Breeding den selection by Arctic foxes (Vulpes lagopus) in southern Yamal Peninsula, Russia

Selecting the right location for a den during the breeding season is a type of habitat selection in the Arctic fox (Vulpes lagopus) that is likely to affect its reproductive success. A den’s suitability likely depends on its ability to provide shelter, as well as its proximity to prey resources. Depending on the different relative risks that Arctic foxes may face across their broad circumpolar range, Arctic foxes may place different emphases on selection for shelter and prey resources in different ecosystems. Understanding the different requirements for reproduction under different ecological conditions is highly relevant to conservation efforts in areas where Arctic foxes are threatened by rapid environmental changes. Here, we investigated the relative selection for shelter and prey resources in southern Yamal Peninsula (Russia) using data from 45 dens collected over a 13-year period. Arctic foxes preferred to breed in dens with more den entrances; an indicator of shelter quality. Arctic foxes also preferred dens surrounded by more prey resources (quantified by the amount of river valley habitat), but this result was less conclusive. These results complement the findings reported from other study areas, illustrating that Arctic foxes in ecosystems with diverse predator communities may put emphasis on selection for shelter quality. In less productive ecosystems, Arctic foxes may rather put emphasis on selection for prey resources. As tundra ecosystems become more productive and generalist predators move north, the reproductive requirements and habitat selection of Arctic foxes may change accordingly, depending on the species’ ability to adapt.

Humans disrupt access to prey for large African carnivores

Wildlife respond to human presence by adjusting their temporal niche, possibly modifying encounter rates among species and trophic dynamics that structure communities. We assessed wildlife diel activity responses to human presence and consequential changes in predator-prey overlap using 11,111 detections of 3 large carnivores and 11 ungulates across 21,430 camera trap-nights in West Africa. Over two-thirds of species exhibited diel responses to mainly diurnal human presence, with ungulate nocturnal activity increasing by 7.1%. Rather than traditional pairwise predator-prey diel comparisons, we considered spatiotemporally explicit predator access to several prey resources to evaluate community-level trophic responses to human presence. Although leopard prey access was not affected by humans, lion and spotted hyena access to three prey species significantly increased when prey increased their nocturnal activity to avoid humans. Human presence considerably influenced the composition of available prey, with implications for prey selection, demonstrating how humans perturb ecological processes via behavioral modifications.

Humans induce differential access to prey for large African carnivores

Wildlife adaptively respond to human presence by adjusting their temporal niche, possibly modifying encounter rates among species and trophic dynamics that structure communities. Here we show that these human-induced modifications to behaviours are prolific among species and alter apex predators’ access to prey resources. We assessed human-induced changes to wildlife diel activity and consequential changes in predator-prey overlap using 11,954 detections of three apex predators and 13 ungulates across 21,430 trap-nights in West Africa. Over two-thirds of species altered their diel use in response to human presence, and ungulate nocturnal activity increased by 6.8%. Rather than traditional pairwise predator-prey comparisons, we considered spatiotemporally explicit predator access to a suite of prey resources to evaluate community-level trophic responses to human presence. Although leopard prey access was not affected, lion and hyena access to 3 prey species significantly increased when prey increased their nocturnal temporal niche to avoid humans. Ultimately, humans considerably altered the composition of available prey, with implications for prey selection, demonstrating how humans perturb ecological processes via behavioural modifications.

What makes Hemidactylus invasions successful? A case study on the island of Curaçao

