Foraging mode of serpentiform, grass-living cordylid lizards: A case study of Cordylus anguina

Abstract

Foraging mode of the Cape grass lizard, Cordylus anguina, was determined by using three criteria: 1) the number of movements per minute (MPM) and the percentage of time spent moving (PTM) during periods of activity; 2) prey chemical discrimination ability; 3) stomach contents. To determine MPM and PTM, observations were made from an observation tower using a semi-natural outdoor enclosure, and through a one-way glass panel using a semi-natural indoor enclosure. Each lizard (n = 10) was observed for a 10 minute period during peak activity and the times it was moving and the times it was stationary were recorded. Data obtained in the indoor- and outdoor enclosures did not differ significantly and were pooled. MPM (0.37 ± 0.21 S.D.) and PTM (1.92 % ± 0.93 S.D.) values recorded for C. anguina fall within the range given as characteristic for sit-and-wait foragers. Nine C. anguina were habituated in glass terraria to accept mealworms offered to them. When all lizards accepted food without hesitation, they were tested for their ability to discriminate among three different odours presented to them in a randomized block design: prey odours consisting of mealworm surface odours, distilled water as an odourless control stimulus, and cologne as a pungency control. The number of tongue-flicks directed at the cotton applicator containing the stimulus odour during 60 seconds was recorded. No statistically significant differences were found among the  responses to the three treatment odours. An analysis of the stomach contents of 21 C. anguina revealed a diet of mostly diurnally active arthropods.

Key words: Cordylidae, movements per minute, per cent time moved, prey chemical discrimination, stomach contents, sit-and-wait foraging.