The face that sank the Essex: potential function of the spermaceti organ in aggression
Department of Biology, 201 South Biology Building, University of Utah, Salt Lake City, UT 84112, USA
* e-mail: carrier{at}biology.utah.edu
Accepted 5 April 2002
![]() |
Summary |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
`Forehead to forehead I meet thee, this third time, Moby Dick!'
Herman Melville's fictional portrayal of the sinking of the Pequod was inspired by instances in which large sperm whales sank whaling ships by ramming the ships with their heads. Observations of aggression in species of the four major clades of cetacean and the artiodactyl outgroup suggest that head-butting during malemale aggression is a basal behavior for cetaceans. We hypothesize that the ability of sperm whales to destroy stout wooden ships, 3-5 times their body mass, is a product of specialization for malemale aggression. Specifically, we suggest that the greatly enlarged and derived melon of sperm whales, the spermaceti organ, evolved as a battering ram to injure an opponent. To address this hypothesis, we examined the correlation between relative melon size and the level of sexual dimorphism in body size among cetaceans. We also modeled impacts between two equal-sized sperm whales to determine whether it is physically possible for the spermaceti organ to function as an effective battering ram. We found (i) that the evolution of relative melon size in cetaceans is positively correlated with the evolution of sexual dimorphism in body size and (ii) that the spermaceti organ of a charging sperm whale has enough momentum to seriously injure an opponent. These observations are consistent with the hypothesis that the spermaceti organ has evolved to be a weapon used in malemale aggression.
Key words: malemale aggression, sperm whale, cetacean, melon, Herman Melville, Moby Dick, Essex, Ann Alexander
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
The attack on the Essex in 1821 is the first documented case of a
sperm whale deliberately striking a ship
(Chase, 1821). At the time,
the Essex was approximately 20 years old and weighed approximately
238 tons (Philbrick, 2000
).
Its hull was composed almost entirely of white oak, one of the toughest and
strongest woods available. Timbers 30 cm square in cross section made up the
ribs of the ship. Over this were oak planks 10 cm thick covered by yellow pine
more than 1 cm thick. This was covered and protected by a thick layer of
copper that extended down from the waterline. The attack occurred while the
crew was engaged in a hunt in which two sperm whales had already been
harpooned (Chase, 1821
). The
first mate had been forced to return to the ship after his boat had been stove
in by a harpooned whale and was in the process of repairing it when an
approximately 26m bull was observed 100m from the ship, floating quietly, as
if observing the ship. It suddenly dived and surfaced less than 30m from the
ship traveling at an estimated speed of 3 knots heading directly for the port
side of the ship. The whale struck the ship, which shook `as if she had struck
a rock' (Chase, 1821
). The
whale then swam approximately 500m leeward from the ship, where it acted as if
it were `distracted with rage and fury'. After several minutes of this
display, it swam directly in front of the ship and then charged the ship
again, this time with a speed near 6 knots. The whale struck the
Essex directly beneath the cathead and completely stove in her bows.
The Essex started sinking bow first, and capsized within 10 min on
its port side.
The Ann Alexander was struck and sunk by a sperm whale in 1851
(Starbuck, 1878;
Sawtell, 1962
). Initially, the
crew pursued the whale in rowing boats. After being harpooned, the whale
attacked and destroyed two of the boats by crushing them in its jaws. The crew
then returned to the ship in the single remaining boat and renewed the chase
with the ship. The ship maintained the pursuit until the fleeing whale
reversed its direction of travel, charged and rammed the bow of the ship with
its snout. The impact did not damage the ship. While the crew debated the
sensibility of continuing the pursuit, the whale attacked a second time and
stove in the bow of the ship with a hole `just the size of the whale's head'
(Sawtell, 1962
). The ship sank
in minutes. The whale was caught 5 months later by the crew of the Rebecca
Simms, weak with infection caused by splinters and harpoons embedded in
its flesh from the encounter with the Ann Alexander
(Starbuck, 1878
). This 5-month
period demonstrates that long-term survival is possible after combat with a
ship and presumably with another whale.
