David X. Soto

1. Despite their small size, bats are exceptional among terrestrial mammals because they can cover long distances in a short time due to their ability for powered flight [1,2]. In the northern temp...

During migration, individuals of migratory species occurring in a specific area can include a mixture of local breeding birds and migratory conspecifics from distant populations. In birds that are legally hunted during migration, the unknown extent of mixing between populations can be problematic for management. The Eurasian woodcock ( Scolopax rusticola ) is a forest‐dwelling wader with a wide Palearctic distribution, where migratory individuals from north‐eastern Europe mix with central European birds during autumn and winter. Because woodcocks are hunted in autumn and winter in Central Europe, poor knowledge of the timing of autumn migration complicates an assessment of to what extent hunting affects local breeding populations. Here, we quantified the timing of autumn migration of woodcocks breeding in a fully migratory population in Switzerland using ringing and tracking data ( n = 110 bird‐years). Additionally, we estimated the proportion of non‐local woodcocks shot in Switzerland using stable hydrogen isotopes ( δ ² H) in flight feathers of 842 individuals. We used a multistate mark‐resight model to estimate the weekly probability of migration departure from late July until the end of December, and developed a hierarchical assignment model to estimate the probability of shot woodcocks to be of non‐local origin, accounting for date and location of the harvest. We found that 95% of the local Swiss population had departed by 7 December (95% credible interval 28 Nov–18 Dec), but that >50% of local woodcocks were exposed to hunting pressure during the legal hunting period in October and November. We estimated that 90.2% (48.8%–99.8%) of shot woodcocks were of non‐local origin, but assigning individuals to an origin was highly uncertain. Practical implication . The late autumn migration departure in Switzerland exposes many locally breeding woodcocks to hunting pressure, and the proportion of local birds being shot was mostly determined by the dilution of local birds by more numerous migrants. A delay of the hunting season after November may further reduce the probability of shooting local birds, but to ensure the viability of migratory populations the hunting effort should be coordinated along the entire flyway.

1. Long-distance migration represents one of the most energetically costly life-history strategies in birds, where individuals often travel thousands of kilometres between breeding and non-breeding...

Aim: The islands of the Sunda Shelf in Southeast Asia represent a global biodiversity hotspot that is under severe threat from deforestation and agricultural expansion. Despite extensive knowledge of the geographic distribution and diversity of small carnivorous mammals coexisting in different habitats, information on how their feeding ecology relates to their persistence (or extinction risk) is lacking for most of them. Here we studied the past history of ecological functions of Southeast Asian carnivorous mammals in their natural ecosystems. Location: Southeast Asia. Time Period: Museum collection of specimens at a period between now and > 150 years ago. Major Taxa Studied: Small carnivorous mammals. Methods: We analysed stable carbon ( δ ¹³ C) and nitrogen ( δ ¹⁵ N) isotope ratios in hair samples from 452 museum specimens of 17 carnivore species, collected over historic times from the Sunda Shelf and mainland Southeast Asia. We estimated dietary niches by calculating isotopic niches for each species and biogeographic region. Results: We established general dietary patterns and niche partitioning for 17 small carnivore mammal species from Southeast Asia, which suggests that these species are flexible with respect to their feeding strategies that occur in response to sympatry, environmental heterogeneity and resource competition. Our results revealed significant differences between Felidae and Viverridae in their respective δ ¹⁵ N and δ ¹³ C values, with lower values for both isotopes in the preferentially fruit‐eating Viverridae. Remarkably, species listed as endangered by the IUCN Red List (e.g., flat‐headed cat, Prionailurus planiceps , and otter civet, Cynogale bennettii ) separated in their isotopic niches from those with more favourable conservation statuses, indicating vulnerable feeding strategies. Main Conclusions: These findings indicate that endangered species from aquatic environments had a higher degree of niche specialisation than closely related species, emphasising the need for targeted conservation efforts to protect the ecological function of these species and their natural habitat.

