GILMAN, Casey*; WOLF, Blair; University of New Mexico: Lizards, eggs, and ultrasound: testing the efficacy of quantifying reproductive effort in squamate reptiles using portable ultrasonography.
Most studies of reproductive effort in lizards have required that individuals be sacrificed to obtain population level data on life history traits such as clutch and egg size. While this approach provides insight into population level life history traits it precludes a critical examination of individual performance over both intra-annual and inter-annual time scales. These insights are crucial for broader knowledge of how individuals allocate resources to reproduction over varying lifetimes in the face of environmental variation. In this study we validated the use of a laptop sized portable ultrasound system as a nondestructive means of quantifying reproductive investment in five species of lizards with a range of body sizes, forms, and life histories. We present data from 46 gravid females in sizes and forms ranging from Uta stansburiana to Crotaphytus collaris and Phrynosoma cornutum. Lizards were scanned live while mechanically restrained, and egg number and dimensions were measured and recorded using virtual calipers. Observations were then validated by sacrifice and dissection. We found that for most species ultrasound scans produced egg counts that deviated from the true counts by 0.19 � 1.12 SD for clutch sizes of 2 to 9 (mean 4 � 1.34 SD) and 2.50 � 6.77 SD for clutch sizes of 18 to 41 (mean 26 � 9.15 SD). Egg measurements using the virtual calipers produced clutch volume measurements that deviated from the true measurements by 0.24 � 0.99 SD cm3 over clutch volumes ranging from 0.07 to 10.76 SD cm3 (mean 2.24 � 2.632 SD cm3), and 2.03 � 6.28 SD cm3 over clutch volumes ranging from 0.58 to 20.26 SD cm3 (mean 10.85 � 8.35 SD cm3). This study shows that ultrasonography in the field is a viable nondestructive method for quantifying reproductive effort in lizards.
