Major Prey Research Articles

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

Stable isotope analysis reveals fish juveniles as a temporal main resource consumed by invasive pumpkinseed (Lepomis gibbosus)

AbstractThe pumpkinseed Lepomis gibbosus (Linnaeus, 1758) is a small centrarchid fish species from North America that has invaded most European basins, with pronounced expected impacts. Analyses of pumpkinseed diet in its invasive range using gut content analysis (GCA) show macrozoobenthos as the most common dietary item, suggesting a competitive effect on native fish communities. Our study uses a combination of GCA and stable isotope analysis (SIA) to document pumpkinseed diet at two sites in its invaded range and relates pumpkinseed diet preferences with parasitic load. SIA revealed juvenile fish as a major prey item at one of the sites (63 and 50% of the diet of small and the large fish), while GCA showed pumpkinseed preying mostly on macroinvertebrates (chironomids, gastropods, Ephemeroptera, and Zygoptera larvae) at both sites. While infrequent infection by trophically transmitted parasitic nematodes could be related to low consumption of zooplankton, substantial infection by metacercariae of Posthodiplostomum centrarchi Hoffman1958 appears to reflect relatively high consumption rates of its intermediate host, physid snails. Using SIA allowed to demonstrate that pumpkinseed feeding in its non-native range can be based on piscivory, emphasising the need for combining multiple methods when studying the impact of non-native species on food webs.

Chemical analysis of flotsam ambergris

The natural product ambergris is only found rarely on beaches, as jetsam. Even more scarce, or even absent, are accounts of flotsam ambergris. Here, we report the chemical analysis of a rare, large piece (>100kg) of flotsam found in the Atlantic in 2019. About 95% of subsamples from the outside of the coprolith was soluble in dichloromethane. Of this, FTIR spectroscopy, APCI-MS and GC-MS indicated the presence of ambrein. Radiocarbon dating indicated that the sample was post 1950s in age. The 13C/12C isotope ratio (−22.5 ‰) was typical of those reported to date for whale ‘body’ ambergris. Metals of ambergris have hardly been reported previously. The distribution found here for the flotsam, was dominated by copper and zinc, which is similar to that of several squid species. This is also consistent with the presence of squid beaks in the coprolith. Squid are a major prey species of sperm whales.

Diet of Rusty-spotted Cat Prionailurus rubiginosus (I. Geoffroy Saint-Hilaire, 1831) (Mammalia: Carnivora: Felidae) in Sanjay Gandhi National Park, Mumbai, India

The 103.68 km2 Sanjay Gandhi National Park (SGNP), Mumbai, exists amidst human densities that figure among the highest in the world. The rich biodiversity of SGNP includes the Rusty-spotted Cat Prionailurus rubiginosus, endemic to India, Sri Lanka, and Nepal, and categorised as ‘Near Threatened’ on the IUCN Red List. Little is known about its ecology and the dynamics of its coexistence with the other small carnivores in SGNP. We conducted a study with citizen volunteers to explore the diet of the Rusty-spotted Cat and other sympatric small carnivores in SGNP and in the adjoining human-dominated areas of Yeur village, Shivaji Nagar, Dahisar Quarry, and Aarey Milk Colony. After initial training, the volunteers collected scat samples from all forest ranges in SGNP and the surrounding areas outside, following defined protocols. Seventy-eight scat samples were analysed for species assignments using standardised molecular techniques, felid-specific primers, and DNA sequencing, and 24 were identified as of the Rusty-spotted Cat. The contents of the samples were examined under a microscope to identify prey remains. Results were presented as the mean number of scat samples containing remains of specific taxa with 95% Confidence Intervals. Diet estimated from 22 Rusty-spotted Cat scat samples and 52 samples of other small carnivores revealed rodents to be the major prey of the entire group. However, a higher proportion of Rusty-spotted Cat scat samples had remains of rodents (95%) and reptiles (6%) as compared to samples of other small carnivores, i.e., 79% with rodent remains and none with remains of reptiles. On the other hand, a lower proportion of Rusty-spotted Cat scat samples had remains of insects (14%), plant matter (9%), and birds (5%) than samples of other small carnivores (40% plant matter, 38% insects, 17% birds). Our results highlight the role of small carnivores, especially Rusty-spotted Cat in regulatory services through pest control.

