SPECIES PROFILE
for
Sperm Whale
(Physeter macrocephalus)
prepared for
MSC 276- Marine Vertebrate Zoology
by
James Buffett
Jbuffett239@mail.cfcc.edu
Submitted: March 6, 2014
Names and Classification
Physeter macrocephalus
Sperm Whale
Synonyms: Cachalote, Spermacet whale, Pot whale, Sea guap, Physeter catadon
Family: Physeteridae (Sperm Whale)
Description
The sperm whale Physeter macrocephalus, has a large rectangular shaped head with a
slender, almost rodlike, lower jaw enclosing approximately 20 to 26 pairs of evenly
space conical teeth (Morrissey, et al., 2012). It possesses a low triangular dorsal fin,
nearly two thirds down the entire length of the body, with a chain of humps on the dorsal
ridge down to the tail stock. The caudal peduncle is deep with a post anal keel
(Jefferson, et al., 2008). The flukes are generally flat with a triangular appearance
(Whitehead, 2009). The skin appears wrinkly all over the body with the exception of the
head and tail (Haley, 1978). Coloring of the sperm whale varies in shades of gray with
blotches of white on the belly (Brown, 1997).
This species of whale is recognized as the largest toothed whale and carnivore in the
ocean (Nybakken, 1997; Brown, 1997). The sperm whale also holds the record for
being the most sexually dimorphic animal known to man, for the drastic size difference
between the male and female. Male sperm whales range in length 14 to 24 meters (40
to 69 feet), and weigh 40 to 60 tons. Females range in length 11 to 14 meters (30 to 39
feet), and weigh approximately 15 tons (Brown, 1997). Females reach only half the size
of males (Matthews, 1978). Along with size, there are several other characteristics to
differentiate between a male and a female sperm whale. Females possess a callus
found on the dorsal fin which becomes more apparent with age. Also, the male’s dorsal
fin is located more posterior than the female’s fin. (Figure 1) (Jefferson, et al., 2008;
Culik, 2012)(Cover photo: Minakuchi, 2012).
Figure 1. Male (top) and female (bottom) sperm whales.
The enlarged head of the sperm whale constitutes just over a third of its total body
length (Parker, 1990). The skull contains the largest brain known to man and the
whale’s large nasal complex; the melon and the spermaceti organ (Whitehead, 2009).
The melon is composed of mainly fat and used as an acoustic lens for the outward
sound waves it produces (Nybakken, 1997). The spermaceti organ, located above the
melon, is a circular structure coated in a waxy oil known as spermaceti. This semi-liquid
fluid is what gave the sperm whale its name with the resemblance to human semen
(Whitehead, 2009). The spermaceti organ is used for buoyancy and sound production.
The skull’s asymmetrical structure encases the organs and builds the whale’s airways.
Its blowhole sits asymmetrical to the left side of the head, while the right side is used for
sound production (Macdonald, 2006). By recirculating air through the nasal airway into a
series of airsacs, the sperm whale is able create a wide variety of sound frequencies
used for echolocation. The spermaceti organ and melon both play key roles in the
animal’s effective echolocation system (Nybakken, 1997). Sperm whales use their
echolocation system to produce clicks and use it as a key component to find food in
deep waters. Clicks have also allowed the mammal to communicate and become highly
social (Figure 2) (Whitehead, 2009; Field, 2014).
Figure 2. Inside diagram of the skull of a sperm whale.
Distribution
The sperm whale is one of the most widely dispersed mammals in the world (Morrissey,
et al., 2012). They are abundant in all oceans and in deep entrances such as the Gulf of
Mexico, Caribbean Sea, Gulf of California, Sea of Japan, and Mediterranean Sea
(Jefferson, et al., 2008). The male and females generally live separate lives, only
interacting to breed. Females and their young normally stay in tropical and temperate
waters in latitudes below 40 degrees (Brown, 1997). Females migrate throughout these
latitudes where food sources are abundant (Whitehead, 2009).
Mature males, on the other hand, migrate to higher latitudes during certain parts of the
year. During the boreal summers, males migrate to northern Arctic waters and in Austral
summers, males migrate to southern Antarctic waters (Haley, 1978). Bull sperm whales
migrate to tropical waters during breeding season (Figure 3) (Whitehead, 2009; Culik,
2010).
Figure 3. Area in red shows the distribution of the sperm whale.
Habitat
Sperm whales generally prefer deeper waters, at least 1000 meters deep (Brown,
1997). Commonly, females are found far away from shore, outside the edges of
continental shelves in temperatures greater than 15 degrees Celsius (Culik, 2012).
Males are able to withstand the icy temperatures in the Polar Regions and can be found
anywhere with no ice coverage. Males have been reported in shallow areas in the
northern Atlantic (Brown, 1997).