The anatomy of the head of sperm whales appears to have characterized the
family Physeteridae since its inception in the Lower Miocene
(Kellogg, 1928) and is unique
among cetaceans (Fig. 1).
Within the nose are two gargantuan oilfilled sacs that can constitute up to
one-quarter of the body mass and extend one-third of the total length of the
whale (Berzin, 1972
;
Clarke, 1978
). The upper sac
is termed the spermaceti sac because of the high-quality oil contained within
it. This oil partially solidifies on contact with air, turning white and
giving it a semen-like appearance. The case surrounding the spermaceti is made
up of extremely tough, thick fibrous connective tissue, which lies below a
strong tendinous-muscular layer. The lower sac, termed the junk, is filled
with a denser oil and is organized into sections by transverse partitions of
connective tissue. The junk is derived from the odontocete melon, whereas the
affinity of the spermaceti sac is not known
(Heyning and Mead, 1990
). The
posterior portion of the skull is curved like an amphitheater and holds the
posterior end of the spermaceti sac. The maxilla, or upper jaw, forms a trough
in which the junk sits. Both the spermaceti sac and the junk are triangular in
shape when viewed in sagittal section. The spermaceti sits on top of the junk
and is larger at the posterior end of the nose, while the junk is larger at
the anterior end (Berzin, 1972
;
Clarke, 1978
).
|
In large bulls, the spermaceti and junk are hypertrophied and can extend up
to 1.5 m beyond the end of the maxilla
(Berzin, 1972). It is this
anterior extension of the spermaceti organ that sperm whales have been
observed to use when striking ships
(Chase, 1821
;
Starbuck, 1878
;
Sawtell, 1962
). Although
observations of males fighting are rare
(Whitehead and Weilgart,
2000
), the belief that the spermaceti organ functions as a weapon
has been held by whalers who witnessed fights between males or who experienced
attacks on their ships (Chase,
1821
; Berzin,
1972
). Similarly, observations of aggressive head-butting behavior
by bottle-nosed whales led Gowans and Rendell
(1999
) to suggest that the
enlarged melon of this species may be a specialization for malemale
aggression. Nonetheless, previous attempts by biologists to explain the
functional significance of the massive size and structural specialization of
the spermaceti organ have focused on biosonar, acoustic sexual selection
(Norris and Harvey, 1972
;
Cranford, 1999
;
Møhl, 2001
), acoustic
prey debilitation (Norris and Møhl,
1983
) and buoyancy control
(Clarke, 1978
). Although the
spermaceti organ may facilitate both sound production and buoyancy control,
the successful attacks on 19th-century whaling ships led us to ask whether the
spermaceti organ might also function as a weapon in malemale
aggression.
To address this question, we performed two analyses. In the first analysis,
we determined whether the relative size of the melon is correlated with the
level of sexual dimorphism in body size among cetaceans. Relative weapon size
is often correlated with the degree of polygyny and sexual dimorphism in body
size (Clutton-Brock and Harvey,
1977; Parker,
1983
; Andersson,
1994
). The greatly enlarged melon, extreme sexual dimorphism in
body size and polygynous mating system of sperm whales
(Caldwell et al., 1966
;
Berzin, 1972
;
Whitehead and Weilgart, 2000
)
raise the possibility that a similar relationship might exist among cetaceans.
Hence, if the melon is used as a weapon during malemale aggression in
some species, we would expect the relative size of the melon to be positively
correlated with sexual dimorphism in body size.
In the second analysis, we used a two-dimensional physical modeling program
to simulate the impact of two sperm whales and asked whether it is physically
possible for the spermaceti organ to function as a weapon. We assumed that, to
be effective as an intraspecific weapon, the spermaceti organ would have to
function simultaneously as a battering ram to injure the target whale and as a
shock absorber to protect the brain and body of the attacking whale.
