Use of portable ultrasonography as a nondestructive method for estimating reproductive effort in lizards
Publication Type: |
Journal Article |
Year of Publication: |
2007 |
Authors: |
C. A. Gilman, B. O. Wolf |
Publication/Journal: |
Journal of Experimental Biology |
Keywords: |
clutch size, egg size, energetics, life history, lizard, reproduction, ultrasound imaging |
ISBN: |
0022-0949 1477-9145 |
Abstract:
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·cm 3 (relative error 25.9%), and estimated clutch volumes that differed from actual volumes by 1.03±0.26·cm 3
(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.