Prey Diversity Research Articles

Fine-scale habitat selection in tree-dwelling spiders: an experimental approach.

Habitat selection by spiders is strongly influenced by biotic factors such as the availability and diversity of prey and abiotic factors such as temperature, humidity, and the structural complexity of the habitat. Structural complexity is an aspect that intensely affects species persistence, population stability, and the coexistence of interacting species. Trees comprise a complex set of microhabitats due to their large biomass and heterogeneity of the architectural components of their trunk surface and branches. Spider species that live on trunks have diversified physiological or morphological adaptations that confer advantages in this environment. In this study, we experimentally examined the habitat choice by the tree-dwelling spiders Selenops cocheleti (Selenopidae), Corinna rubripes (Corinnidae), and Loxosceles gaucho (Sicariidae). We found that microhabitat specialization was restricted to trunk architectural characteristics rather than plant taxonomy. Selenops cocheleti and C. rubripes significantly preferred loose barks and holes in the trunks, respectively, showing that both spider species can evaluate the physical structure of the microhabitat on a fine scale. On the other hand, L. gaucho selected crevices and holes near the base of the trunk without giving much importance to the physical characteristics of the microhabitat per se (e.g., depth, height, length). Our findings indicate that for generalist predators like spiders, coexistence relies heavily on spatial segregation driven by distinct habitat preferences, irrespective of their method for capturing prey.

Foraging by predatory ants: A review.

In this review, we show that predatory ants have a wide range of foraging behavior, something expected given their phylogenetic distance and the great variation in their colony size, life histories, and nesting habitats as well as prey diversity. Most ants are central-place foragers that detect prey using vision and olfaction. Ground-dwelling species can forage solitarily, the ancestral form, but generally recruit nestmates to retrieve large prey or a group of prey. Typically, ants are omnivorous, but some species are strict predators preying on detritivorous invertebrates or arthropod eggs, while those specialized on termites or other ants often have scouts that localize their target and then trigger a raid. They can use compounds that ease this task, including chemical insignificance, mimicry, and venoms triggering submissive behavior. Army ants include 8 Dorylinae and some species from other subfamilies, all having wingless queens and forming raids. Dorylinae from the Old World migrate irregularly to new nesting sites. The foraging of most New World species that prey on the brood of other ants is regulated by their biological cycle that alternates between a "nomadic phase" when the colony relocates between different places and a "stationary phase" when the colony stays in a bivouac constituting a central place. Among arboreal ants, dominant species forage in groups, detecting prey visually, but can use vibrations, particularly when associated with myrmecophytes. Some species of the genera Allomerus and Azteca use fungi to build a gallery-shaped trap with small holes under which they hide to ambush prey.

Prey diversity in the deep ocean: metabarcoding feeding ecology of the commercially important queen snapper in the US Caribbean

The queen snapper, Etelis oculatus, is experiencing a growing fishery presence across the wider Caribbean, yet our understanding of its distribution, biology, and ecology remains limited. To address this gap, we investigated the feeding ecology of this demersal deep-water snapper using two molecular approaches: single-species barcoding and multispecies metabarcoding. Between November 2019 and July 2020, we collected 157 queen snapper from seven locations along the west coast of Puerto Rico. Our analysis identified a diverse array of prey items in the stomachs, comprising 61 species from 31 families, 18 orders, and 38 genera. Our findings suggest that E. oculatus is a large carnivore, primarily preying on squids, shrimps, and deep-water fishes. Notably, common fish prey included Diaphus brachycephalus, D. dumerilii, Dasyscopelus selenops, Coccorella atlantica, Sigmops elongatus, and Zaphotias pedaliotus. In contrast, prevalent invertebrate prey consisted of Abralia veranyi, Doryteuthis pealeii, Abralia redfieldi, Oplophorus gracilirostris, and Systellaspis debilis. Although our data suggest potential variation in diet composition across locations, definitive conclusions remain elusive. However, we observed heightened prey richness at seamount Pichincho, possibly attributable to the high structural complexity of the karst terrain on the seafloor. Additionally, we noted variation in prey species composition across size classes, with certain species more prevalent in larger or smaller queen snapper. Given the challenge of examining the prey of deep-water fish species, our study showcases the utility of both single-species barcoding and multispecies metabarcoding methodologies in characterizing the dietary range of queen snapper and similar demersal deep-water carnivorous fishes. The multispecies metabarcoding approach, in particular, offers a rapid, comprehensive, and effective means of identifying prey species. As the commercial value of the queen snapper continues to rise, our investigation into its feeding behavior provides critical baseline information for future species management efforts. By enhancing our understanding of its ecological dynamics, we aim to contribute to informed conservation and sustainable fisheries practices in the region.

