(DRAFT) - Taxonomy
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

TAXONOMY

NAME - OTTER, SEA, SOUTHERN

OTHER COMMON NAMES - OTTER, SEA, SOUTHERN;OTTER, SEA, CALIFORNIA;OTTER and SEA

ELEMENT CODE -

CATEGORY - Mammals

PHYLUM AND SUBPHYLUM - CHORDATA,

CLASS AND SUBCLASS - MAMMALIA,

ORDER AND SUBORDER - CARNIVORA,

FAMILY AND SUBFAMILY - MUSTELIDAE,

GENUS AND SUBGENUS - ENHYDRA,

SPECIES AND SSP - LUTRIS, NEREIS

SCIENTIFIC NAME - ENHYDRA LUTRIS NEREIS

AUTHORITY -

TAXONOMY REFERENCES -

COMMENTS ON TAXONOMY -
Southern Sea Otter

Enhydra lutris nereis (Merriam, 1904)

KINGDOM: Animal GROUP: Mammal

PHYLUM: Chordata CLASS: Mammalia
ORDER: Carnivora FAMILY: Mustelidae

Sea otters are the largest member of the family Mustelidae (with
the exception of the giant Amazonian otter, Pteronura brasiliensis),
and the smallest species of marine mammal in the world, excepting the
marine otter (Lutra felina). Sea otters are slightly sexually
dimorphic. Adult male California sea otters average 29.5 kg in weight
and 129 cm in length; adult females average 19.5 kg in weight and 120
cm in length (124,01). Pups weigh between 1.4 and 2.3 kg at birth
(03). Alaskan females live 15-20 years, while the male's lifespan
appears to be about 10-15 years (04). Jameson (117) estimates a
minimum lifespan of 11-12 years for male California sea otters.
Unlike most carnivores, a sea otter's teeth lack sharp cutting
edges and are adapted for crushing hard-shelled macroinvertebrates.
Molars are broad and flattened, and the canines are rounded and blunt.
The adult dental formula is i3/2, c1/1, p3/3, m1/2, total 32 (05).
The tail is horizontally flattened to enhance propulsion (05,06).
Taxonomy - 1 (DRAFT) - Taxonomy
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

The hind feet are flattened and flipper-like (07). The hind digits
are progressively lengthened, with the fifth (outer) digit being the
longest, an adaptation which enables the otter to swim on its back
more efficiently at the surface (05,08). The forepaws are used
primarily for grooming and foraging, rather than for propulsion (12).
A loose pouch of skin at the axilla of each foreleg is used to
temporarily store and transport food (05).
Pelage color in adults varies in shades of brown. In some
individuals, the fur may become progressively grizzled and lighter in
color on the head, neck and chest, due to loss of pigmentation in the
guard hairs (05,03,15,16). Molting takes place throughout the year
(05). Newborn pups are characterized by a light brown or yellowish,
wooly natal pelage (42), which is completely replaced by the adult
pelage by 13 weeks of age (43).
Unlike most other marine mammals, sea otters have very little
subcutaneous fat to provide thermal protection and reserve energy, and
therefore depend on an entrapped air layer maintained within their
dense, water-resistant underfur, which provides an insulative barrier
against the cold as well as buoyancy (05,23).
Historically, three subspecies of the genus Enhydra (Fleming,
1822) (24) have been recognized. Enhydra lutris gracilis (Bechstein,
1800) (25), occupyies the Kurile Islands and eastern coast of the
Kamchatka Peninsula. E. l. lutris (Linnaeus, 1758) (26), ranges from
the Soviet Union's Commander Islands and Alaska's Aleutian Islands to
Prince William Sound south to approximately Punta Abreojos in Baja
California. The taxon E. l. nereis (southern sea otter) is
controversial and its existence, as well as its northern range limit,
are currently unresolved.
In 1904, C. Hart Merriam (27) recognized a southern subspecies,
Latax lutris nereis, on the basis of a single skull from San Miguel
Island, California. Grinnell et al. (28) confirmed the validity of
the subspecific designation and used the genera Enhydra (E. l. nereis)
after comparing the type specimen with a single skull from Alaska.
However, Scheffer and Wilke (29) later examined 56 skulls (8 from
California, Oregon, and Washington; 48 from Alaska) and found no
significant differences in skull features. They concluded that E. l.
nereis was not a valid subspecies and should therefore be synonymized
with E. l. lutris. In their reviews of mammalian species, Miller and
Kellog (70) and Hall and Kelson (67) recognized E. l. nereis as a
distinct subspecies, while Kenyon (05) agreed with the conclusion of
Sheffer and Wilke (29) that the subspecific designation E. l. nereis
was incorrect.
Roest (30) examined 50 skulls from California and 214 from
Alaska, and compiled total length and weight measurements reflecting
size differences among the two populations. He concluded the E. l.
nereis was recognizably different from E. l. lutris and constituted a
valid subspecies. However, Roest's subsequent detailed multivariate
analysis of four skull features in over 250 skulls representing sea
otter populations from California and Alaska (Amchitka and Adak
Islands, and mainland southwestern Alaska) led him to conclude that E.
l. nereis was not a distinct subspecies but rather a variation of a
northwest-southeast cline (31,32).
Davis and Lidicker (34) disagreed with Roest's conclusions and
Taxonomy - 2 (DRAFT) - Taxonomy
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

presented an alternative interpretation of his data. They proposed
that a high degree of separability exists between the northern and
southern populations, and that otters from southwestern Alaska (the
Alaskan peninsula, southern Alaska and Prince William Sound) represent
an area of intergradation between the two subspecies. Davis and
Lidicker pointed out that if the intergradation is regarded as clinal,
there is a pronounced shift in the slope steepness of the indicated
cline between Prince William Sound and the Alaskan peninsula. They
concluded that E. l. nereis should continue to be recognized as a
valid subspecies, based on existing morphological and behavioral
differences between the populations, and the degree of geographical
and genetic isolation characterizing the sea otter population in
California.
Rice (66), and Nowak and Paradiso (64) subsequently recognized
E. l. nereis as a distinct subspecies in their respective listings of
marine mammal and mammal species.
Results of a subsequent analysis by Roest (33), in which he
compared skulls representing nine geographical sea otter groups
(rather than four), supported his earlier interpretation that
morphological skull differences represented a clinal variation, and
that all sea otters from the Commander Islands to California should be
included within the subspecies E. l. lutris. The California Dept. of
Fish and Game (62) agreed with Roest's interpretation, concluding
that there is no basis for recognizing California sea otters as a
separate subspecies.
In summary, the Alaskan sea otter and the California sea otter
populations are now geographically and genetically separate from one
another. There exists some morphological and behavioral differences
between the two populations, although morphological differences are
demonstrable from the extremes of the range and behavioral differences
are not widely accepted as evidence of genetic differences. Whether
these differences result from clinal variation in characteristics of a
single subspecies, or from distinct differences of subspecies
historically subjected to intergradation is presently unknown.
Photographs, skeletal material and pelts of California sea otters
are available at the following locations in California: California
Dept. of Fish and Game, offices in Monterey and Morro Bay; the U.S.
Fish and Wildlife Field Stations, in Piedras Blancas and Santa Cruz;
the Monterey Bay Aquarium in Monterey; Polytechnic State University at
San Luis Obispo; and San Jose State University.

