Reduced access to olfactory cues and home-range maintenance in the sleepy lizard (Tiliqua rugosa)

Sleepy lizards Tiliqua rugosa are large, long-lived, Australian skinks that live in stable home ranges. Previous studies showed that the lizards have a good sense of orientation and navigation towards home. However, since the y are active only 4 months in every year, there is a question about which e nvironmental cues enable them to locate their home boundaries. In the prese nt study we determined whether surrounding olfactory and chemical cues are important for the sleepy lizards for home-range maintenance. In the first p art of the study we showed in the laboratory that zinc sulphate (ZnSO4) is a chemical that induces anosmia and prevents detection of chemical cues in sleepy lizards for up to 30 days, with no evident longterm harm to the anim als. We then monitored the location of 50 radio-tagged sleepy lizards. Afte r determining their home ranges they were divided into three groups: an unt reated control, a saline-treated (sham-operated) group and a ZnSO4-treated group. Starting 2 days after the treatment, the home ranges of all lizards were re-determined within the period that ZnSO4 blocked olfaction. Three va riables were calculated comparing home ranges before and after treatments: the change in home-range size, the distance between the centre of activitie s of the lizards, and the overlap between the individual home ranges before and after treatments. Lizard home ranges varied from 1.9 +/- 0.6 ha to 4.6 +/- 1.4 ha before treatment, and 1.3 +/- 0.3 ha to 3.1 +/- 0.7 ha after tr eatment. There was no significant effect of treatments or of sex on the hom e-range size or on the distances between the centre of activities, or on th e overlap between the individual home ranges. Our data indicate that olfact ion and vomerolfaction are not a major cue for home-range maintenance in th e sleepy lizards.