centered on the idea that SICS is a result of suppression, and then enhancement, of chemosensory searching that serves as a key element of the ambush hunting strategy that most viperid snakes use to consume large and well-defended prey. SICS is also present in other venomous and nonvenomous taxa, and we include a taxonomic categorization of SICS studies in our review. We summarize the key findings discovered during decades of research into this remarkable feeding behavior and highlight areas where our knowledge remains incomplete in an effort to foster further research that will increase our understanding of reptilian feeding ecology.

Functional Response and Predation Rate of Dicyphus cerastii Wagner (Hemiptera: Miridae).

Simple SummaryBiological control (BC) is an effective way to regulate pest populations in horticultural crops, allowing the decrease of pesticide usage. On tomato, predatory insects like plant bugs or mirids provide BC services against several insect pests. Native predators are adapted to local conditions of climate and ecology and therefore may be well suited to provide BC services. Dicyphus cerastii is a predatory mirid that is present in the Mediterranean region and occurs in tomato greenhouses in Portugal. However, little is known about its contribution to BC in this crop. In this study, we evaluated how prey consumption is affected by increasing prey abundance on four different prey, in laboratory conditions. We found that the predator can increase its predation rate until a maximum is reached and that prey characteristics like size and mobility can affect predation. Dicyphus cerastii showed high predation rates for all prey species tested, allowing us to conclude that this species is an interesting predator for BC in tomato crops.Dicyphine mirids are important biological control agents (BCAs) in horticultural crops. Dicyphus cerastii Wagner can be found in protected tomato crops in Portugal, and has been observed feeding on several tomato pests. However, the predation capacity of this species is poorly studied. In order to investigate the predation capacity of D. cerastii, and how it is affected by prey size and mobility, we evaluated the functional response (FR) and predation rate of female predators on different densities of four prey species: Myzus persicae 1st instar nymphs (large mobile prey), Bemisia tabaci 4th instar nymphs, Ephestia kuehniella eggs (large immobile prey) and Tuta absoluta eggs (small immobile prey). Experiments were performed on tomato leaflets in Petri dish arenas for 24 h. Dicyphus cerastii exhibited type II FR for all prey tested. The predator effectively preyed upon all prey, consuming an average of 88.8 B. tabaci nymphs, 134.4 E. kuehniella eggs, 37.3 M. persicae nymphs and 172.3 T. absoluta eggs. Differences in the FR parameters, attack rate and handling time, suggested that prey size and mobility affected predation capacity. Considering the very high predation rates found for all prey species, D. cerastii proved to be an interesting candidate BCA for tomato crops.

Integrating multiple chemical tracers to elucidate the diet and habitat of Cookiecutter Sharks

The Cookiecutter shark (Isistius brasiliensis) is an ectoparasitic, mesopelagic shark that is known for removing plugs of tissue from larger prey, including teleosts, chondrichthyans, cephalopods, and marine mammals. Although this species is widely distributed throughout the world’s tropical and subtropical oceanic waters, like many deep-water species, it remains very poorly understood due to its mesopelagic distribution. We used a suite of biochemical tracers, including stable isotope analysis (SIA), fatty acid analysis (FAA), and environmental DNA (eDNA), to investigate the trophic ecology of this species in the Central Pacific around Hawaii. We found that large epipelagic prey constituted a relatively minor part of the overall diet. Surprisingly, small micronektonic and forage species (meso- and epipelagic) are the most important prey group for Cookiecutter sharks across the studied size range (17–43 cm total length), with larger mesopelagic species or species that exhibit diel vertical migration also being important prey. These results were consistent across all the tracer techniques employed. Our results indicate that Cookiecutter sharks play a unique role in pelagic food webs, feeding on prey ranging from the largest apex predators to small, low trophic level species, in particular those that overlap with the depth distribution of the sharks throughout the diel cycle. We also found evidence of a potential shift in diet and/or habitat with size and season. Environmental DNA metabarcoding revealed new prey items for Cookiecutter sharks while also demonstrating that eDNA can be used to identify recent prey in stomachs frozen for extended periods. Integrating across chemical tracers is a powerful tool for investigating the ecology of elusive and difficult to study species, such as meso- and bathypelagic chondrichthyans, and can increase the amount of information gained from small sample sizes. Better resolving the foraging ecology of these mesopelagic predators is critical for effective conservation and management of these taxa and ecosystems, which are intrinsically vulnerable to overfishing and exploitation.

