DEH GAH GOT'IE KOE/FORT PROVIDENCE - Starvation is probably behind the deaths of five bison found outside of Fort Providence, according to wildlife officials.

The carcasses of the animals were reported in mid-March after being spotted during an aerial survey conducted as part of the bison control area surveillance program, said Troy Ellsworth, the manager of wildlife and environment for the South Slave region.

A layer of ice under the snow may have caused the deaths of five bison near Fort Providence. A sixth carcass was so badly destroyed - by what is believed to be wolves - the cause of death could not be determined. - NNSL file photo

Six bison were found within a few kilometres of each other near the old cutline known as Farmer's Road that runs from Fort Providence to the Horn River, said Ellsworth. The dead animals included three calves, an adult cow and two adult bulls.

A bison biologist and a health specialist along with a few pathologists from Saskatoon visited the sites and took samples from the animals. The samples were examined in the field and have also been sent to a lab for further testing.

The field diagnosis is that five of the animals died of starvation, said Ellsworth. The diagnosis was based on the fact the carcasses looked skinny and they showed a loss of muscle mass and fat reserves.

The specialists also examined the bone marrow in the animal's femurs. When a bison can't get enough food they use up their back fat reserves first, said Ellsworth. The last reserve is the bone marrow fat. There was little of that fat left in the animals.

"That's one of the telltale signs that the animals were in really bad shape," he said.

Although the lab results aren't final so far they are supporting the diagnosis of starvation, said Ellsworth.

Predators, likely wolves, probably killed the sixth animal, he said. There wasn't enough of the animal left to determine if it was starving before it was killed, said Ellsworth.

A cluster of deaths like this isn't common.

"It's not something we see every year," he said.

Using information from community members a picture is starting to emerge about how the bison could have starved. During the late fall the area experienced rain which turned to ice and was insulated by deep snow, said Ellsworth.

The ice would have prevented the bison from getting to the grass underneath, he said. Instead of pawing at the ground bison use their heads to move snow aside and reach grass.

"They aren't very good at breaking through the ice," he said.

The ice and snow are the only environmental conditions that could have caused the starvation, said Ellsworth. Ellsworth said he's seen similar deaths in caribou herds after a winter where there was a late rainfall.

This is a localized incident, he said. So far there haven't been any other reports of bison carcasses being found or groups of bison looking skinny.