There is also a western stock of grays off the coast of Asia, but pollution and whaling has placed them on the verge of extinction. Their current numbers are below 100 animals, and this is not sufficient to keep the population viable much longer.
Out of the current eastern stock of approximately 19,000 to 20,000 whales, maybe 1,500 to 2,000 will make the entire round-trip, feeding on krill and amphipods (tiny shrimplike crustaceans) in the summer to build a layer of blubber that acts as both an energy source and insulation for their epic swim. The rest will string out along the western coast of the Americas, wherever they find food.
They are baleen whales, meaning they have a brushy curtain that grows down from the roof of the mouth, made of keratin (like human hair and fingernails). This acts as a filter for these bottom-feeding creatures, which scoop up tons of amphipod-rich silt and push the excess water out with their tongue. The food is trapped on the backside of their baleen, and they lick it off to swallow.
Baleen whales have a double blow hole, and the exhalation of used air combined with water collected in the indentation of the hole produces their “blow,” a heart-shaped mist, by which they are easily spotted.
Most of the calves are born on the journey south after a thirteen-month gestation. They are twelve to fourteen feet long, and weigh 1,000 to 15,000 pounds, gaining up to 150 pounds a day on a diet of mother’s 53-percent-fat milk. The baby does not attach to the mother to nurse. This milk is so thick it is squirted into the water, where it does not readily disperse. The baby then laps it up. Nursing mothers may lose up to a third of their body weight in the lagoon. They are not known to echo-locate as orcas do, but it is thought they have underwater geography imprinted in their DNA after centuries of navigating the Pacific “Rim of Fire.” They do vocalize, but their low guttural sounds are not easily heard by human ears.
Calves will nurse about seven months and then will spend four to six weeks in the lagoon, learning how to survive alone in the vast ocean. Unlike other whales, Pacific gray whales do not travel in pods. After mating, the male takes off. If the mother dies, an unweaned calf will probably also die, as grays are not known to adopt orphans.