Temporal variation in prey selection by adult European sardine (Sardina pilchardus) in the NW Mediterranean Sea

In the North-Western Mediterranean Sea (NWMS), changes in size and taxonomic composition of zooplankton have been hypothesized to underlie observed changes in populations of Sardina pilchardus, one of the main small pelagic fish species. The present study was undertaken to better understand the link between the temporal variability of zooplankton and the diet of adult sardine in the Bay of Marseille over a period of 16 months by comparing the taxonomic and prey size composition of sardine stomach content with net-collected zooplankton samples from a fixed station. A greater similarity was found between sardine stomach content and 80-μm mesh size net samples than with the traditionally used 200-μm net samples. Sardine showed a high diet plasticity over the entire study period, covering a broad diversity of prey species and a wide prey size range (ranging from 400 to 1000 μm in measured total length), including a lot of small copepods (Microsetella/Macrosetella spp., Corycaeidae and Oncaeidae). The most consumed prey groups were not necessarily the most abundant in the zooplankton sampled with nets, suggesting potential prey selection. Sardine showed most often an opportunistic selective predation on larger individuals for most taxonomic prey groups. Results highlighted the diet flexibility of sardine between months and showed seasonal variation in prey size, suggesting a continuous filter-feeding mode on relatively small prey when prey densities were high and more frequent selective particulate-feeding on larger prey when prey densities were low. Sardines were able to feed on a wide diversity of prey and size range and thus to shift their diet between months. This ability probably allows them to adapt to high spatial and temporal variability of the zooplankton community in a context of both human-induced and climatic changes.

Body size and tree species composition determine variation in prey consumption in a forest-inhabiting generalist predator.

Trophic interactions may strongly depend on body size and environmental variation, but this prediction has been seldom tested in nature. Many spiders are generalist predators that use webs to intercept flying prey. The size and mesh of orb webs increases with spider size, allowing a more efficient predation on larger prey. We studied to this extent the orb‐weaving spider Araneus diadematus inhabiting forest fragments differing in edge distance, tree diversity, and tree species. These environmental variables are known to correlate with insect composition, richness, and abundance. We anticipated these forest characteristics to be a principle driver of prey consumption. We additionally hypothesized them to impact spider size at maturity and expect shifts toward larger prey size distributions in larger individuals independently from the environmental context. We quantified spider diet by means of metabarcoding of nearly 1,000 A. diadematus from a total of 53 forest plots. This approach allowed a massive screening of consumption dynamics in nature, though at the cost of identifying the exact prey identity, as well as their abundance and putative intraspecific variation. Our study confirmed A. diadematus as a generalist predator, with more than 300 prey ZOTUs detected in total. At the individual level, we found large spiders to consume fewer different species, but adding larger species to their diet. Tree species composition affected both prey species richness and size in the spider's diet, although tree diversity per se had no influence on the consumed prey. Edges had an indirect effect on the spider diet as spiders closer to the forest edge were larger and therefore consumed larger prey. We conclude that both intraspecific size variation and tree species composition shape the consumed prey of this generalist predator.

Impact of natural salt lick on the home range of Panthera tigris at the Royal Belum Rainforest, Malaysia

Natural salt lick (sira) is a strategic localisation for ecological wildlife assemblage to exhibit geophagy which may act as a population dynamic buffer of prey and predators. Undoubtedly, many agree that geophagy at natural licks is linked to nutritional ecology, health and assembly places facilitating social interaction of its users. Overall, natural salt licks not only save energy of obtaining nutrient leading to health maintenance but also forms the basis of population persistence. The Royal Belum Rainforest, Malaysia (Royal Belum) is a typical tropical rainforest in Malaysia rich in wildlife which are mainly concentrated around the natural salt lick. Since this is one of the most stable fauna ecology forest in Malaysia, it is timely to assess its impact on the Malayan tiger (Panthera tigris) home range dynamics. The three-potential home ranges of the Malayan tiger in this rainforest were selected based on animal trails or foot prints surrounding the salt lick viz (e.g. Sira Kuak and Sira Batu; Sira Rambai and Sira Buluh and Sira Papan) as well as previous sightings of a Malayan tiger in the area, whose movement is dependent on the density and distribution of prey. Camera traps were placed at potential animal trails surrounding the salt lick to capture any encountered wildlife species within the area of the camera placements. Results showed that all home ranges of Malayan tiger were of no significance for large bodied prey availability such as sambar deer (Rusa unicolor), and smaller prey such as muntjacs (Muntiacus muntjac) and wild boar (Sus scrofa). Interestingly, all home range harbour the Malayan tiger as the only sole predator. The non-significance of prey availability at each home range is attributed to the decline of the Malayan tiger in the rainforest since tigers are dependant on the movement of its preferred prey surrounding natural salt licks. Thus, the information from this study offers fundamental knowledge on the importance of prey-predator interaction at salt lick which will help in designing strategy in rewilding or rehabilitation programs of the Malayan tiger at the Royal Belum Rainforest.

