Slip slidin’ away: Demographic variation in movement behavior of the dune-dwelling lizard Meroles anchietae

Abstract

The shovel-snouted sand lizard, Meroles anchietae, is a small lacertid that inhabits the aeolian sand dunes of the Namib Desert. We conducted focal observations to characterize the movement patterns of adult male, adult female, and juvenile M. anchietae in their preferred habitat: dune slip faces. Movement varied considerably among demographic classes. Both adult males and females made longer moves than juveniles, but males moved less frequently than females or juveniles. Males exhibited shorter path lengths and shorter net displacements than females or juveniles. Turn angle distributions varied among classes, with females differing from the other two classes. For all three classes, the distribution of movement directions differed from uniform, with lateral moves across the slip face being most common. Movement across the slip face reflects both the ease with which lizards can navigate the substrate and behavioral factors such as foraging strategy and social interactions. Distance and direction pairings differed both from random expectations and among the demographic classes. Movement characteristics indicate that demographic classes respond to the environment differently, even while using the same habitat.