In fact, despite how often blue colours are suggested to be aposematic [e.g. nudibranch – Nembrotha kubaryana (Karuso & Scheuer, 2002), blue-tongued lizard – Tiquila scincoides (Wilsdon, 2009), blue ringed octopus – Hapalochlaena maculosa (Williams, 2010), mountain katydid – Acripeza reticulata (Rentz, 1996)], studies have rarely directly tested the hypothesis. Blue may be used to direct predators to attack dispensable parts of the body (e.g. tail autotomy in skinks) (Cooper & Vitt, 1985). Juvenile American five-lined skinks Plestiodon fasciatus have a distinctive
blue tail (Fig. 1), while the adults are cryptically coloured. Clark & Hall (1970) refuted this hypothesis in a study where they conducted behavioural assays and showed that adult male P. fasciatus were less likely to attack a juvenile conspecific if it had a blue tail than if it did not. As such, they suggested that instead of redirecting predators, XL765 purchase the blue tail colour enables aggressive adult males to differentiate between other adult males (potential rivals) and juvenile males (not rivals) thus
redirecting males to real rivals and reducing infanticide (Clark & Hall, 1970). However, this assertion was refuted by Cooper & Vitt (1985) as they found that adult males readily eat hatchlings with blue tails and thus the primary function of the blue may not be important in intraspecifc signalling after all. Juvenile Acanthodactylus find more lizards also sport blue tails. Unlike Clark & Hall (1970), Hawlena (2009) suggested that Acanthodactylus use bright blue colouration to direct the attention of predators ABT-263 cost to their tail. Hawlena (2009) showed that bright blue tail colouration persists in juveniles because their increased activity levels negate any advantages of cryptic colouration, while more sedentary adult Acanthodactylus take advantage of non-blue cryptic colouration. The conflicting results from
these studies highlight the need for more empirical data on bright blue juvenile colouration. Here, crypsis is defined as colouration or morphology that makes detection of an animal more difficult (Stevens & Merilaita, 2009). Crypsis is opposed to mimicry in that mimics actively send deceptive signals (I am a twig, not a phasmid) whereas in crypsis, animals aim to remain undetected (I am not here at all) (Starrett, 1993). There is little evidence for the role of blue colours in crypsis. Macedonia et al. (2009) provide the only evidence of blue colouration being used for crypsis, in Dickerson’s collared lizard Crotaphytus dickersonae. They show that in the coastal species, the blue colour of males is more similar to that of the nearby ocean than that of the blue males in the inland sister species. They concede that serpentine and avian predators may not regularly encounter C.