A method for mapping morphological convergence on three‐dimensional digital models: the case of the mammalian sabre‐tooth

AbstractMorphological convergence can be assessed using a variety of statistical methods. None of the methods proposed to date enable the visualization of convergence. All are based on the assumption that the phenotypes either converge, or do not. However, between species, morphologically similar regions of a larger structure may behave differently. Previous approaches do not identify these regions within the larger structures or quantify the degree to which they may contribute to overall convergence. Here, we introduce a new method to chart patterns of convergence on three‐dimensional models using the R function conv.map. The convergence between pairs of models is mapped onto them to visualize and quantify the morphological convergence. We applied conv.map to a well‐known case study, the sabre‐tooth morphotype, which has evolved independently among distinct mammalian clades from placentals to metatherians. Although previous authors have concluded that sabre‐tooths kill using a stabbing ‘bite’ to the neck, others have presented different interpretations for specific taxa, including the iconic Smilodon and Thylacosmilus. Our objective was to identify any shared morphological features among the sabre‐tooths that may underpin similar killing behaviours. From a sample of 49 placental and metatherian carnivores, we found stronger convergence among sabre‐tooths than for any other taxa. The morphological convergence is most apparent in the rostral and posterior parts of the cranium. The extent of this convergence suggests similarity in function among these phylogenetically distant species. In our view, this function is most likely to be the killing of relatively large prey using a stabbing bite.

Variation in the sacroiliac joint in Felidae.

Felidae species show a great diversity in their diet, foraging and hunting strategies, from small to large prey. Whether they belong to solitary or group hunters, the behavior of cats to subdue resisting small or large prey presents crucial differences. It is assumed that pack hunting reduces the per capita risk of each individual. We hypothesize that the sacroiliac articulation plays a key role in stabilizing the predator while subduing and killing prey. Using CT-scan from 59 felid coxal bones, we calculated the angle between both iliac articular surfaces. Correlation of this inter-iliac angle with body size was calculated and ecological stressors were evaluated on inter-iliac angle. Body size significantly influences inter-iliac angle with small cats having a wider angle than big cats. Arboreal species have a significantly larger angle compared to cursorial felids with the smallest value, and to scansorial and terrestrial species with intermediate angles. Felids hunting large prey have a smaller angle than felids hunting small and mixed prey. Within the Panthera lineage, pack hunters (lions) have a larger angle than all other species using solitary hunting strategy. According to the inter-iliac angle, two main groups of felids are determined: (i) predators with an angle of around 40° include small cats (i.e., Felis silvestris, Leopardus wiedii, Leptailurus serval, Lynx Canadensis, L. rufus; median = 43.45°), the only pack-hunting species (i.e., Panthera leo; median = 37.90°), and arboreal cats (i.e., L. wiedii, Neofelis nebulosa; median = 49.05°), (ii) predators with an angle of around 30° include solitary-hunting big cats (i.e., Acinonyx jubatus, P. onca, P. pardus, P. tigris, P. uncia; median = 31.80°). We suggest different pressures of selection to interpret these results. The tightening of the iliac wings around the sacrum probably enhances big cats’ ability for high speed and large prey control. In contrast, pack hunting in lions reduced the selective pressure for large prey.

