**PACIFIC WALRUS RESPONSE PLAN**

I. [GENERAL CONSIDERATIONS]{.underline}

A. [Authorities]{.underline}

The Pacific Walrus Response Plan is one component of the U.S. Fish and
Wildlife Service (Service) *Region 7 Oil Spill Contingency Plan*. The
purpose of the Pacific Walrus Response Plan is to provide guidance to
Service employees during an oil spill in Alaska that could affect
Pacific walrus (*Odobenus rosmarus divergens*) or their habitat. The
Service has responsibility for managing and protecting Pacific walrus
under authority of the Marine Mammal Protection Act of 1972 (MMPA) (16
U.S.C. 1361-1407). In Alaska, the Service\'s management goals are to:

> \* maintain the Pacific walrus population within its optimum
> sustainable population level; and
>
> \* assure that Pacific walrus remain a sustained resource for coastal
> Native residents of the Bering and Chukchi seas, and a functioning
> component of the Bering-Chukchi shelf ecosystem (U.S. Fish and
> Wildlife Service 1994).

Section 109(h)(1) of the MMPA authorizes the Service to take (harass,
hunt, capture, or kill, or attempt to harass, hunt capture, or kill) a
marine mammal in the course of official duties, if done in a humane
manner (including euthanasia) and if such taking is for the protection
or welfare of the mammal, protection of the public health and welfare,
or nonlethal removal of nuisance animals. Section 112(c) authorizes the
Service to "enter into such contracts, leases, cooperative agreements,
or other transactions as may be necessary to carry out the purposes of
this title or title IV and on such terms as \[t\]he \[Secretary of the
Interior\] deems appropriate with a Federal or State agency, public or
private institution, or other person."

Title IV of the MMPA calls for establishment of a marine mammal health
and stranding response program in response to unusual mortality events,
including development of a working group, contingency plan, and sample
collection procedures. While Title IV of the MMPA includes oil spill
events as a type of unusual mortality event, it does not supersede,
modify, or limit the duties and responsibilities conveyed by other laws
(Wilkenson 1996). Oil spill response procedures are conducted under
authority and procedures of the Oil Pollution Act of 1990, Clean Water
Act, and Comprehensive Environmental Response, Compensation, and
Liability Act. In Alaska, oil spill response procedures and personnel
parallel those set forth in the *National Contingency Plan for Response
to Unusual Marine Mammal Mortality Events* (1996). Therefore, oil spill
events should be coordinated with the Alaska Marine Mammal Stranding
Coordinator.

B. [Current Population, Distribution, and Life History]{.underline}

1.  Population

The current size of Alaska's walrus population is unknown but is
believed to be within optimum sustainable levels (U.S. Fish and Wildlife
Service 1998). Findings from the most recent aerial survey, flown in
1990, indicated that the population size was 201,039 animals (Gilbert et
al. 1992). This survey omitted a considerable portion of the eastern
Chukchi Sea, an area usually inhabited by walrus, because no ice was
present. Although historical population information exists, differences
in survey methods preclude comparisons to determine population trend
(Hills 1992, Hills and Gilbert 1994).

2.  General Distribution

The distribution of Pacific walruses varies with the seasons. Walruses
generally inhabit first-year ice that can support their weight and
provide access to leads (linear areas of open water) and polynyas
(non-linear areas of water) for foraging. As the Bering Sea pack ice
advances in the winter, walruses move southward just ahead of the
heaviest ice (Fay 1982). During the breeding season (December to March),
Pacific walruses usually occur either in an area immediately southwest
of St. Lawrence Island, or in outer Bristol and Kuskokwim bays (Fay
1982). In late March -- early April, the southern edge of the pack ice
begins to melt and walruses move northward through the Bering Strait and
into the Chukchi Sea. By the end of May walruses are widely distributed
between northern Kamchatka and the Alaska Peninsula, north to the pack
ice edge in the Chukchi Sea. Although most animals migrate into the
Chukchi Sea for the summer months (June - September), several thousand
animals, mostly adult males, concentrate at terrestrial haulouts in
Bristol Bay and the northern Gulf of Anadyr. Major haulouts in Alaska
occur at Round Island, Cape Peirce, Cape Seniavin, Cape Newenham, and
the Punuk Islands. Other less consistently used haulouts include Amak,
Big Twin, Crooked, St. Matthew, Big Diomede and King islands, and Cape
Lisburne (USFWS 1994).