Taxonomy - 3 (DRAFT) - Status
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

STATUS

Coded Status

T: Federal Threatened
Marine Mammal

Pest
Commercial
Non-consumptive recreational

COMMENTS ON STATUS -
U.S. STATUSES AND LAWS:
The southern sea otter (Enhydra lutris nereis) has been
designated as Threatened pursuant to the Endangered Species Act
of 1973 (50 CFR 17.11; P.L. 93-205, 87 Stat. 884; 16 U.S.C.
1531-1540), as amended. The subspecies has this status wherever found
including the States of California, Oregon and Washington, and in
Mexico.
An experimental population of southern sea otters has been
designated in all areas under U.S. jurisdiction south of Pt.
Conception, CA (34 deg., 26.9' N. Lat.) (50 CFR 17.84(d)). The
status of the experimental population is governed by Public Law
99-625, 100 Stat. 3500. The experimental population consists of
zones: (1) a management zone - which includes all areas designated in
the experimental population except the translocation zone; and (2)
a translocation zone comprising San Nicolas Island, Begg Rock, and
surrounding waters within the following coordinates:

Degrees: Min.: (N. Lat.) Degrees: Min.: (W. Long.)
33 27.8' 119 34.3'
20.5' 15.5'
13.5' 11.8'
06.5' 15.3'
02.8' 26.8'
08.8' 46.3'
17.2' 56.9'
30.9' 54.2

Enhydra lutris nereis is protected by the Marine Mammal
Protection Act of 1972 (50 CFR 18; PL 92-522; 86 Stat. 1027; 16 U.S.C.
1361, 1362, 1371-1384, 1401-1407), as amended.
The International Fur Seal Treaty of 1911 promotes protection of
sea otters on the high seas.
Status - 1 (DRAFT) - Status
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

The Fur Seal Act of 1966, as amended, prohibits, except under
certain conditions, the taking, possession, etc. of sea otters.
The Fishery Conservation and Management Act of 1976 asserts
management authority and an exclusive fishery conservation zone 200
miles wide over fish and "all other forms of marine life".
The Outer Continental Shelf Lands Act of 1953 provides for the
conducting of studies of the environmental effects of leasing
operations outside of State jurisdictions (three miles from the
mainland).
This subspecies is protected by the Lacey Act (P.L. 97-79, as
amended; 16 U.S.C. 3371 et seq.) which makes it unlawful to import,
export, transport, sell, receive, acquire, or purchase any wild animal
(alive or dead including parts, products, eggs, or offspring):
(1) in interstate or foreign commerce if taken, possessed,
transported or sold in violation of any State law or
regulation, or foreign law; or
(2) if taken or possessed in violation of any U.S. law,
treaty, or regulation or in violation of Indian tribal law.
It is also unlawful to possess any wild animal (alive or dead
including parts, products, eggs, and offspring) within the U.S.
territorial or special maritime jurisdiction (as defined in
18 U.S.C. 7) that is taken, possessed, transported, or sold in
violation of any State law or regulation, foreign law, or Indian
tribal law.

RESPONSIBLE FEDERAL AGENCIES:

USFWS -Responsible for the management/recovery, listing, and
law enforcement/protection of this species.

All Federal agencies have responsibility to ensure that any
action authorized, funded, or carried out by that agency is not likely
to jeopardize the continued existence of the species or result in the
destruction or adverse modification of Critical Habitat (50 CFR 402),
and to utilize their authorities to carry out programs for the
conservation of the species.

STATE STATUSES AND LAWS:

STATE: California and Oregon
DESIGNATED STATUS: CA, Marine Mammal, Fully Protected Mammal,
and Recognized Threatened;
OR, Recognized Threatened.
ADMINISTRATIVE AGENCY: California Fish and Game Commission,
California Department of Fish and Game;
Oregon Fish and Wildlife Commission,
Oregon Department of Fish and Wildlife.
STATE STATUTE: CA, FGC, Sec. 4500 and 4700; Gill & trammel net
restrictions, CA FGC, Sec. 8664.5 & 8664.7.
OR, Oregon Admin. Rules, Ch. 635, Div. 7; OR
Rev. Stat. 498.026, 506.001-506.518 and
610.002-610.060.

Status - 2 (DRAFT) - Status
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

STATE: Washington
DESIGNATED STATUS: Endangered [Historically Enhydra lutris
nereis. Current population not considered
E. l. nereis (i.e., Alaskan otters
transplanted to Washington]
ADMINISTRATIVE AGENCY: Washington Department of Game, State Game
Commission.
STATE STATUTE: WA Admin. Code, 232-12-014, 232-12-470 and 480;
Rev. Code of WA. Annot. 77.16.040, 77.16.120, and
77.12320.

INTERNATIONAL STATUSES, TREATIES, AND AGREEMENTS:
Enhydra lutris nereis is listed in Appendix I of CITES. Enhydra
lutris was listed by the U.S. in the Convention on Nature Protection
and Wildlife Preservation in the Western Hemisphere (1967) but does
not appear on the 1970 revision. The sea otter is also listed as
Endangered by Canada.

ECONOMIC STATUSES:
Sea otters (Enhydra lutris) have been recognized as a valuable
fur-bearing animal and commercial exploitation, beginning in the
mid-1700's, greatly reduced their numbers. Sea otter predation on
kelp foraging invertebrates may be responsible for conversion of
"urchin barrens" to kelp forests. Kelp is a product of commercial
significance (30 to 50 million dollars per year in California) that
also provides habitat for certain fin fish species of recreational
and commercial importance. Some commercial and recreational fishery
interests consider the sea otter a pest because of competition for
abalone, clams, and other invertebrates as well as incidental capture
in fishing nets. This species has value to naturalists and attracts
attention from tourists.

