Homeward bound: factors affecting homing ability in a polymorphic lizard

Colour polymorphism is a widespread phenomenon among reptiles and is often associated with alternative physiological and behavioural strategies, including dispersal and movement patterns. To test the homing ability of Podarcis muralis and look for morph-specific responses, we conducted a translocation experiment in two areas of Northern Italy during 2009 and 2010. The first study area is a wall surrounding a city park with a linear and simplified habitat structure; the second one is an archaeological park in a natural area, including stone walls remains, grasses and woods. Lizards of both sexes (203 and 288 for site, respectively) were translocated at 50-200 m distances, using cloth bags to block lizard sight. P. muralis were able to home since 56.7% of translocated individuals in the first site and 35.1% of translocated individuals in the second site successfully returned to their home-range. The homing ability decreased with increasing distances, while body size positively affected homing behaviour, probably depending on the territoriality of adult lizards. More interestingly, homing performance differed among colour morphs, as yellow lizards of both sexes had significantly higher homing skill than other morphs. This result suggests that colour polymorphism could be maintained by different behavioural strategies of colour morphs. Finally, homing success was significantly higher in first than in second site, suggesting that habitat complexity might affect homing with lizards returning more easily when they were able to use visual cues.