I recent took my granddaughter on a dolphin tour out of Pensacola Beach. It was amazing. It was a cool October morning, not a cloud in the sky, the winds were calm, the water crystal clear due to the lack of rain over the past few weeks, and the dolphins were out.
They are amazing animals and always seem to grab your attention no matter how many times you see them. I was a student at Dauphin Island Sea Lab from 1980-81 and taught there from 1985-1990. No matter how many times we heard “dolphins” when out on one of the research vessels, everyone had to run over to look. People do enjoy seeing dolphins. There is just something about them.
During the tour at one location, we saw a group of them (a pod) feeding on fish in the shallow water. They would roll and chase, you could see the sand being kicked up from the bottom as they did. At another location we saw them in breeding mode. Slower moving, caressing, fluke slapping as they turned all around in the water near us. The tour guide told us all sorts of dolphin facts, and some great jokes to go along with them. It was a good program, and my granddaughter was loving it.
She looked over at me at one point and said, “dolphins use to walk on land”. I responded that actually their ancestors did. Dolphins, as we know them, were very much aquatic animals. This led to thoughts on other dolphin questions I have heard over the years.
What is the difference between a dolphin and a whale?
Size… and in some cases teeth.
All whales and dolphins are in the mammalian order Cetacea. Mammalian orders are divided based on the type of teeth they have. Cetaceans are homodonts, meaning they have only one type of tooth. For the toothed whales, these are canines, they lack the molars and incisors that many other mammals have. But some have no teeth rather a specialized fibrous material called baleen, similar to the bristles of a broom, with which they can filter plankton from the water.
There are over 90 species of cetaceans in the world’s oceans, 21 of those are known from the Gulf of Mexico. In a recent published survey by the National Marine Fisheries Service, most of the cetaceans in the Gulf of Mexico are of the toothed whale variety and most occur beyond the continental shelf (which is between 60 and 140 miles south of Pensacola). The only baleen whale in their report was the Byrde’s Whale (Balanopatera edeni). They estimate about 33 of these whales based on their transect surveys and all of these were found beyond the continental shelf between Pensacola and Apalachicola Florida. The largest of the toothed whales reported was the sperm whale, which can reach over 60 feet. They estimate 763 sperm whale in the Gulf, and they were found across the basin beyond the continental shelf.
But it is the bottlenose dolphin (Tursiops truncatus) that we see on the dolphin tours. This is a relatively small toothed whale, reaching lengths of 13 feet, though most in the Gulf region are less than 10 feet. They are the most abundant and most frequently encountered cetacean near shore and within the estuaries and seem to prefer these shallower waters to the open Gulf beyond the shelf. The National Marine Fisheries Service divides them into stocks based on their geographic distribution. They report 37 different stocks of bottlenose dolphins in the northern Gulf. These are divided into western, eastern, and northern stocks, and then subdivided into estuarine stocks. There are separate stocks for the Perdido Bay and Pensacola Bay groups. This report indicated the stock size for the Pensacola and Perdido Bay dolphins was unknown, though our tour guide indicated there were about 250 in the Pensacola Bay stock. The National Marine Fisheries Service did report about 179 dolphins in the Choctawhatchee Bay stock. The reports estimated over 51,000 individuals for the northern Gulf.
Though not listed as endangered or threatened by the Endangered Species Act, there is some concern on the smaller estuarine stocks and so they have been labeled as “strategic”. There has been fishery related mortality with these dolphins in our waters, primarily with longlining and otter trawl operations, but losses are less than four animals/year and do not seem to be impacting their populations.
What is the difference between a dolphin and a porpoise?
Though many associate the long beak as a dolphin, there are dolphins with short snouts. Killer whales are actually large dolphins. The answer goes back to the teeth, as it always does when classifying mammals. Dolphins have conical shaped teeth where porpoise have more spade shaped ones.
How smart are dolphins?
As everyone knows these are highly intelligent animals. They use an audible form of communication that includes squeaks, clicks, and whistles, to keep the pod together. Researchers have discovered that these audible sounds have a sort of “accent” to them that tells dolphins which pod the dolphin communicating is from. This appears to be very important being that dolphins from one social pod may not accept others from different one. I remember in 1993 when a group of five pantropical spotted dolphins stranded on Pensacola Beach. There were four adults and one 3-month year old in the group. After failed attempts to return the dolphins back to the Gulf, it was decided to transport them to a quarantine area near the EPA lab on Pensacola Beach. There was a virus spreading through some European populations and they did not want to risk taking them to the Gulfarium. In route three of the four adults passed away. The remaining adult was named Mango and the juvenile was named Kiwi. After a period of time in quarantine Mango passed away leaving on the young Kiwi. There was a move to return Kiwi to the wild but some of the dolphin experts on scene told me the likely hood of a different pod accepting Kiwi was a risk, and finding her original pod was very unlikely. After determining the dolphin did not have the virus of concern, they decided to move her to the Gulfarium in Ft. Walton Beach, where she lived the rest of her life.
How does dolphin echolocation work?
Echolocation is different than communication, in that it is inaudible. As with communication, the sounds are produced by expelling air through the blowhole. In the case of communication, there is a muscle that partially closes the opening of the blowhole producing the sounds we hear. In echolocation this is completely closed, and the sound waves are moved through a fat filled melon near the head. The shape and density of the melon can be changed by the animal to produce different frequencies of sound but all inaudible to our ears. These sounds are emitted through the melon into the environment, where they contact something and “echo” back to the dolphin. These echoes are received in a fat filled cavity of the lower jaw and transferred to the brain – where the animal is then made aware of the object out in front of them. Some studies suggest that it may be more than knowing there is an object, they may be able to distinguish different kinds of fish. Though it is most effective within 600 feet, studies show their range may be up to 2000 feet. Studies have also shown that some species of toothed whales can alter the frequency of these echolocated sounds to stun their prey making them easier to catch.
Dolphins are amazing animals.
They live between 30 and 50 years in the wild. During this time, they form tight social groups, feed on a variety of prey, and produce new members every 2-3 years. There is so much more to the biology, ecology, and social life of these animals and we recommend you read more. Once you understand them better, we also recommend you take a dolphin tour to view these amazing creatures.
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