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We compared sexual dimorphism of body and head traits from adult lizards of populations of Gallotia caesaris living in ecologically different habitats of El Hierro and La Gomera. Males had larger body sizes than females, and sexual size and shape dimorphisms were greater in a population from La Gomera than in three populations from El Hierro. Multivariate analyses of variance, using linear and shape-adjusted traits, showed that the populations differed significantly in body and head traits, with pileus (head) width, snout–vent length (SVL), and body mass the main traits contributing to the differences. Males had larger SVL, heads, and limbs than females in all populations, but SVL relative to a shape index (calculated as the geometric mean of several body parameters) was larger in females than in males. Moreover, shape-adjusted hind-limb lengths were significantly shorter in lizards from the more densely vegetated habitats than in those from the less vegetated ones. The magnitude of sexual dimorphism was larger for relative limb length and head depth in the populations with less vegetation than in those with more vegetation. Our data suggest that morphological differences between populations reflect local adaptation to habitat structure.
Identification of postcranial reptile pathology unrelated to trauma on the basis of macroscopic (visual) examination is feasible and effective, as previously documented in mammals, birds, and dinosaurs. Such bone disease is rare in most wild-caught lizards, with the exception of Varanids, and is also more common in crocodilians. This provides a basis for evaluation of the fossil record, suggesting that the most productive epidemiologic analyses would be concentrated in the families, Crocodylidae and Varanidae. A specific form of inflammatory arthritis and vertebral pathology, spondyloarthropathy, is clearly established as the major non-traumatic osseous pathology in lizards (although quite rare in all but varanids) and crocodilians. Calcium pyrophosphate deposition disease seems to represent a secondary phenomenon, apparently limited in distribution to individuals with spondyloarthropathy. Only 9% of individual reptiles with osseous pathology examined lacked a clear diagnosis substantiated by validated observations in human and other animals.
We manipulated hatchling cohort density in the Striped Plateau Lizard (Sceloporus virgatus) to investigate density dependence within the juvenile stage of the life cycle. Large-scale field enclosures (800 m2) constructed of drift fencing with pitfall traps for monitoring dispersal were established in the preferred habitat of S. virgatus and treated with high (60) and low (20) densities of hatchlings. Enclosures were monitored over a 10-month period from August 1997 to May 1998 and replicated from August 1998 to May 1999. We found that per capita survivorship, individual growth rates, yearling body lengths, and the proportion of yearlings attaining reproductive maturity were negatively affected by cohort density. Conversely, there was a positive relationship between juvenile dispersal rates and cohort density. These results indicate that density has a significant influence during the juvenile stage of the life cycle and potentially plays a key role in the life-history strategy and population dynamics of S. virgatus.
A new species of Southeast Asian Cnemaspis is described from the rocky foothills in the northwestern section of the Cardamom Mountains, Cambodia on the basis of a light colored chevron marking between the shoulders, tail tip white with black speckling, and several scale characteristics. This population's overall morphological similarity to southern Vietnam species demonstrates that Cambodia is an important biogeographical link between disjunct components of the Indochinese herpetofauna. This species represents the second known species of Cnemaspis from Cambodia and the ninth endemic species to be described from the Cardamom Mountains, highlighting the need for additional fieldwork in this area of Indochina.
We describe a new species of Luperosaurus from Mt. Mantalingajan, southern Palawan Island, Philippines. The new species is distinguished from all other species of Luperosaurus by the combination of its large body size (81.3 mm for the single male specimen), near complete absence of interdigital webbing, absence of cutaneous expansions on limbs except for a minute flap on the posterior margins of the hind limbs, the presence of differentiated, moderately enlarged chin shields, 40 precloacofemoral pore-bearing scales, the limitation of scattered flattened dorsal tubercles to only the posterior portions of the torso, absence of spinose or recurved ornamental tubercles on the head and nuchal region, and convex to posteriorly raised tubercles clustered at the posterior margins of caudal tail annuli. Because the new species shares features with species in both species of Luperosaurus and Gekko, we compare the new species to (and distinguish it from) both genera. The new species is distinguished from all Southeast Asian Gekko by the combination of its smaller body size, relatively short, stout limbs, presence of only moderately enlarged, slightly imbricate ventral body scales, differentiated postmentals not highly elongate, dorsal body tubercles limited to posterior trunk and not arranged in rows, absence of enlarged, spinose tubercles on the limbs and tail, and tail encircled by small scales (enlarged subcaudals absent). The new species further emphasizes the biogeographic distinctiveness (from Sundaland fauna) and level of vertebrate endemism of Palawan Island and underscores the degree to which the biodiversity of the Philippines is not fully understood.
