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A two-phase model for smoothly joining disparate growth phases in the macropodid thylogale billardierii

McMahon, Clive R., Buscot, Marie-Jeanne, Wiggins, Natasha L., Collier, Neil, Maindonald, John H., McCallum, Hamish I. and Bowman, David M. J. S. (2011). A two-phase model for smoothly joining disparate growth phases in the macropodid thylogale billardierii. PLoS ONE,6(10):e24934.

Document type: Journal Article
Citation counts: Scopus Citation Count Cited 2 times in Scopus Article | Citations

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IRMA ID 82057923xPUB61
Title A two-phase model for smoothly joining disparate growth phases in the macropodid thylogale billardierii
Author McMahon, Clive R.
Buscot, Marie-Jeanne
Wiggins, Natasha L.
Collier, Neil
Maindonald, John H.
McCallum, Hamish I.
Bowman, David M. J. S.
Journal Name PLoS ONE
Publication Date 2011
Volume Number 6
Issue Number 10
ISSN 1932-6203   (check CDU catalogue open catalogue search in new window)
Scopus ID 2-s2.0-80053949036
Start Page e24934
Total Pages 9
Place of Publication United States
Publisher Public Library of Science
HERDC Category C1 - Journal Article (DEST)
Abstract Generally, sigmoid curves are used to describe the growth of animals over their lifetime. However, because growth rates
often differ over an animal’s lifetime a single curve may not accurately capture the growth. Broken-stick models constrained
to pass through a common point have been proposed to describe the different growth phases, but these are often
unsatisfactory because essentially there are still two functions that describe the lifetime growth. To provide a single,
converged model to age animals with disparate growth phases we developed a smoothly joining two-phase nonlinear
function (SJ2P), tailored to provide a more accurate description of lifetime growth of the macropod, the Tasmanian
pademelon Thylogale billardierii. The model consists of the Verhulst logistic function, which describes pouch-phase growth
– joining smoothly to the Brody function, which describes post-pouch growth. Results from the model demonstrate that
male pademelons grew faster and bigger than females. Our approach provides a practical means of ageing wild
pademelons for life history studies but given the high variability of the data used to parametrise the second growth phase
of the model, the accuracy of ageing of post-weaned animals is low: accuracy might be improved with collection of
longitudinal growth data. This study provides a unique, first robust method that can be used to characterise growth over
the lifespan of pademelons. The development of this method is relevant to collecting age-specific vital rates from
commonly used wildlife management practices to provide crucial insights into the demographic behaviour of animal
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