75/09/26:40 FR 44329/44331 - Proposed rule, list as Threatened
77/01/14:42 FR 02965/02968 - Final rule, listed as Threatened
82/09/27:47 FR 42387/42388 - Five year review
84/06/27:49 FR 26313/26315 - Notice, prepare EIS - prop. translocation
86/08/15:51 FR 29362/29383 - Proposed rule, experimental population
86/08/15:51 FR 29384/ - Notice, avail. DEIS & hear. on exp. pop.
87/05/08:52 FR 17486/17487 - Notice, avail. Final EIS - translocation
87/07/07:52 FR 25523/25528 - Notice, five year review
87/08/11:52 FR 29754/29790 - Final rule, Experimental population
88/09/27:53 FR 37577/37581 - Final rule, special regulations

Status - 3 HABITAT ASSOCIATIONS

HABITAT - AQUATIC
COASTAL

LAND USE -
Bays and Estuaries
Beaches
Bare Exposed Rock

NATIONAL WETLAND INVENTORY CODES

NWI NWICLS NWIMOD NWISPEC

Marine, intertidal RS3
Marine, intertidal RS2
Marine, intertidal RS1
Marine, intertidal RF3
Marine, intertidal BB2
Marine, intertidal BB1
Marine, intertidal AB2
Marine, intertidal AB1
Marine, subtidal UB3
Marine, subtidal UB2
Marine, subtidal UB1
Marine, subtidal RF3
Marine, subtidal RB2
Marine, subtidal RB1
Marine, subtidal OW0
Marine, subtidal AB2
Marine, subtidal AB1
Marine, intertidal RS3
Marine, intertidal RS2
Marine, intertidal RS1
Marine, intertidal RF3
Marine, intertidal BB2
Marine, intertidal BB1
Marine, intertidal AB2
Marine, intertidal AB1
Marine, subtidal UB3
Marine, subtidal UB2
Marine, subtidal UB1
Marine, subtidal RF3
Marine, subtidal RB2
Marine, subtidal RB1
Marine, subtidal OW0
Marine, subtidal AB2
Marine, subtidal AB1

COMMENTS ON HABITAT ASSOCIATIONS -
Sea otters inhabit a narrow zone of shallow, littoral water along
the central California coast. The majority of otters remain within
approximately 1-2 km of shore, inshore of the outer kelp edge, which
generally corresponds to the 18.3 m (10 fathom) depth curve. Some
individuals, however, may be found further offshore to the 37 m
(20 fathom) depth curve (88,89,90). Foraging activity is generally
restricted to water depths of 25 meters or less (88,45,15), although
otters have been reported feeding in depths of up to 20 fathoms (93).
In California, sea otters are primarily associated with subtidal
habitats characterized by rocky, crevice substrate, although they are
Habitat Associations - 1 also found in sandy substrate areas. A rocky substrate supports a
rich and diverse assemblage of plants and animals, including prey
frequently consumed by sea otters, such as sea urchins, abalones and
crabs. Sea otter density within most of the range (with the exception
of the northern and southern population fronts) is related to
substrate type; rocky bottom habitats support an average density of
five otters per square km, whereas sandy bottom areas support an
average density of 0.8 otters per square km (45).
Although California sea otters may inhabit areas devoid of
canopy-forming kelp and rest in open water, the presence of kelp beds
(consisting of the kelps Nereocystis leutkeana and especially
Macrocystis pyrifera) is an important component of sea otter habitat.
The kelp canopy, which is used for resting and foraging, appears to be
a significant variable influencing sea otter distribution patterns as
well as territorial home range boundaries (94). Otters apparently
prefer to use kelp beds dominated by Macrocystis as resting sites, as
opposed to beds consisting predominantly of Nereocystis (96,117).
Specific kelp beds are used as habitat rafting sites for groups of
otters as well as for individuals (89,94,97,98). Jameson (94) found
that territorial males consistently returned to the same kelp beds to
rest.
Sea otters in California have been observed "hauled-out" on land
throughout their range (03,101,117,134). Preferred haul-out sites are
characterized by low-relief, algae-covered rocks which are exposed at
low tide (101), although sand or cobble beaches are occasionally used
as haul-out sites. Sea otters often haul-out in association with
harbor seals (Phoca vitulina). Although the frequency of haul-out
behavior in California is unknown, southern sea otters do not come
ashore as often or in groups as large as do sea otters in Alaska (05).

Habitat Associations - 2 (DRAFT) - Food Habits
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

FOOD HABITS

TROPHIC LEVEL -
CARNIVORE

LIFESTAGE FOOD FOOD PART
General Fish
General Aves
General Crustaceans
General Molluscs
General Fish
General Aves
General Crustaceans
General Molluscs

Food Habits - 1 (DRAFT) - Environment Associations
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

ENVIRONMENTAL ASSOCIATIONS

Environment Associations - 1 (DRAFT) - Life History
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

LIFE HISTORY

FOOD HABITS:
The California sea otter's diet is almost exclusively of a
variety of nearshore macroinvertebrates. Alaskan sea otters also feed
on epibenthic fish in many areas where the otter populations are near
equilibrium density (103,105). Prey availability varies with location
and length of time an area has been occupied by sea otters, which in
part determines dietary composition. In recently reoccupied habitats
of central California, the diet consists principally of abalones
(Haliotis spp.), rock crabs (Cancer spp.) and sea urchins
(Strongylocentrotus spp.) (88,95,108,110,112). These food items are
higher in caloric value and therefore more rewarding than other prey
species (20). As populations of preferred prey are reduced in an
area, an otter's diet diversifies through consumption of food items
such as kelp crabs (Pugettia spp.), clams (various spp.), turban
snails (Tegula spp.), mussels (Mytilus spp.), octopus (Octopus spp.),
barnacles (Balanus spp.), scallops (Hinnites spp.), sea stars
(Pisaster spp.) and chitons (Cryptochiton spp.) (114,108,115,15,88,95,
112,46,116,117). Sea otter predation on seabirds has been reported
occasionally in California (118,117,119). Predation on fish is
extremely rare (03,46). A complete list of prey items consumed by sea
otters in California and Alaska is provided in the Recovery Plan (46).
Dietary composition is also partially reflected in the habitat
type and time of year. For example, Pismo clams (Tivela stultorum)
make up a significant proportion of the diet of sea otters foraging in
Pismo clam beds in Monterey Bay and Atascadero State Beach near Morro
Bay (121,122,123). Squid appear to constitute a substantial portion
of the diet of some individuals during the fall and spring squid
(Loligo opalescens) spawning in Monterey Bay (45,124).
California sea otters are bottom foragers in rocky-substrate and
soft-sediment sublittoral communities and also forage within the
kelp-plant understory and canopy. Most foraging activity takes place
in subtidal zones, although otters also forage intertidally (15,125,
117). In California, otters usually forage at a depth of less than 25
meters (88,45,15), beyond which canopy-forming kelps, and other sea
otter prey items become scarce (127).
Sea otters capture prey with their forepaws, store food items
in loose pockets of skin located beneath the axilla of each foreleg,
then consume the prey at the surface (13,128). The use of tools
(e.g., rocks) to break open or dislodge hard-shelled
macroinvertebrates is common (114,120,05,130,03). Prey is also
captured by digging in soft substrate with the forepaws (123) and
occasionally by breaking apart aluminum beverage cans to extract
octopuses which have taken refuge inside the cans (132). An otter may
steal a subordinate's food item at the surface (133).
On average, 70% to 73% of diurnal feeding dives result in the
successful capture of prey (89,112). Adult otters may have more
unsuccessful dives than juveniles, and often require several
successive dives to capture less accessible but higher calorie prey
items (e.g., abalone); more dives than is necessary to obtain less
valuable prey (e.g., turban snails) (89,20,112).
Over a 24-hour period, Loughlin (89) found that otters in
Life History - 1 (DRAFT) - Life History
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

