Scientists were fairly certain that a matron killer whale from an endangered pod off British Columbia's coast had given birth to the newest calf – then new evidence made them change that opinion.

Ken Balcomb, from the Center for Whale Research in Washington state, said they spotted bite marks on the female calf that led them to believe another whale acted as a type of marine midwife.

"We suspect what happens sometimes in these troubled deliveries, is that another whale sort of gently bites the little baby and pulls it out, and leaves teeth marks," he said. "We can definitely see the teeth marks and we surmise that it's an assisted delivery."

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A killer whale that's know to be in her early 40s was spotted swimming alongside the new baby near B.C.'s Gulf Islands on Dec. 30.

The orca, known as J-16, has given birth to at least five calves in the past and likely wouldn't need assistance because of her experience, Balcomb said.

Researchers now believe J-16 is instead the offspring's grandmother.

He said experts are working with the Department of Fisheries and Oceans to determine whether J-16 is really the calf's mother, or if she has just been "babysitting" for her daughter, a whale called J-36.

Killer whales exhibit caring for one another, and babysitting is not unusual, especially with grandmothers, said a statement from the Center for Whale Research.

The newborn calf called J-50 is the newest addition to J pod, the dwindling southern resident orca population is found in the waters off B.C. and Washington state.

Before the calf was born, researchers were "betting on several young females on who's going to have the next baby," he said.

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In December, a pregnant whale from the same pod was found dead in the waters off Vancouver Island. Necropsy results show that she died of infection, which likely originated with her nearly full-term female calf and then spread to its mother.

Balcomb said if the mother of the new calf is J-16, she will be the oldest southern resident orca known to give birth in more than four decades of field studies.

The new calf was first spotted with J-16 near Pender Island, a Southern Gulf Island, and the pod has been making its way north toward Nanaimo, on the east coast of Vancouver Island.

He said scientists were thrilled to later discover that the calf is a female.

"This baby is one of the last little hopes we have for this population to survive," he said.

"Because its a female and can have babies of her own, you know, a dozen years from now we might see the population slightly start to increase," he said.

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"There just aren't many reproductive females left in the population and that's a tragedy that we've allowed to happen."

There are only 78 southern resident orcas left, including the new addition.

It will likely be another 12 to 15 years before researchers know if J-50 will be reproductive.

In the meantime, Balcomb said researchers are trying to get both the Canadian and U.S. governments to understand that the whales diet of salmon also needs to be protected.

"We have to have abundant food supplies in order for them to meet the nutritional needs of reproduction and they just haven't done it. You've got to have fish, got to have salmon, got to have chinook salmon, and you've got to have lots of it."