Semen characteristics in free-living koalas (Phascolarctos cinereus)

D. E. Wildt, M. Bush, S. J. O'Brien, N. D. Murray, A. Taylor, J. A. Marshall Graves

Research output: Contribution to journalArticle


Spermic electroejaculates (range in motile sperm/ejaculate, 0.50-122.9 x 106; mean ± s.e.m., 38.6 ± 4.9) were recovered from 47 of 48 adult koalas captured from 3 wild populations in Australia. Semen was characterized by (i) a high density of globular bodies, which prevented the estimation of sperm motility without dilution; (ii) a brownish colour; and (iii) an acidic pH. Spermatozoa were categorized on the basis of 10 head forms, most cells being a curved or hooked shape. The koala populations differed in sperm concentration and motility ratings, but not in testes size, testosterone production or proportions of spermatozoa with various head shapes. These data confirm that free-living koalas normally produce spermatozoa with a high incidence of structural heterogeneity almost solely confined to the head region; and demonstrate the utility and safety of conventional gamete and endocrine studies, approaches which will be useful for determining the impact of genetic isolation and venereal disease and species fertility.

Original languageEnglish (US)
Pages (from-to)99-107
Number of pages9
JournalJournal of Reproduction and Fertility
Issue number1
StatePublished - Jan 1 1991


  • electroejaculation
  • koala
  • marsupial
  • semen
  • spermatozoa
  • testis
  • testosterone

ASJC Scopus subject areas

  • Physiology
  • Embryology
  • Molecular Biology
  • Obstetrics and Gynecology
  • Developmental Biology

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  • Cite this

    Wildt, D. E., Bush, M., O'Brien, S. J., Murray, N. D., Taylor, A., & Marshall Graves, J. A. (1991). Semen characteristics in free-living koalas (Phascolarctos cinereus). Journal of Reproduction and Fertility, 92(1), 99-107.