An endangered goliath grouper (Epinephelus itajara) off the coast of Key Largo, Florida. Photo by William Goodwin.

This Photo of the Day was donated by a participant in the annual National Wildlife Photo Contest. See more photos or sign up for the 42nd Annual National Wildlife Photo Contest.

Great White Shark: Wikimedia Commons

As the feared hunters of the ocean, sharks have long been persecuted and misunderstood. However, when I was a kid, I never saw them as vicious creatures. I was always fascinated and constantly reading up on my shark facts (just ask my parents). Here are five of my favorites:

1. As hunters, sharks rely on their keen sense of smell to find their next meal. They can smell a single drop of blood from over a mile away. In terms of relative volume, this is comparable to detecting a golf ball in Loch Ness.
2. The shark has the greatest electrical sensitivity of any animal. They have electroreceptors near their eyes and nose called Ampulae of Lorrenzini, which helps them sense electric fields emitted by other living creatures. By detecting these electric fields, sharks can find prey hidden in the sand.
3. Most sharks give birth to fully-developed babies, known as pups. In the womb, the litter of fully-grown pups wrestle for the limited space and will eat each other until there are only a few pups left. When they are born, they only have a few minutes to swim away, or else they risk being eaten by their own mother.  Some species of sharks lay egg sacs, known as mermaid’s purses.
4. Imagine that your entire body felt as squishy as your nose or your ear. For sharks, this is a reality, since their skeletons are made entirely of cartilage. Cartilage is flexible and durable, and reduces the skeleton’s weight. This allows the shark to save energy and to swim at high speeds towards prey.
5. A shark’s teeth are its most fearsome set of tools. But with all that wear and tear, sharks lose teeth continuously. Some may lose up to 30,000 or more in their lifetime. But not to worry, sharks constantly replace their lost teeth. Their rate of tooth replacement varies from once every 8–10 days to several months. If humans could do that, our dentists would be furious.

Today, many shark species are threatened or endangered, yet shark finning continues to be a popular commercial fishing practice, due to the high price of shark fin soup. Watch the following video to learn about what it takes to make this expensive Chinese delicacy.

Click here to view the embedded video.

Want to help sharks? You can support NWF and protect sharks by adopting your very own Great White Shark!

More Halloween Fun:

• Crows, ravens, owls and vultures: Nature’s creepiest birds?
• Get your “scary” animal fix, from vampires to zombie ants.
• Take a peek at a “spooky” animal photo gallery … if you dare!
• Halloween roundup: Get fun outdoor kids’ activities and more.

With Shark Week starting on July 31st this year, we wanted to take a few moments to honor these amazing creatures that play vital roles within their ecosystem. You may fear them, but we need to be a lot more afraid of losing sharks altogether. Currently we kill around 100 million sharks a year. I’m thinking there needs to be a human week!

This week is meant to celebrate these creatures, and we have some fun ways you and the kids in your life can learn about sharks!

Ways to celebrate sharks for the kids or the young at heart!

• Read the Ranger Rick magazine article that highlights the importance of saving sharks, and also discusses some of the incredible shark species that inhabit our waters.
• Play the Name that Shark Game! (warning: more challenging than you’d think!)
• Adopt a Great White Shark – a fun way to master fear of sharks introduce them in stuffed animal form.

Want to take a deep dive into Shark Week?

• Learn about how sharks still remain one of the ocean’s greatest mysteries and how scientists are continuing their research
• Check out Georgia Aquarium’s Shark Cam
• Shark Week Photo Frenzy: upload pics of how you celebrate Shark Week

And for the Internet Savvy…

• Shark Week Live: our live co-viewing experience available on the Discovery Channel App for iPad, on iPhone and at SharkWeek.com
• Ultimate Sharks: Discovery’s new, deep-dive iPad app all about sharks
• Follow SharkWeek.com and on Facebook and Twitter.

I hope everyone has a nice week and learns a thing or two about the magnificent sharks!