Diet and Life-History Traits of Savannah Dwelling Waterbirds in Southern Africa: Implications for Their Conservation Status

This study evaluates the relative contribution of reproduction-based life history traits and diet to the population trends in waterbirds from southern Africa. Life history traits (clutch size, incubation period, fledging time, body mass and generation length), diet (prey weight, body lengths and number of taxa represented in its diet (NTD)) and conservation status (declining/not declining) of 163 waterbird species were reviewed. An index of diet generalism was created based on NTD. Cluster analysis was applied on life history traits to define groups of waterbirds. Binomial regressions were used to test if population trends were different across cluster groups and diet variables. Four clusters of waterbirds were defined, with most waterfowl clustering together. Species that feed on small and large prey had higher probabilities of declining (0.17 and 0.26, respectively) compared to those feeding on medium-sized prey (0.08). Amphibians, coleopterans, crustacea, molluscs and tunicates were used by species in all clusters, and the risk of waterbird populations declining further are high given the current dwindling of the prey base. The large proportions of declining species (61%) in waterbirds, which have constrained habitats, calls for continued efforts to mitigate disturbances to wetlands.

Smilodon fatalis Bite Mechanisms: New Functional Considerations in Jaw and Articular Disk Reconstruction

Smilodon fatalis is among the most iconic of fossil sabertooths, best known for elongated canine teeth that enabled it to kill large prey. S. fatalis reconstructions published over the last 150 years (as well as many natural history exhibits) are typically modeled after living large conical tooth cat anatomy because there are no living sabertooths. Dental and correlated musculoskeletal differences between the living and extinct cats with the two different dentition types have led to misinterpretations of the appearance and gape capabilities of Smilodon. Historically, the way in which the S. fatalis skull and mandible soft tissues have been reconstructed does not take into account the bite angles that are the most useful for a living cat. Specifically, the angle at which the mandible and maxilla can move in relation to one another must also account for the effect generated by the muscles and tendons that limit jaw opening and closing. The usual reconstructed display shows a mandible that could not open sufficiently to allow a gape wide enough to encompass the diameter of a chicken's egg. The jaw joint is often oriented so that it would not generate much bite force, as it sometimes is positioned to look as though it is dangling uselessly. The articular disk has been ignored. In this study, we are testing hypotheses related to the typically depicted canine tooth positions and the lack of inclusion of soft tissue influences such as the articular disk that is usually present in the craniomandibular joint. By reconstructing the size, shape, thickness, and then inserting an articular disk, the jaw then lines up correctly, and a bite force can be more accurately calculated. We tried several different methods of estimating the size of the articular disk using paper, leather, felt, and silicone until we found one that allowed the mandible and maxilla to line up precisely. This works to solve the two common issues; computer-based studies that modeled the amount of bite force in S. fatalis with a few showing a powerful bite and secondly, canines are often mounted so far out of their alveoli that the S-shaped dentine margin is exposed. Exposed dentine and jaw misalignment would be very painful to a living animal and would decrease the mechanical advantage of the upper canines. When the upper canine alveoli are not maximally filled, the teeth are less securely anchored. By seating the upper canines properly S. fatalis could use these teeth with a decreased likelihood of breakage from the bite forces generated. S. fatalis evolved with long slender bladelike canines. This tooth configuration would be especially susceptible to breakage from large bending moments and torque. To use these teeth effectively, the bite needs to be in line with the anteroposterior axis of the head and aimed toward the jugular groove of the neck of prey, with minimal side-to-side movement. Anchoring the canines securely in their alveoli helps eliminate this problem. Our data shows that revisioning the S. fatalism skull gives a more accurate picture of the way this cat lived, killed its large prey, and our new data allows for scientists recalculate bite forces.

Geographic variation in body size and plumage colour according to diet composition in a nocturnal raptor

Predator–prey interactions are amongst the strongest selective forces that promote the evolution of local phenotypes in both predators and prey. However, intraspecific spatial covariation in phenotypic traits between predators and prey has been rarely investigated, especially at a large geographic scale. Here, we studied the covariation between prey composition and some phenotypic traits, such as wing length, bill length and plumage colour, of a widely‐distributed nocturnal predator, the western barn owl Tyto alba. By using 3100 specimens collected across its entire range of distribution, spanning from Europe to Middle East and Africa, we showed that wing length positively covaries with prey size, but not with taxonomic composition. This finding suggests that larger prey might have selected for larger body size and/or that larger individuals might be more selective in hunting large prey. In addition, we also found that paler‐plumaged populations generally hunt larger prey. Paler barn owls might be thus better specialized in capturing averagely larger prey and/or mainly hunt in habitats where larger prey are more abundant. In addition, considering that paler individuals are generally larger than brownish ones, it is possible that paler plumage colour might have evolved as a by‐product of selection towards a large body size, which in turn have emerged in response to prey size composition. However, irrespectively of the direction of causality and the phenotypic target of selection, we showed that predator–prey interactions can affect spatial phenotypic variation by promoting the evolution of local adaptations.

