Evolution and Systematics
Perhaps the oldest of all the family of dolphins and whales is Physeteridae dating back to 30 million years ago. They possess many characteristics of a toothed whale (odontocete) precisely due to the fact that both families co-existed previously.
Unlike few characteristics which are primitive there are some that are highly adapted. However, it does not retain any similarity from Eocene cetacens from which they derived.
Physeterid (Ferecetotherium) is thought to be the earliest in Oligocene but it had a reduced head size.
Physeterid is the earliest record belongs to the odontocete family. In the years gone by, Physeterid is thought to have diverse classification of fossil records.
We are lucky to have Sperm Whale (Physeter macrocephalus) as it is the only extant species (of the genus Physeter). Of all the surviving odontocete, Sperm Whale is the most phylogenetically distinctive species.
Sperm Whale Facts
- All the sperm whale species are recognized by a lop-sided rostrum with their forehead seems like a head filled with fat, giving an odd front posture.
- It has a posterior blowhole and a pointed head. Of all the sperm whale species, Kogia indeed has the shortest rostrum.
- All species of this family show a dark-grey color from the above and it fades away as we move towards its belly.
- These species absolutely lacks teeth in their upper jaw though very tiny teeth around 10 are located on each side of the jaw. They would remain intact throughout the life. These teeth are non-eruptible. However, the lower-jaw teeth do erupt once the whale reaches the maturity age. The sperm whale displays 17 to 29 teeth on each side of the lower jaw; the pigmy sperm whale, 12 to 16; while the dwarf sperm whale exhibits 8 to 11. All these species have large and conical teeth. Kogia’s teeth are complete contrast to these species in that it shows thin curved teeth and also lack enamel.
- The sperm whale is the largest odontocete.
- The length of the adults measures around 36 feet (11 meters) with the weight measuring at 33,000 lbs (15,000 kg). However, they can be as long as 41 feet (12.5 meters) and as heavy as 53,000 lb (24,000 kg).
- Physically mature males can reach a length of 52.5 feet (16 meters) and weighs at 100,000 lb (45,000 kg), with the largest ever recorded is 60 feet (18.3 meters) and weight 125,000 lb (57,000 kg).
- In the Kogia species, males and females are roughly of the same size.
- The Physeteridae family has a cosmopolitan distribution. The sperm whale is amongst the few animals in the world that are found almost everywhere in every major waters; ranging from pack ice to the Equator.
- Pygmy and Dwarf whales are not that much distributed but they are nevertheless present in the tropical and warm waters of Pacific Ocean, Indian Ocean, and Atlantic Ocean.
- Unlike pygmy sperm whale, the dwarf sperm whale fancy living in the warm waters. Kogia’s distribution is yet to be measured precisely due to the lack of records.
The Physeteridae predominantly dwells in the oceanic deep waters measuring 3,300 feet (1,000 meters) in depth. They are found at the edge of the continental shelf. The Kogia species particularly dwarf sperm whale lives in the shallow waters over the continental shelves.
- All three species have a stranded behavior, but the pygmy sperm whale shows rather more stranded behavior. These physeteridae species produce a fairly low blow while they come up to the surface.
- Unfortunately due to lack of data, not much is known about the behavior of pygmy and dwarf sperm whales.
- In the pygmy sperm whale, group size mainly comprises 1 to 6 individuals whereas in the dwarf sperm whale the maximum number of individuals is 10.
- The group of dwarf sperm whale is most likely to have males and females; or females with calves; or simply immatures in her group.
- The Kogia species moves slowly towards the surface and as they descend, they do not expose their flukes.
- The sperm whales are known to spend a large amount of time at the surface but they become completely motionless during their stay with some portion of their head becomes visible; their tail hangs floppily down.
- The Kogia is characterized by an interesting behavior against predators. They tend to release a reddish-brown fluid from their intestines in order to disturb their predators.
- They do not produce loud sounds, in fact they only sound echolocative directional clicks.
- The sperm whale is an expressive animal and is known to produce much louder sounds as compared to that of Kogia. Females are extremely colonial species.
- The society of sperm whale is a complex one and it takes time to be built; it is a fairly long-term unit and is composed of almost 10 females with their juveniles.
- Females are most likely to spend their entire lives within single unit and they remain close to their close relatives.
- Sometimes two or more groups combine to form a large group of 20 to 30 individuals.
- Female sperm whales are often found socializing at the surface where they spend considerable amount of time to take rest. They consume 25% of their time in resting. All these activities are done in daylight.
One of the most common things in their behavior is that they can be gathered around to swim side by side; or sometimes they turn upside down while touching its partner. This type of behavior is called ‘logging.’
Like dolphins, sperm whales also leap from the water. It gives the idea that they are happy and sound.
Sperm whales are often found hitting the water with tail flukes. This is not so common behavior in other whales’ family.
The sperm whales also raise their heads vertically out of water, a behavior which is observed when they become highly sociable.
- At times, sperm whales do produce a sound called ‘codas’, a series of 10 to 20 clicks that are somewhat reminiscent of the Morse code.
