Oh yeah, the researchers still need to collect evidence.
From an Alfred Wegener Institute for Polar and Marine Research media release:
Global warming is having an effect on the dive behaviour and search for food of southern elephant seals. Researchers from the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association cooperating in a joint study with biologists and oceanographers from the Universities of Pretoria and Cape Town have discovered that the seals dive deeper for food when in warmer water. The scientists attribute this behaviour to the migration of prey to greater depths and now wish to check this theory using a new sensor which registers the feeding of the animals below water.
The southern elephant seals from Marion Island, located in the south western part of the Indian Ocean, are extreme divers in the truest sense of the word. The animals spend more than 65 per cent of their lives in depths of over 100 metres, diving far deeper than their fellow species in southern areas. The maximum dive depth of these seals is over 2000 metres. However, the water masses through which the elephant seals from Marion Island swim in search of food are becoming increasingly warmer due to climate change and are forcing the animals to dive deeper. The Southern Ocean is warmed primarily in the water levels up to a depth of 1000 metres and therefore in those areas in which squid and fish ought to be found. “This prey is moving down to greater depths presumably due to the increasing water temperatures and this is forcing the seals to follow them“, explains Dr. Horst Bornemann from the Alfred Wegener Institute.
Over the course of several years he and his colleague Dr. Joachim Plötz together with Dr. Trevor McIntyre and other seal researchers from the Mammal Research Institute (MRI) in South Africa have fitted over 30 elephant seals with satellite transmitters. These transmitters, the size of a fist, are attached to the head of the seals using artificial resin immediately after moulting and measure the dive depth, water temperature and salinity every time the animals dive. When the animal resurfaces to breathe the transmitters send their data to the respective research institutes via satellite. The results show that the elephant seals need to dive deeper in warmer water so that they ultimately have less time to actually search for food. “We therefore assume that the animals will find less prey in warmer water masses“, explains Joachim Plötz.
The scientists from Bremerhaven will be going back to Marion Island in April of this year to collect evidence for their theory… [Emphasis added]