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Brown, J. L., Wasser, S. K., Wildt, D. E., & Graham, L. H. (1994). Comparative Aspects of Steroid Hormone Metabolism and Ovarian Activity in Felids, Measured Noninvasively in Feces. Biol Reprod, 51(4), 776–786.
Abstract: Noninvasive fecal assays were used to study steroid metabolism and ovarian activity in several felid species. Using the domestic cat (Felis catus) as model, the excretory products of injected [14C]estradiol (E2) and [14C]progesterone (P4) were determined. Within 2 days, 97.0 +/- 0.6% and 96.7 +/- 0.5% of recovered E2 and P4 radioactivity, respectively, was found in feces. E2 was excreted as unconjugated estradiol and estrone (40%) and as a non-enzyme- hydrolyzable conjugate (60%). P4 was excreted primarily as non-enzyme- hydrolyzable, conjugated metabolites (78%) and as unconjugated pregnenolone epimers. A simple method for extracting fecal steroid metabolites optimized extraction efficiencies of the E2 and P4 excretion products (90.1 +/- 0.8% and 87.2 +/- 1.4%, respectively). Analysis of HPLC fractions of extracted fecal samples from the radiolabel-injected domestic cats revealed that E2 immunoreactivity coincided primarily with the unconjugated metabolized [14C]E2 peak, whereas progestogen immunoreactivity coincided with a single conjugated epimer and multiple unconjugated pregnenolone epimers. After HPLC separation, similar immunoreactive E2 and P4 metabolite profiles were observed in the leopard cat (F. bengalensis), cheetah (Acinonyx jubatus), clouded leopard (Neofelis nebulosa), and snow leopard (Panthera uncia). Longitudinal analyses demonstrated that changes in fecal E2 and P4 metabolite concentrations reflected natural or artificially induced ovarian activity. For example, severalfold increases in E2 excretion were associated with overt estrus or exogenous gonadotropin treatment, and elevated fecal P4 metabolite concentrations occurred during pregnant and nonpregnant (pseudopregnant) luteal phases. Although overall concentrations were similar, the duration of elevated fecal P4 metabolites during pseudopregnancy was approximately half that observed during pregnancy. In summary, steroid metabolism mechanisms appear to be conserved among these physically diverse, taxonomically related species. Results indicate that this hormone-monitoring approach will be extremely useful for elucidating the hormonal regulatory mechanism associated with the reproductive cycle, pregnancy, and parturition of intractable and endangered felid species.
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Brown, J. L., Wasser, S. K., Wildt, D. E., & Graham, L. H. (1994). Steroid Metabolism and the Effectiveness of Fecal Assays for Assessing Reproductive Status in Felids. Biology of Reproduction, 50(suppl 1), 185.
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Ale, S., & Brown, J. (2007). The contingencies of group size and vigilance (Vol. 9).
Abstract: Background: Predation risk declines non-linearly with one's own vigilance and the vigilance of others in the group (the 'many-eyes' effect). Furthermore, as group size increases, the individual's risk of predation may decline through dilution with more potential victims, but may increase if larger groups attract more predators. These are known, respectively, as the dilution effect and the attraction effect.
Assumptions: Feeding animals use vigilance to trade-off food and safety. Net feeding rate declines linearly with vigilance.
Question: How do the many-eyes, dilution, and attraction effects interact to influence the relationship between group size and vigilance behaviour?
Mathematical methods: We use game theory and the fitness-generating function to determine the ESS level of vigilance of an individual within a group.
Predictions: Vigilance decreases with group size as a consequence of the many-eyes and dilution effects but increases with group size as a consequence of the attraction effect, when they act independent of each other. Their synergetic effects on vigilance depend upon the relative strengths of each and their interactions. Regardless, the influence of other factors on vigilance – such as encounter rate with predators, predator lethality, marginal value of energy, and value of vigilance – decline with group size.
