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Item Variation of life-history strategies in pinnipeds with an emphasis on survival rates and spatial distribution of male Weddell seals in Erebus Bay, Antartica(Montana State University - Bozeman, College of Letters & Science, 2020) Brusa, Jamie Louise; Chairperson, Graduate Committee: Jay J. Rotella; Jay J. Rotella, Robert A. Garrott, J. Terrill Paterson and William A. Link were co-authors of the article, 'Variation of annual apparent survival and detection rates with age, year, and individual identitiy in male Weddell seal (Leptonychotes weddellii) from long-term mark-recapture data' in the journal 'Population ecology' which is contained within this dissertation.; Jay J. Rotella, Katharine M. Banner and Patrick R. Hutchins were co-authors of the article, 'A comparative study evaluating how stage-specific survival rates vary with life-history traits in male pinnipeds' submitted to the journal 'Journal of evolutionary biology' which is contained within this dissertation.; Jay J. Rotella was a co-author of the article, 'Influence of age and individual identity in the use of breeding colony habitat by male Weddell seals (Leptonychotes weddellii) in Erebus Bay, Antarctica' submitted to the journal 'Journal of mammalogy' which is contained within this dissertation.This dissertation explores various components of male life-history theory using a species-specific approach focusing on Weddell seals (chapters 2 and 4) and a comparative approach focusing on pinniped (seal and sea lion) species (chapter 3). To better understand how marine mammal populations can function and to gain insight about the evolution of male Weddell seal fitness, my coauthors and I estimated the age-specific survival rates of male Weddell seals living in Erebus Bay, Antarctica. Actuarial senescence (decreasing age-specific survival with increasing age) has been documented for several wildlife species. However, contrary to females, little information exists regarding age-specific patterns of survival, including actuarial senescence, for males. We used 35 years of mark-recapture data to estimate age-specific survival rates in male Weddell seals using a hierarchical model approach in a Bayesian framework. We found that male survival estimates were moderate for pups and yearlings, highest for 2-yearolds, and gradually declined with age thereafter such that the oldest animals observed had the lowest survival rates of any age, illustrating that male Weddell seals in this population exhibit actuarial senescence. We further investigated male Weddell seal ecology by describing the spatial patterns of male Weddell seals in Erebus Bay using regression modeling and kernel density methods. The intermediately aged males tended to have the most reproductive-age female neighbors, but individual heterogeneity played a stronger role than age. We found that younger males tended to settle in more offshore and less crowded areas of the habitat relative to older males. From a comparative approach, we assessed the patterns of tradeoffs among various fitness traits in male pinnipeds by examining the relationships between stage-specific survival rates and body size, baculum size, mating strategies, and delayed social maturity. Comparative studies similar to ours have tended to focus on females of avian and some terrestrial species and have mostly addressed reproductive traits. However, we lack information about males and connections between survival rates and other life-history traits. We found evidence for a relationship between precopulatory, rather than postcopulatory, traits and survival rates. We highlight the need for more empirical survival rate data and robust comparative methods.Item Assessment of non-lethal tools to assign sex, stage of maturity, and reproductive condition in Burbot Lota lota(Montana State University - Bozeman, College of Letters & Science, 2019) McGarvey, Lauren Marie; Chairperson, Graduate Committee: Christopher S. Guy; Molly A. H. Webb (co-chair); Christopher S. Guy and Molly A. H. Webb were co-authors of the article, 'Description of gametogenesis and assessment of non-lethal tools to assign sex, stage of maturity, and reproductive condition in burbot Lota lota' which is contained within this thesis.; Christopher S. Guy and Molly A. H. Webb were co-authors of the article, 'Assessment of gonad size measured by ultrasound to assign stage of maturity and reproductive condition in burbot Lota lota' which is contained within this thesis.; Christopher S. Guy and Molly A. H. Webb were co-authors of the article, 'The assessment of non-lethal tools to identify mass ovarian follicular atresia in burbot Lota lota' which is contained within this thesis.Non-lethal tools (plasma sex steroid concentrations and ultrasound) were assessed to assign sex, stage of maturity, and reproductive condition (non-reproductive and reproductive) in Burbot Lota