Douglas A. Eifler

Foraging Behavior and Spacing Patterns of the Lizard Oligosoma grande

The grand skink, Oligosoma grande, is a diurnal rock-dwelling lizard from the tussock grass- lands of Central Otago, New Zealand. Foraging behavior, diet, and spacing patterns were examined for two populations of individually marked adults. Adults of both sexes search for arthropod prey using pause- move (=saltatory) searching. Males and females spent the same amount of time moving across outcrops but differed in the characteristics of their searching behavior. Females made more frequent but shorter moves than males. The two sexes also differed in diet Males directed most of their pursuit effort towards large flying insects, but occasionally consumed smaller, easy to capture prey and visited fruiting plants. By con- trast, females fed primarily on the small prey types and plant material. Males and females had home ranges (HR) and core areas (CA) of comparable size and with comparable levels of total neighbor overlap However, the patterns of HR overlap differed between the sexes. Both males and females tended to have greater average HR overlap with male neighbors. Core area overlap was less extensive than HR overlap and some animals concentrated their activity in CAs that were exclusive from those of other lizards. Females appeared to be dominant to males; the most common conspecific interaction was adult females chasing adult males.

Habitat use and movement patterns in the graceful crag lizard, Pseudocordylus capensis

ABSTRACT We characterized the habitat use and movement patterns of adult male, adult female and juvenile Pseudocordylus capensis, a diurnal, rock-dwelling, insectivorous lizard. Rock use was vertically stratified: males spent most of their time at local high points, females at mid-level on the rocks, and juveniles were typically in the lower regions. Movement patterns varied with demographic class as well: juveniles moved more frequently and spent a greater proportion of their time in motion than did adults, and the number of moves of different durations varied among the classes. Finally, juveniles scanned their surroundings and appeared to feed more frequently than adults.

Habitat Selection by Foraging Texas Horned Lizards, Phrynosoma cornutum

Abstract The Texas horned lizard, Phrynosoma cornutum, feeds primarily on harvester ants (Pogonomyrmex) across much of its range. We quantified behavior of P. cornutum foraging on Pogonomyrmex relative to habitat and time. For the duration of their morning activity, 14 lizards were observed; we determined their use of habitat and location of ants that were captured. Lizards spent most of their time under vegetation; the type of vegetation used varied throughout the morning. Most feeding took place in the open and involved ants dispersed away from colonies. When feeding under vegetation, most feeding took place under mesquites (Prosopis), and location of mesquites under which lizards fed was nonrandom with respect to distance from entrances to colonies of ants. Feeding at entrances to colonies was restricted to a shorter period of the morning than feeding on dispersed ants. Males and females differed in use of habitat and in foraging behavior, with males more likely to feed in the open and to feed at entrances of colonies than females.

Escape tactics in the lizard Meroles cuneirostris

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.

Use of Habitat by the Semiaquatic Lizard, Norops aquaticus

Abstract We assessed use of habitat by the semiaquatic lizard Norops aquaticus along the Río Java at the Las Cruces Biological Station, Costa Rica. We surveyed the river for lizards and determined characteristics of their perches relative to edge of the water. Individuals preferentially positioned themselves near eddies. Demographic classes differed in height of perches above the river, with adult males using the highest perches. Males were most likely to perch directly above water. In addition, males and juveniles tended to be in exposed areas, whereas females selected cover. Behavior of N. aquaticus on land is dependent on characteristics of rivers.

Characteristics and Use of the Tail in Signaling by the Zebra-Tailed Lizard (Callisaurus draconoides)

Abstract The zebra-tailed lizard (Callisaurus draconoides) is a diurnal territorial insectivore from arid areas of North America. The underside of its tail has a series of black bands on a white background; individuals raise the tail to expose the underside as a social signal and to deter pursuit by predators. We characterized variation in banding of the tail within a population of C. draconoides from Sonora, Mexico, and examined the relationship between characteristics and use of the tail. Number of bands on intact tails was 4–10; individuals who have experienced some natural reduction in their tail can lack bands all together. The proportion of the underside of the tail that was black was 0–0.46. For males, snout–vent length and mass were positively correlated with number of bands and mean length of bars on the tail; snout–vent length, mass, and width of head were positively correlated with the proportion of black on tails. Females in better condition (based on residuals from regression of snout–vent length to mass) tended to have more bars on the tail and a wider head; snout–vent length, mass, and width of head were positively correlated with mean length of band. We simulated predator-prey interactions using humans as predators. Males used tail displays more than females. Individuals encountered in the open were more likely to use tail displays. Neither size of body nor natural reduction in tail was related to use of tail displays. During focal observations for females with reduced tails, rates of tail displays were positively correlated with length of tail. Males with intact tails moved more frequently and fed more often than males with reduced tails.

Social and Environmental Factors Influence Microhabitat Selection in the Brown-Speckled Sphaero, Sphaerodactylus notatus (Squamata: Sphaerodactylidae)

Abstract Both environmental factors and social factors affect an animals choice of microhabitat. We explored the effects of humidity and the presence of conspecifics and predators on microhabitat selection by Brown-Speckled Sphaeros (Sphaerodactylus notatus; Squamata: Sphaerodactylidae). To test the effect of environmental moisture, we provided geckos a choice between shelters of varying humidity and determined that individuals were significantly more likely to choose more humid shelters. In interaction trials between conspecifics of different sizes and sexes and between geckos and predators, we found that lizards were unwilling to share shelters with conspecifics in all situations. We observed aggressive behaviors such as chasing, biting, and head bobbing and noted that subordinate geckos were unwilling to enter a shelter occupied by a dominant individual even in the presence of a predator.

Intraspecific Variation In Habitat Use and Movement In Long-Nosed Leopard Lizards (Gambelia wislizenii) From the Alvord Basin, Oregon

Abstract We studied the long-nosed leopard lizard, Gambelia wislizenii, in the Great Basin Desert of southeastern Oregon to identify intraspecific patterns of behavioral variation. Sex and body size played an important role in determining intraspecific behavioral differences. Males and females showed different habitat preferences, with males spending more time on hardpan and in the center of shrubs. Males made more long moves and clustered their long moves more frequently than females. Smaller lizards displayed more head turns, tongue flicks, and use of elevated perches. Smaller individuals also spent a higher proportion of time moving.

Habitat Use and Activity Patterns in the Nocturnal Gecko, Chondrodactylus turneri

Abstract: Intraspecific variation in behavior is often associated with age or size class, with many animals experiencing ontogenetic differences in diet, predation risk, physiological function, and competition. The nature of intraspecific behavioral variation will depend on the environmental context and has been more thoroughly examined for diurnal species. We studied microhabitat use and activity relative to time of night and the lunar cycle for the nocturnal gecko Chondrodactylus turneri, in the Namib Desert. Geckos preferred larger rocks with more crevices and were clumped in their occupancy of rocks, with some rocks being occupied by as many as eight individuals. Age classes differed in their use of open areas, with juveniles being encountered more often in the open. Activity levels varied with moon phase and time, with adults and juveniles exhibiting different relationships. Our results indicate that multiple factors might be influencing intraspecific behavioral variation.

Intraspecific variation in opportunistic use of trophic resources by the lizard Ameiva corax (Squamata: Teiidae)

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.