Is it like night and day? Nocturnal versus diurnal perch use by dwarf chameleons (Bradypodion pumilum)

Abstract

ABSTRACT Arboreal chameleons must navigate a complex, three-dimensional landscape consisting of trees, bushes and/or grasses of various sizes. This complexity equates to the microhabitat of chameleons, that is, the branches upon which they perch and through which they move. Therefore, chameleons rely on their ability to grip perches available to them, and this is evident by their specialised adaptations such as their prehensile tail and their grasping hands and feet. To date, ecological studies of chameleons have relied on gathering data on perch use only at night because locating chameleons during the daytime is extremely difficult. However, the night-time perch represents the sleeping perch of individuals, and this is not necessarily reflective of overall diel perch use. Many other arboreal reptiles are constrained to using thin perches at night, but by day their microhabitat is more variable, using thicker branches, limbs or tree trunks. To assess whether this well-entrenched paradigm (night-time perch use being constrained to thin perches) also extends to fully arboreal chameleons, daytime and night-time perch diameters were measured for the Cape Dwarf Chameleon, Bradypodion pumilum, and were compared using analyses of variance statistical approaches. Neither perch diameters nor variance in perch diameters differed between the two photoperiods, and the variance in diameters of perches used was remarkably high. Despite this variance, there was a significant, positive relationship between body size and the diameter of perches used. Unlike other reptiles, the results show that for B. pumilum the night-time perch use is not different than diurnal perch use, and there appears to be a fairly wide range of perches used by chameleons of a given body size over both photoperiods. Nevertheless, the positive trend for chameleons of larger body sizes to choose larger perches than smaller chameleons implies that there are some upper and lower constraints for the diameters of perches used, possibly relating to their ability to effectively grip a range of perch sizes.