Rachael A. Orben

North American river otters (Lontra canadensis) are generalist aquatic predators inhabiting both freshwater and coastal ecosystems that are capable of shifting their foraging strategy to use locally available prey. To understand how the diversity and composition of their diets change across a habitat gradient, we identified prey remains in river otter scat samples (n = 675) collected from both freshwater and estuarine areas of 6 coastal rivers in southern Oregon during the summers of 2023 and 2024. These rivers were spread across ∼120 km of coastline and varied substantially in their hydrology and tidal influence. The Shannon diversity of prey items in river otter scat increased in association with ocean proximity along the lengths of individual rivers, suggesting an increase in both the evenness and richness of prey taxa consumed in estuarine areas. Dietary dissimilarity between rivers was significantly higher in estuaries than in freshwater areas, suggesting that the complexity and variability of estuarine habitats drove an expansion of river otter dietary niches. A multivariate probit model demonstrated that while salinity and ocean proximity were the most important variables for explaining prey occurrence, other habitat variables (river flow volume and velocity) also have significant predictive importance. While overall dietary diversity increased, there was no notable change in the general types of prey taken—river otter diets shifted from a freshwater diet dominated by crayfish (60% frequency of occurrence [FO]), prickly sculpin (14% FO), and stickleback (14% FO) to an estuarine diet characterized by saddleback gunnel (23% FO), crab (21% FO), prickly sculpin (19% FO), and staghorn sculpin (10% FO). Salmonid smolts (genus Oncorhynchus) were an occasional prey item throughout all habitat types (2.6% FO). We conclude that both the alpha and beta diversity of river otter diets increase in ecologically complex estuarine habitats, but that this change is not driven by the expansion of their foraging strategy to include truly novel prey types.

Animal telemetry is maturing into a viable method for observing the ocean as it can be used to monitor both environmental conditions and biological metrics along the movement trajectories of marine animals. As part of the Cormorant Oceanography Project, we have augmented a biologging tag with an external fast response temperature sensor to collect ocean temperature profiles from the backs of foraging marine birds. Cormorants dive between 50 and 250+ times a day to forage for prey so they can provide hard-to-match temporal and spatial coverage of coastal ocean conditions within their foraging areas. We process tag measurements to obtain fundamental oceanographic data (e.g., temperature profiles, bottom soundings, surface current measurements). Together, we have tracked 17 marine bird species (including two Spheniscus penguins spp. and a sea duck), originating from 17 countries and foraging along the edges of all major oceans. Tagged birds’ distribution included 191 MPAs in 26 countries, offering a unique ocean monitoring method to complement more widely used methods.

Animal movement and population connectivity are key areas of uncertainty in efforts to understand and predict the spread of infectious disease. The emergence of highly pathogenic avian influenza (HPAI) in South America poses a significant threat to globally significant populations of colonial breeding marine predators in the South Atlantic. Yet, there is a poor understanding of which species or migratory pathways may facilitate disease spread. Compiling one of the largest available animal tracking datasets in the South Atlantic, we examine connectivity and inter‐population mixing for colonial breeding marine predators tagged at the Falkland Islands. We reveal extensive connectivity for three regionally dominant and gregarious species over the Patagonian Shelf. Black‐browed albatrosses (BBA), South American fur seals (SAFS) and Magellanic penguins (MAG) used coastal waters along the Atlantic coast of South America (Argentina and Uruguay). These behaviours were recorded at or in close proximity to breeding colonies and haul‐out areas with dense aggregations of marine predators. Transit times to and from the Falkland Islands to the continental coast ranged from 0.2–70 days, with 84% of animals making this transit within 4 days ‐ a conservative estimate for HPAI infectious period. Our findings demonstrate BBA, SAFS and MAG connectivity between the Falkland Islands and mainland South America over an expansive spatial network and numerous pathways, which has implications for infectious disease persistence, transmission and spread. This information is vital in supporting HPAI disease surveillance, risk assessment and marine management efforts across the region.

Pelagic seabirds cover large distances efficiently and thus may reach a variety of marine habitats during breeding. Previous studies using stable isotope data and geolocators suggested that Thin-billed Prions breeding in the Falkland Islands in the Southwest Atlantic may forage in temperate waters over the Patagonian Shelf or cross the Drake Passage to forage in Antarctic waters south of the Polar Front. We deployed miniature GPS dataloggers to track Thin-billed prions in the Falkland Islands during incubation (3 seasons) and chick-rearing (2 seasons). Thin-billed Prions had a wide distribution during incubation, covering latitudes between 43 and 60° S, with trip lengths of ca. 2000 km over seven days, on average. Thin-billed Prions from two nearby sites (60 km apart) were spatially segregated in their incubation trips, with New Island Thin-billed Prions foraging over the Patagonian Shelf, compared to Thin-billed Prions from Bird Island, that foraged in the region of the Polar Front. During chick-rearing, Thin-billed Prions from New Island undertook both long trips to the Patagonian Shelf and south of the Polar Front (30% of trips were 5–11 days), and short trips (70% of trips were 1–4 days) when they foraged more locally, including in inshore waters around the Falkland Islands. Females carried out more trips to distant sites. Thus, Thin-billed showed a high flexibility in foraging areas, habitats and foraging trip durations, which enable them to benefit from both, temperate and Antarctic environments.