Monterey, CA, spent 34% of their total time foraging, of which about
45% of the feeding activity was nocturnal. Shimek and Monk (136)
reported that groups of otters near Monterey spend 24% of their time
feeding in daylight hours, and Estes et al. (02) found that groups of
otters observed from Monterey south to Point Piedras Blancas foraged
during 21-28% of the daylight hours. Daylight foraging peaked in
early morning and late afternoon (136,02). Sea otter populations in
Alaska and Oregon below equilibrium density, and at equilibrium
density foraged 15-17%, and 50-55% of the daytime, respectively (138).
Diet, and time spent diving and on the surface during foraging
activity seems to vary considerably among individual otters (112,147).

HOME RANGE/TERRITORY:
The center of the California sea otter's range is inhabited
primarily by females of all ages, dependent pups, and recently weaned
juvenile males. During the summer-fall breeding season solitary adult
males move into this area to establish territories (50) but may
maintain territories there throughout the year (89,91). Territory
establishment and maintenance is associated with availability of good
habitat and with reproductive conditions in the local female
population, both varying seasonally. Peripheries of the range (south
of Cayucos and north of Monterey) are occupied predominately by young
nonreproductive males and by adult males that move out of the center
of the range during the winter-spring nonbreeding season (50,94).
The adult male's home range size appears to vary seasonally in
California. In the summer-fall breeding season, resident adult males
have smaller home ranges (equivalent to territory size) than resident
adult females (89,91,99,94). During summer-fall, territorial adult
males tagged near Pt. Piedras Blancas occupied a mean home range of
40.3 ha (N=10) with a mean coastline length of 1.1 km (N=3) (94). The
winter-spring mean home range of five territorial adult males
remaining in female areas was 78.0 ha (mean coastline length of
2.2 km) (94).
The annual home range sizes of adult, subadult, and juvenile
males, are substantially larger than those of adult and subadult
females. Larger yearly male home ranges apparently reflect seasonal
long-distance male movements of 60-100 km to either end of the range
(99,50,94). The mean distance of male life ranges was 80.1 km
(the number of km of coastline known to have been utilized within the
study area) (94). Adult females may utilize an average of only 18 km
(N=22) of coastline throughout their lives (117).
Along the Monterey Peninsula territorial and nonterritorial males
had a mean home range size of 35 ha and 44 ha respectively, while the
mean home range size of adult females was 80 ha (89,91).
Dimensions of the home range may vary in space and time.
Recorded home range size and distance of movements may change
according to the studies duration, the time of year, and the portion
of the range where the otters were marked and studied.
Adult males maintain territories to enhance mating opportunities.
Individual males show strong site-fidelity (89), returning yearly to
the same territory and kelp beds, for up to six consecutive years
(94). The mean size of male territories was 35 ha (N=4) in Monterey
(91) and 40.3 ha (N=10) near Pt. Piedras Blancas (94).
Life History - 2 (DRAFT) - Life History
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

Territorial males rest exclusively within their own territories.
Females are allowed to rest within the territorial boundaries while
other males were not. Males and females were both permitted to pass
through or feed within a territory, although the resident male
occasionally steals food from foraging animals. Fights involving one
or more territorial males appear to be relatively infrequent and
typically involve lunging, pushing, and shoving motions directed
towards the opponent's chest, face and neck (97,89,91).

PERIODICITY:
Sea otters are active diurnally and nocturnally throughout the
year. Diurnal activity cycles are characterized by crepuscular peaks
in foraging activity and a mid-day (late morning - late afternoon)
rest period (120,139,121,89,136,141,140,138,142). In California, a
24-hour observation period showed nocturnal activities to be similar
in nature to diurnal activities, and foraging activity took place
throughout the night (89,135). A third peak in foraging activity may
take place nocturnally between approximately 2300 and 0200 hours (90,
43).
However, considerable individual variation in 24-hour activity
rhythms has been shown to exist (89,135,90). Several aspects of
activity cycles and time budgets may be influenced by a number of
environmental variables (e.g., daily variation in prey availability;
geographical location; and weather and sea conditions (03,139,136,142,
98).
Observations of groups of sea otters along the California coast
show that the average time proportionally allocated to various
activities during daylight falls within the following ranges:
foraging, 21% to 28%; resting 51% to 63%; grooming 5% to 16%; swimming
2% to 9%; and interacting 0% to 8% (107,136,106).
California sea otters appear to be active about half of the time
in a 24-hour period, engaging in the same activities both day and
night (89,90). Individual telemetered otters spent on average 34% of
their time foraging, 54% resting, and 12% engaged in other activities.
About 45% of the feeding activity occurs at night, with substantial
individual variation in the proportion of nocturnal foraging (22% to
73%). Juvenile otters tend to engage in more nonfeeding activities,
such as playful interaction, than adults (89,135).
Each major activity (foraging, resting and grooming) takes place
over a relatively long segment of time. Loughlin (89), noted the
average duration of a foraging bout was 2.5 hours, with at least three
foraging bouts in a 24-hour period. Ribic (90) showed otters average
three or four active periods, lasting about three hours each, followed
by an inactive period of about four hours.

