There are sleeper cells in the marine animal world and they are killing sea lions.
There has been an intense decrease in sea lion population in the Western Aleutians and things aren't getting any better. High-tech tags have been placed on young sea lions to track their daily lives until their demise and it appears sleeper sharks, nocturnal cold-blooded predators, are keeping sea lion population down, according to Alaska Public Media.
Oregon State University ecologist Markus Horning started tagging Steller Sea Lions in Prince William Sound, but these tags aren't just GPS. They record light, temperature and other factors important to scientists who are looking for more information about the animals while they are at sea.
"We don't have proof of sleeper shark being a major driver of the sea lion population, but we have indirect evidence that suggests we need to consider that," Horning told Alaska Public Media.
How does Horning know that the sea lions weren't eaten by a killer whale or great white shark? The tags that were presumably inside the digestive tract of the predator registered cold temperatures, so warm-blooded predators have to be ruled out, according to Alaska Public Media. The sleeper shark is a cold-blooded predator that dwells deep in the ocean.
Bruce Wright of the Aleutian Pribilof Island Association has been following Horning's work. "I'm not surprised at all, no. I predicted a couple of decades ago that sleeper sharks are not mud sharks and don't eat mud, despite what a lot of fishermen will tell you, that they're top predators," Wright told Alaska Public Media. "And when I've looked inside of sleeper shark stomachs I've found chunks of seals, big chunks of great whales, salmon, whole salmon that they've sucked down, adult salmon."
There are a lot of questions and not a lot of funding to study sleeper sharks.
"We also really don't know how many sleeper sharks are out there," Horning told Alaska Public Media. "Are their numbers increasing or are their numbers decreasing? Which of the sleeper sharks are eating sea lions, if they do? Is it the big ones, is it the medium size ones, small ones? Probably the big ones. Are there big ones in Prince William Sound and the Gulf of Alaska? We don't know."