Stable isotopes of carbon (δ¹³C) and nitrogen (δ¹⁵N) are increasingly employed to study the foraging ecology of ectothermic predators like crocodilians. However, accurate and precise estimations of trophic discrimination factors between diet and crocodile tissues (Δ¹³C and Δ¹⁵N) from captive experiments under controlled conditions are necessary to reliably quantify the contribution of different prey items make to their diet. The issue of an isotopically constant diet which leads to isotope equilibrium is an important factor influencing accurate estimations of diet-tissue discrimination factors. We raised Nile crocodiles (Crocodylus niloticus) under controlled experimental conditions feeding them with two isotopically distinct (but constant) diets until tissues reached isotopic equilibrium. We sampled blood (plasma and red blood cells, RBC), scute keratin and collagen, and nail tissues throughout the experiment to estimate diet-tissue discrimination factors. Overall, our estimations of average diet-tissue discrimination factors for δ¹³C were +0.2 ‰ for plasma, +0.1 ‰ for RBC, +0.2 ‰ for keratin, +1.9 ‰ for collagen, and +1.2 ‰ for nail tissue, while for δ¹⁵N values were -0.6 ‰ for plasma, +1.5 ‰ for RBC, +1.5 ‰ for keratin, +2.3 ‰ for collagen, and +1.8 ‰ for nail tissue. Body size did not have a significant effect on these tissue estimates, but plasma Δ¹⁵N was influenced slightly. Understanding these differences in ectotherm isotope ecology is crucial for interpreting trophic relationships within food webs that include animals such as reptiles.

Wind turbines used to combat climate change pose a green-green dilemma when endangered and protected wildlife species are killed by collisions with rotating blades. Here, we investigated the geographic origin of bats killed by wind turbines along an east-west transect in France to determine the spatial extent of this conflict in Western Europe. We analysed stable hydrogen isotopes in the fur keratin of 60 common noctule bats ( Nyctalus noctula ) killed by wind turbines during summer migration in four regions of France to predict their geographic origin using models based on precipitation isoscapes. We first separated migratory from regional individuals based on fur isotope ratios of local bats. Across all regions, 71.7% of common noctules killed by turbines were of regional and 28.3% of distant origin, the latter being predominantly females from northeastern Europe. We observed a higher proportion of migratory individuals from western sites compared to eastern sites. Our study suggests that wind-turbine-related losses of common noctule bats may impact distant breeding populations across whole Europe, confirming that migratory bats are highly vulnerable to wind turbines and that effective conservation measures, such as temporary curtailment of turbine operation, should be mandatory to protect them from colliding with the rotating blades of wind turbines.

Various approaches based on the natural variations of carbon isotopes (C-14 and C-13) in dissolved inorganic carbon (DIC) are routinely used to study groundwater dynamics and to estimate recharge rates by deriving groundwater ages. However, differences in C-14 activities in groundwater samples collected repeatedly from the same wells and discordantly young C-14 groundwater ages compared to noble gases led some authors to question the validity of radiocarbon dating. Poor sampling protocols and storage effects (C-14 contamination) for radiocarbon analysis are a critical factor in explaining age determination discrepancies. We evaluated the impact of storage protocols on carbon isotope exchange with atmospheric carbon dioxide by comparing glass versus standard plastic field sampling bottles for various storage times before radiocarbon and C-13 analyses. The C-14 bias after 12 months in pre-evacuated glass vials was minimal and within analytical precision. However, storage of DIC samples in plastic sampling bottles led to marked changes in C-14 and C-13 contents (up to similar to 15 pmC and similar to 5 parts per thousand, respectively, after 12 months), meaning contamination led to younger groundwater age estimations than it should have been. Protocols for sampling and storing DIC samples for radiocarbon using pre-evacuated glass bottles help avoid atmospheric (CO2)-C-14 contamination and microbial activity.

Marine migration patterns of unique or regional stocks of Salmo salar (Atlantic Salmon) are poorly known. Atlantic Salmon (AS) utilizing the North Atlantic Subpolar Gyre (NASpG) for foraging and growth consist of stocks from the United States (41°N) to Greenland (64°N) in the western Atlantic and from Spain (41°N) to Norway (70°N) in the eastern Atlantic. Wide latitudinal range and unique riverine characteristics probably result in stocks selecting differing suites of marine sea-surface temperatures (SST) within the species' known selection range (i.e., their Grinnellian niche). We analyzed trends in stable carbon isotope (δ13C) composition from archived scale tissues in relation to long-term variation of SST for the North Atlantic Ocean to identify marine feeding regions used by adult AS successfully returning to the Saint John River, Canada, during the period 1982–2011. Marine foraging regions were determined for individuals that spent 1 winter (1SW) or multiple winters (MSW) at sea. During 1982–1991 and 1992–2001, AS which successfully returned, exploited more southern regions of the NASpG, while returning adults from 2002–2011 exploited more northern regions. Historically presumed marine feeding regions, which were identified by the isotopic model as probable during 1982–2001, have experienced a warming trend, and data suggests that AS returning to the Saint John River have been migrating further north in the NASpG in response to recent global climate change. The northward range shift as the North Atlantic warmed is consistent with recent biogeographical changes found among other marine species also following their Grinnellian niche.