Annual cycles in body mass and reproduction of endangered Mt. Graham red squirrels

John L. Koprowski

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


Annual cycles in life-history traits often are interpreted as adaptations. The Mt. Graham red squirrel (Tamiasdurus hudsonicus grahamensis) is an endangered species isolated in the Pinaleno Mountains of Arizona (United States) at the southernmost range terminus where the ecology is poorly known. I monitored annual cycles of reproduction and body mass in male and female Mt. Graham red squirrels. Males with scrotal testes were present during all months except October, with a peak in testis size in April. Lactating females were found from April to September. Male body mass was highest in winter and lowest in summer; females did not fluctuate seasonally in mass. Male body mass exceeded that of females during winter and was positively related to size of testes late in the breeding season. Annual cycles in reproduction and body mass of Mt. Graham red squirrels are similar to those of other red squirrels in similar life zones.

Original languageEnglish (US)
Pages (from-to)309-313
Number of pages5
JournalJournal of Mammalogy
Issue number2
StatePublished - Apr 2005
Externally publishedYes


  • Arizona
  • Body mass
  • Energetics
  • Mating systems
  • Sex differences

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Ecology
  • Animal Science and Zoology
  • Genetics
  • Nature and Landscape Conservation


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