VANCOUVER -- Headless sea lions have been washing up on Vancouver Island since spring, and a marine mammal expert says it's likely the animals were deliberately beheaded by humans.

Anna Hall is a marine mammal zoologist at Sea View Marine Sciences. She says photos of the dead pinnipeds suggest a pattern in their injuries.

"To me, this looks intentional, whether it's by a single person or a group of people," Hall said. "I sincerely hope that fisheries and oceans canada pursues this case to determine who is doing this and to bring them to justice because this is a violation of federal law."

Most of the photos CTV News showed to Hall were taken by Nanaimo resident Deborah Short, who says she's personally encountered several dead sea lions without heads on the shore between Campbell River and Nanaimo.

Short discovered the first one while walking along the beach at Neck Point Park in Nanaimo.

"I was devastated, completely devastated by it," she said. "I couldn't believe that somebody could sever the head of a sea lion … It was shocking to me."

Soon, though, she learned of another headless sea lion that had been found near Campbell River. And then she started encountering more herself.

In total, she says, she's aware of five headless sea lions that have washed up on Vancouver Island since March.

"When you see something like that, it moves you," Short said. "It moves you in a way where you want to find more, and you want to do something about it."

She reached out to conservation groups, including Sea Shepherd and the Animal Alliance of Canada. The latter organization, she learned, is petitioning against a proposed cull of seals and sea lions on Canada's west coast.

While there's no indication that the headless sea lions Short discovered are in any way related to the proposal to cull the local population, she said she's determined to stop the killing of additional marine mammals.

CTV News Vancouver Island reached out to Fisheries and Oceans Canada (DFO) and was told the federal agency is looking into the headless sea lion phenomenon.

On Sunday, the federal department provided a more detailed response. The DFO tells CTV News there has been a slight increase in reports of dead sea lions on Vancouver Island.

“From time to time, individuals may tamper with the animals once beached,” said a DFO spokesperson. “If this is determined to have been done in an effort to knowingly tamper with evidence, this would be an offense under the Criminal Code of Canada.”

DFO’s conservation and protective branch is also aware of pinniped-related social media activities and said is closely monitoring them, the spokesperson said.

Anyone who discovers the carcass of a wild animal should call 1-800-465-4336 right away and not touch it, the DFO says.

Hall, the marine mammal zoologist, said at least one of the sea lions Short photographed appears to be a Steller sea lion, which is a species that has a special conservation status under the Species at Risk Act.

She said all marine mammals are also protected from disturbance, injury or harm by clauses in the Fisheries Act.

Hall hopes Fisheries and Oceans Canada will do a necropsy on one of the deceased sea lions to determine its cause of death.

"It's absolutely horrific and appalling that there's anybody on this coastline that would feel that this is an appropriate course of action with regard to a marine mammal or any animal at all," Hall said.