PORPOISES (Phocoenidae) Many years ago, the term Porpoises, were used by sailors and fishermen to refer to small dolphins. Well, they were almost right. Contrary to the believes of many, porpoises are not dolphins even though they share certain distinct similarities, especially when it comes to scientific classification, intelligence and their usage of echolocation for navigating, communicating and hunting. Just like the dolphins, poropises are considered mammals and are warm blooded. In other words, they give birth to their young and their bodies have a natural way of maintaining a constant warm temperature, just like us. However, despite having these distinct similarities with dolphins, porpoises have many unique attributes which allow us to not only differentiate them from the dolphins but also from other species of the same family. Like any other families, each species within the Phocoenidae category have their own preferences in many different things: food and even habitat. In addition to that, each have their distinct physical anatomy and behaviorial attributes which allow us to single them out. Further down this article, the main differences between dolphins and porpoises will be pointed out. However, to give a brief summary of the family (phocoenidae) as a whole, stated below are some of the charecteristics that one should know about porpoises. – Average lifespan: 15-25 years – Average length: 1.2-2.4 meters Even though the male and female porpoises of most species are about the same size, there are some that are otherwise. For the Harbour Porpoise and Vaquita Porpoise, the females are slightly larger than the male.
Transcript
PORPOISES
(Phocoenidae)
Many years ago, the term Porpoises, were used by sailors and fishermen to refer to small dolphins. Well, they were almost right. Contrary to the believes of many, porpoises are not dolphins even though they share certain distinct similarities, especially when it comes to scientific classification, intelligence and their usage of echolocation for navigating, communicating and hunting.
Just like the dolphins, poropises are considered mammals and are warm blooded. In other words, they give birth to their young and their bodies have a natural way of maintaining a constant warm temperature, just like us. However, despite having these distinct similarities with dolphins, porpoises have many unique attributes which allow us to not only differentiate them from the dolphins but also from other species of the same family.
Like any other families, each species within the Phocoenidae category have their own preferences in many different things: food and even habitat. In addition to that, each have their distinct physical anatomy and behaviorial attributes which allow us to single them out. Further down this article, the main differences between dolphins and porpoises will be pointed out. However, to give a brief summary of the family (phocoenidae) as a whole, stated below are some of the charecteristics that one should know about porpoises.
– Average lifespan: 15-25 years
– Average length: 1.2-2.4 meters
Even though the male and female porpoises of most species are about the same size, there are some that are otherwise. For the Harbour Porpoise and Vaquita Porpoise, the females are slightly larger than the male.
However, for the Burmeister's Porpoise and Spectacled Porpoise, their males are larger than the female.
Interestingly, for Dall's Porpoises, not only their males are slightly larger and thicker than the females, those in the Eastern Pacific are generally smaller than those in the Western Pacific.
– Average weight: 30-220 kg
– Diet: Food that these creatures eat depends on the species and their habitat, but generally, they eat small marine creatures such as, Shellfish, Grey Shrimp, Whiting, Gobies, Squid, Cuttleffish, Octopus, Cod, Herring, Anchovies, Pollock and Sardines
*Porpoises consume about 10% of their body weight each day*
– Habitat : The distribution of porpoises highly depend on the various species as each species have their own preferences. However, on the average, porpoises prefer to live near the shore and can sometimes be found at bays, harbours, rivers, estuaries and inland waters.
1) Harbour Porpoise: Prefer the shallow waters of the Northern Hemisphere from the waters of Mauritania to Alaska.
2) Dall's Porpoise: Found only in the North Pacific and are in abundance at the shelf break of the Berring Sea. They also seem to be confined to colder waters with temperatures of less than 60 Degrees Farenheit (15 Degrees Celcius) and during the Northern winter, they'll move to Baja California.
3) Burmeister's Porpoise: They are endemic to the cold, coastal waters of South America, South-east Pacific and South-West Atlantic Oceans.
4) Finless Porpoise: Prefer the warm and tropical coastal waters of South and East Asia, from the Arabian Gulf East to Japan and South to Java Indonesia. However, one of its subspecies, Neophocaena Phocaenoides Asiaorientalis, lives in the freshwater of Yangtze River.
5) Vaquita Porpose: Being the species who has the most restricted range, it is endemic to the
upper portion of the Gulf of California and is usually within 125km of the shore.
