In a world first, it has been found leopard seals in New Zealand have been feeding on sharks.
While leopard seals are apex predators who have been known to feast on penguins and other seals, this is the first time researchers have found evidence that sharks are also on the menu.
The researchers, from groups, institutes and universities throughout New Zealand and Australia, sorted through more than 100 leopard seal poos to compile the evidence.
Dr Krista van der Linde from LeopardSeals.org, the senior author of the study, said the find was “next level incredible.”
“We were blown away to find sharks were on the menu, but then we also found that elephant fish and ghost sharks were being hunted by the leopard seals,” van der Linde said.
“These fish have large spines which help protect them from predators and sure enough there were wounds on the leopard seals, sometimes even big spines embedded in their faces – one leopard seal had at least 14 such wounds.”
Dr Ingrid Visser, the co-founder of LeopardSeals.org and a co-author on the study, said she had studied orcas for 30 years and had seen them eat sharks regularly.
However, it was surprising that leopard seals were doing this too.
“To know there is another marine mammal also munching on sharks, well, that has implications for the whole food web and our understanding of how it all is interlinked.”
The high level of shark remains they found in the poo meant sharks may be an important part of the leopard seals’ diet, van der Linde added.
Leopard seals are a protected species, mostly found in sub-Antarctic and Antarctic areas.
Leopard seals can remain under the water for approximately 15 minutes during a dive. They have been recorded diving to depths of 304 meters! However, the majority of dives stay within 10m – 50m of the surface as leopard seals are predominantly feeding on prey found within this zone.
Click here to see a video from photographer Paul Nicklen where he shares his story of diving with a leopard seal female in Antarctic waters. Please note, some of the content shows dead penguins.
Leopard seals are known to be very vocal (underwater) during the summer months. Males can produce at least five different, distinctive types of sound:
- High double trill
- Medium single trill
- Low descending trill
- Low double trill
- Hoots with single low trill.
These sounds are presumed to be a part of a “long-range acoustic display” for territorial purposes and/or to attract a mate. Females are known to vocalise when they have elevated reproductive hormones (helping them find a mate) and to get their pups attention when they return to the ice after a foraging trip.
Click here to listen to the sounds a leopard seal can make.
Leopard seals are opportunistic feeders and will prey on anything ranging from krill, squid, fish, sea birds, penguins and even … other seals! Leopard seals on the other hand only have one real predator to worry about: the orca. Click here to view a video from BBC Earth showing how a leopard seal hunts for penguin.
Leopard seals have a very unique set of teeth. Their molars are ‘trident’ shaped allowing them to ‘filter feed’ as they swim, trapping krill in their mouths as the sea water passes through. Their canine teeth can be as long as 2.5cm and are primarily used for grabbing and holding onto prey species such as penguins and fishes, while the other front teeth are used for tearing and cutting up larger prey items.