Malemale aggression that results in injury or death is common among
mammals (Geist, 1971;
Berzin, 1972
;
Silverman and Dunbar, 1980
;
Clutton-Brock, 1982
;
Andersson, 1994
;
Wrangham and Peterson, 1996
),
and the potential for serious injury needs to be real for a male to achieve
dominance (Darwin, 1871
;
Geist, 1971
;
Andersson, 1994
). Because
specific details of the structure of the spermaceti organ and the physical
properties of the tissues that compose it are not known, our modeling was
necessarily very simple and intended to answer two basic questions: (i)
whether there is enough energy in the momentum of the spermaceti organ of a
large swimming sperm whale to damage an equal-sized opponent and (ii) whether
the shock absorption necessary to protect the attacking whale would dissipate
the blow to the target whale and thereby render the spermaceti organ
ineffective as a weapon. Thus, although the model was simple, it did have the
potential to falsify the hypothesis that the spermaceti organ functions as a
weapon in malemale aggression.
![]() |
Materials and methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
|
|
The literature provides estimates of the degree of sexual dimorphism in
body length for a number of cetacean species
(Table 1). To estimate relative
melon size, we measured the lateral projected area of the melon and an index
of the postcranial lateral projected body area from high-quality illustrations
(Carwardine, 2000) using a
digitizing program (NIH Image). We defined the area of the melon as the area
contained within a dorsoventral line between the top of the head and the eye,
a line between the eye and the anterior tip of the upper jaw and a tracing of
the front of the head from the tip of the upper jaw to the intersection with a
line extending vertically from the eye. Our index of postcranial body area was
the dorsoventral depth of the head at the eye multiplied by the body length
from the eye to the caudal tip of the flukes
(Fig. 3). We then divided the
projected area of the melon by the index of the postcranial body area to yield
a measure of relative melon size. 20 of the 21 species were analyzed in this
way. Although large errors in relative melon size are possible because of the
accuracy of the illustrations, we expected the errors to be both random
relative to the level of sexual dimorphism in body size and small relative to
the actual variation in relative melon size among species.
Although mysticetes do not posses a functional melon, they do have a fatty
structure just anterior to the nasal passages that appears to be homologous to
the melon of odontocetes (Heyning and
Mead, 1990). Hence, we determined the relative size of the melon
in Eubalaena glacialis from an illustration by Heyning and Mead
(1990
). In this case, we
measured the area of the melon in the figure and then used the dorsoventral
depth of the body at the eye to scale the figure to the illustration of
Eubalaena glacialis in Carwardine
(2000
).
Modeling of head-butting
The impact of a sperm whale with a target whale of the same mass was
simulated using a two-dimensional physical modeling program, Working Model 2D.
The attacking whale had a total mass of 39 000 kg and consisted of a mass
representing the spermaceti organ (20 % of body mass, 7800 kg) connected by a
damper (spermaceti damper) to a mass representing the rest of the body (31 200
kg). The target whale consisted of a stationary mass of 78 000 kg (39 000 kg
body mass plus the added mass of the attached water; we assumed an added mass
coefficient of 1; Vogel, 1981)
attached via a damper (tissue damper) to a much smaller `bumper' mass
(less than 1 % of body mass). The bumper mass and tissue damper modeled the
shock absorption that would occur due to the tissues of the target whale. The
attacking whale was given a velocity of 3 m s-1 (the estimated sum
of the velocities of the whale and ship in the Essex incident;
Chase, 1821
) and directed so
that the anterior end of spermaceti mass collided with the bumper of the
target whale. Upon impact, the model calculated the instantaneous
accelerations of the masses and the deformations of the dampers.
Because a head-on collision between two whales would result in the same damping values and, therefore, the same forces applied to the two whales, we modeled impacts in which the anterior end of the attacking whale's spermaceti organ struck the side of the head or body of the target whale. We assumed that this would result in greater damping in the target than in the attacking whale.
