creature feature

Creature Feature: Great White Shark

Posted Tue, Aug 14, 2012 by Michelle Cassidy to atlantic, california, creature feature, discovery channel, endangered species act, great white sharks, jaws, mexico, pacific, shark week

greatwhite

Great whites have earned a bad reputation, but they don't deserve it ©Discovery Channel

They’re the stars of Shark Week, one of the most iconic creatures in the ocean. But how well do you really know the great white shark?

White sharks are known by many names—great white, white pointer, Carcharodon carcharias, even white death. They’re the largest existing predatory fish in the ocean, and they’ve been around for about 16 million years. They’re found in coastal waters in all of the world’s major oceans.

The average great white measures in around 14 feet long (the females are generally a few feet longer than the males). An average individual weighs between 1,500 and 2,400 pounds. The largest white sharks ever measured came in around 20 feet long and weighed nearly 5,000 pounds.

All that size makes these sharks powerful predators. Their bite force is an estimated 1.8 tons—that’s 20 times the bite force of the average human! This powerful bite is coupled with multiple rows of sharp, serrated teeth that help the shark saw off pieces of fish.

Great whites also have an additional sense that allows them to detect the electromagnetic field emitted by the movement of living animals. By searching for these tiny electromagnetic pulses and using their excellent sense of smell, sharks can seek out prey from miles away.

In the social structure of white sharks, females dominate males, and size matters. They resolve conflict through rituals and displays of power, and rarely attack one another. Some sharks have even shown behavior that appears playful!

Great whites have earned a bad reputation as ferocious man-eaters due to movies like Jaws and stories about rogue sharks attacking humans. Truth is, great whites aren’t all that interested in humans. They would rather eat a fish or a seal than a human. While a significant proportion of shark accidents around the world involve white sharks, most are not fatal. Great whites are curious sharks, and will give an unknown object a sample bite, then release it.

These powerful creatures may be at the top of the food chain, but their biggest predator is humans. Only a few hundred great whites are left in the population off the coasts of California and Mexico, and they’re not getting the protection they need. Sign today to help get great whites covered by the Endangered Species Act.


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Creature Feature: Seahorse

Posted Tue, Jul 17, 2012 by Michelle Cassidy to algae, coral reefs, creature feature, endangered species, hippocampus, pollution, seagrass beds, seahorse

Camouflaging in coral ©Wikimedia Commons

Though you won’t see them saddled and ready to ride anytime soon, seahorses are pretty fascinating little sea creatures.

Named for their resemblance to the horses that we’re used to seeing on land, the seahorse is one of the slowest moving fish in the ocean. They swim upright, unlike their cousin the pipefish, and flutter their dorsal fin up to 30-40 times per second to move around (more like a hummingbird than a horse).

There are 47 distinct species of seahorses, and all are in the genus Hippocampus, which comes from the Ancient Greek for “sea monster.” You can find them in shallow waters throughout the world, especially in seagrass beds, coral reefs, and mangroves, where they can take cover and hide from bigger fish that might want to make a meal out of them.

Seahorses are fairly small, ranging from 0.6 to 14 inches. But the smallest of all are the pygmy seahorses. Scientists are continuing to discover new species of pygmy seahorse, but they’re tough to find because they camouflage themselves and live in or near coral, algae, or seaweed, where they blend so well that they’re nearly impossible to spot. They often use their tails to anchor themselves to a surface, then use their snouts to catch brine shrimp and other small crustaceans floating by.

One of the seahorse’s most unique characteristics is that males carry the fertilized eggs instead of females. The male seahorse has a brood pouch on his front side where the female deposits eggs during mating. He carries the eggs until they’re fully developed, then releases the tiny seahorses out into the ocean to fend for themselves. A single brood can contain up to 1,500 young!

Because seahorses are so elusive, we don’t know very much about their populations worldwide. But the coral reefs, seagrass beds, and other areas they call home are endangered by habitat depletion, pollution, and ocean acidification, which has made some species of seahorse vulnerable to extinction.


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