Why more right whales have been spotted this year compared with last 3 years

The 10th North Atlantic right whale of the season has been spotted off the coast of South Carolina, but that's no surprise to researchers.

The newest right whale is the calf of Palmetto, No. 1970, a 31-year-old right whale. This is Palmetto's fifth calf. She last gave birth in 2009.

Nine other North Atlantic right whale calves have been spotted this year. Three of the calves were spotted off the coasts of Georgia and Florida last week, raising the total number of endangered right whales born this year above last year's total.

During the 2019 calving season, seven newborns were spotted. No new calves were born in 2018. The last time the number of North Atlantic right whales surpassed 10 was in 2016, when 14 calves were spotted.

Philip Hamilton, a research scientist with the New England Aquarium, said researchers expect at least 30 calves will be born this year.

"That sort of jump is expected after a few years of low calving," Hamilton said.

More calves are being born this year in comparison to the last three years because female right whales are delaying when they give birth, Hamilton said.

During the early 2000s, a female right whale gave birth every three to four years. Now, the species is giving birth every seven to 10 years, Hamilton said.

"The more whales that have delayed their calving, then you get sort of a backlog of available females females that have had a long enough resting time in between calves that they should be able to give birth."

Why whales delay giving birth

Mammals won't give birth if their body condition is not good enough to sustain giving birth and raising the calf, Hamilton said.

"What we believe has been happening is right whales have been having a harder time finding enough food to be in robust physical condition."

Right whales are having a difficult time finding food because the Gulf of Maine, the whale's primary feeding ground, has been warming.

"Right whales are not using some of their historic feeding habitats as much as they used to," Hamilton said.

The whales have pushed north over the last several years because they're relying on other feed grounds like in Cape Cod Bay and the Gulf of St. Lawrence.

"This change in where their food is seems to be impacting their overall body condition, and so that's why the females are not giving birth as frequently as they can when they're in good shape."

There are only about 400 North Atlantic right whales and fewer than 100 breeding females.

Twelve right whales died last year, according to Hamilton.

"The population is not out of the woods because we have ten calves."

If humans can prevent the entanglements in fishing gear and the ship strikes that have killed whales in recent years, the mammals will most likely be able to adapt to the changing feeding conditions, Hamilton said.

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Scientists stop doing surveys and checking for newborn whales at the end of March. The total count of newborn calves won't be tallied until late spring or the end of summer.

Injured calf

One of the 10 newborn calves was injured by a ship's propeller in early January. The calf suffered serious injury to its mouth, making it difficult to feed.

The calf and itsmotherhave not been seen since Jan. 15.

"Most of us are very skeptical that we'll see that calf again," Hamilton said. "It was a very substantial wound and very unlikely that that calf could survive it."