Hence, we assumed that a collision between two whales can be modeled as a series of masses and dampers that exert force in proportion to shortening velocity. The spermaceti organ clearly has mass that must be decelerated in a collision. Whether the tissues of the spermaceti organ respond with spring-like or damper-like properties is not known. It seems likely, however, that the mechanical behavior of the spermaceti organ in a collision will be a combination of spring and damper properties. To keep the model simple, however, we chose to model the two extremes. When the collision was modeled using springs only, an unrealistically wide range of values for spring constants was needed, suggesting that the shock-absorbing qualities of the spermaceti organ result more from dampening than elasticity. Furthermore, given that the mass of the spermaceti organ is composed primarily of a liquid (oil), it seems reasonable to assume that the spermaceti organ's initial absorption of the energy during impact would be due primarily to acceleration of the liquid (i.e. damping) rather than to deformation of elastic elements.
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
Modeling of head-butting
When springs were substituted for dampers in the model, we found that the
stiffness of the tissue spring must be more than 19 times the stiffness of the
spermaceti spring for the acceleration of the target whale to reach the same
acceleration as the mass of the body of the attacking whale. For the
acceleration of the target whale to reach twice the acceleration of the
attacking whale, the ratio of spring stiffness must exceed 76. Corresponding
ratios required for dampers (to achieve the same acceleration and twice the
acceleration, respectively) are 1.15 and 8.30. Because the range of modulus of
elasticity of the tissues and materials that would probably serve as the
elastic elements in the two whales (collagen in the case of the spermaceti
organ of the attacking whale and the bone of the skull of the target whale) is
only 15-fold (Wainwright et al.,
1976), modeling the spermaceti as masses and springs seemed
inappropriate. Skin is an elastic tissue that would be involved in any
collision, but its elastic modulus is relatively low, approximately three
orders of magnitude less than that of tendon
(Wainwright et al., 1978
).
Therefore, we assumed that the skin of the target whale would not serve as an
important elastic element in the absorption of the energy of impact. Hence,
further analysis used a model with dampers in the place of springs.
Given that we do not know the damping constant of a sperm whale's spermaceti organ or the damping constant of the various other parts of a sperm whale that might receive the impact of an attack, we examined the effects of different damping magnitudes and damping ratios (tissue damper/spermaceti damper). The ratio of damping was varied systematically from 2 to 128, and the damping constants were varied within each damping ratio. The modeling yielded a line for each damping ratio when the resulting acceleration of the target whale was plotted against the resulting acceleration of the attacking whale's body (Fig. 5). The slope of the line was greater for higher damping ratios, but in all cases the peak acceleration of the target was greater than the peak acceleration of the attacking whale's body. Fig. 6 shows sample acceleration traces versus time for the target and attacking whale.
|
|
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
One possible clue as to whether some species use their melon as a weapon is
the degree to which relative melon size is correlated with the level of sexual
dimorphism in body size. Among species of mammals, the level of polygyny is
strongly correlated both with the extent to which males are larger in body
size than females and with relative size of weapons
(Clutton-Brock and Harvey,
1977; Parker,
1983
; Andersson,
1994
). In the artiodactyl family Cervidae, male weapons are
largest relative to body size in species with the highest level of polygyny
(Clutton-Brock et al., 1980
).
Most significantly, in the Cervidae and Bovidae, as well as in the marsupial
family Macropodidae, male weapons tend to be largest relative to body size in
species that exhibit the greatest sexual dimorphism in body size
(Jarman, 1983
). Hence, our
finding that the evolution of relative melon size is positively correlated
with the evolution of sexual dimorphism in body size suggests that some
species of odontocetes may use their melons as weapons in contests for access
to females.
Our simple modeling of the accelerations involved in head-butting behavior
by two sperm whales has the potential to falsify the hypothesis that the
spermaceti organ is a weapon used in malemale aggression. If the
spermaceti organ functions as a weapon, males must be able to use it to injure
an opponent (Geist, 1971;
Andersson, 1994
). In all cases,
our modeling showed that the peak acceleration of the target whale was greater
than the peak acceleration of the attacking whale's brain and body. But are
the predicted accelerations physiologically relevant? The acceleration at
which injury occurs is known to decrease as body size increases
(Diamond, 1989
;
Farlow et al., 1995
). Scaling
relationships based on records of injuries sustained by humans in car crashes
(Alexander, 1996
;
Farlow et al., 2000
) suggest
that twice the acceleration due to gravity (2g=19.6 m s-2)
is the acceleration at which a 39 000 kg vertebrate would suffer fatal injury.