Conservation Biology
Life Cycle and Reproduction
The female and male sperm whales live very dissimilar lives. While males generally live
in solitude, females are very gregarious, and form permanent matriarchal social units
(Whitehead, et al., 2012). These families are referred to as nursery schools, or
fundamental schools. A pod normally has an average of twelve life-long members
consisting of females and their calves. Occasionally, other nursery pods may join
together in larger groups to enhance foraging efforts (Matthews, 1978). Sperm whales
use clicks, referred to as codas, in order to communicate with one another and form
strong social bonds. Multiple whales can play codas in a sequence resulting in sounds
similar to echoes. This language is known as coda repertoire and is passed down to
offspring. Social units have been observed in studies noticing differences such as a
change in frequencies of codas, size of pods, and behavior changes in different oceans
of the world. These studies have proven the diversity and complexity of female social
units (Whitehead, et al., 2012).
In contrast, males stray away from these nursery schools at six years old. Male sperm
whales do not reach puberty until they are at least ten years in age, sometimes as old
as twenty. Once a male has reached puberty, they do not actively participate in mating
until they are 30 years old (Morrissey, et al., 2012). Young males that are not sexually
active will join into what are known as bachelor schools. These groups migrate to higher
latitudes to feed. As males age, aggregations decrease in size, called harems, and in
many cases become solitude throughout their matured years migrating further north
with age (Matthews, 1978; Whitehead, 2009). Males are said to communicate using a
much slower series of clicks, possibly to suggest when they are ready to breed
(Morrissey, et al., 2012).
Breeding season for the sperm whale begins in the middle of spring into early summer.
Females are considered sexually mature when they are eight years of age, at ten
meters long (28 feet) (Brown, 1997). During breeding season, males migrate to the
equator to breed. Being a polygynous species, the male will mate with up to 14 different
females from different social units (Matthews, 1978; Jefferson, et al., 2008). Typically
bull males keep their distance from one another during breeding season, but there have
been reports of bulls fighting with one another leaving deep teeth marks on one another
(Matthews, 1978).
Mothers carry their young for a gestation period of 16 months carrying a single calf, on
the odd occasion two calves, until the mother gives birth. When born, calves are roughly
five meters (14 to 15 feet) long weighing over one ton (Brown, 1997). The calf depends
on the mother for milk for a year before it can begin to eat solid food. Even then, a calf
will suckle on its mother for several years (Whitehead, 2009). There is strong evidence
to show that lactating females help feed calves that are not their own (Whitehead, et al.,
2012). A female sperm whale typically goes into heat every year and on average gives
birth around every five years. Once a female has reached the age of 40, the likelihood
of reproducing again drastically declines. Without any major threats, a healthy sperm
whale can live up to 60 years or more (Haley, 1978).
Feeding Habits
Sperm whales are recognized to have one of the most extreme feeding strategies. This
species of whale dives straight down to depths around 1000 meters in order to feed on
its primary food source, squid. Male sperm whales are capable of diving much deeper
depths at up to 3200 meters. With the help of its spermaceti organ and blubber, it is
able to handle the intense pressure changes and regulate its buoyancy (Macdonald,
2006). The sperm whale has fairly small lungs compared to its body size, having twice
the blood cell count compared to any terrestrial animal. This allows the sperm whale to
take in more oxygen for deep dives. During dives, the sperm whale will drop its heart
rate and collapse its lungs to allow air to travel to more rigid passages in the respiratory
system (Haley, 1978). A sperm whale can stay under water for over an hour and is able
to perform even when oxygen has been exhausted (Matthews, 1978). When returning to
the surface, the sperm whale will spend several minutes lying motionless before diving
down again (Jefferson, et al., 2008). This process if referred to as foraging.
Sperm whales generally prefer to feed at night (Brown, 1997). They typically swim with
their jaw hung open, consuming cephalopods whole, which are said to be attracted to
the sperm whales large white teeth and mouth (Matthews, 1978). At deep depths,
sperm whales must depend on their echolocation to find their prey. These whales create
a series of clicks called burst pulses, and with their excellent hearing, are able to detect
the reflected sound pules of their prey (Haley, 1978).
Females typically spend a majority of their time foraging, nearly 75 percent of their life
(Macdonald, 2006). Since females do not dive as deep as males, their diet consists of
smaller species of squid along with cuttlefish, octopus, and a small amount of fish.
During foraging, females spread apart from one another, spreading up to one kilometer
apart in a perpendicular manner (Whitehead, 2009). A juvenile sperm whale is only
capable of diving around 700 meters deep, limiting the mother’s diving depths. Studies
show that females act as babysitters for each other’s young, staggering their dives,
allowing the mother to dive deeper for larger prey (Whitehead, et al., 2012). After
foraging, members of a social unit spend several hours lying next to one another, known
as logging. Whales are said to socialize and perform behaviors such as lobtailing,
breaches, and spy-hopping.
Males typically forage for food alone, traveling to high latitudes for prey. With males
traveling to deeper depths in colder climates, they are able to hunt larger species of
squid, the colossal squid being the most popular (Whitehead, 2009). In many cases,
sperm whales obtain deep scars from the suckers and beaks of the colossal squid. The
diet of mature males is similar to females, with the exception of more fish found in the
male’s diet. Along with cephalopods, males feed on certain species of sharks and rays
(Morrissey, et al., 2012). Males typically compete with elephant seals and beaked
whales for squid in the higher latitudes (Whitehead, 2009).
