Camouflage and escape decisions in the common chameleon Chamaeleo chamaeleon

Abstract

In species with reduced locomotory abilities, camouflage seems to be f a r more important than other behavioural tactics (e.g. running) to elude predatory attacks. In this study, we examined the effects of camouflage on escape decisions in the common chameleon Chamaeleo chamaeleon. The effectiveness of camouflage was assessed by the ability of humans to detect different sized chameleons placed on different backgrounds (vegetation of high and low density, defined here as open and dense bushes), both in the field and in photographs. Escape behaviour was analysed by simulating a predator attack (in our case, approach by a human). As expected, the probability of detection by a potential predator was size-and background dependent. In the field, detection time (but not distance) was significantly higher for chameleons of a given size perched on dense (Myoporum) than open (Retama) bushes. When using photographs, the probability of detection was higher for large (adult) chameleons perched on open (Retama or Nerium) bushes and lower for hatchlings perched on dense (Myoporum or Cupressus) bushes. Conspicuousness greatly influenced the escape tactics of individuals. Chameleons perched on more protected Myoporum allowed closest approach distances than those perched on less protected Retama. In general, antipredatory responses (defined here as 'first movement', 'fleeing', 'mouth opening' or 'free falling') occurred significantly earlier in the trial sequence in chameleons perched on clear Retama than those perched in Myoporum. Two antipredatory responses were size-dependent: juveniles and adults exhibited 'mouth opening' more frequently than hatchlings whereas 'free falling' was more frequently recorded for hatchlings, Our results suggest that size and vegetation greatly influence the risk of detection by predators and this variation influences an individual's decision about when and how to escape. 0 2001 The Linnean Society of London ADDITIONAL, KEYWORDS: crypsisescape decisionsinfluence of vegetationbody size effectscamouflagelizards.

Lizards in the slow lane: Thermal biology of chameleons

“…Chameleons rely on camouflage for predator avoidance (Cuadrado et al, 2001). They are 'cruising' predators that move slowly, but relatively frequently (Butler, 2005).…”

“…Chameleons comprise a relatively large (about 130 species) group of highly specialized arboreal predators (Necas, 1999;Pough et al, 2004). The family is characterized by prey capture by ballistic tongue projection, zygodactylus grasping feet, prehensile tails, slow deliberate movements, and reliance on crypsis for predator avoidance (Wainwright and Bennett, 1992;Cuadrado et al, 2001;Butler, 2005). An a priori expectation from their homogeneous 'slow-lane' lifestyle and energy-conservative behavior is that the family would be characterized by relatively low T b 's.…”

Threat perception in the chameleon (Chamaeleo chameleon): evidence for lateralized eye use

“…Chameleons rely on cryptic coloration and slow motion to reduce predation risk (Heatwole 1968;Cuadrado et al 2001), and motor patterns associated with concealment are related to the level of threat. If a threat stimulus appears on the side of the branch opposite to which a chameleon is perched, it will remain motionless (Heatwole 1968;Cuadrado et al 2001) yet if the threat appears at another angle, the chameleon will flatten its torso laterally and rotate to the side of the branch opposite the threat, thus minimizing its exposure.…”

“…If a threat stimulus appears on the side of the branch opposite to which a chameleon is perched, it will remain motionless (Heatwole 1968;Cuadrado et al 2001) yet if the threat appears at another angle, the chameleon will flatten its torso laterally and rotate to the side of the branch opposite the threat, thus minimizing its exposure. Subsequently, the chameleon tracks the threat visually and, if the threat moves laterally, it will continuously adjust its position, smoothly rotating in the opposite direction, even if the threat is many meters away.…”

To run or hide? Age‐dependent escape behaviour in the common flat lizard (Platysaurus intermedius wilhelmi)

“…Recent work on predation risk and anti-predatory behaviour in lizards has focused on prey-predator honest signalling (Leal & Rodríguez-Robles, 1997;Leal, 1999), influence of conspicuousness on predation risk (Cooper & Vitt, 1991;Olsson, 1993;Cooper, 1998a;Martín & López, 2000), refuge selection in relation to predation risk (Cooper, 1997a(Cooper, , 1998a(Cooper, , 1999aCooper, van Wyk & Mouton, 1999), costs of refuge use (Martín & López, 1999), perception of predation risk (Bulova, 1994;Cooper, 1997aCooper, ,b, 1998b, influence of habitat structure and incline on anti-predatory behaviour (e.g. Bulova, 1994;Martín & López, 1995a,b;Losos & Irschick, 1996;Jayne & Ellis, 1998;Irschick & Jayne, 1999;Cuadrado, Martín & López, 2001), age-dependent escape behaviour (Martín & López, 1995b), trade-offs in social and anti-predatory behaviour (Cooper, 1999b), reactive and anticipatory deflection of predatory attack (Cooper, 1998d,e), costs associated with tail autotomy (e.g. Fox & Rostker, 1982;Althoff & Thompson, 1994;Martín & Salvador, 1997;Fox & McCoy, 2000), thermal dependence of escape behaviour (Hertz, Huey & Nevo, 1982;Cooper, 2000), and combinations of some of the above variables (Bulova, 1994;Smith, 1997).…”