Hemidactylus spp. (House geckos) rank among the most successful invasive reptile species worldwide. Hemidactylus mabouia in particular has become ubiquitous across tropical urban settings in the Western Hemisphere. H. mabouia’s ability to thrive in close proximity to humans has led to the rapid displacement of native geckos in urban areas, however the mechanisms driving this displacement remain understudied. Here we combine data from nitrogen and carbon stable isotopes, stomach contents, and morphometric analyses of traits associated with feeding and locomotion to test alternate hypotheses of displacement between H. mabouia and a native gecko, Phyllodactylus martini, on the island of Curaçao. Consistent with expectations of direct food resource competition, we demonstrate substantial overlap of invertebrate prey resources between the species. Additionally, we found strong evidence from both diet content and stable isotope analyses that H. mabouia acts as a vertebrate predator, preying upon P. martini as well as other native and non-native reptiles. Finally, we show that H. mabouia possesses several morphological advantages, including larger sizes in feeding-associated traits and limb proportions that could offer a propulsive locomotor advantage on vertical surfaces. Together, these findings suggest the successful establishment of H. mabouia likely involves a combination of both exploitative interspecific competition and predation. Given the ubiquity of H. mabouia, illuminating the role of this species as both a competitor and a predator casts new concerns on the ecological and demographic impacts of this widespread urban invader.

Trophic ecology of hawksbill turtles (Eretmochelys imbricata) in Golfo Dulce, Costa Rica: integrating esophageal lavage and stable isotope (δ13C, δ15N) analysis

Hawksbill turtles (Eretmochelys imbricata), considered Critically Endangered, have several small populations in the Eastern Pacific (EP). Knowledge about their diet and habitat use can aid in developing conservation strategies and promoting population recovery in the region. Although considered a spongivore in the Caribbean, data from the EP region indicate that hawksbills consume a wide array of prey species, including angiosperms. We used two approaches to study the diet of hawksbills at Golfo Dulce, Costa Rica: oesophageal lavage and stable isotope (δ13C, δ15N) analysis of bulk skin tissue and blood plasma. Lavage samples collected from 41 turtles revealed macroalgae as the predominant diet item (Rw = 20.22), followed by sea snails and excavating worms. Stable isotope values for blood plasma from 44 turtles ranged from -23.0‰ to -15.7‰ for δ13C and 6.9‰ to 10.4‰ for δ15N, whereas values for skin tissue were -20.4‰ to -13.9‰ and 9.3‰ to 11.0‰ for δ13C and δ15N, respectively. We compared these isotope values with those of five potential prey groups (sponge, sea snail, excavating worm, mangrove, macroalgae) using a multisource stable isotope mixing model analysis in R (SIAR). Our results indicated that multiple prey resources are important for hawksbills in Golfo Dulce, where sea snails, sponges and excavating worms contributed up to 63% of the assimilated diet per individual, and mangrove and macroalgae up to 50%. These data show that hawksbills in Golfo Dulce, and perhaps the wider EP region, are omnivorous, underscoring the importance for considering alternative habitats, aside of coral reefs, for its management and restoration.

Protein Deimination and Extracellular Vesicle Profiles in Antarctic Seabirds

Pelagic seabirds are amongst the most threatened of all avian groups. They face a range of immunological challenges which seem destined to increase due to environmental changes in their breeding and foraging habitats, affecting prey resources and exposure to pollution and pathogens. Therefore, the identification of biomarkers for the assessment of their health status is of considerable importance. Peptidylarginine deiminases (PADs) post-translationally convert arginine into citrulline in target proteins in an irreversible manner. PAD-mediated deimination can cause structural and functional changes in target proteins, allowing for protein moonlighting in physiological and pathophysiological processes. PADs furthermore contribute to the release of extracellular vesicles (EVs), which play important roles in cellular communication. In the present study, post-translationally deiminated protein and EV profiles of plasma were assessed in eight seabird species from the Antarctic, representing two avian orders: Procellariiformes (albatrosses and petrels) and Charadriiformes (waders, auks, gulls and skuas). We report some differences between the species assessed, with the narrowest EV profiles of 50–200 nm in the northern giant petrel Macronectes halli, and the highest abundance of larger 250–500 nm EVs in the brown skua Stercorarius antarcticus. The seabird EVs were positive for phylogenetically conserved EV markers and showed characteristic EV morphology. Post-translational deimination was identified in a range of key plasma proteins critical for immune response and metabolic pathways in three of the bird species under study; the wandering albatross Diomedea exulans, south polar skua Stercorarius maccormicki and northern giant petrel. Some differences in Gene Ontology (GO) biological and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways for deiminated proteins were observed between these three species. This indicates that target proteins for deimination may differ, potentially contributing to a range of physiological functions relating to metabolism and immune response, as well as to key defence mechanisms. PAD protein homologues were identified in the seabird plasma by Western blotting via cross-reaction with human PAD antibodies, at an expected 75 kDa size. This is the first study to profile EVs and to identify deiminated proteins as putative novel plasma biomarkers in Antarctic seabirds. These biomarkers may be further refined to become useful indicators of physiological and immunological status in seabirds—many of which are globally threatened.

