International Fund for Animal Welfare

Anthropogenic pressures have increased the emergence and spread of infectious diseases in wildlife in recent decades, with cascading impacts on ecosystem dynamics and elevated risk to public health. Understanding factors that contribute to disease severity, and population- and community-level impacts, is critical to predicting and mitigating infectious disease outbreaks. We aimed to investigate how host genetic factors contribute to harbor seal susceptibility to phocine distemper virus (PDV), a virus that has caused variable levels of mortality among pinniped populations across the North Atlantic. We conducted whole-genome sequencing of harbor seals that were stranded during and after a PDV outbreak that occurred in the Northeastern United States in 2018 and used genome-wide association and FST-based approaches to identify genetic variants putatively associated with survival. A subset of harbor seals (10 cases, 10 controls) were sequenced at high coverage (~58×) to generate a reference haplotype panel and impute genotypes in the remaining samples (37 cases, 45 controls), which were sequenced at a lower coverage (~4×). On investigation of 148,644 filtered single nucleotide polymorphisms, we identified 33 candidate genes related to innate and adaptive immunity and 37 genes related to the nervous system that were associated with harbor seal survival. These results provide further evidence for the importance of immunogenetic variation and highlight additional key pathways and biological processes that may confer resistance to PDV. Genome-wide approaches, which can reveal the complexity of genetic variation underpinning disease-associated traits, are critical tools to help us understand and potentially predict the impact of future disease outbreaks.

Natural infections of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been documented in over 60 animal species, some distantly related. Several marine mammals have been predicted as highly susceptible to SARS-CoV-2 infection based on the homology of their ACE2 receptors to those of humans. To assess potential exposure of marine mammals to SARS-CoV-2, we conducted an opportunistic survey from 2020 to 2025 and tested 1,808 swabs and 378 serum samples from 21 marine mammal species in the United States. All the swabs tested by RT-qPCR were negative, indicating the absence of active infection. A low level of SARS-CoV-2 neutralizing antibodies was detected in three pinniped species, including Phoca vitulina (harbor seal, 13.6%, 95% CI: 5.2-27.4%), Zalophus californianus (California sea lion, 7%, 95% CI: 1.9-17.0%), and Halichoerus grypus (grey seal, 3.7%, 95% CI: 0.5-12.7%). These findings represent the first serological evidence of SARS-CoV-2 exposure in marine mammals in the United States, highlighting the need for continued monitoring of these populations and further research on SARS-CoV-2 transmission dynamics in wildlife.

Vocalisation rates were measured from North Atlantic right whales (Eubalaena glacialis) in spring 1999-2000 in the Great South Channel and off Cape Cod, USA, and in summer 1999-2000 in the Bay of Fundy, Canada. Vocalisations were classed as either ‘moans’, ‘low-frequency (LF) calls’ or ‘gunshots’. Towed hydrophone recordings (36.1 hours) were made in 21 encounters where loose aggregations of right whales were within about 1,000m. Recordings were also made using acoustic tags attached by suction cups to ten different whales (29.5 hours). Tags also recorded depth data. Moan rates (sounds per aggregation per hour) were correlated with size of whale aggregation. Individual whales produced moans at ~ 0-10 per hour (recorded from tags and the towed hydrophone). Small aggregations (2-10) gave higher moan rates (usually < ~ 60 per hr) and larger aggregations ( > 10) higher still ( ~ 70-700 per hr) (recorded from towed hydrophone). Results from the Bay of Fundy indicate high moan rates at night. Moans were usually produced in clusters. Tag data showed that moans were usually produced when whales were within about 10m of the surface. A passive acoustic system could potentially provide supplementary information on the distribution of aggregations of right whales. This could be useful for management (1) in the long term, by aiding the prediction of right whale distribution, or (2) as a real-time tool for helping to route shipping away from concentrations of right whales. The empirical evidence presented here on vocalisation rates will assist in assessing feasibility. The clustering of moans and the tendency to produce them near the surface could hamper detection and localisation efforts. Further research is underway to investigate other important practical issues such as detectability and source levels.

Animal tolerance towards humans can be a key factor facilitating wildlife–human coexistence, yet traits predicting its direction and magnitude across tropical animals are poorly known. Using 10,249 observations for 842 bird species inhabiting open tropical ecosystems in Africa, South America, and Australia, we find that avian tolerance towards humans was lower (i.e., escape distance was longer) in rural rather than urban populations and in populations exposed to lower human disturbance (measured as human footprint index). In addition, larger species and species with larger clutches and enhanced flight ability are less tolerant to human approaches and escape distances increase when birds were approached during the wet season compared to the dry season and from longer starting distances. Identification of key factors affecting animal tolerance towards humans across large spatial and taxonomic scales may help us to better understand and predict the patterns of species distributions in the Anthropocene.