The porpoise has several teeth
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Porpoise
Porpoises are a group of fully aquatic marine mammals, similar in appearance to a dolphin, all of which are classified under the family Phocoenidae, parvorder Odontoceti (toothed whales). They are, however, more closely related to narwhals and belugas than to the true dolphins. There are eight extant species of porpoise, all among the smallest of the toothed whales. Porpoises are distinguished from dolphins by their flattened, spade-shaped teeth distinct from the conical teeth of dolphins, and lack of a pronounced beak, although some dolphins (e.g. Hector’s dolphin) also lack a pronounced beak. Porpoises, and other cetaceans, belong to the clade Cetartiodactyla with even-toed ungulates, and their closest living relatives are the hippopotamuses, having diverged from them about 40 million years ago.
Porpoises range in size from the vaquita, at 1.4 metres (4 feet 7 inches) in length and 54 kilograms (119 pounds) in weight, to the Dall’s porpoise, at 2.3 m (7 ft 7 in) and 220 kg (490 lb). Several species exhibit sexual dimorphism in that the females are larger than males. They have streamlined bodies and two limbs that are modified into flippers. Porpoises use echolocation as their primary sensory system. Some species are well adapted for diving to great depths. As all cetaceans, they have a layer of fat, or blubber, under the skin to keep them warm in cold water.
Echolocation
Porpoises are abundant and found in a multitude of environments, including rivers (finless porpoise), coastal and shelf waters (harbour porpoise, vaquita) and open ocean (Dall’s porpoise and spectacled porpoise), covering all water temperatures from tropical (Sea of Cortez, vaquita) to polar (Greenland, harbour porpoise). Porpoises feed largely on fish and squid, much like the rest of the odontocetes. Little is known about reproductive behaviour. Females may get one calf every year under favourable conditions. Calves are typically born in the spring and summer months and remain dependent on the female until the following spring. Porpoises produce ultrasonic clicks, which are used for both navigation (echolocation) and social communication. In contrast to many dolphin species, porpoises do not form large social groups.
Porpoises were, and still are, hunted by some countries by means of drive hunting. Larger threats to porpoises include extensive bycatch in gill nets, competition for food from fisheries, and marine pollution, in particular heavy metals and organochlorides. The vaquita is nearly extinct due to bycatch in gill nets, with a predicted population of fewer than a dozen individuals. Since the extinction of the baiji, the vaquita is considered the most endangered cetacean. Some species of porpoises have been and are kept in captivity and trained for research, education and public display.
Their scientific Name
Porpoises belong to the Phocoenidae family and the class Mammalia. There are seven subspecies of porpoises. These include the harbor porpoise, Burmeister’s porpoise, Dall’s porpoise, the narrow-ridged finless porpoise, the spectacled porpoise, the Indo-Pacific finless porpoise, and the vaquita – thought to be the most endangered marine mammal in the world.
The scientific name of a harbor porpoise is Phocoena phocoena. The word ‘Phocoena’ is Latin for ‘pig fish’. A porpoise is sometimes called a puffin’ pig because of the exhaling sound it makes when it reaches the surface of the water after a dive. Some scientists think the noise sounds like a sneeze!
Do Porpoises Have Teeth?
Okay, so you’re here for a reason. Let’s go over everything you’ll need to know about porpoise teeth and just what they use them for.
Porpoise Teeth And Age
Did you know that examining porpoise teeth can help tell you how old the porpoise is? This is done by analyzing the Growth Layer Groups (GLGs) on the teeth. The average age of the porpoise in the wild is 20, but the oldest recorded age is 24 years.
Note: There is a problem with using teeth to find the age of an older porpoise, as the amount of tissue and mineral resorption in older animals can make it difficult to pinpoint the exact age of the porpoise.
Diet
Porpoises eat mostly non-spiny fish such as herring, pollack, hake, cod, and sardines. They also eat squid, octopi, and crustaceans on occasion.
One fascinating fact is that Porpoises don’t use their teeth to eat. Instead, they are used to grab their prey, which they then swallow whole.
While the shape of the teeth isn’t confirmed to aid in their feeding habits, all porpoises have rigid growths between their teeth, called “gum teeth.” These are believed to help the porpoise grasp more slippery prey, such as squid.
