| Home: Special status species: Gray whale: Natural history |
SPECIAL STATUS SPECIES: GRAY WHALE (Eschrichtius robustus)
NATURAL HISTORY |
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| General |
| Taxonomy: |
Suborder Mysticete
(Baleen Whales); Family Eschrichtiidae (Gray whale);
there is only one species in this family and no
subspecies are currently recognized.
|
| Appearance: |
Adults
average 13-14 m (42-46 ft) and 35,000 kg (80,000
lb) with females
being slightly larger than males. The mottled gray
body often has large patches of barnacles and whale
lice on the head. There is no dorsal fin, instead
there is a dorsal hump followed by knuckles running
to the caudal fin. The mouth is slightly downturned
and there are 2-5 deep longitudinal creases along
the throat. |
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| Feeding Behavior |
| Overview: |
Gray whales do not show coordinated
group feeding behavior, but large aggregations can
occur in prime feeding locations. Very little feeding
is thought to occur during the southbound migration
or while on the winter grounds.18 Some gray whales have been observed feeding
during the northbound migration. |
| Prey Items: |
Various
benthic and mid-water invertebrates including: gammarid
amphipods, infaunal polychaetes, ghost shrimp, mysid
shrimp, crab larvae, krill, and fish eggs/larvae7,13,18 |
| Method of
Capture: |
To feed on benthic
prey, they stir up bottom mud by rolling on their
side, sucking up sediment, and filtering food from
the water/mud slurry. Gray whales lunge into and engulf
swarms of mid-water crustaceans and fish eggs/larvae.
They may ingest invertebrates associated with masses
of algae by running the algae through their mouths. |
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| Reproduction |
| Overview: |
Breeding and calving are strongly
seasonal. Males compete for access to females in the
breeding lagoons. Single females are often surrounded
by a group of 2 to 3 males during mating. Sperm competition
may occur at times because females may mate with more
than one male. |
| Time to Maturity: |
Both sexes mature at
an average age of 8 years (range of 5-11 years) and
at a mean length of 11.1 m in males and 11.7 m in
females.18 |
| Longevity: |
Longevity: May live
to be 75-80 years43 |
| Breeding
Season: |
Calves are
born in winter between late December and mid-February
either during the southern migration or in the coastal
lagoons of Baja California, Mexico. Mating also occurs
in the winter either during migration or near calving
areas.18 |
| Frequency
of Breeding: |
Counts of northbound cow with
calves are more consistent with females calving every
third year on average than ever other year.20 |
| Gestation
Period: |
~13 months18 |
| Number of
Offspring per Pregnancy: |
One calf |
| Parental
Care: |
Maternal; mothers nurse
calves for approximately 7 months18
|
| Mating
System: |
Polygamous; males
attempt to breed with multiple females in a season. |
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