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We captured 1078 Blunt-Nosed Leopard Lizards (Gambelia sila) 2396 times between 1989 and 1994 on the Elkhorn Plain, San Luis Obispo County, California. Based on size at first capture, we caught 119 adult (≥90 mm snout–vent length [SVL]) and 430 hatchling/juvenile (<90 mm SVL) males, and 139 adult and 390 hatchling/juvenile females. Sex ratio of males to females was 1.04 (549 males/529 females). Adult G. sila generally became active in April, and activity remained relatively high into July. Hatchlings were first noted in either July or August and generally could be found until early November, except in 1990 when no hatchlings were found at any time. Mean number of adults and hatchlings found active each day differed significantly across years, but as many as 32 adults and 42 hatchlings were seen on a plot during a census. Estimates of population abundance on a plot also varied yearly from 20–164 adults and 0–273 hatchling/juveniles and seemed to be affected either by too little or too much rain. Differences in daily activity varied and were moderately well explained by environmental factors. We estimated survivorship of lizards and found 29.0% of hatchlings from 1992 survived to 1993, and 14.6% of hatchlings from 1993 survived to 1994. The oldest G. sila found was a female estimated to be 4 years, 10 months when last caught, although most adults were not seen after 2 yr. Growth of individuals varied by year: highest growth rates were for lizards that hatched in 1991 and 1992, and lowest growth occurred in lizards that hatched in 1989. We found adult leopard lizards with eggs in all years but 1990. Females generally were gravid by late April or early May, and some females were found with eggs in early July. Female size at first reproduction was about 90 mm SVL, clutch size ranged from 1–6 eggs, and overall mean clutch size regardless of year or clutch order was 3.4 eggs. Many females produced multiple clutches in a year, and we found up to four clutches by a single female.
The metabolic cost of growth in reptiles has been difficult to detect in many previous studies. We designed experiments to detect and quantify added costs of growth by comparing daily energy expenditures of young, growing Desert Tortoises (Gopherus agassizii) with similar-sized, but adult, Parrot-Beaked Tortoises (Homopus areolatus). We measured both field (outdoors, semicaptive) and standard (20°, 25°, and 30°C) metabolic rates of each species in groups matched for body size to minimize body size effects. Mass-adjusted field metabolic rates of the juvenile tortoises were not higher but were, in fact, significantly lower (by 29%) than in adult tortoises. Standard metabolic rates did not differ between species at any temperature, thus failing to support the hypothesized higher energetic costs of growth in the juvenile tortoises. These results, although contrary to expectations, support a growing body of evidence, suggesting that the cost of growth in juvenile reptiles does not increase their field energy expenditures above those expected for adults.
We studied the movement ecology of Coastal Rosy Boas (Lichanura roseofusca) by radio tracking 17 animals across four sites for up to four years. The typical movement pattern included many short distance moves with rare long distance movements. These skewed distributions made the mean a poor descriptor of movement and this is likely a common issue in other studies. Sexes had similar movement patterns and moved less frequently and shorter distances per day during cooler seasons. Rare long-distance movements occurred primarily in the spring. Propensity to move and mean distance moved per day varied across sites. Home-range size increased with additional fixes even after four years and had a seasonal pattern, increasing during warmer seasons and remaining stable or shrinking during cooler seasons. Despite using novel habitat in sequential years, nearly all individuals used the same general area over longer periods of time. Finally, individuals of both sexes had high levels of spatial overlap. The results indicate for L. roseofusca (1) Individual variability in movement is more the rule than the exception; (2) Common seasonal patterns in movement and space use do exist; (3) Home-range sizes vary through time yet remain in the same general location; and (4) A lack of territoriality and considerable overlap in space use exist.
We studied the ecology of Anolis capito in the rain forest of southeastern Nicaragua during late dry season of 1993. These cryptic anoles live low on trunks in shaded rain forest and are active throughout the day but appear to spend most of their time in shade. Body temperatures averaged 28.8 ± 0.5°C, which is 1.3°C higher than substrate temperatures and 1.7°C higher than air temperatures. Females were larger and reach sexual maturity at a larger SVL than males. Females in late dry season often contain two oviductal eggs that differed in shell condition indicating that they were not ovulated simultaneously. Females had evidence of as many as four clutches (two oviductal eggs and two different-sized enlarged vitellogenic follicles) suggesting rapid clutch production. The diet consists of a variety of invertebrates, with grasshoppers, homopterans, insect larvae, and roaches dominating volumetrically. On average, these lizards contained 1.6 ± 0.1 prey items. Prey size varied with lizard size, but no sexual differences existed. These lizards appear to capture a small number of large prey. Many ecological and life-history traits of A. capito are similar to those of other Anolis lizards suggesting an historical origin.
