Foraging mode of a group-living lizard, Cordylus cataphractus (Cordylidae)

Abstract

Cordylus cataphractus is a group-living lizard endemic to the dry western regions of southern Africa. Groups of up to 30 individuals are regularly encountered and, if this species is a sit-and-wait forager like other members of its family, competition for food among group members could be high. Three criteria were used to infer foraging mode in this species: 1) the number and duration of movements related to foraging, quantified as movements per minute (MPM) and percentage of time spent moving (PTM); 2) the amount of tongue-flicking directed at cotton applicators labelled with prey chemicals as a measure of prey chemical discrimination; and 3) the stomach contents of individuals as an indication of the natural diet. We selected a study site in the Graafwater district in theWestern Cape Province, South Africa, and 15 individuals were observed in the field for 10 min periods to determine MPM and PTM. Low MPM and PTM values of 0.23 ± 0.08 and 2.20 ± 0.71, respectively, were recorded indicating that this species is a sit-and-wait forager like other members of the family Cordylidae. In the laboratory, nine lizards were tested for their ability to discriminate among three different odours, including a prey odour, by counting the number of tongue-flicks directed at the odours presented to them on cotton applicators. Only one lizard tongue-flicked once and there was no indication that C. cataphractus can discriminate prey chemicals. Most of the invertebrate prey species identified in the stomach contents were diurnal species. The stomach contents included a wide range of food items, from plant material to scorpions and millipedes. The southern harvester termite, Microhodotermes viator, is possibly the most important prey species of this lizard. An analysis of the stomach contents of 122 C. cataphractus specimens revealed a significantly higher proportion with empty stomachs among group-living than among solitary ones.

Keywords: movements per minute, percent time moved, prey chemical discrimination, stomach contents, sit-and-wait foraging