Whales in rivers, seals in cities: New study documents animals from more than one third of marine mammal species outside of their normal habitats
A new study systematically documents the scale of “out-of-habitat” events in marine mammals for the first time.
- At least one third of known whale and seal species are affected: Individuals of 42 species have been recorded outside their usual habitats or in unsuitable environments
- Extreme cases: Several Arctic walruses have been sighted in warmer European waters; whales have been seen in the Thames and Seine rivers; Galápagos fur seals have established themselves nearly 2,000 kilometres from their native range
- Climate change likely the main driver: rising sea temperatures and changes in prey distribution are most frequently believed to be the causes
Whether it is the humpback whale “Timmy” stranded in the Baltic Sea in Germany or now “Magnus”, the walrus visiting the coast of Scotland – animals far outside their natural habitats capture public attention and empathy.
However, these cases are not isolated incidents. A new study now shows for the first time that marine mammals are increasingly appearing in places where they do not belong – far outside their natural ranges, including up rivers and in coastal cities.
Published in the journal Diversity, the study is the first to systematically assess the global scale of so-called “out-of-habitat” (OOH) events in marine mammals. This includes animals occurring outside their natural range, or within it but under conditions unsuitable for their survival.
The findings are clear: experts from six continents documented 42 species observed “out of habitat” – representing around a third of all known whale and seal species. Some three quarters of respondents reported that such events are increasing, and more than half see them as early indicators of broader distribution shifts.
Climate change is reshaping habitats
Respondents identified rising sea surface temperatures and shifts in prey distribution as the most important factors. According to the researchers, climate change is likely the central driver of this development.
This is particularly visible in striking cases: walruses have repeatedly been sighted far south of their Arctic range in Europe. A minke whale has been recorded in London, and a beluga entered the River Thames. In Peru, Galápagos fur seals – an endangered species – have now established a third-generation colony on an island around 1,800 kilometres from their original native habitat.
Not all regions are prepared
The study also shows that responses to such events are highly inconsistent. Only 40 percent of respondents considered their local authorities or rescue networks to be adequately prepared, while 46 percent viewed them as insufficiently prepared.
Large marine mammals, especially in densely populated areas, pose major challenges for rescue teams. In addition to expertise, clear protocols, resources and training are required – including for managing potential human–wildlife conflicts.
Mark Simmonds, Director of Science at OceanCare and co-author of the study, said:
“When walruses appear on the shores of Europe and whales appear far from their usual home ranges these are not curious one-off events. They are a warning of how profoundly our oceans are already changing. This study shows for the first time that this is a global phenomenon that must be taken much more seriously.”
Laetitia Nunny, Senior Science Officer at OceanCare and co-author, added:
“Marine mammals are highly sensitive to environmental change. As ocean temperatures, prey availability and habitats shift, these animals are forced to move. The priority now is to adapt conservation and response systems to this new reality in order to protect the welfare of both animals and people.”
OceanCare therefore calls for the following steps to better integrate “out-of-habitat” events into conservation, research and response strategies:
- improved international monitoring of such cases
- clear protocols for rescue operations
- stronger support for regional rescue networks
- decisive reduction of greenhouse gas emissions
Further information
Authors: Maia Killian, Laetitia Nunny, Dan Jarvis, Lewis Griffin, Carlos Yaipen-Llanos, Anna Pili und Mark Simmonds
Content-related questions: Laetita Nunny
Press contact
Anton Mattmüller, International Media Relations Officer
amattmueller@oceancare.org, +43 681 106 193 66