Endangered Species Status
The sperm whale has been listed as vulnerable according to the International Union for
Conservation of Nature (Culik, 2012). The species’ population has drastically decreased
due to commercial whaling. As a result, the International Whaling Commission banned
commercial whaling of sperm whales in 1988. Only certain aboriginal groups in the
Caribbean territories and in parts of Indonesia and Japan are currently allowed to hunt
sperm whales (Jefferson, et al., 2008).
Threats and Limiting Factors
The largest threat to the population of the sperm whale has been excessive whaling.
This industry gained popularity in 1712 and peaked in the 1840’s with spermaceti
fueling the beginning of an industrial revolution (Whitehead, et al., 2012). The sperm
whale brought a huge value in the market and high demand for spermaceti. Spermaceti
served as an oily base for many products such as oil for lanterns, skin care, and leather
care. The oily substance also served useful in pharmaceutical ointments, lubricant for
fine-tuned instruments, and transmission fluid for vehicles (Parker, 1990). Many whales
were targeted by open boat whalers, with around 600 kills a year (Whitehead, et al.,
2012). Whales were typically harpooned and stripped of their blubber and spermaceti
organ. With the invention of petroleum based products, demand for spermaceti
decreased in the late 19th century (Whitehead, 2009).
Sperm whales encountered another wave of whaling in the mid-20th century with the
invention of motorized vessels and explosive harpoons. Whalers mainly targeted large
bull whales. On average, nearly 25,000 were killed a year until the late 1980’s when the
International Whaling Commission outlawed the whaling of sperm whales (Macdonald,
2006; Morrissey, et al., 2012). Along with spermaceti, sperm whales possess another
valuable substance known as ambergris. This substance, understood to be a
pathological secretion, appears somewhat solidified with a yellowish color and is formed
in the large intestine. It was sought after for perfumes for its sweet, earthy aroma
(Parker, 1990; Brown, 1997).
Sperm whales are a K-selected species, which means offspring numbers are few,
growth rate is slow, and they are slow to mature. The population has been unsuccessful
in recovering from whaling in past years, unable to repopulate as quickly as the
depletion rate. Because of these factors, sperm whales have a population growth rate of
less than one percent a year (Whitehead, 2009; Macdonald, 2006).
There are still several threats separate of whaling, which have endangered the sperm
whale population. Many sperm whales have been entangled in fishing gear, usually
ending in the whale being mangled in the gear and drowning. Vessel strikes are also a
hazard to whales, with the increasing number of vessels in ocean channels each year.
Chemical pollution has also shown damaging effects to sperm whales. The chemical
content of the melon inside of a number of sperm whales has shown strong levels of
toxins as a result of ocean pollution (Jefferson, et al., 2008).
Sound pollution has been a factor of concern for these animals. Noise pollution can be
caused by any disturbance in the water through oil drilling, seismic research,
underwater explosions, oceanographic experimentations, and military sonar. Little is
known about the effects of noise pollution to sperm whales and whether the effects are
minor or severe. A study in 2006 logged the behavioral changes of killer, sperm, and
long-finned pilot whales during a series of naval sonar exercises to test whether noise
pollution has damaging effects to whales. The results showed a trend of strong
reactions to the exercises from the sperm whale. In many instances, sperm whales fled
the area to avoid the noise. There were several recordings of sperm whales ending their
foraging session after the disturbance. It was concluded that the most responsive
behaviors occurred during foraging, breeding sessions, and when mothers were
nursing. The noise made from the naval exercises concerns researchers that these
exercises may be disturbing important behaviors vital to the sperm whale’s survival
(Miller, et al., 2012).
During times of danger, the sperm whales form a communal group defense known as a
marguerite formation. The adult females form a circle around the baby calves with their
flukes pointing outward and use their flukes as weapons. This defense is common with
the threat of orca attacks (Jefferson, et al., 2008). Another popular defense against
orcas is the heads out formation where females face out using their jaws as weapons.
Sperm whales have even been known to put themselves in danger to save whales that
were separated from the pod (Macdonald, 2006).
Biography of Preparer
James Buffett is in search of new career opportunities by continuing his education and
achieving a certificate in the Marine Technology program at Cape Fear Community
College. Some say James has flown into or over every state in the US except Alaska.
Throughout his travels, he has managed to earn a B.A. degree in Accounting at
Cedarville University in Ohio, experience the evolution of the multimedia presentation
while working in NYC, putter around in the golf industry by operating and maintaining a
small, par-3 golf course and is setting a new course for intrigue on the open seas by
attending classes in Oceanography, Marine Biology and Marine Vertebrate Zoology at
CFCC.
Literature Cited
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http://www.cms.int/reports/small_cetaceans/data/P_macrocephalus/P_mm
acrocephalu.htm
Field, S. (2014). The Sperm Whale. Beautifully Bony. Retrieved from
http://beautifullybony.wordpress.com/bone-of-the-month/the-sperm-whale/
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