Sunday, May 13, 2012

Gray Whale

Eschrichtius robustus
As it is Mother's Day, we're going to learn about one really awesome mother from the Animal Kingdom-- the Gray Whale!

Gray Whale breeding season takes place in November and December, and happens while the Whales are wintering in warmer waters near the Equator. Females gestate for a whopping 13.5 months and give birth to a single calf while in their wintering grounds the following year. Calves are born in safer waters off of Baja, Mexico that are free from predators, and the mothers will help lift their infants up to the surface so that they can breathe... at least until they become stronger swimmers. Calves are around 4ft long at birth, and grow very quickly. They can drink up to 80 gallons of milk a day, and that milk is 53% fat!

Eventually, the mother an calf must travel back to colder climates in order to feed. The wintering waters are safe for giving birth, but that is because there is so little food, and thus very few predators. All Gray Whales migrate, and they actually take part in one of the greatest animal migrations in the world, travelling as far as 12,500 miles (20,000km) round trip each year. Females and calves are the first to leave the warm winter waters, destined for the nutrient rich seas of the north. But the trip is not easy! Not only is the swim difficult for the calves due to it's distance, it is also incredibly dangerous thanks to all the predators (like Killer Whales) that are out to get them.

Calves remain with their mothers for around a year, and will themselves take about 8 years to reach sexual maturity. One fact that I found particularly interesting is that the female Gray Whales are often larger than the males, which is unusual for Cetaceans. Sperm Whales, for example, have some of the most ridiculous sexual dimorphism of any mammal.

Gray Whales also have a very distinctive look to them, thanks to the various parasites and growths that collect on their skin. Calves are born completely smooth, and will collect their barnacles and lice as they age. Doesn't sound especially pleasant, does it?

Currently, Gray Whales can only be found in the Pacific Ocean. Before the growth of Commercial Whaling they also lived in the Atlantic, but they are now extinct in that particular area. Gray Whales almost disappeared from the planet completely, but they are now protected and their population is slowly rebounding. Boat collisions, fishing gear entanglement, habitat degradation, and the effects of climate change all continue to impact the species.

IUCN Status : Least Concern
Location : Pacific Ocean
Size : Length up to 50ft (15m)
Classification : Phylum : Chordata -- Class : Mammalia -- Order : Cetacea
Family : Eschrichtiidae -- Genus : Eschrichtius -- Species : E. robustus

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