Striped hyena Hyaena hyaena (Linnaeus 1758): feeding ecology based on den prey remains in a pastoralist landscape, southern Kenya

Abstract Very little is known about the range, diet and eco-ethology of the African striped hyena, compared to its sympatric hyena species; the spotted hyena. Here we present the results of bone assemblages collected in eight striped hyena dens located in a pastoralists’ area in and near the Shompole conservancy, southern Kenya. We present the dens taxonomical representation; comparing domestic and wildlife prey and their prey age structure. This is to aid in making inferences on the striped hyena’s prey acquisition, selection and mode of transportation. Ultimately, this is to highlight the species’ interaction with pastoralists and some eco-ethological features of this little known near threatened species. Total wildlife proportions were higher than livestock. However, both wild and domestic ungulates are the major prey of the striped hyena and carnivores constitute a greater proportion of its non-ungulate prey. Striped hyena appears to predate on younger livestock when their dens are located closer to human settlements than those away from human occupied areas. Juveniles and old adults of wild ungulates dominated the striped hyena dens than the prime adults and this was reversed in the case of livestock ungulates.

Biological and environmental covariates of juvenile sockeye salmon distribution and abundance in the southeastern Bering Sea, 2002-2018.

Climate change is altering the distribution and abundance of marine species, especially in Arctic and sub-Arctic regions. In the eastern Bering Sea, home of the world's largest run of sockeye salmon (Oncorhynchus nerka), juvenile sockeye salmon abundance has increased and their migration path shifted north with warming, 2002-2018. The reasons for these changes are poorly understood. For these sockeye salmon, we quantify environmental and biological covariate effects within spatio-temporal species distribution models. Spatio-temporally, with respect to juvenile sockeye salmon densities: (1) sea surface temperature had a nonlinear effect, (2) large copepod, Calanus, a minor prey item, had no effect, (3) age-0 pollock (Gadus chalcogrammus), a major prey item during warm years, had a positive linear effect, and (4) juvenile pink salmon (O. gorbuscha) had a positive linear effect. Temporally, annual biomass of juvenile sockeye salmon was nonlinearly related to sea temperature and positively related to age-0 pollock and juvenile pink salmon abundance. Results indicate that sockeye salmon distributed with and increased in abundance with increases in prey, and reached a threshold for optimal temperatures in the eastern Bering Sea. Changes in population dynamics and distribution of sockeye salmon in response to environmental variability have potential implications for projecting specific future food securities and management of fisheries in Arctic waters.

DNA metabarcoding reveals a diverse, omnivorous diet of Arctic amphipods during the polar night, with jellyfish and fish as major prey

IntroductionCurrently, Arctic marine ecosystems are witnessing the most rapid physical changes worldwide, leading to shifts in pelagic and benthic communities and food web structure, concomitant with the introduction of boreal species. Gelatinous zooplankton or jellyfish represent one particular group of which several boreal species are prone to undergo significant poleward range expansions and population increases in the Arctic in the course of the ongoing changes. Historically, jellyfish were considered a trophic dead-end, but an increasing number of studies using modern tools have highlighted their role as major prey items in marine food webs. In this study, we aimed to verify the role of jellyfish and other metazoans as food sources in the Arctic polar night food web, when pelagic resources are limited.MethodsWe identified the diet of different bentho-pelagic amphipod species in the Atlantifying Kongsfjorden (West Svalbard) during the polar night. We regularly sampled lysianassoid and gammarid amphipods using baited traps and hand nets over a period of one month during the polar night and identified their diet spectrum by applying DNA metabarcoding (COI) to their stomach contents.ResultsWe demonstrate that all investigated species are omnivorous. Fish species including polar cod and snailfish, likely in the shape of carrion, played an important role in the diet of the scavengers Orchomenella minuta and Anonyx sarsi. Predation and potential scavenging on jellyfish contributed to the diet of all four investigated species, particularly for the species Gammarus setosus and G. oceanicus, as evidenced by high read abundances and high frequencies of occurrence. Besides jellyfish, crustaceans and macroalgae were important components of the diet of the two Gammarus species.DiscussionThe diverse jellyfish community present in Kongsfjorden in the polar night is clearly being utilized as a food source, either through pelagic feeding or feeding on jelly-falls, albeit to a different extent in the local amphipod community. These findings provide novel insights into the Arctic food web during the polar night and represent the first evidence of feeding on natural (non-experimental) jelly-falls.