MIGRATION PATTERNS:
Sea otters do not undergo long-distance seasonal migrations,
however seasonal movements of adult males have been documented (See
HOME RANGE/TERRITORY above).
Preliminary observations near Piedras Blancas suggest that
generally juvenile males disperse a greater distance from the natal
area than juvenile females (117). Juvenile males appear to leave the
natal area between six months to 2 1/2 years after weaning, to join
Life History - 3 (DRAFT) - Life History
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

the male groups at either end of the range. Several juvenile males
moved an average of 77 km south of the natal area near Piedras Blancas
to male groups, although one juvenile male moved north 187 km to join
a male group located at Soquel Point near Santa Cruz (94). However, a
recently weaned female remained within a 5 km stretch of coastline for
at least two years (117).

COVER/SHELTER REQUIREMENTS:
California sea otters require shallow, coastal marine waters,
generally at depths of 25 meters or less (88,45,15). Important
characteristics of suitable habitat include canopy-forming giant kelp,
sheltered resting areas, and adequate food resources. Preferred
subtidal habitat includes rocky, creviced bottom substrate, supporting
a rich and diverse array of prey species. California sea otters may
also live and forage in sandy substrate areas (45).
Canopy-forming kelp, (Nereocystis leutkeana and esp. Macrocystis
pyrifera), is an important element of preferred sea otter habitat,
however, otters may be found in open-water areas with little or no
kelp. Otters rest in the kelp canopy and forage in the kelp-plant
understory and canopy. Macrocystis kelp beds are preferred by otters
for resting (96,117) and specific kelp beds may be used as habitual
resting sites by individual otters as well as groups (89,94,98).
Sea otters are able to survive and reproduce entirely at sea, and
therefore are not dependent on land. However, California otters
sometimes "haul out" on shore, preferring sites with low-relief, algae
covered rocks which are exposed at low tide (134,03,101).

REPRODUCTIVE SITE REQUIREMENTS:
The reproductive site requirements for California sea otters are
essentially equivalent to cover/shelter requirements. Females with
small pups may prefer to rest and feed in sheltered sites (e.g., calm,
protected coves), especially during winter storms when available
sheltered resting areas are scarce and kelp beds are sparse (139).
Females may give birth in the water (139) or on land (100,99).
Jameson (99) suggests parturition may occur on land in areas where
kelp beds are sparse or absent.
The density, distribution and configuration of the kelp canopy
may play a role in delineating a male's territorial boundaries (117).
Individual adult males may return to the same kelp bed within the same
territory for several consecutive years (89,73,94). Seasonal
kelp-canopy reduction which occurs in winter and spring may diminish
the potential number of male territories in preferred sites,
intensifying competition for remaining available kelp beds (94).

REPRODUCTIVE CHARACTERISTICS:
The general yearly reproductive pattern in the California
population consists of a winter-spring pupping season and a
summer-fall breeding season, although mating and pupping take place
throughout the year. The peak pupping period occurs from January to
March (42,97,139,50,124). Indirect evidence suggests a peak
breeding season from July to October (94,117).
California sea otters seem to show a variable degree of polygyny,
although many aspects of the mating system remain unclear. Successful
Life History - 4 (DRAFT) - Life History
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

mating may take place with or without the formation of temporary
pair-bonds, which last about 3-4 days (97,92,89,91). Copulation is
aquatic, occurring several times throughout the pair-bond (97).
The female abandons the male terminating the pair-bond (97,92).
The onset of sexual maturity and age of reproductive activity in
males has not been established. Green (87) suggests that California
males reach sexual maturity at about five years; however,
establishment of territories and active participation in breeding may
be some time later. Alaskan males reach sexual maturity at 5-6 years
of age, and become active breeders several years later (86).
California females may reach sexual maturity (enter their first
estrus) between three and five years of age (104,117). Most Alaskan
females reach reproductive maturity between four and five years of
age, although some may enter their first estrus as early as three
years (05,86,142,04). Females probably come into estrus several days
to a few weeks after weaning their pups (117,86).
Like all marine mammals, sea otters give birth to a single pup;
twinning (reported only twice in California) is extremely rare (84,
117). Gestation periods have been estimated at 4-6 months (102) and
approximately 6 months (50). Sea otters undergo delayed implantation
(83). Among Alaskan females, the unimplanted gestation period has
been estimated to last from 3.5-4.5 months (86) to 7-8 months (05).
Evidence suggests the length of the pre-implantation period is
variable (06) and in some cases, relatively brief, especially within
the California population (102).
Current estimates indicate that most adult females give birth to
one pup/year in California, with the reproductive cycle ranging from
11 to 14 months (79,77,102,104,117). The composition of sea otter
milk is similar to that of other marine mammals, having high fat and
low lactose content. Milk fat content ranges from 21% to 26% (76).

PARENTAL CARE:
Pup dependency periods in California range from 5 to 8 months
(104). A mean pup dependency period of about 6 months has been
calculated (43,50). Pup dependency periods of 8-8 1/2 months for
three female/pup pairs and 3 1/2-6 months for two female/pup pairs
have been reported.
Parental care is provided exclusively by the female. Mothers
of newborn pups are often aggressive toward other otters and tend to
be solitary. Within several days of parturition the female will
associate and rest with other otters (139,117). Intensive postpartum
grooming of the pup occurs immediately after birth (139,99). Newborn
pups are relatively helpless and depend on their mothers for
nourishment and protection during most of the 5-8 month period of
maternal care.
Maternal behavior in California sea otters has been qualitatively
described by Fisher (42) and Limbaugh (114). Aspects of pup
development and maternal care have been quantified and studied in
greater detail (139,43).
Detailed analysis of the ontogeny of pup growth and behavioral
development (in both wild and captive pups) by Payne and Jameson (43)
revealed that pups could be aged on appearance and behavior as
follows: natal pelage was completely replaced by adult pelage by
Life History - 5 (DRAFT) - Life History
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

thirteen weeks of age; nourishment was derived primarily from mother's
milk during the first month of age; by four months of age, the pup
subsisted mainly on solid food obtained by the mother. The pup's
proficiency at swimming, grooming, and the use of tools, increased
gradually with age; by age fourteen weeks, most pups were able to swim
independently, dive proficiently, and groom themselves without the
assistance of their mother; by 20-24 weeks pups were successfully able
to capture and break open hard-shelled prey, using a rock tool (43);
and at weaning, most pups weighed approximately 12 kg (117).

