Migrating Naturalist: Calf Charisma

Some of my favourite humpback groups to watch are those which include calves. There is just something about watching a massive 12 foot, 1 ton (907kg) baby splashing and playing around in the water that warms your heart. Perhaps it is that these little whales seem endearingly awkward, as they attempt to follow the breaches, chin slaps, and pec slaps seen from their mothers. It is extremely rare to see two mothers sharing the same space, and so most calves have no one their own size to share their excessive energy with. Occasionally you will see a calf attempt to engage a playful dolphin, and our underwater photographers often have to be wary of curious or friendly calves who do not realize their own strength!

A female humpback reaches maturity at about 6-10 years, and will almost always give birth to just one calf at a time. In some rare cases, females have been known to breed in two consecutive years, but usually they will bear a calf once every 2-3 years. Breeding occurs mostly in winter and early spring, and as gestation lasts 11-12 months, the peak birth months tend to be January and February, when the whales are once again dwelling in warm waters.

Calves are born tail first, as is normal for cetaceans, and will instinctively swim to the surface for their first breath, aided by their mother using her pectoral fins and head. They are able to swim within 30 minutes, a necessary skill with predators such as tiger sharks lurking nearby. Humpback calves will remain very close to their mothers, often swimming in the easy slipstream on her back, or being gently carried on her head while resting at the surface. They grow rapidly, feasting daily on 100 lbs of their mother’s rich milk, which has 45 to 60% fat content. This will help them gain the insulating blubber needed for their Northward journey in mid to late spring. They will continue this diet for 6 to 11 months, until they are slowly weaned to solid food. Shortly after this the mother will abandon her calf, at just one year old. In some rare cases the mother will keep her calf for another year, but most will leave it after returning to warm waters, to begin the mating process all over again.

My name is Diana, and for the past two years, I have been travelling between my naturalist position in Tofino with West Coast Aquatic Safaris, and my research intern position with the Hawaii Whale Research Foundation. Throughout my second season with HWRF, I am writing regular blogs, describing my experiences on the water and here in Maui.

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