Pacific walrus usually occur in continental shelf waters of 100 m or
less (Fay and Burns 1988). They are predominantly benthic feeders but
occasionally forage along rock substrate. Their primary prey are bivalve
mollusks and clams but their diet broadens when primary prey is less
abundant. Other prey species include annelids, mollusks, crustaceans,
echinoderms, and phocid seals. They rarely consume fish (Fay 1982).

3\. Life History

Walruses (*Odobenus rosmarus*) are the only living species of the family
Odobenidae, and the largest species of the suborder Pinnipedia, which
also includes seals and sea lions. Two subspecies of walrus occur: the
Atlantic walrus (*O. r. rosmarus*) and the Pacific walrus (*O. r.
divergens*) (Mansfield 1958, Fay 1982). The two subspecies are
geographically isolated with only the Pacific walrus occurring in
American waters.

Walrus mate in the winter from December to March. Females give birth in
late April to early June of the following year after a period of delayed
implantation and an 11 month gestation period (Fay 1982). Calves are
dependent on their mothers for approximately two years and reach sexual
maturity at 4-6 years for females and 9-10 years for males (Fay 1982).

Walruses molt annually between June and October while hauled out (Fay
1982). They require elevated skin temperatures to complete their molt;
therefore, repeated disturbances at haulout sites causing entry into
cold water may result in increased metabolic demands and a longer than
normal molt period (USFWS 1994).

C. [Susceptibility to Oil Spills]{.underline}

Walruses are the most gregarious of marine mammals and are found in
groups ranging in size from a few animals while in the water to several
thousand at major haulouts (Geraci 1990). The most sensitive period for
Pacific walruses is probably during calving (April to June), which
occurs primarily in the northern Bering Sea from St. Lawrence Island to
the Bering Strait. Adult walruses may not be severely affected by the
oil spill through direct contact but they will be extremely sensitive to
any habitat disturbance by human noise and response activities. Like fur
seals and sea lions, Pacific walruses are easily disturbed at haulout
areas; stampeding may result in injury or death of calves and perhaps
even adults by trampling.

Walruses have the characteristics of a density dependent species: late
maturation, slow reproduction cycle, long lived, and an existence
determined largely by the amount of resources available (Geraci 1990).
Walrus also have a unique biennial cycle of reproduction that is driven
by an exceptionally long period of devotion to their young. This factor,
coupled with their late maturity, makes walrus the most vulnerable of
all pinnipeds to population catastrophe (Geraci 1990).

Walrus calves are the portion of the population most likely to suffer
the effects of oil contamination. Calves are normally born on the edge
of the pack ice, an area that increases their vulnerability to an oil
spill because of the tendency for oil to pool at the edge of the ice
(API 1989). Female walruses with calves are very attentive; the calf
will stay close to its mother at all times, including when the female is
foraging for food. Walrus calves can swim almost immediately after birth
and will often join their mother in the water. It is possible that an
oiled calf will be unrecognizable to its mother either by sight or by
smell, and be abandoned. The greater threat, however, may come from an
oiled calf that is unable to swim away from the contamination and a
devoted mother that would not leave without the calf, resulting in the
death of both animals (Geraci 1990).

Walrus migrate in large herds to the Bering Strait and Chukchi Sea,
which forces them to cross areas where oil may be present. This presents
the possibility of a large portion of the population moving through a
potentially contaminated area at the same time. Mobile populations are
generally less at risk than sedentary populations, and the wide
geographic distribution of the walrus makes a large extinction unlikely,
but local crashes are still possible (Geraci 1990). Walrus mate as they
travel northward through the Bering Strait in late winter/early spring.
The majority of female Pacific walrus are in this general area at the
same time. Should they be exposed to oil contamination, pregnant female
walrus may be at a higher risk for spontaneous abortions. Because the
bulk of the sexually mature female walrus population is together in the
same general area at the same general time, a catastrophic contamination
resulting in a crash in that section of the population would be
disastrous to the species. Finally, although adult females may not be
killed outright by the contamination, the entire walrus population may
suffer from a decrease in overall fertility rates with repercussions
felt for years after the spill (Geraci 1990).

