From traits to threats : a global assessment of marine mammal vulnerability

According to IUCN, 27% of marine mammal species are currently classified as Critically Endangered, Endangered or Vulnerable, primarily due to anthropogenic threats. Globally, 98% of marine mammal species are documented to be affected by at least one threat. Effective conservation and extinction prevention require identifying species-specific risks; however, this is hindered by limited data on population size and life history, as well as by the lack of comprehensive assessments evaluating species’ vulnerability to specific threats. To address this gap, we assessed the vulnerability of 125 marine mammal species to 9 major threats: by-catch, commercial harvesting, pollution from solid and liquid wastes, noise pollution, boat collisions, infections, food limitation, and climatic ocean events. The species-specific vulnerability models incorporated a global database of documented threats to marine mammals and 22 potentially critical ecological traits available for 108 marine mammal species. RandomForest and generalized linear models were applied to identify which, and how, specific ecological traits represent a predisposition for species to be affected by different threats. Results indicate that range size, age at sexual maturity, preferred sea surface temperature, longevity, dive depth, group size, body size, and swim speed are important risk factors. However, the importance of the traits differed by threat type. These findings enhance understanding of the traits that drive species-specific vulnerability to particular threats and, importantly, provide a framework for inferring the vulnerability of poorly studied species by identifying shared ecological characteristics with better-known species. This approach is useful for guiding conservation decisions when species-specific data are limited.