Small mammal responses to biosolids on grazed rangelands in British Columbia

Grasslands are globally declining due to habitat conversion, overgrazing, climate change, and changes in fire and drought regimes. Degraded grasslands are less able to support wildlife species, which contributes to the imperilment of many species. Biosolids are used by some ranchers as an organic amendment to support more plant growth and in turn more livestock. We worked on a large cattle ranch in central British Columbia, Canada, to determine how biosolids amendment affected small mammal populations, as mice and voles are major prey for many predators and contribute to seed dispersal and underground dynamics. We found that biosolids‐amended pastures had more grass cover and supported fewer deermice (Peromyscus maniculatus) than did unamended pastures. Voles were scarce, likely due to a cyclic low. Although we sampled sites that had had biosolids applied 1 or 3 years prior to our work started, deermouse populations were similarly low across these sites. The reduction in deermice on sites with biosolids relative to unamended sites could be a signal of habitat restoration, because deermice prefer disturbed habitats rather than ones with high plant cover. Grass cover was more than twice as high on sites amended with biosolids, making these sites less suitable for deermice.

Marine heatwaves affect breeding, diet and population size but not body condition of a range-edge little penguin colony

Significant marine heatwaves (MHWs) developed along the Western Australian coast in 1999 and 2011. Despite ecosystem losses and the southwards occurrence of many tropical fish species during and after the extreme MHW in 2011, there have been few studies on the effects of this MHW on seabirds, and no biological impacts related to the 1999 MHW have been reported. Using data from 1986-2019, we investigated the impacts of these events on breeding outcomes, body condition, diet composition, population size and mortality of little penguins on Penguin Island, in the temperate waters off Western Australia. Breeding outcomes were negatively impacted by the MHWs but body condition was not. Diet composition changed after the MHW, with sandy sprat Hyperlophus vittatus, the penguins’ typical major prey component, replaced by scaly mackerel Sardinella lemuru, a tropical fish species. Using an open robust design analysis that accounts for imperfect capture probabilities and staggered annual arrival and departure dates, we found that the population decreased by 80% following the 2011 MHW. Finally, more penguins died from starvation or from novel protozoal parasitic infections in 2011 and 2012 that were potentially introduced with the changed diet. This research highlights that the temporal and spatial influence of MHWs on seabirds depends on several factors. Furthermore, the magnitude and direction of a prey species’ response can be very localised and have significant impacts on avian predators. There are no obvious ways to mediate climate effects, but perhaps measures taken to reduce any synergistic impacts on prey abundance, particularly during MHW events, could be effective.

Feeding habits and diet composition of Octopus cyanea (Gray, 1849) in Zanzibar waters, Tanzania

The octopus fishery in Zanzibar is an essential activity of coastal communities. To assist with developing fisheries management plans, baseline information on the feeding of Octopus cyanea (Gray, 1849) was collected in relation to sex and maturity stages. The feeding habits and diet composition of 543 O. cyanea were studied over a period of 12 months at Paje, Kizimkazi, Chwaka Bay and Nungwi. Samples at each site were collected on two days per month during spring tide. Digestive tract contents revealed that O. cyanea preyed on 36 species of crustaceans, molluscs and fishes, with crabs a major prey item. The number of prey species in a single stomach ranged from one to six. O. cyanea in Zanzibar is therefore a generalist predator with a mixed diet. The octopus gonadosomatic index (GSI) indicated a peak breeding season in June to October, which correlated with low prey consumption. Mature octopuses ingested a small amount of food from mainly small sessile prey. Females consumed less food than males of similar maturity stages, suggesting that they ate less or had higher digestion rates. The information is useful for developing fisheries management plans for the octopus fishery in Zanzibar.

Morphological and Trophic Features of the Invasive Babka gymnotrachelus (Gobiidae) in the Plain and Mountainous Ecosystems of the Dniester Basin: Spatiotemporal Expansion and Possible Threats to Native Fishes

Over the last few years, the racer goby B. gymnotrachelus quickly expanded in the mountainous rivers of the Dniester basin at aheight of 300 m a.s.l. and above. The occurrence frequency of the racer goby in fish communities in the mountainous rivers of the Carpathian ecoregion remains low (up to 20%), as compared with the plain rivers, where the species occurs in 70–100% of cases. The major prey groups in its diet in both plain and mountainous were Chironomidae, Diptera, and Crustacea. Chironomidae formed the maximal portion (35% at an occurrence frequency of 72.5%), and Trichoptera formed 18%at an occurrence frequency of 41%, whereas fish larvae were absent in their diet in mountainous rivers. The peculiar environmental conditions of mountainous rivers caused the adaptive modifications of the morphological features of the racer goby at the subpopulation level, which compriseda decrease inthe specimens’ size in rivers with a flow velocity of above 1.5 m/s and rivers with pebble contentsof above 50%in the bottom sediments.The modifications showed an increase inbody streamlining as an adaptation to flow velocity and turbulence and the stony substrate of the river’s bottom. Thus, the morphological adaptation of B. gymnotrachelus to the conditions of the mountainous rivers is in progress, and the formationof astable population in these rivers can be expected. In contrast, the native fish species’ resilience in the face of newcomers is still high, and this is because their alevins are not food for invaders.