Walruses have thick skin and blubber layers for insulation and very
little hair. Thus they exhibit no grooming behavior, which lessens their
chance of ingesting oil. Heat loss is regulated by control of peripheral
blood flow through the animal\'s skin and blubber. The peripheral blood
flow is decreased in cold water and increased at warmer temperatures.
Direct exposure of Pacific walruses to oil is not believed to have any
effect on the insulating capacity of their skin and blubber, although it
is unknown if oil could affect their peripheral blood flow. Although
newborn walrus calves, compared to adults, have relatively thin blubber
levels and appear to be prone to hypothermia, they exhibit rapid blubber
accumulation during the nursing period, which lasts from 18 to 24
months.

## Effects of oil on walruses

Geraci reports damage to the skin of pinnipeds from contact with oil:
some of the oil penetrates into the skin, causing inflammation and death
of some tissue. The dead tissue is discarded, leaving behind an ulcer.
While these skin lesions have only rarely been found on oiled seals, the
effects on walruses may be greater because of a lack of hair to protect
the skin (Geraci 1990 and Hansen 1992). Skin irritation from oil will
probably have the greatest effects during the annual molt when the new
skin is just forming (Hansen 1992). Direct exposure to oil can also
result in conjunctivitis, a condition which is reversible. Like other
pinnipeds, walruses are susceptible to oil contamination in their eyes.
Continuous exposure to oil will quickly cause permanent eye damage
(Geraci 1990). Depending on the viscosity of the oil, as it thickens it
may also accumulate and limit the movements of eyelids or vibrissae as
well as impeding the movement of flippers in very young animals (Geraci
1990 and Hansen 1992). Walruses may also expose themselves more often to
the oil that has accumulated at the edge of a contaminated shore or ice
lead if they repeatedly enter and exit the water.

Ingestion of oil can result in digestive tract bleeding, and in liver
and kidney damage. Ingestion of oil is of greater concern for species
that groom themselves with their mouth, such as polar bears and sea
otters. Exact numbers are not known, however because of their large
size, walruses would apparently have to ingest large amounts of oil
(several liters) before any acute damage to organs would occur (Geraci
1990). Continuous ingestion of small amounts of oil through contaminated
prey species may have effects that would only be seen in the long-term
(Geraci 1990). While most of the oil ingested by pinnipeds is excreted,
some portions of ingested oil will be broken down and stored in blubber.
This may present a problem during times of increased metabolic stress
such as molting or pregnancy/lactation, when those blubber stores are
used, releasing the hydrocarbons into the system of the animal, or
passing them to a calf through the mother's milk (Geraci 1990).
Ingestion by calves is a serious threat because they have significantly
less of the enzymes needed to break down the hydrocarbons and thus may
have a much stronger reaction than an adult walrus (Geraci 1990).

Inhalation of hydrocarbon fumes presents another threat to marine
mammals. In studies conducted on pinnipeds, pulmonary hemorrhage,
inflammation and congestion resulted after exposure to concentrated
hydrocarbon fumes for a period of 24 hours (Carpenter et al 1975, 1976
in Geraci 1990). In humans, exposure to fumes at greater than 10,000 ppm
is fatal (Machle 1941 in Geraci 1990). If the walrus were also under
stress from molting, pregnancy, etc., the increased heart rate
associated with the stress would circulate the hydrocarbons more
quickly, lowering the tolerance threshold for ingestion or inhalation
(Geraci 1990). Inhalation of fumes from the spill of the *Exxon Valdez*
in 1989 contributed to emphysema and lung congestion resulting in the
death of many sea otters. However, species without fur (such as the
walrus) will not carry the contamination with them or inhale the fumes
while grooming, and thus are less likely to continuously inhale the
vapors (Hansen 1992). It is also unlikely that a walrus would face
dangerously high concentrations of hydrocarbon fumes when in the open
water.

