James C. Gillingham

Spatial Ecology and Multi-Scale Habitat Selection by a Threatened Rattlesnake: The Eastern Massasauga (Sistrurus catenatus catenatus)

Abstract Using radio telemetry and geographic information systems (GIS), we investigated movement patterns, home ranges, and habitat selection by Eastern Massasauga rattlesnakes from 2003 to 2004 at an 815-ha fen preserve located in southeastern Michigan, USA. We tested habitat selection on three different scales: microhabitat (by modeling differences in climatic and structural variables between snake-selected sites and random sites, using logistic regression), macrohabitat, and landscape-scale (both by compositional analysis comparing proportions of habitat types used versus proportions available). One hundred percent minimum convex polygon (MCP) home ranges averaged 1.3 ha, and daily movement rates averaged 6.9 m/d. Models predicted that snakes exhibit complex microhabitat selection based on multiple climatic and structural variables including soil temperatures, relative humidity, canopy cover, litter depth, and various vegetation parameters. Snakes actively establish home ranges in the broader landscape by selecting areas with disproportionate quantities of emergent wetland, scrub/shrub wetland, and lowland hardwood habitats. Upland hardwood and all human-altered landscapes were rarely used, even though they were available. This has potentially serious conservation implications. Encroachment of these types of landscapes into areas of suitable habitat could severely restrict movement and home range sizes of these snakes. Potential disruption of movement patterns and gene flow of remaining populations could be extremely detrimental to this species.

SOCIAL BEHAVIOR OF THE TUATARA, SPHENODON PUNCTATUS

The social behavior of tuatara, Sphenodon punctatus, was studied in a natural population on Stephens Island, New Zealand, from January to March, 1987-1989. Study sites were located in both wooded (bush) and open (paddock) habitats. Nocturnal observations were enhanced by using night-vision equipment and elevated viewing platforms. Individuals were identified by idiosyncratic differences in crest morphology. At the peak of courtship activity (late January to the end of February), the behaviors of territorial males were observed and their responses to visual stimuli were tested in the field. Visual stimuli were found to be of significance. A radio-controlled, life-sized tuatara model revealed the importance of nuchal and dorsal crests and female head- nodding in the initiation of male courtship and mating behaviors and territorial defense.

Status and longevity of the tuatara, Sphenodon guntheri, and Duvaucel's gecko, Hoplodactylus duvaucelii, on North Brother Island, New Zealand

Abstract A herpetological survey in January 1988 of North Brother Island, Cook Strait, New Zealand, found populations of the tuatara (Sphenodon guntheri) and three species of lizards (Hoplodactylus duvaucelii, Hoplodactylus maculatus, and Leiolopisma lineoocellatum). Tuatara on North Brother I. are significantly smaller than Sphenodon punctatus on nearby Stephens Island, and the estimated density of 134/ha in good habitat is lower than reported on Stephens I. The total adult population size of tuatara is estimated at <300 adults. Two of the captured tuatara had been toe-clipped, one in 1957 and one in 1959. One H. duvaucelii, toe-clipped in 1958, had not grown in the 29 years since first capture; it was probably at least 36 years old. This may represent the longest documented survivorship of a lizard in nature.

A comparison of three methods to investigate the diet of breeding double-crested cormorants (Phalacrocorax auritus) in the Beaver Archipelago, northern Lake Michigan

In order to understand the role of waterbirds in aquatic food webs it is important to first get an accurate depiction of their diet. Three methods of dietary assessment (pellets, regurgitate and stomach contents) are compared here for breeding double-crested cormorants (Phalacrocorax auritus) of the Beaver Archipelago, northern Lake Michigan. By numerical frequency (percent number), each method yielded different depictions of the diet. However, in terms of presence and absence (percent frequency) of possible prey types, stomach content data did agree with both pellets and regurgitate data. However, differences were noted between regurgitate and pellets. In terms of biomass measured (percent biomass) in regurgitate and stomachs, data gathered agreed. In essence, pellets underestimate the importance of alewife (Alosa pseudoharengus) and overestimate the importance of crayfish (Orconectes sp.) in the diet when compared to both regurgitate and stomach analysis. The non-lethal method of regurgitate collection and analysis appears most practical in assessing cormorant diet in this system. In combination with information on avian foraging ecology and prey populations, these data may be used to investigate the relationships among cormorants and their prey, and lead to a better understanding of Great Lake food web dynamics.

An analysis of prey-searching behavior in the western diamondback rattlesnake, Crotalus atrox

Prey-searching behavior in a seminatural arena was observed in adult western diamondback rattlesnakes (Crotalus atrox). Adult house mice were used as prey items and their position in the arena was controlled. Rattlesnakes receiving visual or thermal cues from the mice responded with a depressed tongue-flick rate (TFR) but following the preys disappearance they showed an elevated TFR. These snakes alternated to a chemosensory mode of prey detection in response to cues other than the prey strike sequence. Rattlesnakes may maintain a flexibility in their predatory behavior in nature greater than that which has been indicated in previous studies.