Whole-genome Analyses Reveal Past Population Fluctuations and Low Genetic Diversities of the North Pacific Albatrosses.

Throughout the Plio-Pleistocene, climate change has impacted tropical marine ecosystems substantially, with even more severe impacts predicted in the Anthropocene. Although many studies have clarified demographic histories of seabirds in polar regions, the history of keystone seabirds of the tropics is unclear, despite the prominence of albatrosses (Diomedeidae, Procellariiformes) as the largest and most threatened group of oceanic seabirds. To understand the impact of climate change on tropical albatrosses, we investigated the evolutionary and demographic histories of all four North Pacific albatrosses and their prey using whole-genome analyses. We report a striking concordance in demographic histories among the four species, with a notable dip in effective population size at the beginning of the Pleistocene and a population expansion in the Last Glacial Period when sea levels were low, which resulted in increased potential coastal breeding sites. Abundance of the black-footed albatross dropped again during the Last Glacial Maximum, potentially linked to climate-driven loss of breeding sites and concordant genome-derived decreases in its major prey. We find very low genome-wide (π < 0.001) and adaptative genetic diversities across the albatrosses, with genes of the major histocompatibility complex close to monomorphic. We also identify recent selective sweeps at genes associated with hyperosmotic adaptation, longevity, and cognition and memory. Our study has shed light on the evolutionary and demographic histories of the largest tropical oceanic seabirds and provides evidence for their large population fluctuations and alarmingly low genetic diversities.

Population and Distribution of Himalayan Tahr (Hemitragus jemlahicus) in Lamtang National Park of the Nepal Himalaya

The Himalayan ecosystems, which are among the least studied mountain ecosystems, face threats and habitat degradation due to unplanned development, natural calamities, and overgrazing. Ungulates like Himalayan tahrs (Hemitragus jemlahicus), play a crucial role in mountain ecology as it forms the major prey base of the top predators of mountain ecosystems. Objective: To explore the population status, distribution, and habitat uses of Himalayan tahrs in Lamtang National Park (LNP), Central Nepal by line transect method during May 2022. Methods: Total 20 transects each of about 500 m length were established randomly along the Lamtang River at different elevations from 3100m to 4300m and Himalayan tahrs were observed. Results: A total of 154 Himalayan tahrs were recorded from 9 herds that accounted for an average herd size of 17.1 ± 5.77 individuals. The elevational distribution of the herds ranged between 3107 m and 4200 m asl. Their preferred habitat was rocky cliffs, with grasslands, shrublands, and rhododendron-fir-mixed forests being utilized to a lesser extent. The tahrs predominantly inhabited rugged terrain on south-facing slopes, prioritizing it over other available habitats. Conclusions: The demographic indices of the Himalayan tahrs in the LNP show a remarkable decline when compared with the previous studies in the same area in 1976 and 2006. Therefore, conservation and management initiatives of the Himalayan tahrs are urgently needed in the LNP

Assessment of fishery management parameters for major prey fish species in the lower reaches of the Songhua River

The stability of the ecosystem directly affects the water quality and safety, fishery production, and people’s quality of life along the route. In this study, extensive biological information on five dominant species of prey fish, includingHemiculter leucisculus(Basilewsky, 1855),Acheilognathus macropterus(Bleeker),Rhodeus sericeus(Pallas,1776),Pseudorasbora parva(Temminck &amp;amp; Schlegel, 1846), andSqualidus argentatus(Sauvage &amp;amp; Dabry de Thiersant, 1874), was collected in the lower reaches of the Songhua River, and the population parameters and variation rules of these fish were evaluated. The results showed that at present, the fish resources in the lower reaches of the Songhua River were in an overexploited state. Although the growth rate of prey fish was accelerating, their growth potential was decreasing. In addition to the homogeneous structure of the fish community, it was increasingly evident that a high proportion of small-sized fish were present in the fish community. In addition, the growth length coefficients of the five prey fish species were all greater than 0.2, indicating that the prey fish were growing at a faster rate, and the range of the growth performance indicators were 3.49 ~ 4.37. Our data also demonstrated that the exploitation rates ofHemiculter leucisculusandSqualidus argentatuswere both greater than 0.5, and the exploitation rates of all species were higher thanEmaxexcept forPseudorasbora parva. Finally, based on the above results, the mesh size of all nets should be controlled above 45 mm to ensure the size of the main prey fish populations in the lower reaches of the Songhua River. In summary, these results provided variation rules and growth of prey fish resources in the lower reaches of the Songhua River. At the same time, the distribution of major commercial or endangered baiting grounds in the lower reaches of the Songhua River was determined, which was beneficial to the balance and integrity of the ecosystem.