Walruses are benthic feeders and Bibe (1950) and Fay (1982) reported
typical walrus feeding depths to be from 10-50 meters. Much of the
benthic prey contaminated by an oil spill would be killed immediately,
and others that survived would become contaminated from oil in bottom
sediments, possibly resulting in slower growth and a decrease in
reproduction (Duval, Martin and Fink 1981). Bivalve mollusks, a favorite
prey species of the walrus, are not effective at processing hydrocarbon
compounds, resulting in highly concentrated accumulations and long term
retention of the contamination within the organism (Neff 1987). Studies
indicate that contamination of mollusks impairs growth, fertilization,
and development of embryos, kills gill tissue and encourages cancerous
growths (Fink 1981 and Neff 1987). Hansen states that because walrus
feed primarily on mollusks, they may be more vulnerable to a loss of
this prey species than other pinnipeds that feed on a larger variety of
prey (1992). Furthermore, complete recovery of a bivalve mollusk
population may take ten years or more (Hansen 1992), forcing walrus to
find other food resources or move to non-traditional areas.

An additional threat is the loss of traditional haulout sites due to
oiling. Walrus have in the past shown a tendency to abandon terrestrial
haulout sites for reasons that are not fully understood. It is not
outside the realm of possibility that contamination from an oil spill
would close a traditional haulout site.

Walruses are not generally found near oil pipelines, drilling sites, or
traditional oil tanker routes. This fact alone lowers their chances of
exposure to a major oil spill. Walruses do, however, cross the major
shipping lanes in the Bering Sea and are regularly exposed to vessels of
various type and purpose. It is more likely that they will be exposed to
small spills of diesel fuel oil, etc. than to a major crude oil spill. A
large, catastrophic spill would likely have severe short-term effects
but would in reality have less impact on the population than exposure to
small but sustained spills (Geraci 1990).

In contrast to a spill response for birds, response to potentially
affected marine mammals must recognize that capturing and cleaning oiled
marine mammals generally will not be feasible. One must consider that
procedures involving capturing and treating the animal may induce stress
that could result in greater risk to its well being than contact with
oil. Because of the size and aggressive nature of the walrus, it is
unadvisable to approach or attempt to capture an adult walrus that is
not sedated. However, there is currently no reliable method to
anesthetize a walrus. Various drug combinations have been tried
experimentally with limited success and research is on going to
determine an ideal drug combination that will place the animal at
minimal risk (Jay, personal communication). Additionally, the means to
transport an adult walrus and the facilities to treat the animal are
extremely limited given their remote range. Furthermore, the
predictability of the animal\'s response to any human interference will
be complicated by factors such as its age, sex, season, and general
health. Walruses in general (especially adults) will not be greatly
affected by oil unless they are molting. While it may be easier to
capture and transport an unattended walrus calf that is suffering from
oil contamination, the calf cannot be returned to the wild after
successful treatment. Arrangements with a zoological park willing and
able to take a walrus calf must be made or the animal will face
euthanasia.

D. [Response Plan Training Needs]{.underline}

Response personnel should be provided with the following training:

> \* contents and use of Wildlife Response Plans as well as Contingency
> Plans and the Incident Command System
>
> \* guidance on laws and regulations that apply to handling or
> \"taking\" of marine mammals
>
> \* guidance on the roles and responsibilities of federal and state
> agencies as well as the responsible parties and their contractors
>
> \* marine safety and boat handling
>
> \* standard first aid.

II\. [RESPONSE STRATEGIES]{.underline}

A. [Primary Response]{.underline}

1\. General Considerations

Primary response for protecting Pacific walruses from an oil spill is to
prevent oil from reaching areas where Pacific walruses are concentrated,
such as haulouts ([sensitive areas)]{.underline}. Primary response
strategies should be emphasized for Pacific walrus.