6) Spectacled Porpoise: This species has a southern circumpolar distribution in sub-Antartic waters – southern Atlantic, Indian and Pacific oceans - with temperatures ranging from 5.5 to 9.5 Degrees Celcius.
– Predators: Great White Sharks, Killer Whales (Orcinus Orca), Humans
– Threats: Porpoises often become the bycatch of fishing trawlers, in their gill and drift nets. More often than not, they are also susceptible to chemical (e.g. pesticides) and noise ( e.g. from deforestation) pollutions. In addition to that, due to their near shore habitat, in some countires, they are being caught by humans for their oil, meat or to be made into crab bait. However, for the Vaquita Porpoise, their
main threat is inbreeding due to low population numbers and this can result in increased 2'homozygosity' which may threaten their population as a whole.
*A particular oil for lubricating can be obtained from poropise fat.*
Scientific Classification
Aas mentioned above, just like whales and dolphins, porpoises are considered mammals and all of them are Cetaceans, which also places them under the family of Odontonceti (toothed whales). However, porpoises are neither whales nor dolphins; they are in a league of their own with some having their own sub-species. Up till now, there are only six species of porpoises left in the world and one of them is even stated as being critically endangered, by the International Union for Conservation of Nature (IUCN)
1 Shirihai and Jarrett 20062 Homozygosity means to have two identical alleles of the same gene 3 Rice 1998
3) Burmeister's Porpoise (Phocoena Spinipinnis) a.k.a Black Porpoise, Marsopa Espinosa, Spiny Porpoise or Sea Pig (4Described by Karl Hermann Burmeister in 1856)
4) Finless Porpoise (Neophocaena Phocoenides)
- Indo-Pacific (N.P. Phocaenoides)- Yangtze River (N.P. Asiaorientalis) - Japan and Korea (N.P. Sunameri)
5) Vaquita Porpoise (Phocoena Sinus) a.k.a Gulf of California Porpoise or Cochito
6) Spectacled Porpoise (Phoca Dioptrica)
Evolution
Porpoises are thought to have existed since 15 million years ago and have been confined within the North Pacific basin from where they evolve to the six species that we now know of. Within that 15 million years, porpoises have been distinct from their dolphin relatives for about 511 million years.
The first toothed-whales, which appear 50 million years ago, only started using their ability to use bio sonar 30 million years ago and the porpoises, like dolphins, use echolocation for various reasons. However, during those years of evolution, they have developed the ability to emit higher frequency sound that even killer whales have difficulty hearing. Killer whales hear best when the sound is about 20 kHz and are not able to hear anything that is higher than 100kHz. This makes it
4 Whalefacts.org5 Dallsporpoise.org
hard for the orcas to detect any porpoises that are within their area.
Intelligence
Porpoises are as intelligent as their fellow relatives, the dolphins, and it has been known that both are among the few species in the world that can identify themselves when being shown the 6mirror. This shows that they are able to connect the dots and analyse whatever situations they are in. Take for example, when the food source in a particular area runs low, they will start to outsource and move to the next nearest area where food is in abundance.
Physical Anatomy
As mentioned before, many tend to make the mistake of putting porpoises together in the same family as dolphins. Even though it is understandable why such an assumption is being mad; due to the fact that porpoises and dolphins look similar, from far. Which is why to truly see the difference, one must look a little closer to be able to see the conspicuous distinctions between those two species.
One major similarity between dolphins and porpoises that we have to remember is that, both have a way of maintaining a constant warm body temperature, using the layer of blubber that lies under their hairless (except for a few bristles on their head) skin.
The first major difference that will be pointed out is the shape of their teeth. While dolphins have conical-shaped teeth, porpoises have teeth that are shovel shaped that are flat with long and sharp upper edges. On the average, an
individual porpoise have 60-120 teeth.
Secondly, dolphins have a pointed snout but porpoises have a short and blunt head. The only porpoise to have a bulbous melon is the Finless Porpoise who is also, the only porpoise that lacks in a true dorsal fin which in place, has a ridge that runs down all the way to the back middle. Speaking of dorsal fins, porpoises' fins are triangular in shape (much like a shark) and has a straight leading edge unlike dolphins who have a curved dorsal fin.
Thirdly, if you look at both families as a whole, the porpoises have a shorter (making them the smallest of all toothed-whales) and stouter body shape while the dolphins have a much longer and sleeker body. In addition, porpoises have limited neck mobility compared to dolphins as their neck vertebrae are more fused.