We describe a new species of scincid lizard of the genus Brachymeles from the Luzon Faunal Region of the northern Philippines. We discovered the new species in the Camarines Norte Province of the Bicol Peninsula (Luzon Island) and Catanduanes Island. Until recently, the new species had been mistaken as Brachymeles talinis, a distantly allopatric yet morphologically similar, large-bodied congener from the central Philippines. The new species is the second-largest known species of Brachymeles and differs from its congeners by numerous external morphological features. It is the eighth known Brachymeles from the Luzon Faunal Region and the sixth pentadactyl species in the genus.
Amphibian populations, particularly anurans, are declining worldwide, and programs that use calling surveys have been established to monitor anuran populations. Models that describe the environment's influence on calling may be useful to increase detection allowing optimization of surveys. Using an automated recording system, we evaluated the calling activity of Pseudacris crucifer, Pseudacris feriarum, and Rana sphenocephala at an ephemeral wetland in the Piedmont of North Carolina. We used stepwise logistic regression to model environmental variables that significantly affected calling activity. Models revealed that, for P. crucifer, water and air temperature positively influenced calling, whereas day of year, barometric pressure, and light intensity negatively influenced calling. For P. feriarum, air temperature positively influenced calling, and day of year, relative humidity, wind speed, barometric pressure, and light intensity negatively influenced calling. Finally, air temperature positively influenced calling for R. sphenocephala, whereas water temperature, relative humidity, wind speed, and light intensity negatively influenced its calling. Using these results, we developed comprehensive as well as simpler, “user-friendly” models, predicting the best conditions under which to conduct anuran calling surveys. The user-friendly models were tested using previously collected data from calling surveys performed in the same region of North Carolina and found to accurately predict calling activity approximately 70% of the time. We discuss how weather forecast data may be applied to these models to determine the best times to conduct calling surveys and how models such as those developed in this study can be used to interpret data previously collected during amphibian calling surveys.
Pesticides can be important conservation tool, but they could have unintended impacts on amphibians. The commercial glyphosate-based herbicide Accord is approved for use in wetlands and ponds because it is designed to be safer to aquatic wildlife than other herbicide formulations (e.g., Roundup or Atrazine); however, field experiments are needed to determine whether there are direct, indirect, or sublethal effects on amphibians or effects on wetland community structure. We conducted a replicated field experiment in constructed ponds to test for both the effects of Accord and predator (Tiger Salamanders, Ambystoma tigrinum) density on amphibians and aquatic invertebrates. Herbicide treatment had significant density-dependent effects on Tiger Salamander growth, development, and survival. The survival of anurans and aquatic invertebrates was also affected by herbicide treatment and predator density. At certain Tiger Salamander densities, the community structure was altered such that some species became more common with herbicide treatment, whereas others became less common. Behavior assays of salamander larvae suggest that herbicide treatment alters predator-prey relationships in the experimental pond communities. These results suggest that competition and predation may mediate indirect effects of this herbicide on the aquatic fauna. We conclude that exposure to Accord poses less of a risk to the ecology of amphibians than do other formulations of glyphosate-based herbicides.
Animals in nature use synergistic behavioral and physiological responses to cope with variation in resource availability. We used a combination of traditional tools (i.e., radiotelemetry, body-condition measurements, plasma osmometry, and direct observation) and contemporary techniques (i.e., implanted temperature loggers and portable ultrasonography) to identify seasonal patterns of body condition, hydration state, and surface activity of 16 free-living Gila Monsters during two active seasons. Despite seasonal drought each year, Gila Monster snout–vent length increased during the study; yet body mass, tail volume, and hydration state decreased. Generally, surface activity was associated with rainy periods, and males were significantly more active than females but only during the reproductive season. Our results indicate that Gila Monsters combine flexible behavioral patterns (i.e., the timing and duration of surface activity), resource storage and economical use, and tolerance of substantial physiological disturbance to endure seasonal resource limitations at a site in the Arizona-Upland subdivision of the Sonoran Desert.
