First evidence that leopard seals feed on sharks, researchers find | marine life
In a world first, leopard seals in New Zealand have been found to feed on sharks, making them part of a small and exclusive club of marine predators that do.
The study, led by Krista van der Linde of leopardseals.org, found shark remains in leopard seal feces and visible signs of wrestling with sharks on the seals’ bodies, indicating that marine mammals predate sharks rather than recovering their remains.
“We were blown away that sharks were on the menu,” Van der Linde said.
“But then we also discovered that elephant fish and ghost sharks were also hunted by the leopard seals. These fish have large spines to protect them from predators and of course there were wounds on the leopard seals. , sometimes even large thorns embedded in their face.A leopard seal had at least 14 such injuries.
Van der Linde doesn’t know why seals target sharks, especially given the risk of hunting them. “There could be something nutritionally about sharks that makes them desirable, it could be kind of a treat for [the seals].”
Leopardseals.org was created by Van der Linde and Orca specialist Ingrid Visser to better protect, educate and research seals. It has the largest collection of leopard seal scat in the world, gathered by researchers and volunteers who travel the coastline collecting it for the project, with the aim of learning more about the rare animals. In 2019, a still-functional USB drive was found in a one-year-old frozen feces sample.
“When we founded leopardseals.org, I knew we were going to find some cool stuff, but this is the next level of amazing,” Van der Linde said.
Leopard seals are already known as apex predators, feeding on penguins and other seals, but this is the first time they’ve hunted sharks.
The leopard seals that arrive on New Zealand shores are native to Antarctica. Their presence in the country’s waters is becoming more common and research is trying to determine if this is new or if more frequently reported sightings give the illusion that there are more. New diet research raises questions for Van der Linde about whether seals come to New Zealand because there is more variation in diet and whether climate change could affect food sources more South.
Researchers are still trying to determine if leopard seals have always feasted on sharks, or if this is also new. “It kind of tells us so far that leopard seals are opportunistic predators that come to New Zealand and feast on anything they can get their hands on.”
Van der Linde said it’s very rare to see predators feeding on other predators, and that could have implications for the food web.
“A top predator feeding on another top predator is quite interesting on its own. If leopard seals continue to increase in numbers and that affects shark populations, we really don’t know how that will affect things.