We describe a new species of small Hyla from sub-Andean forest of the Departamento La Paz, Bolivia. The new species is mainly characterized by smooth dorsal skin with few minute scattered tubercles, presence of a tympanic annulus, lack of tarsal folds, a brown dorsum with irregular longitudinal dark brown stripes, a broad dark brown lateral stripe extending to loreal region, and advertisement call. The phylogenetic relationships of the new species remain unknown, but given the morphological similarities of adults, we tentatively place it in the Hyla microcephala group.
From June to October 1994, we used drift fences to sample migrating red efts (Notophthalmus viridescens) in terrestrial habitats near a permanent oligotrophic lake in the Mastigouche Reserve, Quebec. Fences were placed up to 200 m from the shore and yielded a total of 1443 efts. Age was estimated by skeletochronology. More than 1200 efts (modal SVL 20 mm, age 0 , 1, and 2 yr) were caught while migrating toward the forest; most (83%) were caught in fences < 15 m from shore between 7 and 30 September. Efts migrating toward the lake (N = 226) were more frequent in June (39.4%) and August (37.6%). Those from three fences nearest shore (< 87 m) were maturing efts (modal SVL 32 mm; age 3–5 yr). Age and SVL were highly correlated in the eft population. Fence distance from shore and the interaction of this factor with fence side accounted for a significant portion of eft body size variation. Results suggest that maturing efts may need more than one season to migrate from terrestrial home range to spawning lake. Reduced migration during midsummer may be the result of adverse conditions on the forest floor. We estimated the median number of breeding seasons (2.5) in the study population by comparing age structure of the maturing eft population with that of adults in the nearby lake.
Little is known about the biology of the Order Gymnophiona of the Class Amphibia. The organs of their immune system have been described only in adult specimens. We describe the development of the immune system in Typhlonectes compressicauda embryos from stages 24–33. At stage 24, just prior to hatching, the thymus and spleen develop from the fourth, fifth, and sixth visceral pouches. The spleen develops from a bud of cells in the mesentery, situated between the stomach and the mesonephros, and the thymus comprises a medulla and cortex. By stage 28, between hatching and metamorphosis, organelles resembling Hassal's corpuscles develop in the thymus, and are retained to the end of development and throughout adult life. At stage 30, just before metamorphosis, the spleen becomes organized into the red and white pulp. Upon disappearance of blood islets, lymphocytes appear to circulate between the spleen and thymus through the blood vessels. The kidney is never haematopoietic in either embryos or adults. The liver, which has been described as equivalent to the bone marrow, develops earlier than the thymus or the spleen, and becomes granulocytopoietic and monocytopoietic at stage 30. The development of the immune organs of Typhlonectes compressicauda is distinct from that of Anura and Urodela, although apparently closer to the Anura, because the spleen develops distinctly later than the thymus. The presence of a white and a red pulp in the spleen and of a medulla and a cortex in the thymus in early stages of differentiation indicate a highly evolved immune system in this species.
Desert Tortoise surveys and management in the Sonoran Desert typically exclude intermountain valleys, where tortoises are generally thought to be absent. Furthermore, few regional-level surveys have been conducted because of difficulties in sampling in the complex landscape of Sonoran Desert upland habitat. We used distance-sampling to document macrohabitat use and regional density of Desert Tortoises across the 76,800-ha Ironwood Forest National Monument in Arizona. We observed 42 tortoises on transects, and distance sampling produced an estimate of 17,997 tortoises ≥ 150 mm carapace length (coefficient of variation = 41.5%) on the monument. Stratification by habitat type (steep topography with boulders, incised washes, or neither of these components) improved precision slightly (37.2%). Detection probability contributed least to density variance, compared to encounter rate and tortoise detectability on the transect line, indicating that assumptions of the technique were met during sampling. We found tortoises or their sign on 92% of transects in boulder habitat, on 71% that included incised washes, and on 25% in habitat with neither of these features (up to 1.7 km away from the nearest slope). Our results indicate that Desert Tortoises in the Sonoran Desert occur at low density, but are not absent, from intermountain valleys, and the maintenance of these valleys for tortoise movement between local populations may be important for long-term population viability. With this in mind, concentrating survey effort in areas with steep topography and boulders will increase tortoise encounter rate, result in better precision of regional density and trend estimates, and may also reduce survey effort.