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Ale, S. B., Brown, J.S. (2009). Prey behavior leads to predator: a case study of the Himalayan tahr and the snow leopard in Sagarmatha (Mt. Everest) National Park, Nepal. Israel Journal of Ecology & Evolution, 55(4), 315–327.
Abstract: Rare, elusive predators offer few sightings, hindering research with small sample sizes and lack of experimentation. While predators may be elusive, their prey are more readily observed. Prey respond to the presence of a predator, and these fear responses may have population- and community-level consequences. Anti-predator behaviors, such as vigilance, allow us to sidestep the difficulty of direct field studies of large predators by studying them indirectly. Here we used a behavioral indicator, the vigilance behavior of the Himalayan tahr, the snow leopard’s main local prey, to reveal the distribution and habitat use of snow leopards in the Mt. Everest region of Nepal. We combined techniques of conventional field biology with concepts of foraging theory to study prey behavior in order to obtain insights into the predator’s ecology. The Himalayan tahr’s vigilance behavior correlates with the distribution of snow leopard signs. Tahr actually led us to six sightings of snow leopards. We conclude that behavioral indicators provided by prey offer a valuable tool for studying and monitoring stealthy and rare carnivores.
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Johnston, L. A., Armstrong, D. L., & Brown, J. L. (1994). Seasonal effects on seminal and endocrine traits in the captive snow leopard (Panthera uncia). J Reprod Fertil, 102(1), 229–236.
Abstract: The annual reproductive cycle of the male snow leopard (Panthera uncia) was characterized by evaluating seminal and endocrine traits monthly. Testicular volume was greatest (P < 0.05) during the winter months when the quality of ejaculate was optimal. Ejaculate volume, total sperm concentration ml-1, motile sperm concentration per ejaculate, sperm morphology and sperm motility index were lowest during the summer and autumn months compared with the winter and spring. Peripheral LH, FSH and testosterone concentrations were also lowest during the summer months, increasing during the autumn just before the increase in semen quality, and were maximal during the winter months. There was a direct relationship (P < 0.01) between: (1) testosterone and testicular volume, total sperm concentration ml-1, motile sperm concentration per ejaculate and ejaculate volume, and (2) LH and testicular volume and motile sperm concentration per ejaculate. In summary, although spermatozoa were recovered throughout the year, optimal gamete quality was observed during the winter and spring. Although previous studies in felids have demonstrated seasonal effects on either seminal or endocrine traits, this is the first study to demonstrate a distinct effect of season on both pituitary and testicular function.
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Wildt, D., Pukazhenthi, B., Brown, J., Monfort, S., Howard, J., & Roth, T. (1995). Spermatology for understanding, managing and conserving rare species. Reproduction Fertility and Development, 7(4), 811–824.
Abstract: Most conventional spermatology research involves common mammalian species including livestock, laboratory animals and humans. Yet, there are more than 4500 mammalian species inhabiting the planet for which little is known about basic reproductive biology, including sperm characteristics and function. This information is important, not just as adjunct knowledge, but because the majority of these species are threatened with extinction, largely due to human-induced pressures. The field of conservation is changing rapidly, and global cooperation is emerging among a variety of wildlife enthusiasts, ranging from management authorities of nature reserves to curators of rare zoological collections. Conservation progress depends on systematic, multidisciplinary research first to answer basic questions, with new data then applied to endangered species management plans. The reproductive physiologist is a crucial component of this scheme. Reproduction is the essence of species survival, and enormous effort needs to be directed at these 'untraditional' research species, subspecies and populations. Spermatology research combined with simultaneous efforts in endocrinology, embryology and cryopreservation (among others) can lead to the successful application of assisted reproduction. Examples from this laboratory include an array of wild felid species and a rare cervid and mustelid. Obstacles to success are formidable, including unique species-specificities, diminished genetic diversity and a general lack of resources. Nonetheless, the field offers tremendous opportunities for generating unique knowledge of comparative interest and with conservation utility.
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