Seasonal variation in the food composition of the Bolkar Mountain Viper, Montivipera bulgardaghica (Nilson & Andren, 1985), in the Central Taurus Mountains, Anatolia

The Bolkar Mountain Viper, Montivipera bulgardaghica (Nilson & Andren, 1985), is a mountain viper found in the eastern Mediterranean region. In this study, we present data on the seasonal variation in diet composition across two different habitats in the Central Taurus Mountains of Anatolia, Türkiye. The Karboğazı population inhabits a subalpine shrubland, while the Göller Yaylası population resides in forested land. The vipers primarily consumed Lacertidae (47%), followed by Orthoptera (27%), Chilopoda (18%), and Scincidae (8%) in number. In spring, the diet of the Karboğazı population was mainly composed of Lacertidae but shifts toward Orthoptera during summer and autumn. In contrast, the Göller Yaylası population fed on Lacertidae throughout the entire active season. Overall, the Karboğazı population primarily consumed invertebrates, whereas the Göller Yaylası population predominantly fed on lizards. Both populations exhibited partial niche overlap. There was no significant difference in diet composition between sexes, but prey type and quantity varied with the season. Prey diversity increased in summer and decreased in autumn and spring, corresponding with the prey availability in the environment.

Diet and biological characteristics of Atlantic Tomcod or Punamu, Microgadus tomcod (Walbaum, 1792) in Minas Basin, Nova Scotia

Atlantic tomcod are abundant in the Bay of Fundy, but their diet is unreported for Minas Basin. In this study prey content and biological characteristics of tomcod collected in the Avon River estuary of Minas Basin were examined. Their diet was numerically dominated by the amphipod Corophium volutator (Pallas, 1766) (Rate of Occurrence (RO) = 73.2%). Other major prey taxa consumed included Crangon septemspinosa Say, 1818 (29.3%), Gammarus spp. (19.5%), Polychaeta (14.6%), Portunidae (12.2%), Teleostei (9.8%), Isopoda (7.3%), andMollusca (3.3%). Of stomachs examined only 8.9% contained unidentifiable prey items. Every tomcod examined except one contained prey and the fullness index (HI) varied between 0.01-5.85%. Both mean total length and total body weight of females was significantly greater than for males (254 mm vs 202 mm; 143 g vs 78 g), and the condition factor (K) of both sexes was similar throughout the sampling period (Mean ± SD; 0.79 ± 0.13). Both mean male and female gonadosomatic index (GSI) increased significantly when approaching the winter spawning period, rising from 1.2 in early October to 11.6 by mid-December.The diversity of prey consumed indicated that tomcod fed opportunis-tically, but their predominate consumption of C. volutator was likely linked to the large populations of this amphipod on the intertidal mudflats of Minas Basin. Keywords: Atlantic tomcod, Bay of Fundy, condition factor, Corophium volutator, fullness index, gonadosomatic index

Feeding habits of the longfin goatfish Upeneus supravittatus Uiblein and Heemstra, 2010, along Chennai coast, south India

Recognising the need to understand the feeding habits of marine fishes, a study was undertaken on the longfin goatfish Upeneus supravittatus Uiblein and Heemstra, 2010, which contributed to trawl fisheries along Chennai coast (south-east coast of India). Dataon trophic attributes such as mouth gape area, gill raker counts, stomach and intestine lengths and gut condition and contents were collected and analysed to determine condition index, index of relative importance (IRI), niche breadth and trophic level (TrL) with reference to two variables, namely, body size (small, medium and large) and season (post north-east monsoon (PNE); summer (SUM); south-west monsoon (SW); north-east monsoon (NE). The mouth gape area of U. supravittatus was 129.3 mm2. The maximum body depth-total length ratio was 1:5.0; gill rakers in lower arch was 29 and the relative intestine length was 0.48. Empty stomach contributed 56.1% of the samples. U. supravittatus fed on prey belonging to 25 Orders and >40 Genera. Decapods such as shrimps and crablets were the main prey followed by fishes. The IRI of decapods was 6474 and that of fishes was only 193. The maximum prey size predated by the fish was 33.5 and 9.8% in terms of the predator’s length and weight, respectively. Higher prey diversity was noticed in small size group and during south-west monsoon season. The narrow niche breadth of 0.20 showed the selective nature of the fish to feed on decapods. The fish is a benthic carnivore with a mean trophic level of 3.58. The trophic level decreased with body size. Diet similarity was evident between north-east and post north-east monsoon and between summer and south-west monsoon seasons. Diversity indices showed marginal variation in prey diversity among size groups and among seasons. This study paves way for estimating production efficiency of U. supravittatus. Keywords: Diet composition, Index of relative importance, Trophic level, Trophic morphology, U. supravittatus