For easy identification, stated below are some of the unique physical anatomy that each species owns.
1) Harbour Porpoise: They have small dorsal fins, their flukes are notched and their sides are often speckled with white.
2) Dall's Porpoise: Slightly more muscular with a conspicuous white ventral patch on each side which begins at flipper level (similar to a killer whale) and white to light grey 'frosting' on its dorsal fin and fluke. Also, each tooth is seperated by rigid, protruding growths called “gum teeth”.
3) Burmeister's Porpoise: Dorsal fin has a sharp point with 'teeth' on leading edge and have tubercles on the leading edge of its dorsal fin which is longer, has a lower rise and is set further back than the other porpoises. In addition, there is a prominent stripe which runs from the chin to the flipper and is more obvious on the left side.
4) Finless Porpoise: No dorsal fin, overall grey in colour with a paler throat and face. There's a scattering of horny tubercles on the dorsal ridge which acts as an anti-slip surface when female carries its calf on her back.
*It has been argued that the horny tubercles on a Finless Porpoise act as sensory organs with each tubercles containing numerous nerve endings*
5) Vaquita Porpoise: Its lips, chin and eye rings are black. This is the smallest and rarest porpoise to date.
6) Spectacled Porpoise: It has an unusual coloration, small head, peculiar facial features and black lips. More importantly, it has a white rim around black eye patch which resembles a pair of spectacles.
Lastly, porpoises exhibit “paedomorphosis” in their skulls; in other words, they retain juvenile characteristics even in an adult. Therefore, if one looks close enough, the skull of an adult porpoise looks like the skull of any other juvenile cetaceans.
Behaviour
We as humans, are closely related to porpoises; first of all, we are both mammals. Being that, there are some traits that we have in common and one of it is having a character that is uniqely them.
Unlike the dolphins, porpoises are usually found in smaller pods. For example, the Harbour Porpoise is more solitary than the Dall's Porpoise; they normally travel alone – like the Spectacled and Burmeister's Porpoise - or in small group sizes of up to 3 individuals in one pod even though large aggregations have ocassionally been spotted. They tend to avoid boats and thought to remain resident in one area for a extended periods. Like the Finless Porpoise (except those in the Yangtze River who have gotten use to boat traffic), the Vaquitas are shy, elusive, timid and hard to spot in the wild. On the other hand, Dall's porpoises, who travel in pods of 2-20 individuals, are attracted to fast moving vessels and commonly bowride. More interestingly, they are known to associate with Pacific White Dolphins and Short Finned Whale, just like the Harbour Porpoise who are sometimes seen with Fin and Humpback Whales along the Canadian coast in the summer.
Dall's Porpoises are not only the least shy of all porpoises, they are considered to be the 7fastest and most gregarious swimmers among small cetaceans, capable of reaching 30 knots (55 km/h) over short
distances; often swimming in a zig-zag pattern with fast, jerky steep angled turns. Similarly, the Finless
and Burmeister's Porpoise swims just below the surface of the water with sudden, darting movements
and tend to roll onto their sides when breaking the surface, not disturbing the water greatly. Which is
why, it is difficult to spot them unless in calm conditions. On the other end of the spectrum, the Spectacled Porpoise moves slowly by rolling forward in the water; not as acrobatic as other small
ccetaceans.
Unlike dolphins, porpoises rarely leap out of the water especially the Finless, Harbour and Dall's Porpoises. They are known to sphyhop to analyse their surrounding but are not known for breaching. However, Dall's Porpoises are famous for their 8“rooster spray” - a hollow stream of water that arcs, up and over their head – which allows the porpoise to continue breathing while swimming.
All porpoises may not have the ability to swim fast, but most of them are capable of deep dives; diving to a depth of 656 feet (200m), even though they prefer to stay in shallow waters. Especially Dall's Porpoise who can dive up to a depth of 1640 feet (500m).
Feeding/Hunting
Porpoises generally hunt in solitude but there have been reported sightings when a few porpoises come together to herd a school of fish for their meal. In addition, they are mostly opportunistic feeders: consuming various types of fish that's available in their habitat. Dall's Porpoise, are known to feed mostly at night where they are able to eat different food such as squids.
Reproduction
The reproduction process of any species is vital in ensuring the survival of its generation. Similarly, it is important for the porpoises the keep reproducing healthy young especially when most of its species have dwindling numbers.