A type of fish called a large flatfish is dangerous for porpoises. Because the porpoise swallows its food whole, they tend to choke on the flatfish.
This is why they will stick to smaller fish, though this will require them to consume large quantities to satisfy their needs. Porpoises need to eat up to 10% of their body weight every day.
What is the difference between Porpoise and Dolphin?
The answer comes down to the specific species of both dolphin and porpoise. Many think of the bottled-nose dolphin when they think of the species, but there are other dolphins that can look more like porpoises.
While these physical distinctions for either animal can differ between species, here is a list of common differences:
- Dolphins have coned teeth as porpoise have spade-shaped teeth,
- Porpoises are generally smaller in length than dolphins
- Dolphins will typically have a curved dorsal fin; a porpoise’s will be more triangular
- Porpoise body types tend to be more portly, while a dolphin will be leane
Up to 240
Dolphins have one set of teeth to last their whole lifetime and the number of teeth varies considerably from species to species. The long-beaked common dolphin has more teeth than any other dolphin with up to 240. Risso’s dolphins have the fewest; they have between 4 and 14 teeth in their lower jaw only. Risso’s favourite food is squid which they suck into their mouths. Amazon River dolphins (botos) have between 100-140 teeth and uniquely they include molar shaped teeth at the back as well as the conical ones at the front. Botos have a particularly varied diet including more than 40 fish species as well as crabs, snails and even turtles which they crunch using their molars!
Bottlenose dolphins have between 80 and 100 teeth.
Although all dolphins are equipped with teeth not all species use their teeth for eating prey or tearing flesh. Most use their teeth to grab, grip and secure prey and then swallow it whole—head first.
Facts About Porpoises
Size
Porpoises are also shorter than dolphins. They grow to 5 to 6.6 feet (1.5 to 2 meters) and weigh 110 to 265 lbs. (50 to 120 kilograms). In contrast, the bottlenose dolphin grows to around 8 feet (2.5 m) long and weighs between 440 to 660 lbs. (200 to 300 kg).
Habitat
There are six species in three genera of porpoise. As their name implies, Gulf of California harbor porpoises are found around the northern part of the Gulf of California. Black porpoises, also known as Burmeister’s porpoise, live off the coasts of eastern and western South America, according to the International Union for Conservation of Nature (IUCN).
The spectacled porpoise likes cold water and has been found all around the world in a zone just north of Antarctica. The common porpoise, or harbor porpoise, also likes cold water, but sticks to the east coast of North America, around southern Greenland, waters off the northern coasts of Scandinavia and off the coasts of Alaska and Japan.
Dall’s porpoise sticks to the northern rim of the Pacific Ocean. Some finless porpoises can be found in the Yellow Sea between China and Korea, and around southern Japan, while others swim along the coasts of South Asia.
Some porpoises don’t just stay in the ocean. Some swim in rivers and channels, as well, and can handle both salt and fresh waters. For example, the finless porpoises live in coastal waters and rivers along the Indian Ocean and western Pacific Ocean.
Reproduction, Babies, and Lifespan
Porpoises mate throughout the year, but scientists have found more mating activity occurs in the spring and fall seasons. This holds true for dolphins as well.
Male porpoises mate with several females each year. However, a female only has young every two to three years. The gestation period of a female porpoise is 10 to 11 months.
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A female porpoise gives live birth to one baby also known as a calf or pup. She gives birth as she swims through the water and sometimes the birth can take two hours. The porpoise calf comes out tail first. After it is born, the calf stays with its mother and nurses as they both swim along. The father is not involved in caring for the baby.
A porpoise calf is nursed for about eight months and slowly learns how to capture fish during this time. It is fully weaned by about 24 months of age.
There is a special relationship between a mother porpoise and her calf. The calf may stay with her from three to six years as it learns how to become a strong swimmer and survive on its own. The process of learning to stay afloat and swim after prey isn’t easy, so a calf needs a lot of guidance from its mother.
Porpoises can live for up to 23 years. The overall health and strength of a porpoise as well as the number of predators in the area can have an effect on its lifespan.
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