Differential exposure to second-generation anticoagulant rodenticides in raptors from continental and insular regions of the Iberian Peninsula

The global impact of anticoagulant rodenticides (ARs) on non-target species is well-recognized. Birds of prey, as apex predators, are highly vulnerable to AR exposure and are widely used as biomonitors for priority pollutants in Europe. This study investigates differential SGAR exposure in raptors from insular versus continental regions, hypothesizing greater exposure in insular areas due to ecological factors like reduced prey diversity, intensive rodenticide use, and resistant rodent populations. We analyzed the livers of 190 common kestrels (Falco tinnunculus) and 104 common buzzards (Buteo buteo) across the Iberian Peninsula and its archipelagos using LC-MS/MS to assess their role as AR sentinels and the differences between insular and continental areas. Results revealed a high prevalence (>80%) of second-generation anticoagulant rodenticides (SGARs), with brodifacoum and bromadiolone, being the most frequent. Multiple SGAR detections were also common (≈50%). A binomial logistic regression showed that species and region significantly influence the likelihood of SGAR exposure. Kestrels had a greater probability of exceeding 100 ng/g wet weight (ww) compared to buzzards. Raptors from insular territories were ten times more likely to have higher SGAR concentrations than those from continental areas. However, the legal restriction on SGAR bait concentrations that came into effect in 2018 did not significantly impact exposure levels. This study highlights the need for targeted conservation efforts to mitigate AR exposure risk in vulnerable island ecosystems.

To pool or not to pool: Pooled metabarcoding does not affect estimates of prey diversity in spider gut content analysis

Abstract Gut content metabarcoding has provided important insights into the food web ecology of spiders, the most dominant terrestrial arthropod predators. In small invertebrates, like spiders, gut content analysis is often performed on whole body DNA extracts of individual predators, from which prey sequences are selectively enriched and sequenced. Since many spider species are generalist predators, large numbers of samples comprising individual spider specimens must be analysed to recover an exhaustive image of a spider species' prey spectrum, which is costly and time‐consuming. Pooled processing of bulk samples of multiple specimens has been suggested to reduce the necessary workload and cost while still recovering a representative estimate of the prey diversity. However, it is still unclear if pooling approaches lead to bias in recovering the prey spectrum and if the results are comparable with data from individually processed spiders. Here, we test the effects of metabarcoding pooled spider gut content on the recovered taxonomic diversity and composition of prey. Using a newly adapted primer pair, which efficiently enriches COI barcode sequences of diverse arthropod prey groups while suppressing spider amplification, we test if pooling leads to reduced taxonomic diversity or skewed estimates of prey composition. Our results show that pooling and individual processing recover highly correlated taxonomic diversity and composition of prey. The only exception are very rare prey items which were less well recovered by pooling. Our results support pooling as a cost‐effective and time‐efficient approach to recover the diet of generalist predators for population‐level studies of spider trophic interactions.

Variation in the Diet of Hatchling Morelet's Crocodile (Crocodylus moreletii) in the Wild.

