A group of orcas off B.C.’s central coast appears to have less food than usual this summer and researchers say they’ll be monitoring the animals to see how many survive the winter.

The marine mammals usually travel in collections of family groups called super pods at this time of year, but that’s not what scientists are seeing.

"The resident killer whales are travelling in quite small groups, much smaller than usual," said Lance Barrett-Lennard, a marine mammal researcher at the Vancouver Aquarium.

The aquarium’s research team has just returned from a research trip monitoring the orcas and say that in addition to travelling in smaller groups, the whales also are talking less among themselves — another indication that food is scarce.

Barrett-Lennard said orcas share every meal within their pod and they vocalize to draw others near. When fish are scarce, the groups become smaller, with fewer mouths to feed.

"It's a bit like us sitting down to a dinner, it's a ritualized sort of social behaviour that maintains the cohesion of the group. They're basically saying, ‘You're in my group, I'm sharing food with you.’ I think if you're a killer whale it's rude to eat by yourself."

Picky eaters

The group of about 250 orcas are picky eaters, preferring chinook salmon almost exclusively.

But Barrett-Lennard said the whales have to look hard to find chinook this year.

"We were somewhat expecting this low chinook year, because there was a poor year four years ago, but I don't think it was predicted to be quite this bad," he said.

The Northern Resident group, as they’re called, are not endangered like a smaller group in southern B.C. waters. But the northerners are listed as a "threatened" population.

In years with very low chinook returning to coastal waters, studies have shown fewer whales survive the winter, Barrett-Lennard said.

With files from the CBC's Lisa Johnson