Herein is described a new species of hylid frog from low elevations in the Atlantic Rain Forest, along the southern coast of the State of Rio de Janeiro and northern coast of the State of São Paulo, Brazil. The larvae and the site of reproduction are also described. It is a medium-sized species of the genus Hyla and is included in the Hyla albofrenata group by virtue of having lime green color of the body, orange-red iris without bicolored ring, voices sounding like drops of water falling into an empty bottle, and inhabiting mountain stream forests. The new species is very similar to Hyla albofrenata, from which it can be separated by its smaller size, larger calcar, length of the femur and tibia larger than the snout–vent length (SVL), by the clear coloration of the iris, morphology and coloration of the tadpole, and geographic distribution. The new species is also similar to Hyla ehrhardti from which it can be separated by having longer legs, presence of the calcar developed, presence of a supra-anal crest, color of the iris and northern distribution. It can be easily distinguished from Hyla arildae, Hyla musica, and Hyla weygoldti by possessing a curved and short supratympanic fold, by having a well-developed calcar and by its smaller SVL.
Few studies have focused on the thermal biology of tropical or nocturnal snakes. We recorded preferred body temperatures (Tb) of seven Brown Treesnakes (Boiga irregularis) in the laboratory and compared these to operative temperatures obtained with copper models and Tbs obtained by radiotelemetry from 11 free-ranging snakes on Guam. Operative temperatures on Guam did not vary across refuge types, unless the site received direct solar radiation. In a thermal gradient and on Guam, Brown Treesnakes thermoregulated around two distinct temperature ranges (21.3–24.9°C; 28.1–31.3°C). In the gradient, brown treesnakes exhibited elevated Tb into the higher range only in the evening. On Guam, snakes achieved Tbs in the high range only when direct solar radiation was available during the afternoon, a period when snakes were inactive. Higher mean Tbs on sunny days corresponded with observations of basking behavior.
Gastrotheca piperata is described from Andean cloud forest in Bolivia. The new species is similar to Gastrotheca marsupiata but differs in coloration and advertisement call. Upon release from the maternal brood pouch, the tadpoles are in Gosner developmental stages 36 or 37, in contrast to the less developed (stages 30 or 31) tadpoles released by G. marsupiata, a species that inhabits higher and drier nonforested areas.
Variation in the frequency and intensity of territorial displays occurs within individuals and populations. Such variation should be correlated with variation in potential costs and benefits of the behaviors. We examined temporal variation in vocal displays of male Strawberry Poison-Dart Frogs (Dendrobates pumilio) and investigated correlations with environmental and social factors. Forty-three adult male D. pumilio were studied for six-day sessions. Five vocalization characteristics (total time calling, mean call group duration, number of call groups, call note rate, and proportion of days calling) were quantified. Each of these calling variables was greater between 0630 and 0830 h than at other times through the day. Perch use (occupation of elevated display sites) was greater between 0530 and 0930 h than at other times of day, a period that extends one hour before and after the peak in calling activity. There was no difference between vocalization patterns on or off perches for any of the calling characteristics, but males called during a larger proportion of observations when on perches than when off perches. Snout–vent length was not correlated with any of the calling characteristics. Rainfall during the previous 24-h period was positively correlated with all calling characteristics and perch use.
A new species of Bolitoglossa of the Bolitoglossa dunni group is described from an isolated mountaintop in western Honduras. Color and pattern are the most distinctive features of the new species. Less than 1 ha of forest remains on the isolated mountain peak at the type locality, making the new species the most endangered salamander species known in Honduras.
