Growth Rates of Male California Voles During a Peak Density Year: The Chitty Effect Revisited

William Z. Lidicker

in The Quintessential Naturalist

Published by University of California Press

Published in print July 2007 | ISBN: 9780520098596
Published online March 2012 | e-ISBN: 9780520916159 | DOI:
Growth Rates of Male California Voles During a Peak Density Year: The Chitty Effect Revisited

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This chapter directs considerable research effort toward understanding the (Chitty Effect) phenomenon in the expectation that it will lead to elucidation of the cyclic mechanisms. It notes that temporal changes in body mass can serve as sensitive indicators of demographic processes. The chapter explains that in arvicoline rodents undergoing multi-annual cycles, body mass tends to increase significantly during phases of rapid growth to peak numbers. The chapter examines individual body-growth rates in a population of California voles (Microtus californicus) over an 11-month period when the density grew to about 1000/ha and then abruptly declined. It analyzes the results in the context of six hypotheses that have been proposed to account for the Chitty Effect. The chapter concludes that significant influences leading to extra-large sizes include adequate food supply, a long period which is favorable for growth, high starting densities, low population pressure, and, in some individuals, allocation of resources to growth instead of reproduction.

Keywords: cyclic mechanisms; temporal changes; body mass; demographic processes; arvicoline rodents; California voles; Microtus californicus; Chitty Effect

Chapter.  8029 words.  Illustrated.

Subjects: Zoology and Animal Sciences

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