Estimation of total population size of southern elephant seals (Mirounga leonina) on Kerguelen and Crozet Archipelagos using very high-resolution satellite imagery

Southern elephant seals (Mirounga leonina) play a pivotal role in the Southern Ocean as wide-ranging marine predators and major prey consumers within Southern Ocean marine ecosystems. Due to their circumpolar distribution and the remoteness of their habitat, large uncertainties remain about their total population sizes. This is especially true for elephant seal populations in the French Southern Territories in the southern Indian Ocean (i.e. Crozet and Kerguelen Archipelagos) as many breeding sites are inaccessible for ground censuses. Here, we present a simple and efficient approach for estimating the total elephant seal populations of the Kerguelen and Crozet Archipelagos by using very high-resolution satellite imagery (&amp;lt;1m resolution). Twenty-eight satellite images taken during the breeding season to count female elephant seals in inaccessible areas were used and complemented the traditional annual ground counts in accessible areas. For Kerguelen Island sectors likely to host colonies and where no satellite images were available for the breeding season, a statistical predictive model was built to estimate the most likely number of breeding females to be present on a given beach according to its physiographic characteristics. Our results show the reliability of using very high-resolution satellite images, a relatively low-cost platform, to count pinniped populations and provide the first estimation of the total southern elephant seal population for both the Kerguelen 347,995 (s e = 4,950) and Crozet 13,065 (s e = 169) Archipelagos. The combined total represents over 35% of the global elephant seal population with the Kerguelen stock being numerically equivalent to the South Georgia stock. In addition, we re-examined the population trends since the last mid-century for Kerguelen and over the last five decades for Crozet. The demographic trends of the southern Indian Ocean populations show marked growth over the last decade (5.1% and 1.6% annual growth rate for Crozet and Kerguelen respectively), particularly on Crozet where the elephant seal population has more than tripled.

The influence of temperature on Pacific hake co‐occurrence with euphausiids in the California Current Ecosystem

AbstractUnderstanding the influence of ocean conditions on predator–prey relationships can provide insight for ecosystem‐based fisheries management. Pacific hake (Merluccius productus) are abundant and commercially important groundfish in the California Current Ecosystem (CCE) that consume euphausiids (krill) as a major prey item. We used data from the biennial joint U.S.‐Canada Integrated Ecosystem &amp; Acoustic Trawl Survey for Pacific hake (2007–2019, n = 8 surveys) to quantify co‐occurrence of age 2+ hake with krill in relation to bottom depth, continental shelf break location, surface chlorophyll‐a, and 100‐m temperature. Vertical distributions of hake varied among years and were not correlated to krill depth. Hake hotspots occurred primarily off the Oregon coast and near Cape Mendocino, while most krill hotspots occurred in the northern CCE. The probability of co‐occurrence was greatest during cool ocean conditions (100‐m temperature 1°C below average), averaging 41.0% and extending throughout most of the CCE. During warm ocean conditions (100‐m temperature 1°C above average), predicted co‐occurrence averaged 17.0% and was concentrated near Cape Mendocino. These results indicate that hake‐krill co‐occurrence is a function of predator and prey spatial distributions and overall krill abundance. Furthermore, temperature influences hake‐krill co‐occurrence and may explain some of the variation in hake growth and recruitment to the fishery.

