Sunday, June 20, 2010

Sperm Whale

It just dawned on me that I have not yet written a single post about a cetacean! What have I been thinking?! That's going to change, right here, right now. I present Moby Dick himself... the Sperm Whale. Not only is the Sperm Whale (Physeter macrocephalus) one of the most well known of all ocean mammals, but they are very topical creatures as well. 1,665 of these guys live in the Gulf of Mexico, which, as everyone on the planet should probably know, is undergoing a major environmental crisis with the BP oil spill. As top tier predators in the region, Sperm Whales can be hugely affected by the oil. Not only can the spill make them sick directly, but it also affects their prey, which then makes its way back to the whale during consumption. This past week a young whale was found dead 70 miles from the spill, and scientists are looking into cause of death. Sperm Whales have also hit the news this past week due to a new study that shows that their excrement actually removes carbon dioxide from the atmosphere. Interesting creatures indeed!

Sperm Whales live in oceans all around the world. They are huge. They are the largest of all toothed whales (Odontocetes) and males can grow 60 feet long and weigh 45 tons. They have the greatest degree of sexual dimorphism of any cetacean. Females only reach about 35ft and weigh 11-14tons. The head of a Sperm Whale makes up about a third of their overall body length, and posesses the largest brain of any animal.. though in relation to overall body size it isn't that large. The head is also filled with an oily substance called spermaceti. It is still unclear as to what this substance is for, but speculations are that it helps manage buoyancy.
Image from Monterey Bay Aquarium

Sperm Whales can hold their breaths for 90 minutes and dive down 3,200 feet. The whales have several interesting adaptations that allow them to handle the pressure changes while diving. Blood gets directed to only the most vital organs, their heart rate slows considerably, and they are able to partially collapse their rib cages. In between dives the whales rest at the surface and breathe through their blow hole, which is unique in whales in that it is located asymmetrically on the tip of the head. They spout between 3 and 7 times a minute, with the water streams reaching up to 50 feet in the air.

The mortal enemy of all Sperm Whales (that sounds so dramatic!) is the Giant Squid. Whales have been found with scars and marks chronicling their fights with the large cephalopods, which make up a nice chunk of the whales' overall diet. They also consume sharks, rays and other fish. The whales hunt with echolocation, sending out sets of creaks that bounce back to the whale once they hit another object. Sperm Whales have very few predators, man being the most prominent. They were hunted heavily in the 18th and 19th centuries for their ambergris, spermaceti, and blubber. Despite that the population is still fairly numerous. Other predators include sharks (on whale calves), and Killer Whales. IUCN lists the Sperm Whale as a vulnerable species.

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