POPULATION BIOLOGY:
A minimum lifespan of 11-12 years is estimated for California
male sea otters (94). Lifespan of Alaskan males and females appears
to be 10-15 years and 15-20 years respectively (04). Average lifetime
reproductive potential of females is unknown. A California female
otter could potentially give birth to 10-15 or more pups throughout
her life, assuming annual pupping and a 15-20 year lifespan.
From the late 1930's to the mid-1970's, the California sea otter
population appears to have increased at an average rate of 4-5% per
year (45,54,50,47). This average annual growth rate (AGR) is two to
four times less than the 10% to 16% AGR estimated for open-ended
populations in Alaska (05,54). Over the past decade the California
population has not increased in size and may have declined in numbers
from an estimated 1,500 (50) to 1,800 (55) independent otters in the
mid-1970's to about 1,300-1,400 in the early 1980's (54,46,50,52,53).
The reasons for the lack of observable population growth are unclear.
Three demographic variables that can influence rate of growth and
range expansion, or cause a decline in abundance in the population
are: 1) natality rate; 2) emigration rate; and 3) mortality rate.
Each may differ with respect to age-classes of individuals, and each
may be variably affected by density-dependent and density-independent
processes (46,47).
Annual recruitment to the California population appears to be
within the expected range compared to that observed in open-ended
Alaskan populations. In both California and Alaska, average ratios of
20-30 pups per 100 independent otters are found during censuses at the
end of the pupping season. Average ratios of 15-16:100 are observed
throughout the year, although California range-wide censuses indicate
year to year variations (52). Overall birth rates appear similar in
both populations (54,50). It seems unlikely that significant losses
are occurring through emigration (54,46), since extralimital
occurrences of sea otters are relatively rare (60,61).
The current lack of growth and possible decline in numbers shown
by the California population may be due to an elevated mortality rate
(54). The annual mortality rate, while thought to be relatively high,
is unknown, because the annual recorded otter deaths represent only a
portion of the total mortality. Incidental drowning of sea otters in
commercial gill and trammel nets may have been a significant source of
mortality (74,78). Such mortality seems to have declined
substantially or entirely since late January 1985, due to prohibitions
on commercial gill and trammel net fishing within the 15-fathom
isobath throughout the sea otter's range. Other causes of mortality
include white shark (Carcharodon carcharias) attacks (88,38,58,74),
Life History - 6 (DRAFT) - Life History
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

shooting incidents (51,88,38,74), and a combination of lethal
conditions associated with adverse weather, starvation and various
pathological disorders (38,74).
Density-independent factors (e.g., mortality caused by gill and
trammel net entanglement) may be comparatively more important in
regulating population abundance and distribution, particularly near
the range peripheries. Miller (133) believes the California
population is at carrying capacity and starvation is the principal
(density-dependent) limiting factor. Estes et al. (02) suggest the
California population is not at equilibrium density and is not limited
by food availability, based on the proportion of time allocated to
foraging activity.
Density-dependent processes may be operating primarily in the
center of the range where the population has been long established,
while density-independent factors may be affecting population growth
at either end of the range where the frequency of set-net fishing,
white shark attack (northern periphery), and shooting (southern
periphery) mortality is highest (74).

SPECIES INTERRELATIONSHIPS:
Sea otter predation on herbivorous macroinvertebrates in central
California may influence the abundance and species composition of kelp
assemblages and animals within nearshore marine communities in some
areas. Numerous other biotic and abiotic variables may also affect the
structure of such marine communities. The evolution of complex
relationships between sea otters and the nearshore marine ecosystem
has also been documented in Alaska (103,105) and British Columbia
(44).
In areas of central California, sea otters are known to
reduce and effectively limit populations of various benthic
invertebrate prey, such as abalone (Haliotis spp.), sea urchins
(Strongylocentrotus franciscanus and S. purpuratus), and clams (e.g.,
Tivela stultorum) (108,195,88,121,40,112).
Competitive interactions occurring between sea otters and other
predators in central California whose diets overlap that of otters
(e.g., asteroids, octopus (Octopus spp.), crabs, harbor seals (Phoca
vitulina) and fishes such as cabezon (Corpaenichthys marmoratus) and
wolf eels (Anarrhichtyys ocellatus)) are not well known.
McLean (194) and North (22) suggest that enlargement of kelp
canopies may be associated with the presence of sea otters in some
areas. Reduction of previously dense populations of sea urchins in
central California by sea otter predation appears to have led to three
fundamental changes occurring within macroalgal assemblages: 1) the
size of existing kelp forests has substantially increased; 2) new kelp
beds have become established where kelp was entirely absent prior to
the recolonization of sea otters; and 3) the kelp canopy composition
has shifted in favor of the competitively superior Macrocystis over
the opportunistic kelp Nereocystis (19,17).
The reestablishment and expansion of Macrocystis kelp beds may
promote an increase in the population sizes of some finfish species
associated with kelp forests in California, by providing shelter (esp.
juvenile fishes) from predators by increasing available substrate
area, and by expanding food bases and habitats available to
Life History - 7 (DRAFT) - Life History
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

surface-associated organisms which in turn provide food for nearshore
finfish (14,11,21,19). In the Aleutian Islands the enhancement of
kelp beds by means of sea otter predation has also resulted in
significant enlargement of kelp-associated finfish populations (49).

OTHER LIFE HISTORY DESCRIPTORS:
Sea otters' lungs are large when related to body size (nearly 2.5
times that of similar sized mammals), as are the liver and kidneys.
Large lungs serve to regulate buoyancy and store oxygen (35,36,37,18).
An enlarged liver may play a role in maintaining the high metabolism
(05,38); and the large, lobulate kidneys allow the production of large
volumes of moderately concentrated urine (05,23). Costa (20)
showed that sea otters drink seawater. Consumption of invertebrates
(which posses higher electrolyte concentrations than teleost fish),
requires processing large amounts of electrolytes (nitrogen and
water). Therefore sea water ingestion may promote urea elimination by
increasing the urinary osmotic space without increasing the
electrolyte concentration of the urine (23).
Little information on the sensory organs is available.
Chemoreceptive and tactile senses appear to be well developed. The
paws and vibrissae are used to locate and capture prey underwater
(10,05). Sea otters may have slightly poorer underwater vision than
California sea lions (Zalophus californianus) or harbor seals (Phoca
vitulina), and may have better vision in air than underwater (09).
The sense of hearing appears to be moderately well developed (05).
The external ear resembles the otariid seal ear, is somewhat curled
and is held erect above the surface but folds sharply downward during
underwater dives (05). Unlike other mustelids, the sea otter lacks
functional anal scent glands (05). Descriptions of sea otter
vocalizations are provided by Kenyon (05).

