| Home: Special status species: Sperm whale: Natural history |
| SPECIAL STATUS SPECIES: SPERM WHALE (Physeter macrocephalus) NATURAL HISTORY |
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| General |
| Taxonomy: |
Suborder Odontoceti (toothed whales); Family Physeteridae (sperm whales). There is some debate over the correct specific name for this species; some use Physeter catodon to refer to this species, but P. macrocephalus is most commonly used.5
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| Appearance: |
Largest of the toothed whales. Males are much larger than females; males reach a length of 16 m (53 ft) and 45 tons while females reach 11 m (36 ft) and 15 tons.16 Sperm whales have an exceptionally large head to body ratio: the head makes up about 1/3 of the total body length. A single blow hole is located near the front of the left side of the head. The bottom jaw is very narrow and holds 17-29 pairs of teeth. The body is dark gray except for some white around the mouth (all white individuals are observed infrequently). The skin posterior to the head region is wrinkled. The dorsal fin is low and rounded and followed by knuckles along the spine. |
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| Feeding Behavior |
| Overview: |
This species may feed alone (adult males), in loose aggregations (“bachelor” schools), or in larger “mixed” groups comprised of females, juveniles of both sexes, and calves. Foraging dives average 30-45 minutes and 300-800 meters deep.2 However, adult males can reach depths of over 1,300 m.2 |
| Prey Items: |
Large and medium-sized deep-dwelling cephalopods (squid and octopus), rays, sharks, various fish (e.g. ragfish, dogfish, rockfish). Males and females differ somewhat in their preference for fish species.17 |
| Method of
Capture: |
It is unknown how sperm whales find and catch prey. One hypothesized method is swimming with an open mouth and using tactile sense to find prey. Another hypothesis is luring prey toward the mouth using either the whale’s white lips or some form of bioluminescence. The most widely supported method is an active search-and-pursue strategy using a highly developed echolocation system, potentially assisted by eyesight, to navigate and locate food in the deep ocean.18 Sperm whales may stun their prey with a burst of sound. |
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| Reproduction |
| Overview: |
Adult female and immature sperm whales (<6 years old) of both sexes appear to live in a fission-fusion society with the observed “group” being comprised of temporary associations between more stable social “units”.19,3,20 Both units and groups contain clusters of close genetic relatives, but some individuals have no close relations21,22,23; no strictly matrilineal unit or group has been observed to date through genetic or photo-identification studies. Juvenile males leave their natal groups and form “bachelor” schools. These loose schools appear to be comprised of predominantly of unrelated individuals.22 In their 20’s, sexually mature adult males migrate solitarily back to warmer waters to breed and appear to rove among groups of females.24,25 |
| Time to Maturity: |
Females mature at approximately 9 years and a length of 9 m and males mature in their teens, but do not show reproductive behavior until the late 20’s at a length of approximately 12 m.2 |
| Longevity: |
Females can live for over 80 years and possibly to 100.2 |
| Breeding
Season: |
Females in the northern and southern hemispheres are thought to be six months out of phase in their breeding cycles with peaks in ovulations in spring in the northern hemisphere and during autumn in the southern hemisphere.26 Calving occurs in summer and early fall.27 |
| Frequency
of Breeding: |
Mature females usually give birth every 4-6 years.2 The calving interval increases with the age of the mother. |
| Gestation
Period: |
15 months2 |
| Offspring per Pregnancy: |
One (twins have been reported by whalers, but it is unknown if they can survive)2 |
| Parental
Care: |
Maternal; mothers nurses calves for at least 24 months. The lactation period may become longer in older females. |
| Mating
System: |
Probably polygamous. Based on large male body size, large head with extensive scarring, loud “clangs”, the infrequent occurrence of broken teeth and jaws, and rare observations of fights between adult males, it appears that males compete physically and acoustically for mating opportunities with females. However, sometimes more than one adult male may be found with groups of females without observed aggression, thus there remains much unknown about mating behavior.24 |
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