Body size plasticity and local variation of relative head and body size sexual dimorphism in garter snakes ( Thamnophis sirtalis )

For snakes, prey size and sex are two possible determinants of head and body size. In garter snakes Thamnophis sirtalis , females are generally longer and have greater body weights than males, and also have larger relative head sizes, which may facilitate foraging success. The selective pressures that account for sexual size dimorphism in garter snakes have not been unequivocally demonstrated. In this study, the body (length and mass) and head (head length, head width, jaw length, inter-ocular distance) sizes of garter snakes inhabiting two nearby but ecologically dissimilar sites with different types of available prey were compared. Overall, the adult female snakes were larger and had greater relative head sizes than males. Males from the two sites did not differ significantly in body or head sizes. However, the mean body length and mass of females from a site where vertebrates are included in the diet were greater than that of females feeding almost exclusively on earthworms. There were also significant site differences in all four head measurements in females, although the direction of the difference varied by site. Diet-induced morphological plasticity is well documented and was evident in this study, although the relative roles of genotype, ontogeny, and competing selective forces in the expression of such plasticity can only be ascertained through future experimental studies.

Male-male agonistic behaviour of the copperhead, Agkistrodon contortrix

Male-male agonistic behaviour of Agkistrodon contortrix was studied in the laboratory. Contests occurred during the periods of mating (Feb.-Apr. and Aug.-Oct.). Thirteen staged dyadic trials were run and larger males (mass/length ratio) were scored as winners in 11 of the 13 trials. Evidence for dominant-subordinate relationships in this species was obtained. Nine agonistic acts were coded from direct observations and from films. Seven of the acts were used in sequential analyses of intra- and inter-individual transitions. Numerous transitions were significant in both intra- and inter-individual analyses. Sequences greater than two events were detected in 3 of 4 males in the intra-individual analysis. Males that won contests exhibited certain acts significantly more frequently than males that lost, but there was no significant difference in the mean durations of like acts. Larger (mass/length ratio) males were always successful in defending a mate during courtship and in deposing smaller males from potential mates. Males introduced to pairs in copula exhibited few courtship or agonistic acts toward the pair, and in no case did introduced males depose smaller males.

Courtship, Male Combat and Dominance in the Western Diamondback Rattlesnake, Crotalus atrox

The courtship behavior of Crotalus atrox, always initiated by males, follows a tri- phasic schema: tactile-chase, tactile-alignment, and intromission and coitus. The third phase is longer than in other snakes (20-28 h). Female lateral tail-whipping and the slower tail-waving are apparently not indicative of her receptivity, although the latter is correlated with an increased male tongue-flick rate. Cloacal gaping by females apparently indicates female receptivity and occurs prior to successful intromission. Combat behavior between males is similar to other viperids. The vertical display is punctuated by periodic topping movements until a dominant individual is es- tablished. Evidence is presented that indicates subordinate males are refractory to courtship while dominant males actively court females following combat. In one instance a female assumed a

Sleep-site fidelity in two Puerto Rican lizards

Abstract Observations on the sleep behaviour of the brown anole, Anolis gundlachi , and the crested anole, Anolis cristatellus , were conducted at two ecologically distinct sites on the island of Puerto Rico. Lizards returned nightly to specific sleep locations, and for at least 5 consecutive nights, up to 98% returned to within 1 m of their initial nights sleep site. Additionally, 55% of the A. gundlachi and 21% of the A. cristatellus returned to within 10 cm of the original nights sleep site. Daytime activity ranges were significantly greater than nightly variation in sleep-site location. Additional data were collected on (1) sleep posture and body dimensional plane (2) sleep-site height, and (3) the type of vegetation used for sleep sites (e.g. broad leafed plants versus narrow leafed plants etc.). Lizards selected sleep sites in proportion to the plant type available in the respective habitat. Sleep-site height was positively correlated with lizard size, and the modal pattern of sleep posture included a snout direction toward the stem of the leaf and the head above or aligned with the horizontal body plane. The consistent selection of a site near the previous nights location suggests that lizards have reserved a specific area of their home range for sleep. A survey of nocturnal predators and observations of a predatory event on a lizard displaced from its sleep site suggest that immobilization on the foliage surface is an adaptive strategy for avoiding predation.

Courtship, mating and male combat in Tuatara, Sphenodon punctatus

The tuatara, Sphenodon punctatus, is the sole extant member of the reptilian order Rhynchocephalia. Although formerly more widely distributed, this species is presently restricted to about 30 islands off of the coast of New Zealand (Robb, 1977; Gans, 1983). Its relict status and structural similarity to Mesozoic rhynchocephalians have prompted numerous studies on its life history (Dawbin, 1962; Sharell, 1966), physiology (Stebbins, 1958; Werner and Whitaker, 1978) and morphology (Ostrom, 1962; Maderson, 1968; Robb, 1977; Gorniak et al., 1982). Sphenodon is unique among the Recent reptiles in its diapsid skull, associated with a mammal-like food-reduction system (Gorniak et al., 1982), and in its lack of a copulatory organ (Robb, 1977). However, literature dealing with behavior of the tuatara remains scanty (Northcutt and Heath, 1973; Ireland and Cans, 1977; Robb, 1977; Dawbin, 1982a; also other papers in Newman, 1982). The only account of its social behavior is a brief, recent report (Dawbin, 1982b); indeed it is uncertain whether it has ever been bred in captivity. The present report documents successful courtship, mating and male combat with dominance in Sphenodon punctatus. Two adult males and one adult female were