Life History - 8 (DRAFT) - Management Practices
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

MANAGEMENT PRACTICES

RESULT MANAGEMENT PRACTICE

Adverse Commercial Exploitation
Adverse Gas/Oil Development
Adverse Harassment/Vandalism/Indiscriminate Killing
Adverse Incidental Capturing/Killing
Adverse Oil Spills
Adverse Predation
Beneficial Maintaining undisturbed/undeveloped areas
Beneficial Controlling/Restricting Mining
Beneficial Controlling pollution [thermal, chemical, physical]
Beneficial Land Acquisition
Beneficial Restricting/regulating human disturbance of populations
Beneficial Rehabilitating Individuals
Beneficial Restricting Poaching
Beneficial Transplanting wild animals
Existing Commercial Exploitation
Existing Gas/Oil Development
Existing Harassment/Vandalism/Indiscriminate Killing
Existing Incidental Capturing/Killing
Existing Oil Spills
Existing Predation

COMMENTS ON MANAGEMENT PRACTICES -
Southern sea otters have been listed as a Threatened species
since 1977 under the Endangered Species Act of 1973 (42 FR 2965-2968).
Historically, the sea otter population along the California coast has
been estimated to number between 16,000-18,000 (45), 18,000 to 20,000
(46), and 20,000 (47). Intensive commercial exploitation of the sea
otter for its valuable fur took place throughout the worldwide range
in the 18th and 19th centuries. This severely reduced the entire
population to an estimated 1,000 animals by the early 1900's (48,05).
In California, a small remnant population near Point Sur containing an
estimated 50 otters was found in 1914 (45). The current California
population is estimated to contain roughly 1,400 independent animals
(46,50,52,53). However, since the mid-1970's the population has not
grown and may possibly have declined in numbers (54,46,50,52,53).
The principal threat to the California sea otter population stems
from the possibility of a major oil spill occurring along the central
California coast, which could potentially contaminate a substantial
portion of the sea otter's range (56,57) and seriously impact the
population. Otters are among the most sensitive marine mammals to
effects of direct oil contamination (59,75). A large oil spill could
cause significant mortality due to direct contamination of oil on the
otter's fur and possible toxicity associated with oil ingestion (63,
18,65). Loss of thermal insulation resulting from oil-fouled fur
subsequently leads to thermoregulatory distress, along with an
abnormally high rate of heat production, bouyancy loss, hypothermia,
pneumonia and weight loss, all of which may result in death (72,05,63,
65). Indirect effects of an oil spill may include the loss of habitat
Management Practices - 1 (DRAFT) - Management Practices
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

available to sea otters as kelp-forest communities become
contaminated, and a reduction in food resources due to mortality or
unpalatability of the otter's prey (e.g., 68,69,71).
The potential for an accidental oil spill occurring within the
sea otter's range is promoted by the increase in oil and gas resource
development and transportation activities along the California coast,
as well as the existence of marine terminals for tankships up to
50,000 dead weight tons (DWT) at Moss Landing and at Port San Luis and
Estero Bay, which respectively represent the northern and southern
ends of the sea otter's range.
Additional current threats to the California population are
associated with sources of documented as well as potential mortality.
The apparently high mortality rate may be responsible for the lack of
observable population growth and possible decline in abundance, and
the relatively slow rate of range expansion (54,74). Incidental
drowning of sea otters in commercial gill and trammel nets appears to
represent a substantial source of mortality (74,78). Ames et al. (74)
suggest that the rate of northward and southward range expansion may
be reduced due to mortality resulting from shallow water gill and
trammel net fisheries, most of which are located near either end of
the range. In addition, northward range expansion may be inhibited by
the relatively high frequency of great white shark (Carcharodon
carcharias) attacks taking place near the Monterey Peninsula, while
southward emigration may be curbed to some degree by the comparatively
frequent shooting incidents occurring in the southern part of the
range.
Another potential but unverified source of mortality or
diminished fertility may be associated with the presence of
environmental contaminants such as polychlorinated biphenyls (PCBs),
chlorinated hydrocarbons (DDT and its derivatives), and heavy and
trace metals within the sea otter's range. Because environmental
contaminants exhibit biomagnification as they progress up the food
chain (e.g., 80,81), top level predators such as sea otters may
accumulate high and potentially toxic residue levels of such
contaminants. Although variable residue levels of a number of
environmental toxicants have been found in sea otter tissues, no
evidence has been found to suggest a harmful cause-and-effect
relationship between sea otter mortality or pathological conditions
and residues of any toxicants, with the possible exception of
naturally-occurring cadmium (82,74,85).
Future risks to the California sea otter population are similar
to current threats. Entangling fishing nets pose a serious threat to
the population. Commercial gill and trammel nets were prohibited by
State law through temporary emergency closures and subsequent
permanent closures. The length of coastline and distance from shore
affected by the fishing closures has increased significantly since
1982 when the State prohibited the use of entangling nets in Monterey
Bay in waters less than 10 fathoms (60 feet). On May 24, 1985, the
Governor signed into law gill and trammel net fishing closures (for
nets with mesh size equal to or greater than 3.5 inches) in waters
less than 15 fathoms from Monterey Bay to the Santa Maria River,
essentially prohibiting entangling nets throughout the sea otter's
range. On September 20, 1986, legislation was enacted extending the
Management Practices - 2 (DRAFT) - Management Practices
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

gill and trammel net closures in two areas in the center of the sea
otter's range, specifically between Point Sur and Pfeiffer Point and
between Cape San Martin and Pico Creek. The Director of the
California Dept. of Fish and Game has the authority to extend the
20-fathom closure throughout the length of the State's Sea Otter
Refuge that comprises about 100 miles of coastline between the Carmel
River (just south of Monterey Bay) and the Santa Rosa Creek (just
south of San Simeon) should subsequent observations of otters drowned
in nets warrant it. The permanent restrictions prohibiting commercial
gill and trammel net fishing in waters less than 15-20 fathoms should
reduce or eliminate sea otter entanglements and thus reduce a
significant risk to the population.

APPROVED PLAN:
U.S. Fish and Wildlife Service. 1982. Southern Sea Otter Recovery
Plan. U.S. Fish and Wildlife Service, Portland, OR. 66 pp.

