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The infrared organs of boas, pythons, and pit vipers are true eyes that function not by a photochemical reaction but on the basis of heat generated in the receptors (called terminal nerve masses, TNMs), by electromagnetic radiation. In the pythons and pit vipers, the pit opening acts as the aperture of a pinhole camera, a virtual lens that permits the receptors to encode the movements of an infrared source sufficiently for the brain to form an image. Many boid snakes possess TNMs identical to those of the pythons but lack an opening that could serve as a lens. All TNMs are irrigated by a dense capillary network that serves as a heat regulator, mimicking the role of the photochemical cycle in the lateral eyes. Thus, the pits are an integral part of the snakes' visual system, which makes use of the longer waves of the electromagnetic spectrum for which there are no appropriate photoreceptive pigments in nature; they do everything the eyes do. They are definitely not, as they have often been treated, a “sixth sense,” useful only for the detection and acquisition of prey. Just as the world that most insects see includes both the visual and the ultraviolet spectra, so the world that boas, pythons, and pit vipers see includes both the visual and the infrared spectra.
Large-scale amphibian conservation often relies on remotely sensed data to describe spatial patterns in occupancy. Commonly used data include ownership, forest type, soil class, and proximity of wetlands. We evaluated the influence of these variables on terrestrial amphibian occupancy in southern Michigan. We trapped amphibians using drift-fence arrays in 82 forest patches and estimated detection probabilities for all captured species. Ten species were captured, but only three were detected at levels suitable for occupancy modeling. We concluded that drift-fence arrays alone were not sufficient for adequately detecting the majority of terrestrial amphibians. The best detection models for American Toad (Anaxyrus americanus), Wood Frog (Lithobates sylvaticus), and Spring Peeper (Pseudacris crucifer) consistently included a positive relationship with temperature and precipitation. Detection-adjusted occupancy models for the three anurans indicated relatively high occupancy (>0.43). Ownership, forest type, and soil class did not occur in higher ranking occupancy models. Rather, the higher ranking models often included the distance to National Wetlands Inventory (NWI) wetland and sample year factors. However, these effects were highly variable and of no use in consistently predicting terrestrial amphibian occupancy. Our results substantiate the importance of incorporating detection probabilities into studies of amphibian habitat relationships and suggest that coarse descriptors of environmental conditions may not adequately portray factors important to terrestrial amphibian occupancy.
In North America, most efforts to monitor pond-breeding anurans have focused on call surveys. Egg-mass counts offer an alternative monitoring strategy that has been used extensively in Europe because this technique can produce precise and accurate estimates of annual reproductive effort at many study sites. We surveyed egg masses of Wood Frogs (Lithobates sylvaticus) at 18 ponds for up to 16 years from 1993–2008 in the largest contiguous forest tract in southern New England. We detected an average of 441.5 ± 343.7 egg masses per pond. Based on annual egg-mass counts, coefficients of variation (CV) were slightly higher than previous estimates for this species. We detected no relationship between mean annual population size and CV or between length of time series and CV. Population fluctuations in these ponds exhibited evidence of annual synchrony, in part because annual fluctuations at individual ponds were large enough that it was difficult to assess differences in population trends among ponds. However, the overall trend suggests this population was probably increasing slightly, which was expected because ponds were located in contiguous forest that remained intact during the study. Egg-mass counts appear to represent a feasible technique to monitor Wood Frog populations, given that all local breeding ponds are monitored.
Toe clipping is widely used in studies of amphibian ecology and behavior, but its impact on return rates and survival remains controversial. We evaluated the effect of toe clipping on apparent survival, using four comprehensive mark–recapture data sets of four anuran species covering four different time scales and varying life histories. The effect of toe clipping was evaluated by comparing frogs with different numbers of toes removed. Two species, Eleutherodactylus coqui and Hemisus marmoratus, showed minimal effects of toe clipping on apparent survival with seasonal and annual apparent survival decreasing by 0.1% and 1.5% with toe removal, respectively. In Hyperolius nitidulus, daily apparent survival increased on average by 4.1% with toe removal, an effect than can be attributed to disproportionate emigration of the lowest toe-removal group. Finally, in Phrynobatrachus guineensis, individuals with three toes clipped showed an additional 5.0–19.7% decreased apparent survival between weeks when compared to individuals with only one toe clipped. However, the data set was characterized by an interaction between the number of toes clipped and week of marking, thus confounding interpretation. To minimize any effects of toe clipping, we recommend that not more than four toes should be clipped and at most a single toe removed on each leg. In addition, functionally important toes such as the proximal toes of front feet and fourth toes of hind feet should be spared. Furthermore, toe-removal groups should be equally distributed over time to facilitate the analysis of potential toe-clipping effects.
Corucia zebrata (Scincidae) is endemic to the Solomon Archipelago and widely distributed across the island group. Corucia is evolutionarily distinct and diverged from its nearest relatives about 30 MYA. Little is known about its life history, basic ecology, or behavior in the wild. We conducted a six-week study of movement patterns of C. zebrata on the island of Ugi to determine home-range sizes and overlap among conspecifics. Twenty-five lizards were fitted with radio transmitters and were followed for periods of 5–38 days. Telemetry results indicated that the average home range over the period studied was equivalent to the canopy of one tree. Radio-tagged individuals were located more often in the canopy than on the trunk of the tree, where humans typically search for the lizards. The home range is smaller than expected for a similar-sized herbivorous lizard occupying a terrestrial habitat, but the small home range is consistent with results from other arboreal animals. The study increased our knowledge of the behavior and habitat preferences of an ecologically unusual lizard species. We noted that conventional survey methods, searching tree trunk habitats, have low detection probability, an important consideration for further ecological studies of the species, in particular for the purpose of assessing its conservation status.