lota from Lake Roosevelt, Washington. Gonadal tissue, plasma samples, and gonadal sonograms were collected from Burbot. Gonadal tissue was processed for histological analysis to describe gametogenesis and confirm sex, stage of maturity, and reproductive condition. Plasma testosterone (T) and estradiol-17beta (E2) concentrations were measured by radioimmunoassay. Plasma 11-ketotestosterone (11- KT) concentrations were measured by liquid chromatography-mass spectrometry. Gametogenesis was described by gonadal histology during the entire reproductive cycle. Plasma sex steroid profiles, gonadosomatic index, and ovarian follicle diameter were also described during the entire reproductive cycle. Plasma 11-KT concentrations were used to assign sex with 81% accuracy during the entire reproductive cycle, and plasma 11-KT and E2 concentrations were used to assign sex with 98% accuracy during the reproductive phase (i.e., November to March in Lake Roosevelt). In females, plasma T concentration, plasma E2 concentration, and month were used to assign stage of maturity with 87% accuracy, and plasma T concentration and plasma E2 concentration were used to assign reproductive condition with 98% accuracy. In males, plasma 11-KT concentration, girth at the urogenital pore, and month were used to assign stage of maturity with 73% accuracy, and plasma T concentration was used to assign reproductive condition with 90% accuracy. Ultrasound was used to assign sex with 97% accuracy, and ultrasound measurements of gonad size were a promising tool to assign stage of maturity and reproductive condition. Non-lethal tools (plasma sex steroid concentrations, gonad size measured by ultrasound, and ovarian follicle diameter) were also assessed to identify mass ovarian follicular atresia in female Burbot. Plasma T concentrations and ovarian follicle diameter were promising tools to identify mass ovarian follicular atresia. Nonlethal tools to assign sex, stage of maturity, and reproductive condition will enable fisheries biologists to assess indices of reproductive potential for the Burbot population in Lake Roosevelt. Indices of reproductive potential can be used characterize and monitor population demographics, improve models of population growth, establish sustainable harvest regulations, monitor the effects of management actions, and monitor the effects of environmental stressors.Item Sources of variation in maternal allocation to offspring during lactation in the Weddell seal(Montana State University - Bozeman, College of Letters & Science, 2018) Macdonald, Kaitlin Rose; Chairperson, Graduate Committee: Jay J. RotellaVariation in the allocation of energy to reproduction by mothers can have fitness consequences for mothers and offspring. Diverse features of a mother, and annual environmental fluctuations may affect the amount of energy a mother allocates to offspring and may obscure age-specific patterns that are of interest when evaluating predictions made from existing life history theory. To properly evaluate possible sources of variation, especially age-specific variation in maternal allocation, analyses of data for known-age mothers with a wide range of ages, diverse reproductive histories, and multiple measures of allocation to reproduction are needed. We used data from a long-term study of Weddell seals that were individually marked as pups and monitored annually and a Bayesian hierarchical modeling framework to characterize age-specific variation in maternal allocation and test predictions about age-specific variation while considering additional maternal features that might influence maternal allocation. Based on masses for 311 mothers and associated pups from 2002 to 2016, we found that maternal allocation was moderately associated with maternal age and strongly associated with maternal body mass at birth of her pup. We found that heavier mothers lost a greater proportion of mass during the entire lactation period but that the efficiency with which mothers transferred this mass to their pups was lower than that of lighter individuals. The proportion of mass lost by a mother during the entire lactation period was greater for mothers that had reproduced the previous year and for those who started reproducing young, which suggests that individual quality and perhaps experience are determinants of maternal allocation in this species. Our study did not find support for our predictions that older mothers would allocate more body reserves, be more efficient at transferring mass during early lactation, or alter their behavior in ways that would improve mass transfer efficiency during late lactation, relative to prime-age mothers. The large variation we found in energy allocation to pups translates to large variation in pup weaning mass. Our results highlight that maternal multiple features should be considered when evaluating patterns of age-specific variation in maternal allocation.