| Summary: | Thesis (Master's)--University of Washington, 2013 Reproduction of walrus (Odobenus rosmarus) in zoos and aquaria has met with limited success. While basic information on reproductive characteristics is available, there is limited knowledge of reproductive physiology and endocrinology for walrus. The overall goal of the research was to monitor reproductive events and seasonal changes that occur in ex situ walrus of North America by utilizing a variety of methods. To track changes in males, longitudinal hormonal analysis of saliva samples, changes in testicular size, presence or absence of spermatozoa and seasonal fluctuations in behavior were examined. Saliva samples were collected from six male walrus for periods of 12 to 36 months. Measurements of testicular length and width were collected on a weekly basis. Baseline testosterone values for each animal were established using an iterative process that eliminated elevated values. Elevations were defined as values ≥ 2 times the individual’s baseline (range 0.838-4.228 ng/ml). The mean combined baseline testicular measurement for individuals (R linear length + R linear width + L linear length + L linear width) was 54.81±2.13 cm while the mean combined increased testicular measurement (an increase of 15% or more over minimum values) was 65.38±1.71. Three of six animals displayed the typical rise and fall of testosterone concentrations observed in seasonal breeders in the wild and elevations were coincident with reproductive behaviors. Behaviors included visual and vocal courtship displays, pursuit of females, clasping and penetration. Sperm presence in a single walrus during two years coincided with increased testicular measurements and mean duration of spermatozoal presence was 131±3 days. Endocrine profiles varied extensively among animals, demonstrating within-animal decline in testosterone levels over time, a lack of testosterone elevations coincident with the wild walrus breeding season and a blind male with a unique derivation in his endocrine profile, ...
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