We reviewed the literature on sexual segregation in polygynous ungulates in an effort to clarify terms and concepts, summarize recent information that supports or discredits three broadly defined hypotheses, and suggest directions for future research that should help resolve when and why the sexes segregate in these large mammals. The hypotheses discussed include those based on intersexual differences in energetics and security (reproductive-strategy hypothesis), body size dimorphism and dietary requirements (sexual dimorphism-body size hypothesis), and social mechanisms (social-factors hypothesis). These hypotheses represent ecological, physiological, and social perspectives and are not mutually exclusive. Most evidence reviewed supported the reproductive-strategy hypothesis. Less support was available for either the sexual dimorphism-body size hypothesis or the socialfactors hypothesis. Nonetheless, most available evidence is provided by field studies that contend with many confounding variables. We suggest several areas of future study that may serve as critical tests and are likely to be productive in resolving why sexual segregation occurs in polygynous ungulates.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. American Society of Mammalogists is collaborating with JSTOR to digitize, preserve and extend access to Journal of Mammalogy. I examined influence of body size and mating systems on sexual-size dimorphism by summarizing characteristics and testing for associations among the most dimorphic mammalian taxa-Macropodidae, Primates, Mustelidae, Pinnipedia, Elephantidae, Ruminantia. The most dimorphic taxa were seals in Otariidae. On average, males were three times larger than females, and all otariids displayed extensive dimorphism. Except for the Strepsirhini, most taxa had dimorphism ratios (mass of males:mass of females) between 1.2-1.8. Extent of dimorphism increased with body size but the effect was slight (power function between masses of males and females, 1.04-1.05) for most taxa. Phocid seals and macropodid marsupials had power functions of ca. 1.2. Mating systems were associated with size dimorphism in simian primates and ruminants. Monogamous simian primates were less dimorphic than simians that had polygynous mating systems. Ruminants with tending and harem mating systems were more dimorphic than those with territorial polygynous and monogamous mating systems. Polygyny and how it was conducted were associated with the extent of sexual size dimorphism. Most evolutionary biologists agree thatsexual selection is the source of sexual-size dimorphism in polygynous mammals (Charnov, 1992; Darwin, 1871; Ralls, 1977; Reiss, 1989). Whether males are the smaller sex, as in Hawaiian monk seals (Monachus schauinslandi), or the more common pattern of males larger than females (Ralls, 1977), hypotheses founded in sexual competition explain much about existing patterns of dimorphism (Alexander et al., 1979; Clutton-Brock et al.

We experimentally evaluated alternative techniques of attaching radiotransmitters to captive white-winged doves (Zenaida asiatica) in Kingsville, Texas during 1998. Our evaluation consisted of monitoring physiological, pathological, and behavioral parameters in doves subjected to 6 radiotransmitter attachments (backpack harnesses, adhesive, subcutaneous implants, intracoelomic implants, subcutaneous surgeries without implantation, intracoelomic surgeries without implantation). We analyzed physiological parameters across 2 pretreatment and 4 post-treatment periods using a model-selection approach of mixed-effect models. Birds did not differ in physiological variables among treatment groups and a control. Time-activity budgets analyzed using nonparametric Friedman's tests did not differ in any activity category among treatment groups and a control. Subcutaneous implants were the most effective method of attachment based on retention rates, lack of mechanical difficulties associated with external attachment techniques, and minimum levels of pathology reported following necropsies.

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Natal features (e.g. Julian birth date and birth mass) often have fitness consequences and can be influenced by endogenous responses by the mother to seasonal fluctuations in nutritional quality and photoperiodic cues. We sought to further understand the biological and environmental factors that influence the natal features of a polytocous species in an environment with constant nutritional resources and limited seasonal variation. During a 36-year study we assessed the influence of biological factors (maternal age and litter type [i.e., litter size and sexual composition]) and environmental factors (total precipitation and mean maximum temperature during months encompassing conception, the last trimester of gestation, and the entire length of gestation) on Julian birth date and birth mass using linear-mixed effects models. Linear and quadratic functions of maternal age influenced both natal features with earliest Julian birth dates and heaviest birth masses occurring at prime-age and older individuals, which ranged from 5–9 years of age. Litter type influenced Julian birth date and birth mass. Interestingly, environmental factors affected Julian birth date and birth mass even though mothers were continuously allowed access to a high-quality diet. Random effects revealed considerable variation among mothers and years. This study demonstrates that, in long-lived polytocous species, environmental factors may have a greater influence on natal features than previously supposed and the influence from biological factors is also complex. The documented responses to environmental influences provide unique insights into how mammalian seasonal reproductive dynamics may respond to current changes in climate.

We evaluated the precision of age estimates produced by cementum annuli analysis (CAA) of blind‐duplicate specimens taken from 994 southern mule deer (Odocoileus hemionus) collected over 15 years. We found that the mean annual proportion of unreliably aged incisor pairs was greater for females (0.48, SD = 0.13) than for males (0.22, SD = 0.07). Most of the 308 unreliably aged tooth pairs disagreed by only 1 year. Sex, precipitation, and certainty codes assigned by Matson's Lab to the age estimates were the best predictors for agreement of estimated ages within incisor pairs. Our estimated overall age error rate of CAA (17%) was >2 times as large as estimated error rates from Montana and South Dakota, but less than half of error rates estimated for Mississippi and south Texas. Knowing the error rate of age estimates from a specific deer population allows wildlife managers to perform tasks requiring specific age class information such as monitoring the harvest rate of older female deer in a hunted population or performing population reconstruction. © 2011 The Wildlife Society.

Predation by curculionid larvae, tannic acid content, and germination were measured in acorns from individual trees of Quercusalba and Quercusrubra from two sites at the Meeman Biological Field Station, Shelby County, Tennessee, U.S.A. A crossed and nested analysis of variance design was used, and no significant differences were found among trees or between sites in percentages of acorns that were attacked nor in tannic acid contents. Quercusrubra acorns had significantly less predation and higher amounts of tannic acid than Q. alba acorns. Acorns of both species that were not attacked had significantly higher germination success (82% for Q. alba and 98% for Q. rubra) than acorns that were attacked. There was no significant relationship between amount of predation and tannic acid content for acorns from trees of either species. Tannic acid content appears to have an impact by reducing seed predation and may interact with seed crop size to increase annual germination success of trees.