How Marine Animals Sleep

Whales and dolphins sleep in unique ways.  As mammals, these animals have to be able to go to the surface and breathe quite frequently.  They even need to breathe while they sleep.  In order to do so, whales and dolphins have developed unique sleeping techniques.  One method is to rest vertically or horizontally in the water.  They either sleep in groups, where it is safer from predators, or they sleep alone.  According to Scientific American (1998), "Individual dolphins...enter a deeper form of sleep, mostly at night. It is called logging because in this state, a dolphin resembles a log floating at the water's surface" (para. 1).  Thus, the dolphins sleep at the surface of the water so that their blowholes have access to air to breathe. 

Bottlenose dolphins have a unique sleeping technique, too.  The Scientific American says, "While sleeping, the bottlenose dolphin shuts down only half of its brain, along with the opposite eye. The other half of the brain stays awake at a low level of alertness" (para. 4).  The dolphins do this so that they can protect themselves against potential predators.  They have adapted this sleeping technique for survival. 

Sharks are different from whales and dolphins.  They are fish, not mammals, and they get their oxygen through water passing through their gills.  Some sharks need to swim all of the time in order to get this oxygen flow in their gills, but nurse sharks do not.  Nurse sharks have special muscles that move the water over their gills without the shark having to swim.  According to the Florida Museum of Natural History (2014), "Some sharks such as the nurse shark have spiracles that force water across their gills allowing for stationary rest. Sharks do not sleep like humans do, but instead have active and restful periods" (para. 8).  Sharks sleep in different patterns than humans because of their gill requirements. 

Overall, marine animals have unique sleeping techniques and patterns.

 

Photograph courtesy of Wikipedia (2014) 

References

Florida Museum of Natural History. (2014). FLMNH Ichthyology Department: Most Commonly Asked Shark Questions. Retrieved from https://www.flmnh.ufl.edu/fish/education/questions/Basics.html

Scientific American. (1998, February 2). How do whales and dolphins sleep without drowning? Retrieved from http://www.scientificamerican.com/article/how-do-whales-and-dolphin/

Wikipedia. (2014, August 19). The sickle-shaped pectoral fins of the tawny nurse shark are one of its characteristic traits [Photograph]. Retrieved from http://en.wikipedia.org/wiki/Tawny_nurse_shark

Cetaceans: Who are they?

Many people do not understand the correct relationship of whales to dolphins.  Some people think they are unrelated, but they are wrong.  Dolphins and whales are part of the same family, which is called cetaceans.  According to the NOAA's Office of Protected Resources (2014), "Cetaceans are relatively large, generally characterized by streamlined bodies that glide easily through the marine environment" (para. 1).  Cetaceans include "approximately 78 species of whales, dolphins, and porpoises" (para. 1).  Dolphins and whales both have the defined characteristics, and many species of each are part of this family.  For example, bottlenose dolphins and killer whales are both cetaceans and are, therefore, related.

According to the Marine Mammal Center (2014), "Cetaceans are separated into two groups: toothed and baleen whales" (para. 3).  Toothed whales are just as they sound: whales and dolphins that have teeth.  This includes dolphins, whales, and fresh-water river dolphins.  River dolphins are very unique.  They have been found to be a variety of colors, and Dolphins-World (2014) says, "Due to the many different colors, they are often mistaken for other forms of aquatic life" (para. 2).  Many people do not know much, if anything at all, about river dolphins.  Their unique color variety gets them confused with other marine animals.

Picture courtesy of Exploring Nature Educational Resource (2005)

 

References

 

Dolphins-World. (2014). River Dolphins - Dolphin Facts and Information. Retrieved from http://www.dolphins-world.com/river-dolphins/

Exploring Nature Educational Resource. (2005). Whales and Porpoises Poster [Picture]. Retrieved from http://www.exploringnature.org/db/detail.php?dbID=94&detID=1839

The Marine Mammal Center. (2014). Cetaceans. Retrieved from http://www.marinemammalcenter.org/education/marine-mammal-information/cetaceans/

NOAA Fisheries., & Office of Protected Resources. (2014, October 8). Cetaceans: Whales, Dolphins, and Porpoises. Retrieved from http://www.nmfs.noaa.gov/pr/species/mammals/cetaceans/



Diet of Sharks

Contrary to popular belief, sharks do not normally eat humans.  There are many shows and movies out there that portray sharks as these vicious, man-eating monsters.  However, this is not the truth in the real-life wild.  Sharks only attack humans if they feel threatened or get confused.  According to the Discovery Channel (2014), "The National Oceanic and Atmospheric Administration (NOAA) explains that sharks do not normally hunt humans, but if they do attack, it is usually a case of mistaken identity" (para. 4).  A shark's diet typically consists of sea lions, seals, and sometimes sea turtles.  When sharks go to attack their prey, they often come up from underneath it, and when looking underneath a swimmer or a seal, the two look very similar.


