The sea turtle death toll continues for Tofino as the body of a fourth tropical reptile washed in on the surf last weekend.

The death of the metre-long green sea turtle comes after another two of the same species and an olive ridley turtle were found cold-shocked in December. Their heartbeats were faint and they were transported to the Vancouver Aquarium for treatment of hypothermia and rehydration but none survived.

Pacific Rim National Park public safety specialist Todd Windle rushed to the scene with staff on Saturday when a park visitor said they had spotted the hard-shelled reptile on Wickaninnish Beach.

"Up until this last winter, it certainly wasn't common at all and certainly not something I had ever seen until this past winter," said Windle of the turtles.

Unfortunately this time, there was nothing that staff could do to save the turtle, which had died at sea.

Park resource manager Peter Clarkson said the appearance of four sea turtles over the last three months is unprecedented.

"Looking back we've had four previous to this year but spread out in the history of the park," Clarkson said.

Biologists speculate the latest turtle, like the others, swam from warmer Pacific waters near Mexico or Hawaii but still have no idea how so many have ended up in B.C.

"It's a bit of a mystery but definitely the oceans are changing," said biologist Josie Osborne. "There are lots of hypotheses - - things like changing currents, different prey in situations in the sea and over-fishing of certain top predators."

The turtle's body was preserved onsite in a deepfreeze before it was cleaned and taken to Nanaimo's Pacific Biological station for analysis.

Dozens of tests are expected to be performed on the carcass in hopes of uncovering the mystery behind how these tropical creatures keep getting lost in freezing northern waters.

With files from CTV Vancouver Island's Scott Cunningham