Sea Otter and North American River Otter: Biology and Disease

Tatiana Weisbrod - 2026

what are mustelids’s closest relatives

raccoons

what are mustelid’s closest marine relative

pinnipeds

north american river otter and sea otter have a common ancestor in what taxonomic group?

subfamily (Lutrinae)

what is the range of sea otters

russia, japan, alaska, some in west continental US

why are sea otters susceptible to disease

genetic bottleneck

why was the range limited in sea otters

fur trade in 18th and 19th century

sea otters are the ____ marine mammal

smallest

sea otter males are (larger/smaller) than females

larger

do males or femals rear pups

females

sea otters are the ____ mustelid

largest

life span of sea otters

15-20 years in the wild

sea otters are ____-vorous

carnivorous

dental formula for sea otters are adapted for

crushing

diet of sea otters

invertebrates, fish

coat / pelage of sea otters

• up to 1M hairs per sq inch

• squalene (hydrophobic) and interlocking hair cuticle scales to trap air

• no blubber or scent glands

• grooming is essential

how much time do sea otters spend grooming

10-20% of the day

sea otters rely on what for thermoregulation?

hair coat

sea otters have a ____ GI transit time

fast

sea otters have a preference for what side for tool use

left side

features of sea otter buoyancy

• lean body

• prominent thorax

  • 4x capacity of pinnipeds

• air trapping

benefits of positive buoyancy

• rest

• rearing young

• eating

• grooming

con of positive buoyancy

• energetically demanding dives

where is the largest oxygen storing capacity of sea otters?

lungs (also have a lot of blood)

sea otters have a ___-lineal group

matrilineal (female and pup only)

TF: sea otters form bachelor groups

T

sea otters are mono/polygynous

polygynous

when do male sea otters sexually mature

5-6y

when do females sexyally mature

3y

where does mating occur for sea otters, and what are the consequences

water

facial injuries

how long is gestation in sea otters

avg. 7mo, can be delayed to result in 4-12mo

what causes delayed gestation

delayed implantation

litter size of sea otters

1

% survival of first year

30%

what is the leading cuase of death in female otters

mating wounds

what are threats to sea otters

• anything impacting foraging or grooming

• infectious disease

• climate change (weather, decreased prey)

• natural events (algal blooms)

• humans (poaching, habitat loss)

• trauma (entanglement, boat strikes, mating)

• predation

otters are a ____ species

keystone

protozoal infectious disease of sea otters

• toxoplasma

• sarcocystic

acenthocephalan disease of sea otter

• profilicollis

• corynosoma enhydri

nasal mite of sea otters

halarachne sp.

what does toxoplasm gondii cause

chronic meningoencephalitis

what is toxoplasma gondii correlated with

cardiac disease

definitive host of toxoplasma gondii

felids

Transmission of BOTH toxoplasma gondii and sarcoystis neurona

• infective oocysts shed in feces

• terrestial contamination

• run-off to sea

what protozoal disease is implication in sea otter slow population rebound

toxoplasma gondii (biofilm on kelp, and aquatic snail)

there is an increased/decreased risk of death when infected with toxoplasma gondii

increased (shark attack)

16% of sea otters primary cause of death by ____

toxoplasma gondii

>50% of sea otters are seropositive for

toxoplasma gondii

recrudescence is high for

toxoplasma gondii

gross lesions of toxoplasma gondii

• meningoencephalitis (chronic)

• lymphadenitis

• placentitis

• myocarditis? (more assoc. with sarcocystis neurona)

what does sarcocystic neurona cause

acute meningoencephalitis

definitive host of sarcocystis neurona

opossum

what is associated with sarcocystis neurona infection

myocarditis

gross lesions of sarcosystis neurona

• SC hemorrhage

• systemic inflammation

what type of death is associated with sarcocystis neurona

epizootic die-offs

when is sarcocystis neurona most common seasonally

spring (bc rainfall)

what threat to sea otters is associated with toxoplasma gondii

land use change

• incr. concrete

• incr. cats

• decr. wetlands

what kind of eater is more likely to get toxoplasma gondii

snail specialist

what lesion is associated with acanthocephalans (profilicollis)

septic peritonitis

keratosoma enhydri is clinical/nonclinical

nonclinical

what is the IH and DH of acanthocephalans

IH - crab

DH - shorebird

what drives acanthocephalan infection

pups and females out competed → forced to eat in sandy habitat

pathologic effects of nasal mites (halarachne, direct and indirect)

