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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Hawaiian monk seals (Pietraszek and Atkinson 1994) – Steller sea lions (Harmon 2001)– Fur seals and sea otters (Larson, unpublished data)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
0500
10001500200025003000350040004500
pg/m
l
Date
Testosterone
0
500
1000
1500
2000
2500
3000
3500
4000
4500
pg/m
l
Date
Testosterone
0
500
1000
1500
2000
2500
3000
3500
4000
4500
pg/m
l
Date
Testosterone
0500
10001500200025003000350040004500
pg/m
l
Date
Testosterone
25; never sired 20; sired
20; never sired 13; never sired
Results - endocrinology
0
1000
2000
3000
4000
5000
6000
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
E pg
/ml
P pg
/ml
Date
Progesterone
Estradiol
45
50
55
60
65
70
75C
entim
eter
s
Date
Combined testicular measurements
Results – testes
0
500
1000
1500
2000
2500
3000
3500
4000
4500
45
50
55
60
65
70
75C
entim
eter
s
Date
Combined testicular measurements
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
?????