Defection on the bounty? Kinship and cooperative exploitation of a rich, essential but dangerous resource

We develop a game-theoretic model to explore the question of whether two animals should cooperate in the dangerous activity of obtaining a rich and essential resource. We consider variation in the risks incurred to individuals and in how the activities of the two animals interact to influence the probability of success. We also consider that the animals may be relatives and thus share evolutionary interests. The model is general and can, for instance, be applied to mammalian predators attempting to capture and subdue large and dangerous prey or to female parasitoid wasps that attack and, if successful, paralyse aggressive hosts that then provide the only feeding resource for their offspring. This minimal model of cooperation contains three dimensionless parameters: vulnerability (the ratio between the average time for a lone attacker to subdue the defending resource and the average time for the defender to fatally strike the attacker), the dilution ratio (the extent to which attack by animals acting in tandem reduces a defender's ability to kill its attackers) and the relatedness between the potential attackers. The model predicts that higher values of all three parameters favour cooperation and that for small values cooperation is not evolutionarily stable. Cooperation can arise from an ancestral state of non-cooperation if values of all parameters are sufficiently high but cannot arise among non-relatives, irrespective of other parameter values. Once cooperation has emerged in a population, it can be maintained among non-relatives at modest values of dilution ratio and vulnerability. We discuss these general predictions in particular relation to the parasitoid genus Sclerodermus, in which multiple females may attack unusually large and aggressive hosts and in which host attack behaviour is mediated by kinship.

Functional ecological convergence between the thylacine and small prey-focused canids

BackgroundMorphological convergence is a fundamental aspect of evolution, allowing for inference of the biology and ecology of extinct species by comparison with the form and function of living species as analogues. The thylacine (Thylacinus cynocephalus), the iconic recently extinct marsupial, is considered a classic example of convergent evolution with the distantly related placental wolf or dog, though almost nothing is actually known regarding its ecology. This lack of data leads to questions regarding the degree of convergence with, and the similarity of, the functional ecology of the thylacine and the wolf/dog. Here, we examined the cranium of the thylacine using 3D geometric morphometrics and two quantitative tests of convergence to more precisely determine convergent analogues, within a phylogenetically informed dataset of 56 comparative species across 12 families of marsupial and placental faunivorous mammals. Using this dataset, we investigated patterns of correlation between cranial shape and diet, phylogeny, and relative prey size across these terrestrial faunivores.ResultsWe find a correlation between cranial, facial, and neurocranial shape and the ratio of prey-to-predator body mass, though neurocranial shape may not correlate with prey size within marsupials. The thylacine was found to group with predators that routinely take prey smaller than 45% of their own body mass, not with predators that take subequal-sized or larger prey. Both convergence tests find significant levels of convergence between the thylacine and the African jackals and South American ‘foxes’, with lesser support for the coyote and red fox. We find little support for convergence between the thylacine and the wolf or dog.ConclusionsOur study finds little support for a wolf/dog-like functional ecology in the thylacine, with it instead being most similar to mid-sized canids such as African jackals and South American ‘foxes’ that mainly take prey less than half their size. This work suggests that concepts of convergence should extend beyond superficial similarity, and broader comparisons can lead to false interpretations of functional ecology. The thylacine was a predator of small to mid-sized prey, not a big-game specialist like the placental wolf.

Naturally-occurring tooth wear, tooth fracture, and cranial injuries in large carnivores from Zambia.

Determining the incidence and causes of craniodental damage in wild carnivores is often constrained by limited access to specimens with associated ecological data, such as prey type and abundance. We assessed dental condition and cranial injuries in lion, leopard, and spotted hyena in relation to prey and predator populations in Zambia’s Luangwa Valley, where large prey are more abundant and lion and leopard more numerous, and the Greater Kafue Ecosystem, where smaller prey species are more prevalent and lion and leopard less common. In Luangwa, lions had significantly higher rates of tooth fracture, and blunt trauma injuries attributable to prey-handling, compared to Kafue lions. In contrast, leopards in both regions had similar rates of tooth wear and breakage. Overall, lions showed a significantly higher tooth fracture rate than leopards on a per tooth basis. Spotted hyenas had the highest rates of tooth wear and fracture among all three carnivores, and greatly exceeded previously recorded rates based on historical samples. Despite larger numbers of lion and leopard in Luangwa, there was no difference in incidence of intraspecific injuries between regions. These results are consistent with a greater abundance of large prey species, especially buffalo, in the diets of Luangwa lions, and previous work showing a reliance on smaller prey species in Kafue throughout the large carnivore guild.