Photograph retrieved from the World Open Water Swimming Association (2012)

Other than the obvious visual of shape similarity, another reason that the sharks get confused is that they cannot see colors.  The World Open Water Swimming Association (2012) says, "According to researchers at the University of Western Australia and the University of Queensland, sharks are completely color blind and have only one type of photoreceptor in their retina" (para. 5).  Thus, they easily confuse the shape of a surfer for the shape of a seal, which they associate with food.  It is especially confusing when a surfer is wearing a dark wetsuit.  The shark just sees a dark shape that looks like its usual prey, so it will attack.  To reiterate, however, sharks only attack humans because of this confusion or if they feel threatened themselves.  They are not actually on the hunt for humans.

Next time you label sharks as these ruthless, threatening creatures, just remember that humans kill way more sharks than sharks do humans.  Who is the real bad guy?

The video link below shows a shark eating its natural prey of seals in the wild.  This video belongs to Henrythaeif from YouTube and was posted on January 8, 2012.
https://www.youtube.com/watch?v=v8IUFu1KXrM

References

Discovery Channel. (2014). Why Do Sharks Attack? Retrieved from http://www.discovery.com/tv-shows/shark-week/about-this-show/why-do-sharks-attack.htm

Henrythaeif. (2012, January 8). Great white shark grabs seal - amazing HD Quality footage - Must See. Retrieved from https://www.youtube.com/watch?v=v8IUFu1KXrM

World Open Water Swimming Association. (2012, July 14). [Photograph]. Retrieved from http://dailynews.openwaterswimming.com/2012/07/myths-in-open-water-wetsuits-lead-to.html

World Open Water Swimming Association. (2012, July 14). The Daily News of Open Water Swimming: Myths In The Open Water: Wetsuits Lead to Shark Attacks. Retrieved from http://dailynews.openwaterswimming.com/2012/07/myths-in-open-water-wetsuits-lead-to.html

The Interesting Facts of Dolphins

Many people have heard that dolphins and humans are very similar.  Dolphins are very intelligent and playful.  Even in the wild, they are not a significant threat to humans' safety.  Dolphins are very playful and curious animals.  According to the Defenders of Wildlife (2014), "Dolphins are well known for their agility and playful behavior, making them a favorite of wildlife watchers" (para. 5).  The dolphins enjoy people-watching as much as people enjoy dolphin-watching.  When people take boats out in the open ocean to view dolphins in their natural habitats, dolphins enjoy jumping and playing in the wake of the boat.  They are very curious and playful animals.  Below is a video of dolphins jumping in a wake taken by a person's camera near Marco Island, Florida.

https://www.youtube.com/watch?v=lkgDlI924GY

Not only are dolphins known for their playfulness and intelligence, but they are also known for their use of echolocation.  According to Dolphins-World, echolocation is the process of making a click-like noise that sends sound waves to bounce vibrations off of an object back to the dolphins; "This allows them to identify where objects are located. It also gives them information about the location of the object and some indication of the shape and size of it" (para. 1).  Echolocation is a fascinating ability that dolphins have and people do not.

The most well-known dolphins in the United States are bottlenose dolphins.  These are at SeaWorld and are the most commonly-seen dolphins when people go to the ocean.  Bottlenose dolphins stay closer to shore than other dolphins.  They play and have their calves in the shallow water.  According to Michael J. Davenport (2011), "They are found in the Atlantic, Indian, and Pacific Oceans" (para. 3).  Bottlenose dolphins are very common, and people all over the country know what they look like.  Dolphins are a well-known species among humans, but there is always more research to be done.


Photograph taken by Willy Volk

References

Davenport, M. J. (2011). Wildlife Field Guide for New Jersey's Endangered and Threatened Species - Conserve Wildlife Foundation of New Jersey. Retrieved from http://www.conservewildlifenj.org/species/fieldguide/view/Tursiops%20truncatus/

Defenders of Wildlife. (2014). Dolphin - Basic Facts About Dolphins. Retrieved from http://www.defenders.org/dolphin/basic-facts

Dolphins-World. (n.d.). Dolphin Echolocation - Dolphin Facts and Information. Retrieved from http://www.dolphins-world.com/dolphin-echolocation/

GBTexas1. (2011, June 5). Dolphin Jumping in Boat Wake near Marco Island Florida Part 1. Retrieved from https://www.youtube.com/watch?v=lkgDlI924GY

Volk, W. (2011). Bottlenose Dolphin [Photograph]. Retrieved from http://www.conservewildlifenj.org/images/artinline_1012.jpg