Here is an interesting fact. The males of the Harbour Porpoise are always having a sperm competition. They have a marked development of the testes seasonally which may weigh up to 4.6% of the body, adding 1.5 pounds to their overall body weight during mating season.
7 NOAA Fisheries; Office of Protected Resources8 Alaskan Department of Fish & Game; Text by John Wells, Printed in 2008
For them, sexual maturity occur at a very young age of about 3-9 years old for both male and female. The females have an average gestation period of 7-12 months, giving birth to one calf at a time every 1-3 years depending on the species. Their calves are born half the size of the female, whom she will then bring up to the surface to take the first breath; she will also swim on her side to suckle her young whom she wil nurse for only 7-12 months. Their mating season is usually during the summer of the Northern Hemisphere.
9*Females of the Finless Porpoise have been spotted carrying her single calf on the back as on a saddle when she comes out to breathe*
Sound
This is the one attribute that porpoises share with dolphins and that is using echolocation for various reasons such as hunting, communicating and navigating. Both will produce this sound most of the time and using it to their advantage. Most of us deem dolphins to be talkative because we always hear them 'talking' unlike porpoises, whose sounds we rarely hear. That is because, porpoises produce sound at about 130kHz and we humans are only able to hear sounds that are only up to 20kHz and dogs, up to 60 kHz. Scientists think that porpoises don't make audible sounds, like the dolphins, due to structural difference in their blowholes.
On the other hand, the Harbour Porpoise makes a distinctive and explosive noise as it comes to the surface to exhale hence the name “Puffing Pig” which is sometimes being used to refer to this particular species of the porpoise family.
Echolocation, a sensory sonar system, are too complex and remains a mystery. However, we do know the basic mechanics of it. They will release a focused beam of clicking sounds (sound waves).Once they've listen to the echo, these porpoises are able to determine the following about an object:
• Size• Shape
• Distance• Speed
• Direction• Internal Structure (depending on the
object). Sound waves can enter beneath the surface
9 Whales and Dolphins Conservation
therefore giving feedback and information of the internal structure of an object.
However, due to their 10sophisticated echolocation abilities, which sets them apart from the rest of the toothed whales, they are able to locate small fishes and even small objects such as net floats or fine fishing nets and this is done by producing very short clicks which are higher in frequency.
Killing of Porpoises
Unfortunately, porpoises have a similar fate as the dolphins, where in certain areas, they are being hunted for various reasons, especially for oil and meat. In some of those places, porpoises are eaten by humans, but generally, the meat is not considered palatable.
*During the middle ages, harbour porpoise meat was considered a delicacy suitable for a royal feast*
Here are the current statuses of each species as on the IUCN Red List:
1) Harbour Porpoise: Least Concern2) Dall's Porpoise: Least Concern3) Burmeister's Porpoise: Data Deficient4) Finless Porpoise: Vulnerable5) Vaquita Porpoise: Critically Endangered6) Spectacled Porpoise: Data Deficient
11*Japanese hunts Dall's porpoises in the Northern Pacific as a source of meat for human consumption. Currently, about 18000 are being taken each year*
In the News
– Recently, scientists have noticed that the carcass of a porpoise washed ashore have bite marks and are obvious that it was a victim of foul play by an unsuspecting culprit, the Bottlenose Dolphin. This is what scientists call a “porpicide”: the intentional slaying of a porpoise. (San Francisco Chronicle, 11/17/11)
*A Bottle-nosed Dolphin throwing a porpoise out of the water*
– There were a number of porpoises being washed up on Bay Area shores. Necropsies showed
10 Explained by Lee Miller from Institute of Biology, University of Southern Denmark (SDU)11 According to N.O.A.A
multiple fractures from blunt-force trauma while some had tooth marks. In addition, activity of the attack was focused on the genital area of the porpoise. This shows that attacks might not be solely territorial but also sexual. (Huffington Post, 11/21/11)
– World Conservation Union currently lists Harbour Porpoise as a vulnerable species. (National Geographic)
– On June 6, 2013, the Mexican government announced it would begin to phase out drift gillnets used for shrimp fishing in the upper Gulf of California, and substituting them with more selective and vaquita-friendly fishing gear which will reduce bycatch of the vaquita porpoises. (WWF)
Hi, I'm Sally. I'm a porpoise. Is that a peanut butter sandwich you're eating? Could I have a bite? No? Okay. Will you be my friend?
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