Friday, February 6, 2015

Body Size and Growth of the Eastern Collared Lizard in Central Arkansas

Because of habitat fragmentation and population declines, the Eastern Collared Lizard is designated as a vulnerable species in Arkansas. Fertility is a major component of population dynamics, and size is related to fertility, it makes sense that age-specific size and growth can indicate the health of Eastern Collared Lizard populations.

Methods and Materials

Studies were done on a privately owned rock quarry near the Arkansas River Valley region in Central Arkansas that contained 4-5 colonies of Eastern Collared Lizards. No evidence of migration was found between adjacent colonies, even though it wouldn't be that hard for the lizards to migrate, as colonies were separated by grass and dirt roads. All colonies were treated as a population. Most of the site had large areas of rocks and boulders, with some vegetation and hardwood forest. Between May and October 2011, data on body size and growth was recorded to the nearest millimeter, gender of lizard, and age class. Bodies of female lizards were examined to see how well they were doing reproduction-wise. It was not attempted to distinguish the gender of hatchling lizards. After the lizards were captured, they were given a toe clip and mark with a paint pen. Growth rates of this Central Arkansas population were compared to the Sandy Ridge population's growth rates. Raw data and comparisons of individual growth rates weren't available for Sandy Ridge pre-suppression due to sample size. Sandy Ridge raw data was not available for post-suppression either, so comparisons were used via the mean, standard deviation, and sample size for each size/age class.

Results

Over the course of the study, 141 yearling and adult lizards were captured and there were 77 recaptures of 37 hatchlings. Body size was similar for all age/size classes between the central Arkansas and pre-suppression Sandy Ridge populations. Except for adult females, the lizards were larger in central Arkansas than in Sandy Ridge post-suppression populations. It was concluded that in their first full activity season, yearling females must reach a minimum body size of 77 mm to lay eggs. Egg sacs were detected in all but the two smallest yearling females. Growth rates did not differ significantly between the central Arkansas and Sandy Ridge post suppression populations. The mean size of lizards from central Arkansas and pre-suppression Sandy Ridge compared favorably with each other. However, most lizards from the central Arkansas population were much larger than Sandy Ridge post-suppression and do not differ from pre-suppression Sandy Ridge lizards in size. Data on the yearling females' body size and growth suggested that the annual fertility of the central Arkansas lizards should be fairly high. Six of eight yearling females in the Central Arkansas population reached the predicted minimum body size of 77 mm necessary for reproduction. Furthermore, the mean size of adult females in Central Arkansas was similar to that of Sandy Ridge pre-suppression. Thus, it was shown that this Central Arkansas population was fairly healthy.


Brewster, Casey, Sikes, Robert, Gifford, Matthew. "Body Size and Growth of the Eastern Collared Lizard (Crotaphytus collaris) in Central Arkansas" Herpetological Review, 45(4), 580-583. 2014.

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