Patterns of body size and habitat use in a lizard assemblage
2004
James, Sarah E. | M’closkey, Robert T.
We quantified differences in the distribution and behaviours of three territorial species of phrynosomatine lizard (Urosaurus ornatus, Uta stansburiana, and Sceloporus undulatus) between two habitats on the elevated mesas of western Colorado. Community lizard density was greater on rock ridges dissecting pinyon-juniper woodland than in the surrounding flat, open areas. The frequency of community-level interactions, or behaviours directed towards another lizard of any species, was also greater in the rock compared to the flatland habitat for S. undulatus. Snout-vent length frequency distributions of all three species differed between habitats, with larger lizards residing in the rock habitat. For each species, the distribution of hatchling lizards between habitats was opposite to that expected based on the distribution of conspecific adult females, with the majority of adult females residing in the rock habitat and the majority of hatchlings in the flatland. Indices of juvenile recruitment (number of hatchlings per adult female) in the flatland habitat approximated average clutch size for U. ornatus and U. stansburiana despite known high rates of juvenile mortality in these species. We suggest that ontogenetic habitat shifts may explain the observed age and size distributions of species between habitats. Hatchlings may disperse from rock to flatland to avoid aggression and predation from adult lizards in the rock habitat and return when they have attained larger body size and thus face reduced predation risk, being presumably more able to compete within social hierarchies.
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