Sunday, August 1, 2010

Thresher Shark

Shark Week 2010 starts today, so in honor of that fine tradition I'm going to talk about one of my favorite sharks, the ever so strange looking Thresher Shark. Alopius vulpinas can be found in ocean waters worldwide, though they are most abundant in temperate zones. It is typically a pelagic species, meaning that it inhabits the open sea, though they will occasionally travel to coastal waters. Thresher Sharks are also referred to as Fox Sharks, which lines up with their species name vulpinas, a derivation of the Latin word for fox.

Image from Flickr
Thresher Sharks are pretty easy to pick out. They have an upper caudal (tail) fin that can make up 50% of their overall body length. They usually grow to between 10 and 15 feet. Their tail is used to assist in hunting. The diet of a Thresher Shark consists mostly of fish that they round up and stun with their tails. They have even been known to kill they prey by whipping their tails. Thresher Sharks also eat cephalopods and crustaceans. Thresher Sharks are very strong swimmers, and are capable of leaping completely out of the water.

I get to use one of my favorite words to describe the reproductive habits of the Thresher Sharks. They are ovoviviparous! This means that they lay eggs, but they are laid inside the mothers body, and incubated there. The young pups, usually between 4 and 6 in number, are then born live into the open sea.

There are other members of genus Alopius besides vulpinas, and all of the species are listed as vulnerable. Fishing net entanglement and a slow livespan have led to decreasing numbers in recent years.

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