The portion of Fig. 5 above the
horizontal line (2g on the y-axis) represents accelerations
above injury threshold for the target whale and below injury threshold for the
attacking whale's body. These results suggest that the momentum of the
spermaceti organ of a large swimming sperm whale could seriously injure a
stationary opponent of similar body mass. Further, and most importantly, the
level of damping necessary to protect the attacking whale from injury would
not necessarily diminish the effectiveness of the system as a weapon.
To conclude, we raise several additional observations that are consistent
with the weapon hypothesis. First, the spermaceti organ is considerably larger
relative to body size in males than in females
(Cranford, 1999). Weapons used
in malemale aggression often exhibit sexual dimorphism in size
(Andersson, 1994
). Second,
although not all cetaceans have fused cervical vertebrae, the posterior six
cervical vertebrae form a fused mass in sperm whales
(De Smet, 1972
). This would
presumably facilitate the transfer of the energy of impact from the head to
the body and would reduce the chances of spinal compression injury. In
addition, the skin on the anterior end of the spermaceti organ (i.e. impact
surface) is unusually thick and tough
(Chase, 1821
;
Berzin, 1972
), and in large
males it is often covered extensively with scars
(Best, 1979
;
Kato, 1984
). The scars tend to
be concentrated on the ventral portion of the spermaceti organ, known as the
junk (Fig. 7). The junk is
reinforced with collagenous partitions and is directly in line with the
cervical vertebrae (Berzin,
1972
; Clarke,
1978
). These observations, combined with the results of our study,
suggest that the spermaceti organ does function as a weapon in malemale
aggression. Although the spermaceti organ probably serves a variety of
functions, possibly including vocal communication, echolocation, acoustic prey
debilitation (Norris and Harvey,
1972
; Norris and Møhl,
1983
; Cranford,
1999
) and buoyancy control
(Clarke, 1978
), we suggest
that its great size and structural specialization may represent the result of
selection for use as a battering ram.
|
![]() |
Acknowledgments |
---|
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Alexander, R. McN. (1996). Tyrannosaurus on the run. Nature 379, 121.
Andersson, M. (1994). Sexual Selection. Princeton: Princeton University Press.
Baker, C. S. and Herman, L. M. (1984). Aggressive behavior between humpback whales (Megaptera novaeangliae) wintering in Hawaiian waters. Can. J. Zool. 62,1922 -1937.
Bernard, H. J. and Reilly, S. B. (1999). Pilot whales Globicephala Lesson, 1828. In Handbook of Marine Mammals, vol. 6, The Second Book of Dolphins and the Porpoises (ed. S. H. Ridgway and R. Harrison), pp. 245-265. London: Academic Press.
Berzin, A. A. (1972). The Sperm Whale. Jerusalem: Israel Program for Scientific Translations.
Best, P. B. (1979). Social organization in sperm whales, Physeter macroephalus. In Behavior of Marine Animals, vol. 3, Cetacea (ed. H. E. Winn and B. L. Olla), pp.227 -290. New York: Plenum Press.
Brownell, R. L. J. and Clapham, P. J. (1999). Burmeister's porpoise Phocoena spinipinnis Burmeister, 1865. In Handbook of Marine Mammals, vol. 6, The Second Book of Dolphins and the Porpoises (ed. S. H. Ridgway and R. Harrison), pp.393 -410. London: Academic Press.
Caldwell, D. K., Caldwell, M. C. and Rice, D. W. (1966). Behavior of the sperm whale Physeter catondon L. In Whales, Dolphins and Porpoises (ed. K. S. Norris), pp. 677-717. Berkeley: University of California Press.