The Giant Gartersnake (Thamnophis gigas) is restricted to wetlands of the Central Valley of California. Because of wetland loss in this region, the Giant Gartersnake is both federally and state listed as threatened. We conducted mark–recapture studies of four populations of the Giant Gartersnake in the Sacramento Valley (northern Central Valley), California, to obtain baseline data on abundance and density to assist in recovery planning for this species. We sampled habitats that ranged from natural, unmanaged marsh to constructed managed marshes and habitats associated with rice agriculture. Giant Gartersnake density in a natural wetland (1.90 individuals/ha) was an order of magnitude greater than in a managed wetland subject to active season drying (0.17 individuals/ha). Sex ratios at all sites were not different from 1 ∶ 1, and females were longer and heavier than males. Females had greater body condition than males, and individuals at the least disturbed sites had significantly greater body condition than individuals at the managed wetland. The few remaining natural wetlands in the Central Valley are important, productive habitat for the Giant Gartersnake, and should be conserved and protected. Wetlands constructed and restored for the Giant Gartersnake should be modeled after the permanent, shallow wetlands representative of historic Giant Gartersnake habitat.
Research on landscape connectivity for amphibians that use isolated wetlands has focused on terrestrial and semiterrestrial species. Although aquatic species are commonly encountered in isolated wetlands, their dispersal capability and mode of dispersal has yet to be conclusively determined. For these salamander species, temporary waterways formed during heavy rains may provide transient dispersal opportunities among otherwise terrestrially isolated wetland patches and large contiguous sources (e.g., river swamps, lake systems). We assessed the vagility of two aquatic salamanders, the Greater Siren (Siren lacertina) and Two-Toed Amphiuma (Amphiuma means), under three simulated environmental conditions: terrestrial (damp but no standing water); shallow standing water (1 cm of water); and complete submergence (approximately 5 cm of water). Salamanders were placed inside a modified Living Stream container and stimulated into moving through each treatment. Both species demonstrated a trend toward exhaustion for all treatments and failed to move more than 8 m in the terrestrial or shallow water treatments. As expected, animals in the fully submerged treatment were able to disperse the farthest. Physical characteristics of salamanders did not affect vagility. To disperse, these species likely rely on the formation of aquatic corridors during flooding events. Therefore, successful dispersal among isolated wetlands depends on the ability of the surrounding landscape either to be periodically inundated with water or to form temporary waterways during heavy rains. Human activities that alter flooding events and watershed connectivity, such as flood control regimes and roads, may have important implications for wetland connectivity and, thus, metapopulation viability of aquatic salamanders.
Landscape composition and configuration affect ecological processes at the population and community levels, but few studies have demonstrated the effects of landscape pattern on individuals. Because heterogeneity influences abundance and distribution of critical resources, it is hypothesized that it indirectly affects home range size of individuals. To examine the spatial ecology of the declining Eastern Diamond-backed Rattlesnake (Crotalus adamanteus; EDB), we conducted a two-year study in southwestern Georgia. We obtained home range estimates via radio-telemetry, employed Euclidean distance analysis to examine habitat associations at two spatial scales, and used the software program FRAGSTATS to analyze landscape heterogeneity and examine its effect on home range size. Although no significant habitat associations were detected, there were trends for a positive association with pine habitat at the landscape scale and a negative association with agriculture within the home range. Home range size was negatively correlated with several landscape metrics representing heterogeneity in patch configuration, such that individuals in heterogeneous landscapes had small home ranges. This relationship was strongest at three spatial scales: the first was similar to mean home range size of EDBs; and the others were three and four times as large as the largest home range recorded. Together, these results suggest that management regimes to enhance population densities of EDBs emphasize the preservation of pine uplands, while maintaining a mosaic of other habitat types, and limit the conversion of forest to agriculture. Also, our results underscore the importance of using robust analytical tools and multiscale approaches in studies of spatial ecology.