The relationship between diet and behavior is essential to understanding an animal's strategies to obtain food, considering ontogenical changes. In reptiles, there is a relationship between the length of the individual and the size of the prey it consumes. Studies have focused on the ontogenetic changes in reptile diets from hatchling to adult, but only a few studies have focused on the transition from hatchling to juvenile. We aimed to describe and analyze the composition, variation, diversity, and overlap in the diet of hatchling Morelet's crocodiles (Crocodylus moreletii) for three size intervals during the hatchling-juvenile transition. We captured 31 hatchling Morelet's crocodiles in an urbanized lagoon in Tabasco. We performed stomach-flushing to determine the diet. Additionally, we estimated the volume, frequency of occurrence, and relative importance of diet items and analyzed the relationship between prey type and the total length of the individuals. The diversity of the hatchling prey suggests a generalist diet. We observed two items not previously described in the diet of hatchling crocodiles. In addition, we found differences in diet between the initial and final size intervals, as increases in the length of prey appeared that they did not consume when they were hatchlings. Our results contribute new information to the dietary changes that occur during the hatchling-juvenile transition.

Reduced trophic niche breadth is associated with higher productivity in a recovering apex predator population

AbstractUnderstanding the trophic and demographic dynamics of apex predators is of paramount importance for ecosystem conservation. Apex predators are usually free from predation, and thus, the main driver of population dynamics is the availability of trophic resources, which affects breeding performance. Albeit food habits have been described in many apex species, the effects of changes in the trophic niche on long‐term demographic dynamics are poorly known. We describe the long‐term (N = 25 years) changes in trophic niche breadth of a recovering golden eagle population in a Mediterranean landscape (northern Spain) and search for potential correlates with their productivity (i.e., number of fledged eaglets per controlled pair) as a proxy for their breeding performance (N = 290 pair‐years). We identified a total of 3475 prey items from 77 species; rabbits, hares, and red‐legged partridges were the most frequent prey consumed (overall 51%), followed by roe deer (10%), red‐billed chough, red foxes, and woodpigeons, all of them with >5%. Prey diversity in eagles' diet decreased during the study period. Consumption of rabbits and roe deer increased, while that of hares and partridges decreased; no significant trends were observed in the consumption of foxes, choughs, and woodpigeons. Prey diversity and red‐legged partridge consumption were negatively correlated with productivity at the territory level, while rabbits, corvids, and pigeons showed a strong positive relationship with productivity. The size of the territory showed the strongest positive relationship with productivity, while roughness was negatively correlated. Rabbits and ungulates showed negative and positive correlations with roughness, respectively, while predator consumption exhibited a negative relationship with the size of the territory. Our findings give insights into the potential trophic mechanisms driving the dynamics of recovering apex predator populations; a reduction in the trophic niche breadth toward specific groups of prey, which could be due to a higher availability and individual specificity toward these prey species, might enhance productivity at the territory level and, ultimately, influence population dynamics facilitating the recovery process. The remarkable increase in the consumption of wild ungulates, predators, and other apex consumers suggests that the current population recovery and reduced trophic niche breadth may facilitate this eagle population to exhibit its apex role and contribute to ecosystem functionality.

Combining biotracer and stomach contents analysis to understand trophic dynamics in the northern Gulf of Mexico

The northern Gulf of Mexico (nGOM) is a taxonomically rich ecosystem. Previous work based on a meta-analysis of stomach contents data has shown the trophic connectivity of predators and prey to be substantial. However, the trophic dynamics of many economically and ecologically important species are still not well understood. Sportfish, such as Spotted Seatrout (Cynoscion nebulosus), Red Drum (Sciaenops ocellatus), and Southern Flounder (Paralichthys lethostigma), support recreational fisheries throughout the region. Gulf Menhaden (Brevoortia patronus), a high biomass forage fish with the region's largest commercial fishery, is considered an important forage species. In this study, we use information from meta-analysis of stomach contents and stable isotope analysis to investigate the importance of prey taxa, including Gulf Menhaden, for nGOM nearshore predators. Stomach contents and stable isotope analyses are generally evaluated independently, with stomach contents used to directly identify trophic interactions, while stable isotopes of carbon (δ13C) and nitrogen (δ15N) provide insight into a consumer's long-term feeding habits. We used a multispecies trophic model, EcoDiet, developed by Hernvann et al. (2022), that integrates information of both stomach contents and stable isotopes into a single framework to estimate trophic link probabilities and diet proportions. Data in the model include n = 41 predators, n = 173 prey, and n = 497 unique predator and prey interactions. The results indicate that nGOM nearshore predators are generalists using the diverse prey base, and in concordance with previous findings, there is no single Menhaden-dependent predator. Our findings better quantify the trophic interactions of the highly diverse nGOM region and have important implications regarding future ecosystem modeling and management considerations for the Gulf Menhaden stock.