Caldwell, M. C., Caldwell, D. K. and Brill, R. L. (1989). Inia geoffrensis in captivity in the United States. In Biology and Conservation of the River Dolphins (ed. W. F. Perrin, R. L. Brownell, Z. Kaiya and L. Jiankang), pp. 35-41: Occasional Papers of the IUCN Species Survival Commission, no. 3.
Carwardine, M. (2000). Whales, Dolphins and Porpoises. London: Dorling Kindersley.
Chase, O. (1821). Shipwreck of the Whale-Ship Essex. New York: Gilley.
Clarke, M. R. (1979). The head of the sperm whale. Sci. Am. 240,128 -141.[Medline]
Clarke, M. R. (1978). Buoyancy control as a function of the spermaceti organ in the sperm whale. J. Mar. Biol. Ass. U.K. 58,27 -71.
Clutton-Brock, T. H. (1982). The function of antlers. Behavior 70,108 -125.
Clutton-Brock, T. H., Albon, S. D. and Harvey, P. H. (1980). Antlers, body size and breeding group size in the Cervidae. Nature 285,565 -566.
Clutton-Brock, T. H. and Harvey, P. H. (1977). Primate ecology and social organization. J. Zool. Lond. 183,1 -39.
Connor, R. C., Read, A. J. and Wrangham, R. (2000). Male reproductive strategies and social bonds. In Cetacean Societies, Field Studies of Dolphins and Whales (ed. J. Mann, R. C. Connor, P. L. Tyack and H. Whitehead), pp. 247-269. Chicago: University of Chicago Press.
Cranford, T. W. (1999). The sperm whale's nose: sexual selection on a grand scale? Mar. Mammal Sci. 15,1133 -1157.
Darwin, C. (1871). The Descent of Man, and Selection in Relation to Sex. London: John Murray.
De Smet, W. M. A. (1972). The regions of the cetacean vertebral column. In Functional Anatomy of Marine Mammals (ed. R. J. Harrison), pp. 59-80. London: Academic Press.
Diamond, J. (1989). How cats survive falls from New York skyscrapers. Nat. Hist. 8, 20-26.
Evans, P. G. H. (1990). The Natural History of Whales and Dolphins. New York: Facts on File.
Farlow, J. O., Dodson, P. and Chinsamy, A. (1995). Dinosaur biology. Annu. Rev. Ecol. Syst. 26,445 -471.
Farlow, J. O., Gatesy, S. M., Holtz, T. R., Hutchinson, J. R. and Robinson, J. M. (2000). Theropod locomotion. Am. Zool. 40,640 -663.
Felsenstein, J. (1985). Phylogenies and the comparative method. Am. Nat. 125, 1-15.
Geist, V. (1971). Mountain Sheep: A Study in Behavior and Evolution. Chicago: University of Chicago Press.
Goley, P. D. and Straley, J. M. (1994). Attack on gray whales (Eschrichtius robustus) in Monterey Bay, California by killer whales (Orcinus orca) previously identified in Glacier Bay, Alaska. Can. J. Zool. 72,1528 -1530.
Gowans, S. and Rendell, L. (1999). Head-butting in northern bottlenose whales (Hyperodon ampullatus): A possible function for big heads. Mar. Mammal Sci. 15,1342 -1350.
Herzing, D. L. and Johnson, C. M. (1997). Interspecific interactions between Atlantic spotted dolphins (Stenella frontalis) and bottlenose dolphins (Tursiops truncatus) Bahamas, 1985-1995. Aquat. Mammals 23.2,85 -99.
Heyning, J. E. and Mead, J. G. (1990). Evolution of the nasal anatomy of cetaceans. In Sensory Abilities of Cetaceans (ed. J. Thomas and R. Kastelein), pp.67 -79. New York: Plenum Press.
Irwin, D. M. and Arnason, U. (1994). Cytochrome b gene of marine mammals: phylogeny and evolution. J. Mammal. Evol. 2,37 -55.
Jarman, P. J. (1983). Mating system and sexual dimorphism in large, terrestrial, mammalian herbivores. Biol. Rev. 58,485 -520.
