An Investigation into How Marine Mammal Distribution Is Being Affected by Climate Change, with a Focus on Out of Habitat Marine Mammals, Based on Expert Opinion

Climate change is altering the marine environment in many ways, including increasing sea surface temperatures and decreasing sea ice. Species distributions are changing and ‘out of habitat’ marine mammals are being recorded. ‘Out of habitat’ (OOH) refers to individuals recorded outside of their natural range or within environments unsuitable for their survival. This phenomenon is currently understudied. This study aimed to identify the scale of the issue, identify consensus opinions on trends and possible causes of these OOH events, as well as assessing the preparedness of local authorities and rescue networks in responding to OOH marine mammals. This study is the first to assess and quantify this issue through a formal consultation process, conducted through an online questionnaire and a detailed examination of two case studies, from the UK and Peru. Sixty-three questionnaire responses were received from six different continents and the majority (60%) reported OOH events in their region. Through the questionnaire and case studies, 42 different marine mammal species were reported to be affected. This clearly indicates this is a global phenomenon, affecting at least 32% of all known pinniped and cetacean species. Most participants (77%) also believed these OOH events are increasing, and 55% believe these events are forerunners to distribution changes. Data from Peru showed an endangered species, the Galápagos fur seal (Arctocephalus galapagoensis), had made a range shift. Of the reported OOH species, four are classified as either endangered or critically endangered. The consensus opinion was that climate change is the leading driver of these OOH events, with sea surface temperatures and changes in prey distribution reported as the most important factors. The success of OOH responses was reported as highly inconsistent and, in many cases, requires specialist training, e.g., in human–wildlife conflict. The information derived from this study can be used to advise conservation plans, as well as provide a foundational step for future research into the possible trends in these OOH movements.