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Sex ratio of breeding Common toads (Bufo bufo) - influence of survival and skipped breeding

Publiceringsår: 2010
Språk: Engelska
Sidor: 509-524
Publikation/Tidskrift/Serie: Amphibia-Reptilia
Volym: 31
Nummer: 4
Dokumenttyp: Artikel
Förlag: BRILL


Anuran sex ratio at breeding sites is typically male biased. Such sex ratios may be due to poor female survival, to females not breeding as frequently as males and/or to males becoming sexually mature earlier than females. In the present study, the first two factors are analyzed in a common toad (Bufo bufo) population in southern Sweden. Toads were captured, marked and recaptured at the breeding site during 5 years. Within season capture patterns were analyzed using the Jolly-Seber model and among-year captures using the Closed robust design model. Population estimates of males and females yielded an among year variation in breeding population sex ratio, ranging from 16% to 34% females. On average, 41% (proportion adult alive but not breeding) of the females skipped breeding seasons, whereas the corresponding estimate for males was less than 5%. Yearly survival averaged 42% for adult female and 63% for adult male toads. First year adult males and females had a lower survival rate than older toads. Our results demonstrate that both a female biased mortality rate and a higher proportion of skipped breeding in females contribute to the observed male biased sex ratio. However, a deterministic model suggests other factors may also be involved to obtain this degree of male biased sex ratio, the most likely being that females mature at a later age than male toads.



  • Biological Sciences
  • MARK
  • life history
  • semelparous
  • breeding strategy
  • capture-recapture
  • temporary emigration


  • ISSN: 0173-5373

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