- Most of the time sperm whales are silent. Codas long no more than two seconds and whales usually produce it in order to communicate with their counterparts.
- Each group has a distinctive dialect of its codas. This variation in dialects is transmitted from mothers and clan to offspring.
- Sperm whales often produce ‘clicking sound’ which are uttered two times in one second. Their sole purpose to make these loud directional sounds is to find food via echolocation.
- The adult males are generally known to produce slow ringing clicks on the breeding grounds. They produce it in order to make their presence feel to others.
- Once male sperm whales reach the age of six, they leave their natal units in order to form a bachelor school. These bachelor schools are loosely bound groups comprises only of males.
- It is a group of like-minded individuals. The largest adult males fancy living solitary lives whereas those that are still growing, tend to form smaller schools.
- All of the Physeteridae members are most likely to feed on mid and deep-water squids though they also consume octopus and some fish. Their anatomy explains a lot about their dietary habits and it is evident that they employ powerful suction feeding.
- The sperm whales predominantly rely on deep-oceanic water squids weighing around 0.2 to 15.5 lb (0.1 to 7.0 kg), and it rarely feeds on jumbo and giant squid that are 50 feet (15 meters) long.
- The sperm whales are often involved in battles with large squids as few specimens (of whales) showed squids’ sucker marks on their heads. Males are most likely to eat fish but they also devour larger species belong to the same species.
- Kogia shows off a flattened snout that indeed suggests that they also feed at the bottom though for a fewer time. Evidences imply that Kogia eats crabs and other bottom-dwelling fish species.
- Unlike sperm whales, Kogia also eats shelf-dwelling squids because these species live in continental shelves.
- The Pyseteridae members are known to dive deep into the water with the Sperm Whale being a champ. Sperm whales can dive as deep as 3,300 to 6,500 feet (1,000 to 2,000 meters), possibly even 10,000 feet (3,000 meters).
- The average diving range is 1,000 to 2,600 feet (300 to 800 meters). Dives are typically 30 to 45 minutes in length with 7 to 10 minutes at the surface between dives to breathe. These dives can last more than one hour.
- Female whales usually spend 75% of their time in foraging while 25% of time is used in resting. The dwarf and pygmy sperm whales are adept to go as deep as 1,600 feet (500 meters) and it depends on the prey it takes.
sperm whale facts
- Both male and female sperm whales show a separate pattern of their distribution in that males dwell in higher latitudes while females fancy living in warm waters below 40o C.
- As males reach their maturity age, they move towards higher latitudes and large adults breathe in the edge of pack ice. Males cover great distances as they begin to migrate to the tropical waters to mate. The sperm whale is polygynous. Mature males rarely come into conflict with each other.
- Sperm whales litter once after every five years. The young remains with their mother for two to three years in order to suckle.
- These juveniles will take solid food once they reach one year. They are the only marine species that have this much longer parental care as calves can suckle more than 2 years.
- Calves however, cannot go as deep as their mother and indeed this inability to dive deep makes them vulnerable (at the surface) to predators like killer whales or sharks.
- The gestation period lasts for 14 to 16 months for sperm whales; for pygmy whales 11 months; and for dwarf sperm whales nine months.
- All three species of sperm whales have devoured some non-eatables such as plastic bags that indeed lead them to death. Apart from these incidents, some species are also struck by ships thereby causing a considerable damage.
- The Kogia’s population is yet to be accounted for. The global estimate for the population of Sperm Whales is 360,000. IUCN have classified sperm whales as vulnerable species while U.S. Endangered Species Act listed them as endangered.
- Sperm whales are thought to have occupied most of the major waters in the early eighteenth and nineteenth centuries. However, twentieth century did not prove to be healthy one as in this century around 30,000 sperm whales were killed every year. Hunters liked to kill specifically large adults.
- Finally in 1988 International Whaling Commission’s moratorium put a ban on commercial whaling of sperm whales.
- Sadly enough, sperm whales have yet to recover from the widespread whaling of the past with only 1% recovery rate. Chemical pollution and noise pollution are some of the other threats facing sperm whales as it relies on sound for all aspects of its life.
Significance to Humans
- One of the most famous Herman Melville’s novels, Moby Dick also mentions sperm whale. Japan had begun whaling in 2000 as they embrace five to eight sperm whales each year.
- It goes without saying that whale-watching has become an increasingly a profitable business around the world, as it collects significant revenue each year. The dwarf and pygmy sperm whales are seldom employed as whale-watching in the Pacific and Indian Oceans, and the Caribbean.
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Perrin, W. F., B. Würsig, and J. G. M. Thewissen, eds. Encyclopedia of Marine Mammals. San Diego: Academic Press, 2002.
Rice, D. W. Marine Mammals of the World: Systematics and Distribution. Lawrence, Kansas: Allen Press, 1998.
European Cetacean Society. Web site: <http://web.inter.nl.net/users/J.W.Broekema/ecs>
Society for Marine Mammalogy. Web site: http://www.marinemammalogy.org
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