Establishing Endocrine and Behavioral Parameters of Reproduction in Captive Pacific Walrus(Odobenus rosmarus divergens)

Lisa TriggsUniversity of Washington

School of Aquatic and Fishery SciencesMasters Candidate

Introduction – wild population

• ~ 200,000

• Petitioned for listing under the ESA in 2008.

• Range – continental shelf waters of the Bering and Chukchi Seas.

• Breeding locations – Gulf of Anadyr to SW of

St Lawrence Island– SE Bering Sea from south

of Nunivak Island into NW Bristol Bay

• Threats

Introduction – captive population

• Captive population – 7.12 in 7 facilities– U.S. since the 1930’s

• Limited reproductive success– 17 births– 6 successful

• Determine causes of reproductive inefficiency/develop strategies for success

• Enhance the propagation of a species -fundamental attributes of it’s reproductive biology

• Seasonal breeder – hormones differ between seasons

Introduction - saliva

• Serum vs. urine vs. feces vs. saliva– Serum – logistically difficult and potentially stressful to obtain – The use of non-invasive hormonal analysis has been utilized in

reproductive studies in domestic and non-domestic species since the 1990’s

– Urine and feces – terrestrial animals

• Saliva used in: – Bottlenose dolphins (Hogg et al. 2005)– Hawaiian monk seals (Pietraszek and Atkinson 1994) – Steller sea lions (Harmon 2001)– Fur seals and sea otters (Larson, unpublished data)

Introduction – mammalian reproduction

Testosterone, estrogens and progesterone– Maintain

reproductive organs

– Elicit reproductive behavior

– Physiologically prepare animal for mating and pregnancy

Introduction – mammalian reproduction

• Breeding season– Testes active (enlarged)

• Testosterone production• Sperm production

• Non-breeding season– Testes inactive (regressed)

• Testosterone – Dominant male reproductive

hormone– Spermatogenesis– Aggressive behavior for

territory establishment and maintenance

Introduction – mammalian reproduction

• Seasonal breeders – Testicular recrudescence and

regression– Fluctuating testosterone

levels

• Hypotheses– Increased testicular size

during breeding season– Decreased testicular size

during non-breeding season– Increased testosterone levels

preceding breeding season– Peak testosterone levels

during breeding season– Decreased testosterone levels

during the remaining months

Introduction – mammalian reproduction

• Breeding season– Ovaries active

• Follicles maturing• Estrus• Ovulation

• Non-breeding season– Ovaries “inactive”

• Estrous cycle – Follicular phase– Luteal phase

Introduction – mammalian reproduction

• Follicular phase – Dominated by estradiol (initiates sexual

receptivity and behavior)– Concludes with ovulation

• Luteal phase– Begins with corpus luteum (CL)– CL – transient endocrine gland –

secretes progesterone – Mating behavior ceases– Body prepares for pregnancy

• Hypothesis– Changes will be depicted in the

reproductive hormones for estrus and pseudo-pregnancy

– If successful reproduction occurs –delayed implantation and pregnancy

Introduction – walrus reproduction

• Gestation - 15 to 16 months– Delayed implantation - 4 to 5 months

• After the egg is fertilized it arrests at the blastocyst stage and remains free-floating in the uterus

• DI in many mammalian species• Rule in pinnipeds

– Active gestation – 11 months – Pseudopregnancy

• Males – spermic - November to March

• Females – estrus - December to June– Functionally monoestrus

• Parturition – April to June

Introduction – reproductive rate

• One of the lowest reproductive rate of any pinniped species– Become sexually mature relatively late in life

– Cycle > one year and prolonged maternal care - lowers minimum interval between successful births to 2 to 3 years

• Most pinniped cyles are equal to 1 year

– Fertility ↓ in breeding season following the birth of a calf

– Walruses give birth several months after the breeding season.

• Most pinnipeds mate within days/weeks of parturition

Objectives

• Validate the measurement of reproductive steroid hormones in saliva.

• Define the endocrine patterns of estrous cycles and male rut.

• Determine the seasonal changes in testicular size.

• Define behavioral changes in male and female walruses associated with seasonal hormonal fluctuations.

Methodology - hormones

• Study animals– 11 walruses (5.6)– Males – 13 to 28– Females – 12-26– Voluntary blood and saliva collection

• Hormone collection and assays – Saliva samples collected for at least one

year – Collection schedule – Competitive enzyme immunoassays– Values graphed to create a reproductive

hormone profile for individuals

Methodology – testicles

• Testicular measurements – Conducted weekly for at least one year– Trained to lay in dorsal recumbence– Easily palpated– During rut testes increase by about 15% (Fay 1982) – Graphed to evaluate seasonal changes in testicular

recrudescence and regression

Methodology - behavior

• Behavioral data – Collection

• Breeding season - December through April

• Non-breeding season - June through September

– Instantaneous scan sampling

– Data plotted to correlate behavioral changes in male and female walrus associated with seasonal hormonal fluctuations

Methodology – rut

• Vocalizations– Whistling, belling, teeth-clacking, drumming,

demonic • Displays

– Flipper slapping; clasping females; head bobbing; blowing bubbles; “bottling” with head back producing demonic sounds

• Attitude – Pushy with trainers; normal to poor behavioral

control• Appetite

– Normal appetite to going off feed completely• Appearance

– Testes enlarge; more scratches/rashes • Miscellaneous

– Mounting, penetration, copulation, self-stimulation

Methodology - estrus

• Vocalizations – whistling, knocking• Displays- no noticeable changes;

clasping to other female/male; presenting rear end; more receptive to male; follows male; swims in contact with male

• Attitude – irritated; spacey; lazy and sloppy with behaviors

• Appetite – No change, intake decreases, no intake for several days

• Appearance - vaginal/genital area swells

• Initiates mating • Change in swim pattern

Results - endocrinology

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Testosterone

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Testosterone

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Testosterone

25; never sired 20; sired

20; never sired 13; never sired

Results - endocrinology

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Estradiol

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Combined testicular measurements

Results – testes

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Testosterone

Results - behavior

• Male rut:– Increased interest in females– Courtship displays– Clasping females– Penetration– Copulation

• Female estrus:– Solicits male’s attention– Permits penetration– Permits copulation

Results – behavior

What’s next?

• Continue running samples

• Analyze data

• Figure out why the reproductive inefficiency– Low hormone levels– Lack of synchronized cycles– ?????

Questions

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