A new species of Dibamus from Pulau Nias, located off the southwest coast of Sumatra, Indonesia, is described based on a single specimen previously referred to as Dibamus novaeguineae and Dibamus alfredi. The new species differs from all congeners in the following combination of characters: snout–vent length (SVL) 123.1 mm; body relatively slender, 3.0% SVL, postoculars two; midbody scale rows 22; ventrals 178; subcaudals 37; frontonasal entire; incomplete rostral suture; labial and nasal sutures complete; preanal pores absent; nuchal collar and body band absent; presacral vertebrae 126; postsacral vertebrae 23; and a relatively short tail (12.75% SVL). The new species from Nias further adds to the endemicity of the vertebrate fauna of these islands and calls for more intensive inventories of the isolated islands to the southwest of Sumatra.
The Florida Worm Lizard (Rhineura floridana) is the only extant representative of the suborder Amphisbaenia occurring in the United States and the only living representative of the Rhineuridae. We updated the known distribution of this species from 510 records with known localities. We further examined geographic genetic structure within this species using 1360 bp of mitochondrial DNA sequence data from 18 samples of R. floridana. Our results suggest an ancient divergence between populations in the north-central Florida peninsula from populations in the south-central peninsula. High genetic distances are observed within south-central populations, whereas genetic structure within northern populations is less discrete and characterized by much shallower divergences. Our findings suggest that south-central populations may be candidates for taxonomic recognition (or recognition as distinct management units) if additional genetic and morphological data support our results.
Animals that are susceptible to predation sometimes engage in crypsis to conceal themselves from predators. Such behavior often consists of background color matching via substrate choice. Intraspecific color variation may result in differential substrate preference among color morphs. I investigated this idea using juvenile Northern Leopard Frogs (Rana pipiens), which exhibit either green or brown background color. Both color morphs spent more time on dark, concealing substrates than light, revealing ones and hopped less frequently when located on dark, concealing substrates. Frogs did not respond differently to green and brown fabric substrates, and they preferred brown natural substrates over green ones. Because green and brown frogs did not behave differently in any experiment, this study suggests that juvenile Northern Leopard Frogs exhibit a generalized cryptic behavior pattern independent of background body color.
Using mark-recapture methodologies, we estimated the number of adult Wood Turtles (Glyptemys insculpta) inhabiting an agricultural site in southern Québec, Canada. Two estimates, made seven years apart, revealed that the adult population declined by 50% during this period. Different hypotheses likely to explain this situation are discussed, and, although none seems more likely than the others, our data suggest that this decline resulted from increased adult mortality and poor recruitment.
A critical component of amphibian life history relates to understanding the role of embryonic mortality in regulating recruitment and, therefore, population size. We examined the predictions that small populations have higher embryonic mortality and reduced clutch sizes in the Western Australian frog, Heleioporus albopunctatus. Embryonic mortality was low, averaging 3% per clutch. Four of 55 clutches examined (∼ 7%) were infested by dipteran larvae. We found no significant relationship between clutch size or embryonic mortality and population size.
The tadpole of Bufo taitanus is described from material recently collected at the type locality. Tadpoles of B. taitanus possess a crownlike structure on top of the head. Observations suggest that the crown likely acts as an accessory respiratory organ. Development in B. taitanus is rapid with metamorphosis completed after just 13 days. Based on its similarity to tadpoles of Stephopaedes anotis and Mertensophryne micranotis, a close phylogenetic relationship between these three taxa is proposed.
Morphological studies have proven inconsistent in establishing the phylogenetic placement and taxonomic assignment of Elgaria parva. Originally classified as Gerrhonotus parvus Knight and Scudday, this taxon was reassigned to Elgaria based on morphology. To investigate its phylogenetic affinities, we generated mitochondrial DNA sequence data and conducted phylogenetic analyses together with published sequences for a broad taxonomic sampling of anguid lizards. We conducted parsimony, likelihood, and Bayesian analyses of the data. Our results indicate that E. parva forms a clade with other Gerrhonotus rather than Elgaria. Furthermore, Elgaria and Gerrhonotus are not sister taxa. Based on our new molecular evidence, we suggest that E. parva be classified as Gerrhonotus parvus as originally described.
The tadpole of Atelopus franciscus from French Guyana is described. It resembles other larvae of the genus, especially those displaying a color pattern of symmetrical light marks. Among them, A. franciscus is most similar to those tadpoles having submarginal papillae (i.e., Atelopus balios, Atelopus flavescens, Atelopus nanay, Atelopus tricolor). The tadpole of A. franciscus shares several similarities with the larva of A. flavescens from French Guyana but differs from it by being smaller in size and in certain measurement. The phylogenetic relevance of tadpole characters in Atelopus is discussed, including body proportions, submarginal papillae, length of upper beak.