• turbinate destruction and inflammation

• respiratory infections

risk factors of nasal mites

• older, females (direct infection)

• history of rehab

• shared haul out with harbor seals (coughing / breath exchange)

where are nasal mites found

• trachea

• bronchi

• lungs

family of morbillivirus

paramyxoviridae (RNA)

what is the most important (viral) diease of sea otters

morbillivirus

what does morbillivirus cause

• encephalitis

• endothelial damage (→ opportunisitc infection)

• immunosuppression in survivors

• histo: intracytoplasmic and intranuclear viral inclusion

what is the leading cause of death for norther sea otters

streptococcus lutetiensis

what life stage of sea otter is affected by strep lutetiensis

usually healthy / prime of life

disease of strep. lutetiensis

• systemic

• fatal sepsis

• endocarditis (vegetative valvular)

• meningoencephalitis (thromboembolic dz)

what types of death is seen in strep. lutetiensis

acute AND chronic

what causes significant morbidity and mortality in souther sea otters

streptococcus phocae

is strep. phocae primary or opportunisitc

opportunisitc

what does strep. phocae cause

• systemic disease

• fatal sepsis

• abscessation

• meningoencephalitis

leptospira interrogans (Pomona) - sea otters

• zoonotic

• spirochete

• interstitial nephritis

• 2% seroprevalence captured (10% stranded)

brucella sp.

• rare

• zoonotic, marine origin

• low to mod. seroprevalence

• granulomatous osteoarthritis

• septic arthritis

what is the most common pathogen causing systemic mycosis in marine mammals along the central Calif. coast

Coccidioides immits

what does coccidioides immits cause

• disseminated/systemic granulomatous, pulmonary disease

• pleuropneumonia

non-infectious diseases of sea otters

• predation (shark attachs - sharp tears, vertebral fractures)

• environmental intoxicants

• pollutants

• cardiac disease

• orphans

domoic acid

• environmental intoxicant

• marine biotoxin (glutamate analog)

• diatom Pseud-nitzchia spp.

• accumulates in prey items (invertebrates - crabs, bivalves)

• full stomach and GIT, good condition on necropsy

domoic acid disease types

• acute

• subacute

• chronic

domoic acid acute disease

• severe neurologic signs

• hemorrhages

• don’t have time to mount immune response

• congestive and microhemorrhage CNS, CVS, eyes

domoic acid subacute disease

• progressive CVS and neuro pathology

domoic acid chronic disease

• severe CVS signs

• less so, neuro pathology

• paresthesia (chewing paws and toes)

how can you test for domoic acid

urine, GI contents

types of pollutants

• oils spills and volative gas exposure

• tributylin (TBT)

• others: heavy metals, organochlorines, pesticides, PCB

oil spills and volatile gas exposure

• acute tox

• ocular damage

• severe pulm. compromise

• fur contamination → fatal hypothermia

  • soils coat

• ingestion from grooming

• GI ulcers

• chemical burns

• physical obstruction

• pneumonia

• melana

tributylin (TBT)

• marine paint / biocide

• potential immunocompromise

cardiac disease

• myocarditis, endocarditis, DCM

• CHF

• females > males

• assoc. with infectious disease and toxin exposure

what infectious disease / toxins assoc. with cardiac disease

• domoic acid

• toxoplasmosis and sarcocystis

• strep

strandings

• pups - orphans

• adults - disease / environment/trauma

north american river otter range

throughout US (shrunken)

north american river otters are often cooperatie or territorial?

cooperative

types of groups of north american river otters

• female family groups

• bachelor groups

are males or females more social

females

differences in north american river otters (vs. sea otters)

• males sex mature 2y

• females sex mature 1-2y

• 61-63d true gestation (same delayed implantation)

• can mate in water or on land

• 1-3 pups typical

life span of north american river otters

8-13y in wild

diet of north american river otters

• fish

• amphibians

• invertebrates

• small reptiles

• small mammals

dentition of north american river otters

rapid piercing closure, with sharp carnassial teeth (sea otters don’t have this)

fur coat of north american river otters

370K hairs / sq inch (less than sea otters)