We do not know whether the availability of food plants is the primary factor enabling Angulate Tortoises to inhabit a wide variety of habitats along the southern and western coasts of South Africa. Here we used focal observations to study the diet of Angulate Tortoises over four seasons at two distinct sites in the southwestern Cape, the West Coast National Park (WCNP), and Dassen Island (DI). Seasonal fluctuations in temperature, rainfall, and food plant availability influenced the activity pattern and feeding activity of Angulate Tortoises. Tortoises were more active during the wet season, winter and spring, than during the dry season, summer and autumn. Diet differed between sites and among seasons. WCNP tortoises had a diverse diet of grasses, shrubs, herbs, and succulents, whereas DI tortoises ate mostly herbaceous plants. DI tortoises had few dietary choices available compared to choices available to WCNP tortoises. At both sites, herbs and seedlings were important diet components during the wet season. The dry season diet consisted largely of dry plant material. Angulate Tortoises on DI supplemented their intake of dry plant material with rabbit feces, which comprised more than 27% of the diet in summer and autumn. The opportunistic feeding behavior of Angulate Tortoises helps explain their distribution among a wide variety of habitats. Their persistence in disturbed areas is probably determined by the abundance of easily digestible, herbaceous plants during the wet season and the tortoises' low activity and low metabolic demands during unfavorable periods.
Exotic plants can make up a major component of the diet for some Desert Tortoises (Gopherus agassizii) in the Mojave Desert. If introduced plants differ nutritionally from native plants, they may influence the growth and welfare of young tortoises. Minerals available from a native grass (Achnatherum hymenoides), an introduced grass (Schismus barbatus), a native forb (Malacothrix glabrata), and an introduced forb (Erodium cicutarium) were measured for juvenile Desert Tortoises voluntarily eating single-species diets. We offered tortoises weighed amounts of chopped foods daily for ∼130 days (dry grasses; summer diet) or ∼90 days (green forbs; spring diet). Orts and feces were collected daily and dried to constant mass, and calcium, phosphorus, and magnesium contents of food and feces were measured and used to calculate nutrient digestibilities. Overall, tortoises gained more minerals from forbs than from grasses. Tortoises lost small but significant amounts of phosphorus when eating grasses, which may have contributed to observed decreases in tortoise mass and shell volume on grass diets. There were few nutritional differences between native and exotic forbs or between native and exotic grasses. Comparisons of nutrient availability to estimated requirements for growth by juveniles and for egg production by adult females suggest that phosphorus is more limiting than calcium or magnesium and that calcium may pose a significant osmotic challenge for excretion in this desert species. Management practices that promote availability of forbs could increase growth rates and shell ossification, which would enhance predator resistance of juvenile tortoises.
Little is known about many aspects of the ecology of the Desert Nightsnake (Hypsiglena chlorophaea). I studied the ecology of H. chlorophaea from 121 specimens collected May to October 2004 and 2005 in central Washington State. In this region, males ranged in size from 184–382 mm SVL (283.7 ± 5.8 mm, N = 49), whereas females were 158–532 mm SVL (335.5 ± 69.4 mm, N = 58). Body mass of males was 2.6–22.1 g (10.2 ± 5.04 mm) and females 2.3–53.9 g (15.1 ± 9.49 mm). In Washington, H. chlorophaea feeds on a wide variety of prey such as scincid and anguid lizards, thamnophiine snakes, anurans, and the eggs of other squamate reptiles. In addition, I report the first mammalian prey item taken by H. chlorophaea. The reproductive ecology differs little from other parts of the range of H. chlorophaea. Males (N = 22) with enlarged testes were found from mid-May through late August. Females (N = 17) with enlarged follicles and ova were found from May through June, with recent hatchlings collected during mid-August. Based upon these data, in Washington, H. chlorophaea has a more varied diet compared to southern populations but shows a similar preference for lizards. With regard to reproductive patterns, Washington populations of H. chlorophaea differ very little from other populations.
Karyotypes of Leposoma show a clear differentiation between species of the scincoides group from Brazilian Atlantic Forest (2n = 52, without distinctive size groups of chromosomes) and those of the parietale group from the Amazon (2n = 44, with 20M 24m). In a previous study, we found that in the parietale group the parthenoform Leposoma percarinatum from the state of Mato Grosso, Brazil, exhibited a triploid karyotype (3n = 66) with 30 macrochromosomes and 36 microchromosomes. It was suggested that this karyotype arose after hybridization between a bisexual species with N = 22 (10M 12m) and a hypothetical unisexual cryptic diploid form of the L. percarinatum complex. Herein, we describe the karyotypes for two species of the parietale group occurring sympatrically in the Arquipélago das Anavilhanas, lower Rio Negro, in Amazonian Brazil. The first represents a distinctive diploid parthenogenetic clone of the L. percarinatum complex, and the other is the recently described Leposoma ferreirai. Both species have 44 biarmed chromosomes clearly represented by 20 macrochromosomes and 24 microchromosomes and present Ag-NORs in one pair of the smallest sized microchromosomes; heteromorphism of size for these regions was detected in L. percarinatum. C-banding revealed blocks of constitutive heterochromatin on the telomeric and pericentromeric regions of macrochromosomes and some microchromosomes. The description of a diploid karyotype (2n = 44, 20M 24m) for the L. percarinatum complex and its sympatric congener L. ferreirai provides new insight for a better understanding of the origin of parthenogenesis in the L. percarinatum complex.
