#40: The Calving Ground

The North Atlantic right whale calving ground off the coast of Georgia and northeast Florida was known to fisherman long before researchers discovered it. Historic whaling records show numerous mother and calf pairs hunted in the now critical habitat. In January 1935, local fisherman off the coast of St. Augustine, FL spotted and hunted a mother and calf. After a six-hour stand off, the calf's injuries proved too much and it succumbed to the trauma. The mother managed to elude the whalers, but suffered multiple gunshot wounds (read more about this story here). Following this event, a moratorium was put on hunting right whales in U.S. waters.

Almost 50 years later in 1984, researchers at the New England Aquarium, with the help of Delta Airlines pilot David Mattingly and a group of volunteer Delta Airlines pilots, decided to fly aerial surveys in this historic habitat. The results were momentous and would change the way coastal waters were used along the eastern U.S. Researchers discovered the only known calving ground for the North Atlantic right whale, later designated one of three critical habitats in U.S. waters.

These southeastern U.S. waters provide a winter habitat for more than just pregnant females; juveniles, non-pregnant females and some adult males are also seen here. The migration is no easy undertaking; these whales must travel over 1,200 miles, evading clusters of fixed and ghost fishing gear while crossing major shipping lanes into Boston, New York, New Jersey and Charleston. Once in the habitat, the threats are not diminished; the ports of Brunswick, St. Mary and Jacksonville are all within the critical habitat.

Birthing females, or cows, give birth to a single calf at a minimum rate of 1 every 3 years, presuming the calf survives long enough to be weaned from the mother. The calving season spans from December through March with a peak in calving events between January and February. Nearly all cows appear to use the calving ground regardless of where they spend their time the rest of the year. Through extensive survey effort, it is known that not all cows bring their calves to the main summer feeding grounds in the Bay of Fundy. Some go to other feeding areas in the Gulf of Maine, Gulf of St. Lawrence, and likely other summer feeding habitats that have yet to be discovered.

Zooplankton productivity in the calving ground is low and right whale's preferred prey species, Calanus finmarchicus, in not available. This means that all right whales in the calving ground, those not nursing milk from their mother, are metabolically converting lipid storages into a useable energy source. Through the cost of lactation and providing enough energy for herself, birthing mothers can lose up to 1/3 of their total body weight during the calf's first year of life.

Nearly all sightings of mother and calf pairs in the calving grounds are in cool water, with temperatures below 20 C, with a few sightings in warmer waters. Temperatures during summer in the Gulf of Maine feeding grounds are 21.8 C, similar to the warmer water sightings in the southeast calving grounds. To many, this suggests an upper thermal limit for right whales. If the prevailing determinant for the selectivity of a calving ground is temperature, then it is possible that rising ocean temperature may cause a shift in the right whale calving ground. Only time, and a watchful eye, will tell.

-Jonathan

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