Walruses often haulout in protected, lower-energy shoreline areas such
as bays. The topography of these areas encourages a concentration of oil
along the shoreline and makes them less likely to be cleaned by natural
forces. If oil does contact shorelines in important haulout areas, those
shorelines should be afforded a high priority for cleaning with due
regard to birthing and molting schedules.

Oil should be prevented from entraining under the pack ice. The oil is
likely to concentrate in breathing holes, leads and cracks within the
ice -- all areas where walrus will surface to breathe (Geraci 1990).
Leads and polynyas are similar to shorelines in that they will also
accumulate and confine oil spilled in the area. Special emphasis should
be placed on the protection and cleanup of polynas and leads in the ice.
Heavy pack ice conditions will make mechanical cleanup ineffective.

Known haulouts (Appendix \_\_\_) should receive priority protection
regardless of their level of occupancy at the time of the spill.
Walruses are very particular when choosing an area on which to haulout
and return to the same haulouts year after year. The exact requirements
for preferred terrestrial haulouts are unknown, but it appears that
favorable terrain for entering and leaving the water and protection from
strong surf are prime factors in choosing a haulout site (USFWS 1994).
Walruses are easily disturbed from their haulout and will probably not
endure secondary or tertiary response strategies being used while they
rest on the beach. Their likely response will be to enter the water and
remove themselves from the disturbance, actions that will interrupt
their molting or resting periods, and may increase their exposure to the
contamination. Prolonged clean up activities may force the herd to find
another suitable haulout to use.

All response activities should be conducted as far from marine mammals
as possible to prevent a disturbance that may result in mass stampedes
of the animals into the ocean, followed by possible abandonment of the
beaches. This disturbance can result in more severe effects than those
caused by an oil spill, including direct physical injury to newborn,
small, or weak animals; separation of mothers and calves; disturbance of
established social hierarchies; and movement to less‑favorable areas.
The distance at which disturbance occurs is variable and depends on the
level of activity, local conditions of visibility, group size, and other
factors (Kruse 1997).

2\. Oiled Carcass Collection

All walrus carcasses should be retrieved and delivered to collection or
morgue sites as directed by the Service\'s Regional Oil and Hazardous
Substance Spill Response Coordinator (RRC) to prevent oil from getting
into the food chain. Each carcass should be accompanied by a form
containing the following information:

> \* date found
>
> \* location where carcass was found
>
> \* name of vessel or point of contact.

Forms should be kept in a ziplock bag for protection; indelible pen or
pencil should be used. If the carcass is [not]{.underline} retrieved a
form should still be filled out and submitted to the Service collection
or morgue site.

Individual carcasses should be double bagged. Carcasses should be kept
cool, but not frozen during transport to the nearest collection or
morgue site.

Resource trustees designated as Damage Assessment specialists will be
responsible for maintaining a chain of custody record for specimens
required for the Natural Damage Assessment (NRDA) process.

3\. Skimming

Generally, the initial response for recovering spilled oil is to
mechanically collect it with skimmers. Skimming vessels may be capable
of recovering oil over large geographic areas in the spill zone. These
vessels may be positioned to recover oil before it reaches sensitive
areas. Skimmers must be careful to maintain an appropriate distance from
walruses to avoid unnecessary disturbance.

4\. Booms

Walrus sensitive areas may be boomed using shoreline exclusion or
shoreline diversion booming techniques. Protective and sorbent booms may
be effective in controlling or reducing contamination in confined areas
(polynas and ice leads) or to protect shorelines and ice edges where
Pacific walruses may be found. Booms should be placed at sufficient
distance to avoid disturbance and prevent the flow of oil into sensitive
areas. **What about letting the animals out of the protected shore to
feed?**

[Shoreline exclusion booming]{.underline} involves anchoring one or more
lengths of boom between two or more stationary points to prevent oil
from entering an area occupied by walruses.

[Shoreline diversion booming]{.underline} is used to divert a spill
headed toward an area occupied by walruses to a less sensitive area,
such as toward a skimmer or open water.

5\. Dikes/Berms

During pipeline spills earthen berms may be constructed to contain oil
around the leak, if terrain permits. Dikes filled with excelsior or
sorbent materials may be used on spills in smaller streams Because
walrus rarely are found near a pipeline, this has very little
application to this species.

