1. Gestation periods range from 10 to almost 14 months depending on the species and are linked to the annual migration cycle.
2. A pregnant female's energy needs increase greatly during the second half of the gestation period. Pregnant females of some species increase their food intake by as much as 50% to 60% above normal during the last six months of pregnancy. Excess energy is stored until it is spent during lactation.
3. Newly pregnant females are usually the first to leave the breeding grounds and first
to arrive in the summer feeding grounds.
1. Most species of baleen whales exhibit a seasonal breeding cycle, giving birth primarily during the winter and spring in sub-tropical to tropical breeding grounds.
2. Giving birth in warmer water reduces the energy requirements on a newborn to stay warm while it develops an insulating blubber layer.
3. Near-term pregnant females are usually the first to arrive in the calving grounds.
1. Baleen whales give birth to a single calf. Twins are extremely rare. If twins are conceived, they are unlikely to survive to full term. In rare cases where twins are born, they are not likely to survive, due to a limited milk supply from the mother.
2. In most species, females may bear a calf every two to four years.
1. Observations of baleen whale births at sea are extremely rare. The usual delivery seems to be tail-first, but a few head-first deliveries have been documented.
2. The placenta seperates from the uterine wall during or soon after delivery.
3. Some species seek protected coastal areas to give birth.
1. Calves can swim at birth.
2. Baleen whale calves range from about 1.5 m (5 ft.) for pygmy right whales to about 7 m (23 ft.) for blue whales.
3. In general, a calf is approximately one-quarter of the mother's length.
4. Birth weight is approximately 3% to 4% of the mother's weight. Blue whale calves weigh about 2,700 to 3,600 kg (6,000 to 8,000 lb.) at birth.
5. Baleen whale calves have small, soft baleen plates. See also baleen.
A gray whale calf named "Gigi" spent one year at Sea World of
California, from March 1971 to March 1972. Research on Gigi helped us learn about baleen
whale physiology, growth, and development.
1. Nursing.
a. The nursing period lasts from 4 to 11 months. A calf is weaned by its first summer in time to feed.
b. The calf suckles from nipples concealed in its mother's abdominal mammary slits. Calves nurse under water, close to the surface.
c. A high fat content (up to 40% to 50% fat) allows the calf to rapidly develop a thick insulating layer of blubber.
2. All species of baleen whales establish strong mother/calf bonds. The pair stay in close physical contact throughtout the nursing period.
a. A mother baleen whale stays close to her calf and attentively directs its movements. The baby swims close to its mother and is carried in the mother's "slip stream," a type of hydrodynamic wake which develops as the mother swims.
b. The mother may teach the calf certain behaviors.
c. Whalers noticed that females became aggressive when protecting their young.
3. There is probably a considerable amount of learning involved in mothering and teaching the calf.
4. Calf development rates vary by species.
a. Sei whales are 4.5 m (15 ft.) at birth and grow about 2.5 cm (1 in.) each day.
b. Blue whale calves gain 90 kg (200 lb.) each day while nursing.
c. Gray whale calves double their weight in about three months and double their length in about two years.
d. Humpback whales grow 45 cm (1.5 ft.) per month during nursing.
SeaWorld/Busch Gardens Animal Information Database
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