The primary objective of the Southern Sea Otter Recovery Plan is
to restore the species to a non-threatened status and to maintain the
present population at its optimum sustainable level while the health
and stability of the nearshore ecosystem is likewise maintained.
Delisting may be considered when the population is stable or
increasing in a large enough area of its original range that only a
small proportion of the total population would be decimated by a
catastrophe.
The recovery activities necessary to achieve the primary
objective are:

A. Restore the southern sea otter to a non-threatened status by:
(1) minimizing the risk of threats from oil tanker accidents or other
sources of oil spills; (2) minimizing the possible effects of oil
pollution, including capturing, cleaning and rehabilitating oiled
otters; (3) establishing one or more sea otter colonies outside
the present range (may require cooperative agreement); (4) minimizing
vandalism/harrassment/incidental take; (5) monitoring recovery
progress; and (6) integrating provisions of the recovery plan into
development and management plans of local government agencies.

B. Manage the southern sea otter population to an obtain optimum
sustainable level by (1) identifying optimum distribution/abundance/
productivity, (2) determining the best methods to obtain and maintain
optimum distribution/abundance/productivity, developing/implementing a
long term management plan, and (4) integrate the management plan into
local government plans.

C. Assess and monitor the status of the southern sea otter
population and habitat by improving currently known demography and
dynamics of the; (1) population; (2) habitats; (3) relationship
between sea otters and their habitat; and (4) implementation of a long
term management plan.

Management Practices - 3 (DRAFT) - Management Practices
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

APPROVED PLAN:
U.S. Fish and Wildlife Service. 1982. Southern Sea Otter Recovery
Plan. U.S. Fish and Wildlife Service, Portland, OR. 66 pp.

Management Practices - 4 (DRAFT) - References
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

References

***** REFERENCES FOR ALL NARRATIVES EXCEPT N-OCCURRENCE *****

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summary of knowledge of the sea otter, Enhydra lutris L., in
California and an appraisal of the completeness of biological
understanding of the species. Final. Rept. to U.S. Mar. Mam. Comm.
Contract No. MM6AC008. 71 pp.
02 Estes, J.A., K. Underwood, and M. Karmann. 1984 (Draft). Activity
time budgets as indicators of the population status of sea otters
in California.
03 Miller, D.J. 1974. The sea otter, Enhydra lutris. Its life
history, taxonomic status and some ecological relationships.
Marine Resour. Leaflet No. 7. The Resour. Agency, Ca. Dept.
Fish Game. 13 pp.
04 Calkins, D.G. and K.B. Schneider. 1984. Species Account: The sea
otter Enhydra Lutris. Ak. Dept. Fish Game. 14 pp.
05 Kenyon, K.W. 1969. The sea otter in the eastern Pacific Ocean.
N. Am. Fauna No. 68. Bur. Sport Fish. Wildl., U.S. Gov't. Print.
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06 Kenyon, K.W. 1981. Sea otter -- Enhydra lutris. Pages 209-223.
IN: Handbook of marine mammals. S.H. Ridgeway and R.J. Harrison,
eds. Academic Press, New York. 235 pp.
07 Murie, O.J. 1959. Fauna of the Aleutian Islands and Alaska
Peninsula. N. Am. Fauna 6:1-406.
08 Tarasoff, F.J. 1972. Comparative aspects of the hindlimbs of the
river otter, sea otter, and harp seal. Pages 333-359. IN:
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09 Gentry, R.L. and R.S. Peterson. 1967. Underwater vison of the sea
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10 Radinsky, L.B. 1968. Evolution of somatic sensory specialization
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11 Leamon, B.M. 1980. The ecology of fishes in British Columbia kelp
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12 Howard, L.D. 1973. Muscular anatomy of the forelimb of the sea
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13 Barabash-Nikiforov, I.I. 1947. Kalan (the sea otter). Soviet
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14 North, W.J. and C.L. Hubbs. 1968. Pages 35-56, 143-150, and
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16 Garshelis, D.L. 1984. Age estimation of living sea otters. J.
Wildl. Mgmt. 48(2):456-463.
17 VanBlaricom, G.R. 1984b. Sea otters enhance valuable resources in
kelp forests of central California. USFWS Res. Info. Bull.
No. 84-12.
18 Costa, D.P. and G.L. Kooyman. 1982. Oxygen consumption,
References - 1 (DRAFT) - References
Species OTTER, SEA, SOUTHERN
Species Id ESIS051003
Date 14 MAR 96

thermoregulation, and the effect of fur oiling and washing on the
sea otter, Enhydra lutris. Can. J. Zool. 60:2761-2767.
19 VanBlaricom, G.R. 1984. Relationships of sea otters to living
marine resources in California: A new perspective. Pages 361-381.
IN: Collection of papers presented at the Ocean Stud. V. Lyle,
ed. Symp., Nov 7-10, Asilomar, CA. CA Coastal Comm. & CA Dept.
Fish & Game.
20 Costa, D.P. 1978. The ecological energetics, water, and
electrolyte balance of the California sea otter, Enhydra lutris.
Ph.D. Diss., Univ. Calif., Santa Cruz.
21 Wilson, K.C., P.L. Haaker, and D.A. Hanan. 1977. Kelp restoration
in southern California. Pages 183-202. IN: The marine plant
biomass of the Pacific Northwest Coast. R.W. Krauss, ed. Or.
State Univ. Press, Corvallis.
22 North, W.J. 1965. Urchin predation. Pages 57-61. IN: Ca. Inst.
Tech. Kelp Hab. Improv. Proj. Ann. Rept., 1 Feb. 1964 - 31 Mar.
1965. W.J. North, ed. 70 pp.
23 Costa, D.P. 1982. Energy, nitrogen and electrolyte flux and
sea-water drinking in the sea otter, Enhydra lutris. Physiol.
Zool. 55(1):35-44.
24 Fleming, J. 1922. The philosophy of zoology. Archibald Constable
Edinburgh. 2:187-188.
25 Bechstein, J.M. 1800. Thomas Pennant's allgemeine uebersicht der
vierfuessign Thiere. Weimar 2:401-418.
26 Linnaeus, C. 1758. Systema Naturae, 10th ed. L. Salvii, Uppsala
1:1-823.
27 Merriam, C.H. 1904. A new sea otter from southern California.
Proc. Biol. Soc. Washington 17:159-160.
28 Grinnell, J., J.S. Dixon and J.M. Linsdale. 1937. Furbearing
mammals of California, Vol.1. Univ. Ca. Press, Berkeley. 375 pp.
29 Scheffer, V.B. and F. Wilke. 1950. Validity of the subspecies
Enhydra lutris nereis of the southern sea otter. J. Wash. Acad.
Sci. 40(8):269-272.
30 Roest, A.I. 1971. A systematic study of the sea otter, Enhydra
lutris. Pages 133-135. IN: Proc. 8th Ann. Conf. Biol. Sonar
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