Successful escape from predators may involve the use of multiple tactics. The wedge-snouted desert lizard (Meroles cuneirostris) flees from predators through a series of discrete moves with each move representing a specific manoeuvre type. By simulating the approach of a predator, we examined the role of sex and age (adult vs. juvenile) on the manoeuvre types used during escape, as well as the relationship between the number of moves needed to escape and the number of manoeuvre types employed. The eight defined manoeuvre types were used by all demographic groups, though there were differences among groups in the tendency to use certain manoeuvre types. In general, there was a strong difference in how adults and juveniles fled from predators. The number of manoeuvre types used by a lizard tended to increase with the number of moves required to escape and adults more readily added new manoeuvre types to an escape sequence. Demographic differences in escape behaviour might result from differing predation pressures incurred by juveniles and adults, and might also be related to the ontogeny of escape behaviour.
We examined the relationship between body size and pursuit success in the lizard Cnemidophorus uniparens. Using grasshoppers as prey in experimental feeding trials, we found a significant positive relationship between lizard body size and pursuit time. In addition, larger individuals were significantly more likely to be unsuccessful at capturing the grasshoppers. We also examined the relationship between the mean body size of Cnemidophorus populations and diet composition. We found a significant negative relationship between mean body size and the proportion of grasshoppers in the diet and a significant positive relationship between mean body size and the proportion of termites in the diet.
Ameiva corax is restricted to a small island (<2 ha), off the coast Anguilla. We present information on intraspecific variation in its diet, based on observations of 190 marked individuals. Larger individual were more likely to attempt to enter active seabird nests and only large males were observed to successfully enter a nest and break open an egg. Flower eating was commonly observed and its occurrence was not related to lizard size or sex. More than half the population was observed visiting areas where fisherman mixed their bait, a foraging strategy also unrelated to lizard size or sex. Ameiva corax is known to socially feed at large food items such as seabird eggs. The individuals that can initially access these food items may occupy key roles in the social network.
Ecologically versatile Anolis schwartzi from St. Eustatius (Lesser Antilles) occurs in various habitats, usually in shaded situations and often in higher densities when associated with rock piles, rock slides, and stone walls. In order to evaluate the mating systems of A. schwartzi in different habitats, we examined populations in rocky and adjacent forested plots in Boven National Park to test the following predictions: (1) Population densities would be higher in habitats with rocks or rock slides than in nearby areas of forest without rocks. (2) Males would be larger in favoured habitats with higher population densities. (3) Behaviours related to territoriality and aggression would be more prevalent in habitats with higher population densities. In fact, population densities were higher in rock plots, males and females were larger in rock plots, and males engaged in territorial/aggressive behaviours (push-ups, movements, presumably necessary for surveying territories, and chases) more frequently in rock plots. Large male A. schwartzi in rock plots with high population densities apparently exclude small males (social exclusion hypothesis). Average female:male densities in forest plots approached 1:1, which is suggestive of monogamy, whereas that in rock plots was 0.72. Consequently, the mating systems of A. schwartzi appear to vary in a predictable manner along the spectrum of monogamy to polygyny between proximate habitats between which no genetic isolation is possible.
Predation risk influences decision making, escape behaviour, and resource use. Risk assessment and behavioural responses to predation can depend on demographic and environmental factors. We studied the escape behaviour of the long-nosed leopard lizard (Gambelia wislizenii) when approached by a human predator (= “simulated predator”), analysing flight initiation distance (FID) and flight distance (FD) relative to demographic and environmental variables. Starting distance (SD) of the simulated predator and orientation of prey lizards relative to the simulated predator influenced FID, but body size of the prey lizard did not. Sex interacted with SD to affect FID. Females lengthened their FIDs as SD increased, while male FID was unrelated to SD. Flight distance increased with increasing SD. Gambelia wislizenii’s ecological role as an ambush predator may explain their escape behaviour; reproductive status potentially affected the interaction between sex and SD.