Climate crisis puts Antarctic sea lion survival at risk, study finds

It is increasingly difficult for female sea lions to access krill, a vital crustacean in their diet, during the breeding season due to the effects of climate change. which puts their survival at risk, according to a study done by marine biologists from the University of Barcelona.

The research, published in the scientific journal Scientific Reports, has been done through telemetry by researchers from the Faculty of Biology and the Biodiversity Research Institute of the University of Barcelona (IRBio) Lluís Cardona, Manel Gazo, David March, Massimiliano Drago and Diego Rita, and the researcher from the association SUBMON, Mariluz Parga.

Cardona explains to EFE that thawing caused by global warming has reduced krill populations, as they are closely linked to the extent of ice, which has a negative effect on the reproductive success of the species.

In addition, according to the biologist, the number of penguins in the area, the main prey of the leopard seal, has also decreased, so hunting of sea lion cubs by this predator has increased.

The study has been carried out thanks to satellite telemetry, a method that consists of placing small devices on mammals to collect information from a distance through magnetic waves, a process that has allowed the Antarctic lion to be studied in the winter months , when cold, wind and sea ice make it difficult to study Antarctic ecosystems.

The sea lion, a mammal that lives exclusively in Antarctic waters, was heavily exploited by the leather industry in the first half of the 19th century and, although it experienced a remarkable recovery, the populations of this animal have decreased again since 2003.

“In summer, the sea lions return to the breeding colonies, and the decrease in krill, which is much easier to catch than fish, affects the females, that they cannot devote so much energy to hunting with their young on land“, Says Cardona.

During the winter, however, the animals are separated, and while the females go to warmer areas near the south of the American continent, the males follow the krill to the Antarctic areas.

For this reason, the team of experts, which carried out the research since 2019 in the Antarctic base of the South Shetland Islands archipelago, mostly followed the young males, who represent more than 80% of the specimens that are they remain in Antarctic waters during the winter.

“The areas in which males spend most of the winter, which are less than 1,000 meters deep, a high level of chlorophyll and a temperature of less than 2 ° C, coincide with the preferred habitat of Antarctic krill,” he says Cardona.

Male sea lions follow krill to deep areas

The study has revealed that as winter progresses, krill migrate to deeper areas and male sea lions follow them to feed, reaching submerge up to 180 meters.

The physical differences between males and females of the species may explain why they prefer to stay in less cold areas even though their basic food is scarce.

The body mass of females varies between 20 and 50 kilograms, while that of males can reach 140, what conditions skills such as the ability to immerse or regulate its temperature, essential to adapt to an extreme environment and to feed successfully.

“More body mass implies more capacity to store oxygen reserves and, therefore, easier to dive deeper in prolonged apneas in search of food”, emphasizes Cardona.

In addition to the problem of reduced food, the high adult mortality of males defending the breeding territory causes them to live for a few years and, therefore, the youngest specimens predominate, unlike the females, which predominate adult specimens.

Cardona remembers that climate change is altering the ecosystems of the peninsula and the Atlantic Ocean, and warns that species such as the sea lion are exposed to these transformations that can affect their survival.

“To adapt to these changes, colonies of sea lions should move south along the Antarctic peninsula, but this is an extremely slow and unlikely process, since females tend to breed in the same place where they were born ”, concludes Cardona. (I)