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First published online May 21, 2007
Journal of Experimental Biology 210, 1859-1867 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.001875
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Use of portable ultrasonography as a nondestructive method for estimating reproductive effort in lizards

Casey A. Gilman* and Blair O. Wolf

University of New Mexico, Department of Biology, MSC03-2020, 1 University of New Mexico, Albuquerque, NM 87131-0001, USA

* Author for correspondence (e-mail: cgilman{at}unm.edu)

Accepted 7 March 2007

Obtaining population-level life history data such as egg and clutch size in reptiles has most often required that individuals be sacrificed. This prevents a reexamination of individuals over intra-annual and inter-annual time scales, limiting insight into the effects of varying environmental conditions on reproductive output. Here, we test the use of a laptop-sized portable ultrasound imaging system as a nondestructive means for quantifying reproductive investment in five species of lizards with a range of body sizes, forms and life histories. Ultrasound scans produced egg counts that were accurate for clutch sizes of two to seven eggs, and provided good estimates (within 5.5±1.69 eggs, mean ± s.e.m., relative error 21%) for clutch sizes of between 18 and 41 eggs. Egg measurements using virtual calipers produced average egg volumes that deviated from actual volumes by 0.09±0.01 cm3 (relative error 25.9%), and estimated clutch volumes that differed from actual volumes by 1.03±0.26 cm3 (relative error 29.5%). We also monitored development in five lizard species and found that changes in follicle and egg size and degree of embryonic development can be measured over periods of just a few days.

Key words: ultrasound imaging, lizard, egg size, energetics, clutch size, life history, reproduction






© The Company of Biologists Ltd 2007