The Cormorant Oceanography Project is using sensors deployed on diving marine birds to collect broadly distributed oceanographic data in coastal regions around the world.

Static (fixed‐boundary) protected areas are key ocean conservation strategies, and marine higher predator distribution data can play a leading role toward identifying areas for conservation action. The Falkland Islands are a globally significant site for colonial breeding marine higher predators (i.e., seabirds and pinnipeds). However, overlap between marine predators and Falkland Islands proposed Marine Managed Areas (MMAs) has not been quantified. Hence, to provide information required to make informed decisions regarding the implementation of proposed MMAs, our aims were to objectively assess how the proposed MMA network overlaps with contemporary estimates of marine predator distribution. We collated tracking data (1999–2019) and used a combination of kernel density estimation and model‐based predictions of spatial usage to quantify overlap between colonial breeding marine predators and proposed Falkland Islands MMAs. We also identified potential IUCN Key Biodiversity Areas (pKBAs) using (1) kernel density based methods originally designed to identify Important Bird and Biodiversity Areas (IBAs) and (2) habitat preference models. The proposed inshore MMA, which extends three nautical miles from the Falkland Islands, overlapped extensively with areas used by colonial breeding marine predators. This reflects breeding colonies being distributed throughout the Falklands archipelago, and use being high adjacent to colonies due to central‐place foraging constraints. Up to 45% of pKBAs identified via kernel density estimation were located within the proposed MMAs. In particular, the proposed Jason Islands Group MMA overlapped with pKBAs for three marine predator species, suggesting it is a KBA hot spot. However, tracking data coverage was incomplete, which biased pKBAs identified using kernel density methods, to colonies tracked. Moreover, delineation of pKBA boundaries were sensitive to the choice of smoothing parameter used in kernel density estimation. Delineation based on habitat model predictions for both sampled and unsampled colonies provided less biased estimates, and revealed 72% of the Falkland Islands Conservation Zone was likely a KBA. However, it may not be practical to consider such a large area for fixed‐boundary management. In the context of wide‐ranging marine predators, emerging approaches such as dynamic ocean management could complement static management frameworks such as MMAs, and provide protection at relevant spatiotemporal scales.

Understanding encounters between marine predators and fisheries across national borders and outside national jurisdictions offers new perspectives on unwanted interactions to inform ocean management and predator conservation. Although seabird–fisheries overlap has been documented at many scales, remote identification of vessel encounters has lagged because vessel movement data often are lacking. Here, we reveal albatrosses–fisheries associations throughout the North Pacific Ocean. We identified commercial fishing operations using Global Fishing Watch data and algorithms to detect fishing vessels. We compiled GPS tracks of adult black‐footed Phoebastria nigripes and Laysan Phoebastria immutabilis albatrosses, and juvenile short‐tailed albatrosses Phoebastria albatrus. We quantified albatrosses‐vessel encounters based on the assumed distance that birds perceive a vessel (≤30 km), and associations when birds approached vessels (≤3 km). For each event we quantified bird behaviour, environmental conditions and vessel characteristics and then applied Boosted Regression Tree models to identify drivers and the duration of these associations. In regions of greater fishing effort short‐tailed and Laysan albatrosses associated with fishing vessels more frequently. However, fishing method (e.g. longline, trawl) and flag nation did not influence association prevalence nor the duration short‐tailed albatrosses attended fishing vessels. Laysan albatrosses were more likely to approach longer vessels. Black‐footed albatrosses were the most likely to approach vessels (61.9%), but limited vessel encounters (n = 21) prevented evaluation of meaningful explanatory models for this species of high bycatch concern. Temporal variables (time of day and month) and bird behavioural state helped explain when short‐tailed albatrosses were in close proximity to a vessel, but environmental conditions were more important for explaining interaction duration. Laysan albatrosses were more likely to associate with vessels while searching and during the last 60% (by time) of their trips. Our results provide specific species–fisheries insight regarding contributing factors of high‐risk associations that could lead to bycatch of albatrosses within national waters and on the high seas. Policy implications. Given the availability of Global Fishing Watch data, our analysis can be applied to other marine predators—if tracking data are available—to identify spatio‐temporal patterns, vessel specific attributes and predator behaviours associated with fishing vessel associations, thus enabling predictive modelling and targeted mitigation measures.