Join Bob at the rose Auditorium on the Marco Island Historical Museum campus on February 20th at 7 PM when he talks about the different types of dolphins found around the globe. Learn how their varied habitats have a direct effect on how they feed, what they eat and their social behavior. Bob’s last presentation drew more than 150 guests so arrive early to get a good seat! Free for MIHS members and only $10 for the public.
It’s always a thrill to watch the excitement on people’s faces when a dolphin comes to the surface and take a breath! Here, in the Marco Island area, the species known as Bottlenose dolphins are residents and have learned how and where to feed, play and rest. But what about the rest of the planet? Do we only find this one type of dolphin? The answer is a resounding no, so let’s meet several species right now.
First of all, like all other animals, dolphins are classified into a Kingdom, Phylum, Class, Order and, for dolphins, then into an Infraorder then Parvorder and Species. The word “Dolphin” originated from the Greek “delphus” meaning womb. Loosely translated, it means “fish with a womb.” Under the Parvorder Odontoceti—with teeth—we will find about 38 species in the Delphinidae category, which are ocean dolphins and 5 more river dolphin species, giving us a total of at least 43 types of dolphins.
As mentioned, we find the Bottlenose variety of them in the Marco area. However, there are at least 8 more species as we venture from the offshore currents to the depths of the Gulf. Some of the most prominent of these are the Atlantic Spotted Dolphin, Rough-toothed dolphin, Fraser’s Dolphin, Clymene Dolphin and a few more. The Bottlenose tend to hug the coastline throughout the Gulf. Occasionally a Spotted Dolphin is seen closer to shore while some of the other varieties tend to enjoy the deeper waters, with some diving more than 1,000 feet deep to get to their food. All of these dolphins have a diet comprised of fish, with some enjoying squid and octopus.
Are there any really large dolphins in the world? You bet! Weighing up to 6 tons and growing to more than 30 feet long, the Orca is the largest species of the dolphin family. Also known as Killer Whales, they are one of the most powerful predators on the planet. Being at the top of the food chain they will feed on fish, penguins, seals, sea lions and even other whales and dolphins. While most oceanic and river dolphins have teeth in the 1-inch range, Orca teeth can become as big as 4 inches long. Adult females will give birth every 3 to 10 years and the pregnancy period is 17 months. They give birth to only 1 calf at a time and the young will nurse from mother’s milk for up to 2 years.
Orcas will swim up to 40 miles a day, playing and looking for food. Also, they will dive as deep as 500 feet several times per day and every day of the year. They sleep just like other dolphin species. They allow one half of their brain to rest while the other half stays alert, allowing them to stay alert and continue breathing. They can alternate which side is sleeping, just like other dolphins do, so they can get a needed rest but never lose consciousness. This is known as a “Unihemispheric” sleep.
We mentioned that there are several species of River Dolphins as well as oceanic dwellers. 1 such WAS known as the Baiji, and I emphasize WAS. This freshwater dolphin lived only in the Yangtze River in China. It is the only member of the mammal family called Lipotidae because of a unique skeletal structure and, while other dolphins have 2 compartment stomachs, the Baiji had 3. It evolved from other river species more than 20 million years ago, but sadly, this species was pronounced extinct in 2007. Their ability to communicate, avoid danger, find food and navigate using echolocation became more difficult as the Yangtze became busier. Habitat loss due to human expansion was the culprit for the demise of this river species.
We can’t end this without talking about the always favorite Pink Dolphin. Found in the Amazon and Orinoco river basins of South America, this freshwater cetacean has an estimated population in the tens of thousands. The primary threat to this species is a diminishing food supply. They primarily eat catfish and are considered a competitor for this fish by humans. Catfish brings a huge price in this area. Many Pink Dolphins are killed or injured because of this. In addition, gold mining industries in the Bolivia area takes a toll on them as well. Mercury pollution from these mines reaches the dolphins through the bottom–feeding catfish. These fish are greatly affected by water metals.
There are many, many more types of dolphins out there and, since the planet is 2/3 covered by water, surely more species have yet to be discovered. When the talk of so many animal and plant species becoming extinct, wouldn’t it be nice to find some new mammals, some unexpected wonders of nature, to give a sign of hope that nature may still progress?
Bob is a naturalist for the 10,000 Island Dolphin Study Team onboard the Dolphin Explorer. He is the author of 2 books and a frequent speaker at public venues throughout south Florida. An award-winning columnist for Coastal Breeze News. Bob loves his wife very much!