In situ food compositions reveal niche partitioning in small marine cladocerans and copepods in Daya Bay, South China Sea

Marine cladocerans and small copepods (&lt;0.7 mm) share similar food resources based on their size and feeding modes but little is known about the mechanisms allowing their coexistence. Using the high-throughput sequencing (HTS) method, the in situ eukaryotic diets of the small cladocerans Penilia avirostris and Pseudevadne tergestina and the calanoid copepod Parvocalanus crassirostris during spring and summer in Daya Bay, South China Sea, were analyzed and their dietary preference and potential niche overlap were described and compared. Approximately 195 operational taxonomic units belonging to metazoans, phytoplankton, protists, and fungi were detected in the gut contents of the 3 species. Overall, animal and phytoplankton prey contributed evenly to the sequences of gut contents of P. avirostris, with diatoms and cnidarians being the most important prey, whereas arthropods were the major prey resource for P. tergestina, with an extremely high percentage (86.2%). P. crassirostris contained a high percentage of phytoplankton prey, with dinoflagellates and diatoms as the major prey (24.3 and 12.9%, respectively). Both P. avirostris and P. crassirostris consumed a higher percentage of phytoplankton with the seasonal transition. Low niche overlap (0.001-0.19) among the 3 small crustaceans highlights their strong dietary niche partitioning and explains their coexistence in Daya Bay.

Anthropogenic pressure on large carnivores and their prey in the highly threatened forests of Tanintharyi, southern Myanmar

AbstractThe Tanintharyi Region in southern Myanmar is rich in biodiversity yet is facing threats from varying degrees of anthropogenic pressure. In this research we examine how anthropogenic pressures are influencing large carnivores (tiger Panthera tigris, leopard Panthera pardus and dhole Cuon alpinus) and their major prey species (wild pig Sus scrofa, muntjac Muntiacus spp., sambar Rusa unicolor, gaur Bos gaurus and banteng Bos javanicus) in the Lenya Reserved Forest and adjacent areas of Sundaic forest. We used data from camera-trap surveys during May 2016–March 2018 and logistic regression to analyse the relationships between the presence of large carnivores and explanatory variables such as human disturbance, landscape variability and changes in prey distribution. Tiger presence was positively associated with the occurrence of gaur and distance to villages. The occurrence of prey did not explain the detection of leopards in the study area. We suspect this was because leopards have a broad diet, including arboreal primates, and their prey was not fully recorded in our camera-trap survey. Dholes were positively associated with wild pigs and the total number of prey but not associated with forest type and landscape variables. To restore the carnivore population and conserve the biodiversity of this area, effective protection of predators and habitat management for large ungulates are crucial.

Seasonal and interannual variability in the diet of young and subadult male Antarctic fur seals as revealed by stable C and N isotope ratios

Detailed knowledge of marine mammal diet is critical to understand their ecological roles and for the adequate management of marine resources. Antarctic fur seals ( Arctocephalus gazella) in the Southern Atlantic Ocean rely largely on Antarctic krill ( Euphausia superba) during the summer months, but their winter diet remains largely unknown. Here, stable carbon and nitrogen isotope ratios in whiskers and blood of young (2–3 years old) and subadult (4–7 years old) Antarctic fur seal males from the South Shetland Islands were used to assess the seasonal and interannual changes in the krill contribution to their diet. The stable isotope ratios revealed that krill dominated the diet of young and subadult male Antarctic fur seals year-round, with penguins, and not fish, as the second major prey, regardless of year and season. The year-round reliance of young and subadult male Antarctic fur seals on krill should be considered for ecosystem-based fisheries management, as they represent the bulk of the fur seal population remaining off Antarctica during the winter months.

The Impact of a Southern Ocean Cyclonic Eddy on Mesopelagic Micronekton

AbstractMesoscale eddies shape the foraging ecology of predators such as marine mammals and seabirds. A growing number of animal tracking studies show that predators alter their swimming, diving, and foraging behavior within mesoscale eddies. However, little is known about how Southern Ocean eddies influence the distribution of mesopelagic micronekton (fish, squid, and crustaceans), which are major prey items of megafauna. Studies in other oceanic regions have found that eddies can influence the abundance and community composition of micronekton. Here, we analyze acoustic observations from a 14‐day survey of a cyclonic mesoscale eddy, its surrounding waters, and the Polar Frontal Zone (PFZ) waters where the eddy formed. We report and interpret spatial patterns of acoustic backscatter at 18 and 75 kHz, proxies indicating combined changes in species, size, and abundance of micronekton. We find that the vertical distribution of acoustic backscatter matched the underwater light conditions characteristic of the eddy core, periphery, and surrounding waters, at scales smaller than 10 km. The median water‐column integrated acoustic backscatter values in the eddy core were only half of those measured in the Sub‐Antarctic Zone waters surrounding the eddy, but similar to those measured in the PFZ, where the eddy originated 27 days prior. These results suggest that, as for physical and chemical tracers, the eddy maintained its biological characteristics from its source waters creating a unique habitat compared to its surroundings.