Octopus diet during the settlement period using DNA metabarcoding

The settlement phase is a challenging period for meropelagic octopus, as they adapt to their new life in the sea bottom after a planktonic period. Their ecology and trophic interactions with the surrounding fauna in the wild are practically unknown. To understand their predatory role in the littoral zone, the diet of recently settled Octopus vulgaris from a Mediterranean sandy bottom was studied through molecular methods. Amphipods were present in all the analysed stomach contents, with a total of 20 amphipod taxa recorded as prey. Jassa slatteryi and Microprotopus maculatus were the most commonly found amphipod species. Hydrozoans, decapod crustaceans, cephalopods and bivalves followed amphipods in importance. Niche breadth index assigned to small recently settled octopus the role of a specialised predator, increasing the diversity of prey as they grow. Larger juveniles displayed a higher number of prey taxa suggesting a decreasing predatory specialisation with octopus size and an ontogenetic shift in trophic ecology from diet mainly based on amphipods to a richer diet. The considerable arm elongation and the strong muscular arm crown development after settlement probably allow the juvenile benthic octopus to develop ambush predation and speculative hunting, increasing the range of potential benthic prey species along its adaptation to the benthos.Graphic abstract

Domača mačka – tiha grožnja divjim živalim v primestni lokaciji Maribora

The monitoring of domestic cats' prey brought home was conducted between the 13th of March and the 1st of May 2023 in two residential areas near Maribor, Slovenia. This study aimed to provide information about the amount, diversity, and frequency of prey that the cats captured to identify the predatory impact of domestic cats in peri-urban areas. We present the results of the prey captured, whether the prey was brought alive or not, and whether it was eaten or not. We further provide information about the predation frequency of domestic cats concerning circadian activity, according to weather conditions and air temperature. The frequencies of various taxonomic groups of prey captured were described concerning land use in a location and species' biology. Our results include a total of 50 records of 12 species (3 species of birds and 9 of mammals). Domestic cats were more active during the mornings, on days without rain and the frequency of bringing home prey increased with higher temperatures.

Ontogenetic, Spatial and Inter-Annual Variability in the Diet of European Hake Merluccius merluccius Linnaeus, 1758, in the North Aegean Sea

This study contributes to filling knowledge gaps regarding recent information on the diet of the European hake, Merluccius merluccius Linnaeus, 1758, in the Greek seas, particularly its ontogenetic shifts and its spatiotemporal variability. The trophic preferences of M. merluccius were investigated in the North Aegean Sea during the summers of 2019 to 2023 with visual stomach content analysis to assess its composition, diversity, and variability across body-size classes, years, and subareas. The identified prey are functionally diverse and in many cases also primary targets for local fisheries. The ontogenetic trophic niche of hake was characterized by two distinct shifts, delineated by 10 and 50 cm body-size thresholds. Cephalopods were a prevalent dietary component for large hake individuals. The intermediate body-size classes demonstrated greater trophic niche breadth concerning prey diversity and absolute prey-size ranges. A feeding strategy characterized by the specialization of individuals was also revealed. The effect of the temporal and spatial context on the hake diet was occasionally correlated with spatiotemporal variations in the sizes of their populations. In conclusion, ontogenetic and spatiotemporal variability in the hake diet were found to be significant and should be considered in the data collection design and analyses of the trophic interactions of the species.

Evaluating mountain lion diet before and after a removal of feral horses in a semiarid environment