Kato, H. (1984). Observations of tooth scars on the head of male sperm whales, as an indication of intra-sexual fightings. Sci. Rep. Whales Res. Inst. Tokyo 35, 39-46.
Kellogg, R. (1928). The history of whales their adaptations to life in the water. Q. Rev. Biol. 3,174 -208.
Kingdon, J. (1979). East African Mammals, vol. III. London: Academic Press.
Klinowska, M. (1991). Dolphins, Porpoises and Whales of the World, The IUCN Red Data Book. Gland, Switzerland: IUCN.
Losos, J. B. (1990). The evolution of form and function: morphology and locomotor performance in West Indian Anolis lizards. Evolution 44,1189 -1203.
Martins, E. P. (2001). Compare, version 4.4. Computer program for the statistical analysis of comparative data www://compare.bio.indiana.edu/ . Bloomington: Department of Biology, Indiana University.
Melville, H. (1851). Moby-Dick. London: Penguin Books.
Messenger, S. L. and McGuire, J. A. (1998). Morphology, molecules and phylogenetics of cetaceans. Syst. Biol. 47,90 -124.[Medline]
Møhl, B. (2001). Sound transmission in the nose of the sperm whale Physeter catodon. A post mortem study. J. Comp. Physiol. A 187,335 -340.[Medline]
Norris, K. S. and Harvey, G. W. (1972). A theory for the function of the spermaceti organ of the sperm whale (Physeter catodon L.). In Animal Orientation and Navigation. NASA Special Publication 262 (ed. S. R. Galler, K. Schmidt-Koenig, G. J. Jacobs and R. E. Belleville), pp.397 -417. Washington, DC: NASA Scientific and Technical Office.
Norris, K. S. and Møhl, B. (1983). Can odontocetes debilitate prey with sound? Am. Nat. 122,85 -104.
Parker, G. A. (1983). Arms races in evolution an ESS to the opponent-independent costs game. J. Theor. Biol. 101,619 -648.
Philbrick, N. (2000). In the Heart of the Sea. Harmondsworth, UK: Penguin Books Ltd.
Reilly, S. B. and Shane, S. H. (1986). Pilot whale. In Marine Mammals of Eastern North Pacific and Arctic Waters (ed. D. Haley), pp. 133-139. Seattle: Pacific Search Press.
Ross, H. M. and Wilson, B. (1996). Violent interactions between bottlenose dolphins and harbor porpoises. Proc. R. Soc. Lond. B 263,283 -286.
Sawtell, C. C. (1962). The Ship Ann Alexander of New Bedford, 1805-1851. Mystic, CN: Marine Historical Association.
Silverman, H. B. and Dunbar, M. J. (1980). Aggressive tusk use by the narwhal (Monodon monoceros L.). Nature 284,57 -58.
Starbuck, A. (1878). History of the American Whale Fishery, from its Earliest Inception to the Year 1876. New York: Argosy-Antiquarian Ltd.
Vogel, S. (1981). Life in Moving Fluids. Boston: Willard Grant Press.
Wainwright, S. A., Biggs, W. D., Curry, J. D. and Gosline, J. M. (1976). Mechanical Design in Organisms. New York: John Wiley & Sons.
Wainwright, S. A., Vosburgh, F. and Hebrank, J. H. (1978). Shark skin: function in locomotion. Science 202,747 -749.
Whitehead, H. and Payne, R. (1981). New techniques for assessing populations of right whales without killing them. In Mammals of the Seas, vol. III, FAO Advisory Committee on Marine Resources Research, pp. 189-209. Rome: Food and Agriculture Organization of the United Nations.
Whitehead, H. and Weilgart, L. (2000). The sperm whale, social females and roving males. In Cetacean Societies, Field Studies of Dolphins and Whales (ed. J. Mann, R. C. Connor, P. T. Tyack and H. Whitehead), pp.154 -172. Chicago: University of Chicago Press.
Wrangham, R. and Peterson, D. (1996). Demonic Males: Apes and the Origin of Human Violence. Boston: Houghton Mifflin Company.
Related articles in JEB: