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Author Cameron, E.Z.; Setsaas, T.H.; Linklater, W.L. url  doi
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  Title Social bonds between unrelated females increase reproductive success in feral horses Type Journal Article
  Year 2009 Publication (up) Proceedings of the National Academy of Sciences of the United States of America Abbreviated Journal Proc. Natl. Acad. Sci. U.S.A.  
  Volume 106 Issue 33 Pages 13850-13853  
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  Abstract In many mammals, females form close social bonds with members of their group, usually between kin. Studies of social bonds and their fitness benefits have not been investigated outside primates, and are confounded by the relatedness between individuals in primate groups. Bonds may arise from kin selection and inclusive fitness rather than through direct benefits of association. However, female equids live in long-term social groups with unrelated members. We present 4 years of behavioral data, which demonstrate that social integration between unrelated females increases both foal birth rates and survival, independent of maternal habitat quality, social group type, dominance status, and age. Also, we show that such social integration reduces harassment by males. Consequently, social integration has strong direct fitness consequences between nonrelatives, suggesting that social bonds can evolve based on these direct benefits alone. Our results support recent studies highlighting the importance of direct benefits in maintaining cooperative behavior, while controlling for the confounding influence of kinship.  
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  Notes 10.1073/pnas.0900639106 Approved no  
  Call Number Equine Behaviour @ team @ Serial 5152  
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Author Linklater, W.L.; Cameron, E.Z.; Minot, E.O.; Stafford, K.J. url  doi
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  Title Feral horse demography and population growth in the Kaimanawa Ranges, New Zealand Type Journal Article
  Year 2004 Publication (up) Wildl. Res. Abbreviated Journal  
  Volume 31 Issue 2 Pages 119-128  
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  Abstract Although feral horses are a common management problem in numerous countries, detailed and long-term demographic studies are rare. We measured the age and sex structure, and pregnancy, birth and death rates in a population of 413 feral horses in New Zealand during 1994&#8211;98 and used them to construct a model simulating population growth. Survivorship increased with age (0&#8211;1 years old = 86.8%, 1&#8211;2 = 92.3%, 2&#8211;4 = 92.4%, &#8805;? 4 years old = females 94%, males 97% per annum). Birth sex ratio parity, a slight female bias in the adult sex ratio (92 males per 100 females) and higher adult male survivorship indicated lower average survivorship for young males than females that was not detectable in mortality statistics. Pregnancy and foaling rates for mares &#8805;? 2 years old averaged 79 and 49%, respectively. Foaling rates increased as mares matured (2&#8211;3-year-old mares = 1.9%, 3&#8211;4 = 20.0%, 4&#8211;5 = 42.1%, &#8805;? 5 = 61.5% per annum). Young mares had higher rates of foetal and neonatal mortality (95% of pregnancies failed and/or were lost as neonatal foals in 2&#8211;3-year-old mares, 70.6% in 3&#8211;4, 43.2% in 4&#8211;5, and 31% in mares &#8805;? 5 years old). Population growth was 9.6% per annum (9.5&#8211;9.8, 95% CI) without human-induced mortalities (i.e. r = 0.092). Our model, standardised aerial counts, and historical estimates of annual reproduction suggest that the historical sequence of counts since 1979 has overestimated growth by ~50% probably because of improvements in count effort and technique.</p>  
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  Call Number Equine Behaviour @ team @ Serial 3695  
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