Deconstructing the Gestalt: New concepts and tests of homology, as exemplified by a re-conceptualization of "microstomy" in squamates.

Snakes-a subset of lizards-have traditionally been divided into two major groups based on feeding mechanics: "macrostomy," involving the ingestion of proportionally large prey items; and "microstomy," the lack of this ability. "Microstomy"-considered present in scolecophidian and early-diverging alethinophidian snakes-is generally viewed as a symplesiomorphy shared with non-snake lizards. However, this perspective of "microstomy" as plesiomorphic and morphologically homogenous fails to recognize the complexity of this condition and its evolution across "microstomatan" squamates. To challenge this problematic paradigm, we formalize a new framework for conceptualizing and testing the homology of overall character complexes, or "morphotypes," which underlies our re-assessment of "microstomy." Using micro-computed tomography (micro-CT) scans, we analyze the morphology of the jaws and suspensorium across purported "microstomatan" squamates (scolecophidians, early-diverging alethinophidians, and non-snake lizards) and demonstrate that key components of the jaw complex are not homologous at the level of primary character state identity across these taxa. Therefore, rather than treating "microstomy" as a uniform condition, we instead propose that non-snake lizards, early-diverging alethinophidians, anomalepidids, leptotyphlopids, and typhlopoids each exhibit a unique and nonhomologous jaw morphotype: "minimal-kinesis microstomy," "snout-shifting," "axle-brace maxillary raking," "mandibular raking," and "single-axle maxillary raking," respectively. The lack of synapomorphy among scolecophidians is inconsistent with the notion of scolecophidians representing an ancestral snake condition, and instead reflects a hypothesis of the independent evolution of fossoriality, miniaturization, and "microstomy" in each scolecophidian lineage. We ultimately emphasize that a rigorous approach to comparative anatomy is necessary in constructing evolutionary hypotheses that accurately reflect biological reality.

Contrasting levels of social distancing between the sexes in lions

SummaryUnderstanding sexual segregation is crucial to comprehend sociality. A comparative analysis of long-term lion data from Serengeti and Ngorongoro in Tanzania, and Gir in India, reveals that male-female associations are contingent upon male and female group size, prey-size and availability, and the number of prides that each male coalition currently resides. Males maintain proximity with females, whereas females are responsible for segregation except at large kills. Lions feed on the largest prey in Ngorongoro and the smallest in Gir, and females spend the most time with males in Ngorongoro and the least in Gir. Females roar less often in prey-scarce circumstances in Serengeti and throughout the year in Gir possibly to prevent being tracked by males that parasitize on female kills. However, females readily associate with males when available prey is large and abundant. Contrasting availability of resources between Gir and Serengeti/Ngorongoro helps explain the varying degrees of sexual segregation and appears to drive differences in mating systems between these lion populations.

Functional Adaptations in the Forelimb of the Snow Leopard (Panthera uncia).

The snow leopard (Panthera uncia) is anatomically and physiologically adapted for life in the rocky terrain of alpine zones in Central and South Asia. Panthera uncia is scansorial, and typically hunts solitarily by using overhead ambush of prey, rather than the typical stalking pattern of other large pantherines. In this study, we conducted dissections, detailed documentation, and illustrated the forelimb anatomy of two adult P. uncia specimens (1M/1F). Qualitative and quantitative data revealed an intriguing combination of functional adaptations illustrating a balance between the diverse demands of head-first descent, pouncing, climbing across rocky terrain, restraint of large prey, rapid pursuit, and navigating deep snow. In many forelimb proportions, P. uncia is intermediate between the cursorial Acinonyx jubatus (cheetah) and the scansorial forest dwelling Panthera onca (jaguar). Enlarged scapular and pectoral musculature provide stability to the shoulder girdle during grappling with large prey, as well as support during jumping and climbing. A small, unarticulated bony clavicle may provide greater stability to the forelimb, while still allowing flexibility. In the brachium and antebrachium of P. uncia, there is a functional compromise between the powerful grip needed for grasping large prey and the stability necessary for rapid pursuit of prey over uneven, rocky terrain. A unique bifurcation in the tendon of m. biceps brachii may provide additional functional stability at the radiohumeral joint. Intrinsic muscles of the palmar manus are broad and fleshy, acting as an enlarged surface area to evenly distribute body weight while walking on soft snow. However, muscles that act to provide fine manual manipulation are reduced, as in other large prey specialists. Overall, P. uncia displays morphological adaptive parallels with scansorial, large prey specializing pantherines, such as P. onca, while also showing adaptations for running.