West European Rock Lizards within the Iberolacerta group have a restricted distribution, with small, widely separated ranges in highland areas. The aim of this study was to identify possible habitat requirements (including habitat structure, type of vegetation, and refuge availability) and topographic factors (altitude and orientation) that may determine variations in the abundance of Iberolacerta cyreni on a 300-km2 mountain range and to discuss the implications of our results for the conservation of this endangered endemism. Both a stepwise regression and a best model selection approach showed that lizard abundance was positively correlated with only two predictors: altitude and cover of large rocks. Thus, the successful exploitation of alpine habitats by I. cyreni seemed to depend on the abundance of large rocks that may provide suitable basking substrates while minimizing predation risk. The positive association between altitude and lizard abundance predicts a fragmented distribution with isolated populations in the mountain peaks.
We determined annual survivorship and causes of mortality at two Desert Tortoise, Gopherus agassizii, study sites in the Sonoran Desert, Arizona, based on radio-telemetry data. Annual survivorship was high (89–97%), did not differ between sexes, and was comparable to previous studies using mark–recapture methods. Survivorship between sexes differed seasonally at one site, based on differences in seasonal activity patterns and differential exposure to predation by mountain lions, Puma concolor. In the absence of mammalian predation, seasonal survivorship did not differ between sexes. The next leading cause of mortality was failure to right oneself after a fall or after being flipped during reproductive or combat events.
In Southeast Asia, virtually all knowledge about sea turtle biology is derived via nesting beach studies. This study investigated life-stage parameters for a foraging population of immature Green Turtles Chelonia mydas off the coast of Borneo, Malaysia, to elucidate a significant portion of the at-sea life-stage component. Mark–recapture provided new data on localized movements between captures, growth, and residency period. Laparoscopic examination provided information on sex ratios and maturity. Turtles moved only an average of 380 m between recaptures and exhibited site-fidelity over several recaptures spanning up to two years. Size classes suggested all animals were juveniles and ranged from 38–80 cm CCL. Growth rates among recaptures averaged 3.6 cm yr−1. Laparoscopic examinations of the gonads confirmed that all individuals were immature, with a sex ratio of 1M ∶ 4F. These initial data on foraging C. mydas population structure and dynamics are of use for life-stage population models and turtle management and recovery planning.
We used skeletochronology to estimate the age and growth patterns of a subtropical high-elevation Torrent Frog, Amolops mantzorum, based on 138 adult specimens from western China. The lines of arrested growth in phalanges were distinct, and each line was assumed to represent one year of age. Mean age of adult male frogs was 4.3 yr (SD = 1.3, range 2–7), significantly younger than 5.2 yr (SD = 1.4, range 3–9) in adult females. At the same age, males were significantly shorter in body length than females, and females appeared to require an extra year postmetamorphosis to reach maturation. The von Bertalanffy model described the growth of the frogs well, with males having a growth rate significantly lower than females.
We describe sexual dimorphism in coloration and the reproductive cycle in Tropidurus semitaeniatus, a widely distributed lizard species in the caatinga of northeastern Brazil. Yellow and yellow-and-black patches occurred on the ventral surface of the thighs and precloacal flap in 15 and 11 adult males, respectively. Thirteen reproductively active males (collected November to March) had ventral patches with intense pigmentation, contrasting with the faded pigmentation of these patches in two males during the maturation stage (collected in October) and in 11 individuals in regression phase (collected April to September). Thirty-six adult females, reproductively active and not, and 21 juveniles lacked ventral color patches. There was a significant relationship between snout–vent length and testis volume during maturation and regression stages in males with both types of color patches. We conclude that ventral color patches displayed by male T. semitaeniatus are closely associated with their reproductive cycles.