Smaller Seals: A Consequence of Climate Change

Antarctic fur seals are being born smaller and breeding less, experts are reporting. This, they say, is a direct result of changing climate conditions in their natural habitats.

A study recently published in the journal Nature details how nearly three decades of data is showing an alarming trend: fur seal pups, namely the females, are being born smaller and smaller.

"Over 27 years, we see pups being born with eight percent less body mass. We also see the females breeding later in age - at least by one or two years," explained study author Jaume Forcada.

Forcada, a member of the British Antarctic Survey, told BBC News that when these females finally choose to start breeding, they are much larger than they were 30 years ago.

That is definitely not a good thing, the researcher said. When mammals start waiting until they are fatter to have children, it shows that they are worried that they won't have access to enough food later in the season. They pack in as much excess energy as they can prior to pregnancy to make sure developing pups receive adequate nutrients prior to being birthed.

"This kind of thing has been seen before in all sorts of mammals, and is classically an indication of food stress," Forcada added.

The study focused on fur seal populations on the coast of South Georgia, an island south-east of South America. Here, the fur seals rely heavily upon Antarctic krill populations to survive.

Unfortunately, these tiny crustaceans have been in sharp decline in recent years as their reproduction habitats are heavily dependant on sea ice from the White Continent.

Interestingly, the study also notes that while genetic diversity among fur seal populations has been on the rise, the seals around South Georgia show the same genetic pattern each generation, indicating that all weaker genetic inheritance is being quickly weeded out by harsh birthing conditions.

"They're showing a selection process that acts mostly through the survival of the fit young females, and then at each generation the clock re-sets," Forcada said.

The study goes on to warn that if this trend continues, breeding success will likewise continue to dwindle until fur seals disappear from the island all together.