Spring Migration Route of Atlantic Humpback Whales Map courtesy of MacalesterCollege Each spring, the humpbacks of the northern hemisphere begin to leave the breeding area and swim thousands of miles north. Some animals arrive as early as April and begin to feed.The mothers and calves are among the last to arrive. Scientists believe that the mother-calf pairs will stay in the calving grounds as late as possible to give the calves the best chance of gaining strength before making the long commute north. The adult females who are not pregnant go to the breeding grounds searching for a mate. If they become pregnant, there is no further reason to stick around, so they may be the earliest arrivals to the feeding grounds. The pregnant whales probably want to build up as much of a reserve of blubber to support themselves and their fetuses during the year-long pregnancy as well as provide reserves for the nursing period. Researchers also believe that males may stick around the breeding rounds for longer periods to mate with as many females as possible. Juveniles may or may not make the trip down south. Those that do go may accompany their mothers and keep the same schedule. Those that don't make the southern migration may be staying in more northern waters where the trip back to the feeding grounds is quicker (juvenileNorth Atlantic humpbacks have traditionally been seen off the Virginia and North Carolina coasts during the winter months). Every day, a mother humpback whale must produce between 100 and 130 gallons of rich, caloric milk for her calf. She must do this throughout the first eight to twelve months of the calf's life. Nourished with this nutritional diet, the calf grows up to a foot per month in its first year. This quantity is so enormous it is difficult to imagine! Want a fun project to get you thinking about milk? Try this! Got Milk? Daily Food Requirements of a Humpback Calf Copyright 2002 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form