6\. In-situ Burning

The request for an ISB permit is approved by the Federal On Scene
Coordinator (FOSC) pending completion of the ISB checklist (Appendix 1).
The Service concurs with in-situ burning as a response strategy if
impacts from burning are less harmful to humans and wildlife than
impacts of the non-burned oil. All wildlife in the proposed burn area
must be identified prior to Service concurrence of the ISB permit.

In most instances in-situ burning of spilled oil is preferable to
potential oiling of fish and wildlife. Short-term effects associated
with burning are preferable to long-term effects associated with oiled
walruses and additional wildlife, as well as the potentially damaging
effects of shoreline cleanup on biologically sensitive coastlines.

The Service\'s RRC and Marine Mammal Management (MMM) determine the
potential risk to walrus population(s) specific to the spill zone, and
fill out Section VII, Resources at Risk, of the ISB checklist. The RRC
reports Service recommendations to the FOSC through the Department of
Interior (DOI) Regional Environmental Officer (REO).

7\. Dispersants

The request for a dispersant use permit is approved by the FOSC pending
completion of the dispersant use checklist (Appendix 2). The Service
concurs with dispersant use as a response strategy if associated impacts
are less harmful to humans and wildlife than impacts of the
non-dispersed oil. All wildlife in the proposed use area must be
identified prior to Service concurrence of the permit.

Approved dispersants can be used to accelerate the natural dispersion
process, that is, breaking up an oil slick on the ocean surface by wave
action.

Dispersants are very controversial in terms of both chronic and acute
effects on wildlife. The Alaska Regional Response Team (ARRT) has
developed the Dispersant Use Guidelines in an effort to apply
dispersants with the least amount of deleterious environmental effects.
Dispersants must be approved by the Environmental Protection Agency
(EPA).

B. [Secondary Response]{.underline}

1\. General Considerations

The secondary response strategy to protect Pacific walruses from an oil
spill is to deter them from the slick or contaminated habitat. Major
consideration should be given to the degree of risk associated with the
animal actually contacting oil. Shock and stress may result from an
animal being pursued, captured, and relocated. In the case of adult
walruses, this stress may actually do more harm than contact with the
oil.

Pre-authorized permits to handle or take walruses are not available to
anyone under any circumstances. However, under Section 18.22 of the
Marine Mammal Protection Act, the Service is authorized to handle and do
whatever is necessary to protect walruses in the event of an emergency,
such as an oil spill. This authority can also be sub-delegated (in
writing) to contractors during an oil spill.

All response activities involving walruses must be performed in
coordination with the Service\'s RRC, as identified in Section III of
this document.

2\. Deterrents

[Herding]{.underline} Pacific walruses away from an oil spill site may
be feasible for those animals already in the water. However, hauled out
animals should probably be left alone, due to the risk of trampling if
stampeding occurs. Herding walruses with vehicles, boats and aircraft
has not been successfully demonstrated.

[Hazing]{.underline} (dispersal of) walruses by aircraft requires
special permits from the Service\'s Law Enforcement Division and should
never be used anywhere in the vicinity of haulout sites.

Use of [auditory deterrents]{.underline} such as the firing of propane
cannons or warning shots from firearms may be effective for short term
deterrence of walruses that are already in the water; however, this
method should not be used anywhere in the vicinity of haulout sites.

There are no data indicating that [visual or olfactory deterrent
methods]{.underline} are effective in keeping walrus away from specific
sites.

3\. Pre-emptive Capture, Handling and Transport

Attempting to capture Pacific walruses is not feasible because of their
sensitivity to disturbance and the potential danger to personnel posed
by the walrus's large size and belligerent behavior. Also, as mentioned
earlier, there are currently no reliable methods for anaesthetizing
walrus.

4\. Other

No other secondary response strategies that have been demonstrated
effective are currently available.

