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

Transcription

1 Establishing Endocrine and Behavioral Parameters of Reproduction in Captive Pacific Walrus (Odobenus rosmarus divergens) Lisa Triggs University of Washington School of Aquatic and Fishery Sciences Masters Candidate

2 Introduction wild population ~ 200,000 Petitioned for listing under the ESA in 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

3 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

4 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Hawaiian monk seals (Pietraszek and Atkinson 1994) Steller sea lions (Harmon 2001) Fur seals and sea otters (Larson, unpublished data)

5 Introduction mammalian reproduction Testosterone, estrogens and progesterone Maintain reproductive organs Elicit reproductive behavior Physiologically prepare animal for mating and pregnancy

6 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

7 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

8 Introduction mammalian reproduction Breeding season Ovaries active Follicles maturing Estrus Ovulation Non-breeding season Ovaries inactive Estrous cycle Follicular phase Luteal phase

9 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

10 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

11 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

12 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.

13 Methodology - hormones Study animals 11 walruses (5.6) Males 13 to 28 Females 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

14 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

15 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

16 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

17 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

18 Results - endocrinology 25; never sired 20; sired pg/ml Testosterone pg/ml Testosterone Date Date 20; never sired 13; never sired Testosterone Testosterone pg/ml pg/ml Date Date

19 Results - endocrinology Progesterone Estradiol P pg/ml E pg/ml Date

20 Results testes Centimeters Centimeters Combined testicular measurements Testosterone Combined testicular measurements Date Date

21 Results - behavior Male rut: Increased interest in females Courtship displays Clasping females Penetration Copulation Female estrus: Solicits male s attention Permits penetration Permits copulation

22 Results behavior

23 What s next? Continue running samples Analyze data Figure out why the reproductive inefficiency Low hormone levels Lack of synchronized cycles?????

24 Questions?????