Dolphin does not really create a shelter.  However, like other animals, they are vulnerable when they sleep.  In addition to danger from their predators, Dolphin must remain awake to breathe.  If he looses consciousness completely he would suffocate or drown.  Thus, Dolphin only allows one half of his brain to sleep at a time (called unihemispheric sleep).  The other half of his brain remains engaged to control breathing and to be alert to danger.  Dolphin will close the left eye when the right half of the brain sleeps, and the right eye when the left half of the brain is asleep.  This switch will happen about every 2 hours.  

Bottlenose dolphins are found all around the world in tropical and temperate waters.  The populations that live closer to the shore are called “inshore” and are generally smaller and lighter with shorter fins and snouts.  They tend to stay in their area.  Populations that live further out to sea are referred to as “offshore”.  These dolphins are larger, darker, and have bigger fins and snouts.  Offshore populations migrate much longer distances and may travel up to 2,600 miles in a season.

The common bottlenose dolphin is a carnivore with a varied diet.  He will consume about 15 pounds of food a day, usually swallowing it whole.  His teeth are instead used to grip his dinner.  Favorite foods includes a wide range of fish, squid, shrimp, crustaceans, and eels.  Dolphin will hunt individually and cooperatively by herding, charging, and trapping his prey. 

Dolphins are polygamous and although they can copulate all year round, they are most likely to breed in the spring.  Sexual maturity will occur between 8 and 13 years for the boys and 5 to 10 years for the girls.  Some studies suggest dolphins have a liberal sex life, fornicating for learning, play, dominance, or pleasure.  When it comes to breeding however, there is a real power struggle.  A male alliance of 2-3 dolphins will surround and capture a female in estrous in order to monopolize her reproductive window. While this is sometimes done by force, she is not without her own power which lies in her complex spiral shaped vagina.  If she cannot avoid a male that she does not fancy, she can reposition herself during copulation steering the penis and subsequent sperm away from her treasured egg and instead into a fold or pocket, thereby controlling paternity.

Dolphins gestate for a full year, and will typically bear a calf every three to six years.  The babies are usually born tail first, weighing in at 30-50 pounds and about 2.5-4.5 feet long.  For the first month of his life, both he and his mother will stay awake always because he is not born with enough body fat to keep him afloat.  All this swimming tires him and his mother, making them vulnerable to attack and infections.  Once they can begin the unihemispheric sleep cycle, they gain strength and stamina.  He will likely nurse for 20 months or so and will linger with his mom for several years. 

Bottlenose dolphins are considered top predators in the oceans.  They occasionally become prey to sharks and orcas, but the largest danger to them are humans.  Dolphins become entangled in fishing gear and are still hunted by humans.