Include detection section? **Ask Susi**

C. [Tertiary Response]{.underline}

1\. General Considerations

Tertiary response is the treatment of walruses contaminated with oil.
The components of tertiary response are the capture, handling,
transportation, treatment, holding, and release of walruses. Little is
known about the recovery of oiled walruses. Logistical and monetary
constraints may limit the feasibility of this response. In addition,
attempting to capture and treat adult Pacific walruses is not feasible
because of their sensitivity to disturbance and the potential danger to
personnel posed by the walrus's large size and belligerent behavior and
the lack of a reliable method to sedate walruses. Service MMTLs have
oversight for all phases of tertiary response.

2\. Capture

Capture with traps or drugs is not recommended.

3\. Handling

Any handling should be accomplished by arctic marine mammal biologists.

4\. Transport

Transportation of Pacific walruses is not recommended.

5\. Treatment

There are presently no acceptable guidelines established for captive
care of Pacific walruses.

6\. Holding

There are presently no acceptable guidelines established for holding of
Pacific walruses.

7\. Release

There are presently no acceptable guidelines for release of captive
treated Pacific walruses.

III\. [LIST OF CONTACTS]{.underline}

Ron Britton

Regional Response Coordinator

1011 E. Tudor Rd.

Anchorage, AK 99503

\(907\) 786-3483

Everett Robinson-Wilson

Chief, Division of Environmental Contaminants

1011 E. Tudor Rd.

Anchorage, AK 99503

\(907\) 786-3411

IV\. [REFERENCES]{.underline}

American Petroleum Institue. 1989. Effects of Offshore Petroleum
Operations on Cold Water Marine Mammals; a Literature Review.

Chen-Valet, P. and Gage, L. 1990. Recommendations in the Rescue, Wash
and Care Techniques, and Rehabilitation of Oiled Pinnipeds in
California.

Engelhardt, F.R. 1983. Petroleum Effects on Marine Mammals. Aquatic
Toxic 4:139-179.

Fay, Francis H. 1982. Ecology and Biology of the Pacific Walrus,
*Odobenus rosmarus divergens*.

Geraci, J.R. and D.J. St. Aubin, eds. 1990. Sea Mammals and Oil:
Confronting the Risks. Academic Press, Inc.

Hansen, D.J. 1992. Potential Effects of Oil Spills on Marine Mammals
that Occur in Alaskan Waters. OCS Report MMS 92-0012. U.S. Department of
the Interior, Minerals Management Service, Alaska OCS Region.

Kruse, Susan. 1997. Behavioral Changes of Pacific Walrus (*Odobenus
rosmarus divergens*) in Response to Human Activities. U.S. Fish and
Wildlife Service, Marine Mammals Management Technical Report MMM 97-4.

Manen, Carol-Ann, et.al. . Oil Dispersant Guidelines: Alaska. In: L.
Michael Flaherty, ed. Oil Dispersants: New Ecological Approaches.

Mate, Bruce R. and James T. Harvey, eds. 1897. Acoustical Deterrents in
Marine Mammal Conflicts with Fisheries. Proceedings of a February 17-18,
1986, Workshop in Newport, Oregon. Oregon State University Sea Grant
College Program, Corvallis Oregon.

Neff, J.M, et.al. 1987. Histopathologic and Biochemical Responses in
Arctic Marine Bivalve Molluscs Exposed to Experimentally Spilled Oil.
Arctic 40, supp. 1:220-229.

Ridgeway, S.H. and R.J. Harrison, eds. 1981. Handbook of Marine Mammals,
Vol 1: The Walrus, Sea Lions, Fur Seals, and Sea Otter. Academic Press,
New York.

Smiley, B.D. 1982. The Effects of Oil on Marine Mammals. In: J.B.
Sprague, J.H. VandermeuIen, and P.G. Wells, eds. Oil and Dispersants in
Canadian Seas ‑ Research Appraisal and Recommendations. Environmental
Protection Service, EPS 3‑EC‑82‑2, Canada

Stirling, Ian. 1988. Preliminary Observations on the Immobilization of
Male Atlantic Walruses (*Odobenus rosmarus rosmarus*) with Telazol^^.
Marine Mammal Science 4(2):163-168.

U.S. Fish and Wildlife Service. 1994. Conservation Plan for the Pacific
Walrus in Alaska.