Prey-size plastics are invading larval fish nurseries

Life for many of the world’s marine fish begins at the ocean surface. Ocean conditions dictate food availability and govern survivorship, yet little is known about the habitat preferences of larval fish during this highly vulnerable life-history stage. Here we show that surface slicks, a ubiquitous coastal ocean convergence feature, are important nurseries for larval fish from many ocean habitats at ecosystem scales. Slicks had higher densities of marine phytoplankton (1.7-fold), zooplankton (larval fish prey; 3.7-fold), and larval fish (8.1-fold) than nearby ambient waters across our study region in Hawai‘i. Slicks contained larger, more well-developed individuals with competent swimming abilities compared to ambient waters, suggesting a physiological benefit to increased prey resources. Slicks also disproportionately accumulated prey-size plastics, resulting in a 60-fold higher ratio of plastics to larval fish prey than nearby waters. Dissections of hundreds of larval fish found that 8.6% of individuals in slicks had ingested plastics, a 2.3-fold higher occurrence than larval fish from ambient waters. Plastics were found in 7 of 8 families dissected, including swordfish (Xiphiidae), a commercially targeted species, and flying fish (Exocoetidae), a principal prey item for tuna and seabirds. Scaling up across an ∼1,000 km2 coastal ecosystem in Hawai‘i revealed slicks occupied only 8.3% of ocean surface habitat but contained 42.3% of all neustonic larval fish and 91.8% of all floating plastics. The ingestion of plastics by larval fish could reduce survivorship, compounding threats to fisheries productivity posed by overfishing, climate change, and habitat loss.

Photosynthetic cyclic electron transport provides ATP for homeostasis during trap closure in Dionaea muscipula

Background and Aims The processes connected with prey capture and the early consumption of prey by carnivorous Dionaea muscipula require high amounts of energy. The aim of the present study was to identify processes involved in flytrap energy provision and ATP homeostasis under these conditions. Methods We determined photosynthetic CO2 uptake and chlorophyll fluorescence as well as the dynamics of ATP contents in the snap traps upon closure with and without prey. Key Results The results indicate that upon prey capture, a transient switch from linear to cyclic electron transport mediates a support of ATP homeostasis. Beyond 4 h after prey capture, prey resources contribute to the traps’ ATP pool and, 24 h after prey capture, export of prey-derived resources to other plant organs may become preferential and causes a decline in ATP contents. Conclusions Apparently, the energy demand of the flytrap for prey digestion and nutrient mining builds on both internal and prey-derived resources.

Winter movement behavior by swift foxes (Vulpes velox) at the northern edge of their range

Winter can be a limiting time of year for many temperate species, who must access depressed prey resources to meet energetic demands. The swift fox (Vulpes velox (Say, 1823)) was extirpated from Canada and Montana (USA) by 1969, but was reintroduced in the 1980s to Canada, and subsequently spread into northern Montana. Swift foxes in this region are at the current northern range edge where winter conditions are harsher and persist longer than in their southern range (i.e., Colorado (USA) to Texas (USA)). We collected fine-scale locational data from swift foxes fitted with global positioning system collars to examine movement and resource-use patterns during winter of 2016–2017 in northeastern Montana. Our results suggest that swift foxes displayed three distinct movement patterns (i.e., resting, foraging, and travelling) during the winter. Distance to road decreased relative probability of use by 39%–46% per kilometre across all movement states and individuals, whereas the influence of topographic roughness and distance to crop field varied among movement states and individuals. Overall, while our findings are based on data from three individuals, our study suggests that across movement states during the critical winter season, swift foxes are likely using topography and areas near roads to increase their ability to detect predators.