A Field Study of the Ontogeny of Social Behavior in the Lizard Anolis Aene Us

Abstract

AbstractThe spacing behavior, displays and aggression of hatchling and juvenile lizards (Anolis aeneus) were compared to the behavior of the adults. Tn adults these behaviors are sexually dimorphic, but juveniles of both sexes show similar behavior. Hatchling lizards a few days old have nonoverlapping home ranges or participate in dominance hierarchies of up to six steps. Status in dominance hierarchies is almost entirely size dependent. The particular type of social system shown varies with microhabitat. Juvenile home ranges are smaller than those of adults and enlarge with age. Home ranges of juveniles are more variable in size than those of adults. Temporal elements of the species specific bob pattern are very stereotyped in both juveniles and adults. Intraindividual variation in display element duration is low and interindividual variation high in all age and size groups. However, mean duraton of elements is longer for larger lizards. Two other displays are significantly more variable in juveniles than in adults. Most of this variation is due to added interindividual variance in juvenile display elements. Juveniles and adults of both sexes are able to give all displays except courtship displays. The frequency with which certain displays are given is significantly different for juveniles, adult females and adult males. Juveniles are more apt to give certain aggressive displays than are adults of either sex. Longterm ontogenetic studies of individual females indicates that initially they give the aggressive displays characteristic of juveniles in general, but that the frequency of these displays decrease when they become sexually mature. When territorial resident lizards of any age are exposed to tethered intruders they react aggressively. Aggressive responses were ranked and aggression computed for certain size ratios of intruder and resident juveniles (I/R ratio). This aggression was compared to that predicted on the basis of food competition between different lizard size ratios. At both large and small lizard size ratios (I/R) juvenile Anolis aeneus are more aggressive than are either adult males or adult females at the same size ratios. This added aggressiveness to very large and very small intruders cannot be explained in terms of food competition between juvenile lizards of different sizes.