AbstractNon‐native species can affect ecosystems by influencing native predator‐prey dynamics. Therefore, management interventions designed to remove non‐natives may inadvertently lead to increased predation on native species. Feral horses are widely distributed throughout the arid parts of western North America. A growing body of research indicates that horses can be an important prey species to mountain lions in ecosystems where they overlap. In December 2020, the Bureau of Land Management removed 455 horses from the Delamar Mountains, Nevada, USA. We leveraged this management intervention to implement a before–after–control–impact study to test hypotheses about predation on horses and native ungulates. We predicted (1) that horses would comprise an important part of the diet in this mixed‐prey community, (2) following removal, the proportion of horses in the diet would decrease and native ungulates would increase, and (3) mountain lion home ranges overlapping the treatment areas would increase in response to decreased prey availability. From 2018 to 2022, we investigated 1360 clusters from 29 GPS‐collared lions and identified 1056 prey items. To model the probability of a predation event (a kill), we fit a mixed‐effects logistic regression model for ungulate prey as a function of lion sex, treatment area (in/out), and treatment period (pre‐/post‐removal). We used a log‐linear regression model to evaluate changes in home range size. The most common prey were mule deer (55%), feral horses (32%), and coyotes (4%). Twenty‐two of 29 lions consumed horses, although the rate of horse consumption was highly variable across individuals. Horses of both sexes and all age classes were predated. In contrast to predictions, our models detected no effect of removals on diet composition (βinteraction = 0.30 ± 1.1), nor did the removal influence home range size (βinteraction = 0.02 ± 0.02). Despite a 46% reduction in horse abundance, we found no evidence for prey‐switching following the horse removal treatment. Removal magnitude, rapid horse immigration, and/or behavioral specialization of individual mountain lions may help explain these results. Our findings have important implications for mountain lion and feral horse management in arid environments characterized by high prey diversity, but low prey abundance.

Can biochemical tracers reveal ontogenetic trophic shift and individual prey selection in white sharks from Guadalupe Island, Northeast Pacific?

Refining the role of apex predators in marine food webs is a necessary step in predicting the consequences of their global decline under the footprint of fishing activities. White sharks (Carcharodon carcharias) are vulnerable predators, performing large migrations and able to forage on a variety of prey in different habitats. In the Northeast Pacific, juvenile and adult white sharks are found seasonally at the same aggregation sites, such as Guadalupe Island off Mexico. While adults are thought to target local pinniped colonies, very few predator-prey interactions have been documented and the diet of juveniles in this area remains poorly understood. Here we used carbon/nitrogen stable isotopes and fatty acids to characterize the trophic ecology of white sharks at Guadalupe Island. In contrast to the ontogenetic trophic shift paradigm, we detected no influence of size on muscle stable isotope and fatty acid composition, revealing no significant dietary variation between juvenile and adult sharks. Stable isotopes did not allow definitive conclusions to be drawn regarding the diet of white sharks at Guadalupe Island, due to significant variability in the contribution of different potential prey depending on the trophic discrimination factors used. However, most sharks were rich in polyunsaturated fatty acids (such as long-chain omega 3), suggesting a local diet of mainly pelagic prey (potentially large fish or cephalopods). A few individuals appeared to show recent consumption of pinnipeds, with higher proportions of saturated and monounsaturated fatty acids. These individual differences in fatty acid composition could reflect an ecological trade-off between consumption of prey rich in fat (marine mammals) versus prey rich in polyunsaturated fatty acids (pelagic prey), respectively meeting the energetic and physiological needs of white sharks. Although ontogenetic trophic changes were not able to be discerned, our results provide new insights into the physiological drivers of predator-prey interactions, which can benefit the definition of conservation strategies in a changing ocean.

ECOLOGY OF THE NILGIRI LARGE BURROWING SPIDER HAPLOCLASTUS NILGIRINUS POCOCK, 1899 (ARANEAE, THERAPHOSIDAE) OF NILGIRIS, INDIA

The Nilgiri large burrowing spider, Haploclastus nilgirinus Pocock, 1899, an endemic tarantula in the Nilgiris Region of India, is critical for conservation yet poorly understood in terms of its ecology and habitat. This study addresses this gap by examining the nesting habits, tree-hole dynamics, and prey diversity of the species in Coonoor, The Nilgiris, specifically within tea plantations and fruit orchards. Observations focused on seven pear trees serving as nesting sites, with detailed measurements of nesting holes, including outer and inner circumference, depth, trunk base, ground-based height (gbh), and height from the ground. Data were collected over four consecutive months, both morning and evening. Insect diversity in the orchard was also assessed through counts and diversity indices, revealing variability among trees. The seventh tree had the highest spider population, with 13 spiders in 10 nests. Insect orders such as Blattodea, Orthoptera, Diptera, Hemiptera, and Lepidoptera were most prevalent around the seventh tree’s nests. Across all trees, a total of 25 spiders in 21 nests were documented, with variations in hole size and other tree measurements. This research provides crucial insights into the nesting habits, tree-hole dynamics, and prey diversity of this species, informing conservation efforts for this vulnerable species. As H. nilgirinus faces threats from habitat destruction, climate change, and illegal trade, understanding its ecological needs is vital for developing effective conservation strategies and sustaining ecosystem health.