We present the first data collected in situ on clutch and egg size for the Mountain Chameleon (Chamaeleo montium). In addition, we examine within and among clutch variation and its relationship with female body size. We caught wild females from January to June 2003 and held them until egg deposition. We collected morphometric data on females and clutches immediately post-egg deposition. Of the 49 reproductive females, the smallest measured 65 mm snout–vent length (SVL), the largest 90 mm SVL (mean = 75.4 mm). Clutch size varied from 3–12 (mean = 6.5) and mean relative clutch mass = 40%. Female post partum mass was positively correlated with clutch mass and egg number. Female mass (in grams) was not significantly related to relative clutch mass but was weakly correlated with egg volume. There was consistent size uniformity of eggs within and among clutches.
The large mass of a turtle's shell presumably reflects a trade-off between its protective function and its imposition on the energy cost of locomotion. To examine this, we developed a relationship between body mass and shell linear dimensions in Ornate Box Turtles, Terrapene ornata, from north-central Nebraska. Using the relationship between body mass and plastron width, we estimated body mass of box turtles killed on roadways, and we cleaned and weighed their shells. Shell mass may be a linear function of body mass in these turtles, amounting to approximately a constant 30% of their body mass. Alternatively, shell mass may be an exponential function of body mass, increasing with body mass to approximately the 1.2 power; in this case, shell mass increases more quickly than body mass in these animals. We are unable to distinguish between these models based on our analysis, but the increase in shell mass with body mass is more consistent with the shell serving a supportive, rather than a protective, function. Plastron thickness increases with body mass to approximately the 0.47 power in our animals, which is also higher than expected if the shell serves solely a protective function.
Seasonal changes in the frequencies of green and brown Pacific Treefrogs (Pseudacris regilla) were recorded at a site in southern California. Changes in the proportions of green and brown individuals in the population appear to track seasonal changes in the availability of green and brown background substrates. We show that the change in the frequencies of green and brown frogs is not just caused by a change in the proportion of frogs with fixed green and brown body colors but also by the ability of a newly described morph to change color. The findings add further support to the hypothesis that maintenance of this complex color polymorphism likely involves a response to seasonal change in the abundance of green foliage, perhaps driven by differential predation on green and brown frogs that are either plastic or fixed in color.
Ectotherms from high latitudes experience a reduction in the length of their seasonal activity period, which may have consequences for life-history strategies. I studied winter survivorship and spring reproduction of a population of Common Side-Blotched Lizards, Uta stansburiana, in eastern Oregon. Results suggest that winter survivorship is much higher than estimates from other populations of this species; up to two-thirds of lizards survived winter. Data also suggest that one-third to one-half of females failed to reproduce in 2004. Larger females were significantly more likely to reproduce successfully. Over the course of the breeding season I found no animals that attempted to produce a second clutch despite a relatively early breeding season. Near the northern limits of their range, Uta may shift from maturing in less than one year and producing multiple clutches to requiring multiple years to mature and producing only a single clutch of eggs.
Texas Horned Lizards, Phrynosoma cornutum, were tracked using fluorescent powder to determine exact daily movements. Daily linear movements and daily space use were compared between adult males and females. Lizards that traveled the greatest linear distances also covered the largest areas. In Oklahoma, adults emerge from hibernation in late April and early May and mate soon afterward. Males traveled significantly greater distances (and covered significantly larger areas in a day) than females in May but not after May. We propose that males move more and cover more area than females early in the mating season to intercept receptive females.
Extension and retraction of the throat fan or dewlap is one of the most conspicuous aspects of display behavior of male Anolis lizards. Although dewlap display plays a role in species recognition, signal detection, and even predator defense, the importance of the male dewlap in male mating success in nature has not been established. The present study tested whether the display of the dewlap by males of Anolis sagrei affected the mating success of free-ranging males. We compared the number of males that copulated and their copulation rates between two groups: experimental males that were surgically prevented from extending their dewlaps and control males that were sham treated. Experimental and control groups did not differ significantly in the proportion of males that copulated or in copulation rate. These results do not support the hypothesis that the male dewlap affects male mating success in A. sagrei. If the male dewlap does have an effect on male mating success in this species, then the effect was too subtle to be detected by our study.