Evaluating drivers of recent large whale strandings on the East Coast of the United States.

Anthropogenic stressors threaten large whales globally. Effective management requires an understanding of where, when, and why threats are occurring. Strandings data provide key information on geographic hotspots of risk and the relative importance of various threats. There is currently considerable public interest in the increased frequency of large whale strandings occurring along the US East Coast of the United States since 2016. Interest is accentuated due to a purported link with offshore wind energy development. We reviewed spatiotemporal patterns of strandings, mortalities, and serious injuries of humpback whales (Megaptera novaeangliae), the species most frequently involved, for which the US government has declared an "unusual mortality event" (UME). Our analysis highlights the role of vessel strikes, exacerbated by recent changes in humpback whale distribution and vessel traffic.  Humpback whales have expanded into new foraging grounds in recent years. Mortalities due to vessel strikes have increased significantly in these newly occupied regions, which show high vessel traffic that also increased markedly during the UME. Surface feeding and feeding in shallow waters may have been contributing factors. We found no evidence that offshore wind development contributed to strandings or mortalities. This work highlights the need to consider behavioral, ecological, and anthropogenic factors to determine the drivers of mortality and serious injury in large whales and to provide informed guidance to decision-makers.

Análisis de las causantes de los recientes varamientos de ballenas en la costa este de los Estados Unidos Resumen El estrés antropogénico amenaza a las ballenas en todo el mundo. El manejo efectivo requiere comprender en dónde, cuándo y por qué ocurren las amenazas. Los datos de varamientos proporcionan información clave sobre los puntos críticos geográficos de riesgo y la importancia relativa de varias amenazas. Actualmente existe un interés público considerable por el incremento en la frecuencia de varamientos de ballenas que ocurren en la costa este de los Estados Unidos desde 2016, al cual el gobierno nacional ha denominado un "evento inusual de mortalidad" (EIM). El interés se acentúa debido a la supuesta conexión con el desarrollo de la energía eólica marina. Revisamos los patrones espaciotemporales de los varamientos, mortandad y lesiones graves de las ballenas jorobadas (Megaptera novaeangliae), la especie involucrada con mayor frecuencia. Nuestro análisis resalta el papel de las colisiones con navíos, agudizados por los cambios recientes en la distribución de la especie, y el tráfico de navíos. Las ballenas jorobadas se han expandido hacia nuevas áreas de forrajeo y los años recientes. La mortandad causada por las colisiones con navíos ha incrementado significativamente en estas regiones ocupadas recientemente, las cuales también muestran un tráfico elevado de navíos que también incrementó durante el EIM. La alimentación superficial y en áreas someras podrían ser factores contribuyentes. No encontramos evidencia de que la energía eólica marina contribuya a los varamientos o a la mortandad. Este trabajo resalta la necesidad de considerar los factores ecológicos, antropogénicos y de comportamiento para determinar las causas de la mortalidad y las lesiones graves en las ballenas y de proporcionar orientación informada para quienes toman las decisiones.

Trait-mediated shifts and climate velocity decouple an endothermic marine predator and its ectothermic prey.

Climate change is redistributing biodiversity globally and distributional shifts have been found to follow local climate velocities. It is largely assumed that marine endotherms such as cetaceans might shift more slowly than ectotherms in response to warming and would primarily follow changes in prey, but distributional shifts in cetaceans are difficult to quantify. Here we use data from fisheries bycatch and strandings to examine changes in the distribution of long-finned pilot whales (Globicephala melas), and assess shifts in pilot whales and their prey relative to climate velocity in a rapidly warming region of the Northwest Atlantic. We found a poleward shift in pilot whale distribution that exceeded climate velocity and occurred at more than three times the rate of fish and invertebrate prey species. Fish and invertebrates shifted at rates equal to or slower than expected based on climate velocity, with more slowly shifting species moving to deeper waters. We suggest that traits such as mobility, diet specialization, and thermoregulatory strategy are central to understanding and anticipating range shifts. Our findings highlight the potential for trait-mediated climate shifts to decouple relationships between endothermic cetaceans and their ectothermic prey, which has important implications for marine food web dynamics and ecosystem stability.

Microplastic abundance in gull nests in relation to urbanization.

Human activity and urbanization are having profound effects on natural landscapes and ecosystems. The presence and persistence of human-made materials such as microplastics can have major impacts on the health of organisms in both marine and terrestrial environments. We quantified microplastics in herring gull (Larus argentatus) and great black-backed gull (Larus marinus) nests at three colonies in the northeast United States that varied in their degree of urbanization: Jamaica Bay (JB) in New York City, Youngs Island (YI) on Long Island, New York, and Tuckernuck Island (TN) in Massachusetts. Nests in urban colonies contained a higher proportion of microplastics than those in the more remote colony. Our results link urbanization with microplastic accumulation in coastal environments and suggest that assessing microplastics in seabird nests could provide a means of evaluating microplastics encountered by seabirds and other coastal marine animals.

Closely related gull species show contrasting foraging strategies in an urban environment.

The expansion of urban landscapes has both negative and positive effects on wildlife. Understanding how different species respond to urbanization is key to assessing how urban landscapes influence regional wildlife behavior and ecosystem structure. Gulls are often described as strong urban adapters, but few studies have explored species-specific differences in habitat use. Here, we use GPS tracking in conjunction with stable isotope analysis (SIA) to quantify the habitat use and trophic ecology of great black-backed gulls (Larus marinus) and herring gulls (L. argentatus) in an urbanized area. Non-Metric Multidimensional Scaling (NMDS) of foraging locations revealed significant differences in the habitat use between species. Great black-backed gulls foraged primarily in marine habitats and herring gulls foraged primarily in specific urban habitats (e.g., landfills, dumpsters) and showed higher site fidelity in terms of the proportion of foraging sites revisited. Further, great black-backed gulls had significantly higher δ15N and δ13C than herring gulls, reflecting the use of marine, rather than urban, food sources. This study highlights the variability in urban habitat utilization among closely related species, assesses stable isotope signatures of urban diets in wild birds, and discusses ecological implications of the relative contribution of urban and marine foraging.

Effects of El Niño-driven changes in wind patterns on North Pacific albatrosses.

Changes to patterns of wind and ocean currents are tightly linked to climate change and have important implications for cost of travel and energy budgets in marine vertebrates. We evaluated how El Niño-Southern Oscillation (ENSO)-driven wind patterns affected breeding Laysan and black-footed albatross across a decade of study. Owing to latitudinal variation in wind patterns, wind speed differed between habitat used during incubation and brooding; during La Niña conditions, wind speeds were lower in incubating Laysan (though not black-footed) albatross habitat, but higher in habitats used by brooding albatrosses. Incubating Laysan albatrosses benefited from increased wind speeds during El Niño conditions, showing increased travel speeds and mass gained during foraging trips. However, brooding albatrosses did not benefit from stronger winds during La Niña conditions, instead experiencing stronger cumulative headwinds and a smaller proportion of trips in tailwinds. Increased travel costs during brooding may contribute to the lower reproductive success observed in La Niña conditions. Furthermore, benefits of stronger winds in incubating habitat may explain the higher reproductive success of Laysan albatross during El Niño conditions. Our findings highlight the importance of considering habitat accessibility and cost of travel when evaluating the impacts of climate-driven habitat change on marine predators.