HIGH FREQUENCY OF BATS IN THE DIET OF THE BARN OWL TYTO ALBA IN A LOWLAND DRY FOREST IN TOLIMA, COLOMBIA

The cosmopolitan distribution of the Barn Owl Tyto alba and its relatively well documented diet through the study of pellets have provided evidence of the broad diversity of prey it relies on. In most studies, both in tropical and temperate regions, rodents are its main prey, with other small mammals and vertebrates, and insects complementing its diet. Although bats have been recorded in the diet of T. alba at many localities, they seldom represent an important part of its diet. This study describes the diet of a small colony of T. alba from a mosaic of agricultural fields, pastures for cattle ranching and tropical dry forests in Tolima, central Colombia. Overall, we collected 516 pellets between 2016 and 2017 in a non-systematic manner, and recovered 335 skulls of rodents (67%), bats (29%), birds (3%) and shrews (1%), as well as invertebrate prey. The large proportion of bats in the diet of T. alba in this study is only matched by a few other studies, and further documents the wide range of prey included in the diet of this nocturnal raptor. This is one of the first studies on the diet of T. alba in tropical dry forests in Colombia and complements the existing data on its diet in the American tropics and worldwide.

Implications of human–wildlife conflict on the diet of an endangered avian top predator in the northern Andes

Conflicts between rural people and the Endangered Black-and-chestnut Eagle (Spizaetus isidori) are a prominent conservation concern in the northern Andes, as at least 60 eagles were poached between 2000 and 2022 in response to poultry predation. Here, we conducted direct observations to analyze the Black-and-chestnut Eagle diet and evaluated how forest cover affects the feeding habits of the species during nestling-rearing periods in 16 nests located in different human-transformed Andean landscapes of Ecuador and Colombia. We analyzed 853 prey items (46 species) delivered to nestlings. We used Generalized Linear Models to test whether the percent forest cover calculated within varying buffer distances around each nest and linear distances from the nest to the nearest settlement and pasture areas were predictors of diet diversity and biomass contribution of prey. Forest cover was not a factor that affected the consumption of poultry; however, the eagle regularly preyed on chickens (Gallus gallus) (i.e., domestic Galliformes) which were consumed by 15 of the 16 eagle pairs, with biomass contributions (14.57% ± 10.55) representing 0.6–37% of the total prey consumed. The Black-and-chestnut Eagle is an adaptable generalist able to switch from mammalian carnivores to guans (i.e., wild Galliformes) in human-dominated landscapes, and eagles nesting in sites with low forest cover had a less diverse diet than those in areas with more intact forests. Management actions for the conservation of this avian top predator require studies on the eagle’s diet in areas where human persecution is suspected or documented, but also maintaining forest cover for the wild prey of the species, development of socio-economic and psychological assessments on the drivers behind human-eagle conflicts, and the strengthening of technical capacities of rural communities, such as appropriate poultry management.

Importance of a Lake-Wetland Complex for a Resilient Walleye Fishery

Wetlands serve as unique habitats that can support high biodiversity. Large-scale loss of wetland habitats can threaten important linkages between lake and wetland habitats that could affect diversity and growth of aquatic organisms. In this study, we compare prey diversity and abundance as well as Walleye (Sander vitreus) diets and condition in a large glacial lake (Lake Kampeska, South Dakota) with a connected wetland to better understand seasonal changes in the benefits provided by each habitat. We examined seasonal differences (spring, summer, and fall) through two years (summer 2021 through fall 2022) between the habitats using prey fish catch per unit effort, richness, Shannon diversity, and Bray–Curtis dissimilarity as well as Walleye relative weight, percent of empty stomachs, diet weight, stomach fullness, diet energy, and diet taxa importance. The prey fish community was more diverse and abundant in the wetland, and Walleye consumed more prey (by weight) in the wetland during all seasons except spring. Wetland reconnection can be a tool for managers to improve water quality while providing seasonal habitat needs for fish. Additionally, the diversity of prey resources provided by wetlands, many of which are unique, support resilience in the face of ecological change. Protection of wetlands may be critical for maintaining healthy and resilient fisheries into the future.