Forest cover mediates large and medium-sized mammal occurrence in a critical link of the Mesoamerican Biological Corridor.

Connectivity of natural areas through biological corridors is essential for ecosystem resilience and biodiversity conservation. However, robust assessments of biodiversity in corridor areas are often hindered by logistical constraints and the statistical challenges of modeling data from multiple species. Herein, we used a hierarchical community occupancy model in a Bayesian framework to evaluate the status of medium and large-sized mammals in a critical link of the Mesoamerican Biological Corridor (MBC) in Costa Rica. We used camera traps deployed from 2013-2017 to detect 18 medium (1-15 kg) and 6 large (>15 kg) mammal species in a portion of two Jaguar Conservation Units (JCUs) and the Corridor linking them. Camera traps operated for 16,904 trap nights across 209 stations, covering an area of 880 km2. Forest cover was the most important driver of medium and large-sized mammal habitat use, with forest specialists such as jaguars (Panthera onca) and pumas (Puma concolor) strongly associated with high forest cover, while habitat generalists such as coyotes (Canis latrans) and raccoons (Procyon lotor) were associated with low forest cover. Medium and large-sized mammal species richness was lower in the Corridor area ([Formula: see text] = 9.78±1.84) than in the portions evaluated of the two JCUs ([Formula: see text] = 11.50±1.52). Puma and jaguar habitat use probabilities were strongly correlated with large prey species richness (jaguar, r = 0.59, p<0.001; puma, r = 0.72, p<0.001), and correlated to a lesser extent with medium prey species richness (jaguar, r = 0.36, p = 0.003; puma, r = 0.23, p = 0.064). Low estimated jaguar habitat use probability in one JCU (Central Volcanic Cordillera: [Formula: see text] = 0.15±0.11) suggests that this is not the jaguar stronghold previously assumed. In addition, the western half of the Corridor has low richness of large mammals, making it necessary to take urgent actions to secure habitat connectivity for mammal populations.

Recolonizing carnivores: Is cougar predation behaviorally mediated by bears?

Conservation and management efforts have resulted in population increases and range expansions for some apex predators, potentially changing trophic cascades and foraging behavior. Changes in sympatric carnivore and dominant scavenger populations provide opportunities to assess how carnivores affect one another. Cougars (Puma concolor) were the apex predator in the Great Basin of Nevada, USA, for over 80 years. Black bears (Ursus americanus) have recently recolonized the area and are known to heavily scavenge on cougar kills. To evaluate the impacts of sympatric, recolonizing bears on cougar foraging behavior in the Great Basin, we investigated kill sites of 31 cougars between 2009 and 2017 across a range of bear densities. We modeled the variation in feeding bout duration (number of nights spent feeding on a prey item) and the proportion of primary prey, mule deer (Odocoileus hemionus), in cougar diets using mixed‐effects models. We found that feeding bout duration was driven primarily by the size of the prey item being consumed, local bear density, and the presence of dependent kittens. The proportion of mule deer in cougar diet across all study areas declined over time, was lower for male cougars, increased with the presence of dependent kittens, and increased with higher bear densities. In sites with feral horses (Equus ferus), a novel large prey, cougar consumption of feral horses increased over time. Our results suggest that higher bear densities over time may reduce cougar feeding bout durations and influence the prey selection trade‐off for cougars when alternative, but more dangerous, large prey are available. Shifts in foraging behavior in multicarnivore systems can have cascading effects on prey selection. This study highlights the importance of measuring the impacts of sympatric apex predators and dominant scavengers on a shared resource base, providing a foundation for monitoring dynamic multipredator/scavenger systems.