Larval amphibians are increasingly being reared for conservation initiatives to bolster declining populations. Few researchers, however, have asked whether reared individuals are functionally equivalent to their wild counterparts. Compared with those in the wild, amphibians reared in captivity may develop in relatively stress-free environments, because they are usually fed ad libitum, raised in the absence of predators and pathogens and in controlled environments. Thus, with few challenges throughout development, would their resting stress levels or reactions to acute stressors be normal? We addressed this question by rearing Litobates sphenocephalus and Ambystoma opacum from eggs and 10-day-old larvae through to late larval stages in artificial pond environments and by determining their ratios of neutrophils (N) to lymphocytes (L) (two leukocytes that covary with stress hormones) before and after a standardized stressor. We obtained similar samples from wild-caught larvae of equivalent developmental stages and from the same source pond. Baseline and stress-induced N∶L ratios of reared L. sphenocephalus were statistically similar to those of wild individuals. In contrast, baseline N∶L ratios of reared A. opacum were slightly higher than those of wild individuals. In general, the magnitude of the leukocyte response to stress for both species (a 3-fold increase in N∶L over baseline), was similar to that of wild individuals, suggesting that captive-reared amphibians are capable of mounting a normal physiological stress response. Although this last point provides support for the use of captive-rearing for conservation and research purposes, the unusually high baseline N∶L ratios of reared salamanders will require additional research to determine the functional meaning.
Acoustic signals play an important role in intraspecific communication for most anurans. We investigated the vocal signals, communication, and ear morphology of captive Kihansi Spray Toads (Nectophrynoides asperginis), an Extinct in the Wild diurnal species that is endemic to a specialized spray zone created by waterfalls of the Kihansi River Gorge in Tanzania. We found that N. asperginis have reduced ears, and their calls are soft and simple, comprising short call notes with a fundamental frequency of ∼4.1 kHz and harmonics extending into the ultrasonic range. Observations of the toads' interactions while calling indicate that males call primarily when they are in visual contact or behaviorally engaged with a conspecific. These observations suggest that social interactions in Spray Toads likely involve multimodal sensory communication. Nectophrynoides asperginis has apparently adapted to communicate amid high-level ambient noise produced by the waterfalls in its native environment by specializing in short-range communication within high-density aggregations.
How habitat edges affect the spatial dynamics of snakes has become an increasingly popular subject because of a massive increase in anthropogenic edges in many landscapes. Here, we used a novel randomization-based procedure to examine patterns of edge association for the Timber Rattlesnake (Crotalus horridus) within upland forest in St. Louis County, Missouri. For each set of locations, the minimal distance from each location to the nearest edge feature was measured, averaged, and compared to an expected null distribution of average minimal distances (AMDs) under the assumption that points are randomly located with respect to edges. The significance of the observed value was estimated by determining the proportion of AMDs from the randomized set that were equal to or less than the observed average distance. Results indicated considerable variation from year to year in test results for individuals, resulting in variation in the results of combined significance tests for subgroups (i.e., males, females, and gravid females). Although results for different edge types were not compared statistically, our results indicated that individuals were found most frequently in nonrandom proximity to fence edges. In general, results were consistent with previous studies of habitat selection in midwestern snakes, which failed to find a consistent association between snakes and edges.
In South Africa, particularly Gauteng Province, populations of the large, explosive-breeding Giant Bullfrog (Pyxicephalus adspersus) are suffering increasing habitat loss due to encroaching urbanization. To investigate the spatial habitat requirements of this regionally threatened species, 70 adult frogs were radio- or spool-tracked during five summers around a periurban breeding site. Male and female P. adspersus moved a maximum overnight distance of 350 m when returning to their burrows postspawning. On average, animals of either sex used one long-term burrow (LTB) in a summer. Four males each used a single LTB or burrowing area for two or three consecutive summers. The LTBs of females were situated almost 4 times further (mean = 446.8 m) from the seasonal dams where spawning occurred than those of males (mean = 131.0 m). Female body condition was significantly positively correlated with distance of their burrows from the seasonal dams (rs = 0.77). Limited evidence indicated that adult P. adspersus probably forage mostly within 20 m of their burrows. To protect the LTBs of all radiotracked animals a 950-1,000-m wide buffer would be necessary around the seasonal dams. Because adult P. adspersus seem to be philopatric, juvenile dispersal is predicted to be largely responsible for gene flow among populations.
In an era of rapidly changing environments and greater human mobility and penetration into wild areas, organisms are being discovered in increasingly unexpected places. One such finding is a road-killed juvenile gartersnake (Thamnophis) outside of Haines, Alaska, in August 2005. The poor condition of the specimen prevented a positive identification based on morphology alone. Furthermore, no snakes are known to be native to this region. We therefore undertook a molecular approach to determine the species and geographic origin of the individual. We sequenced two partial loci of mitochondrial DNA (cytochrome b and NADH subunit 2) from the Alaska specimen and seven specimens from localities in the lower northwestern United States. Phylogenetic reconstruction using our sequences and additional GenBank samples unambiguously revealed that the Alaska specimen is Thamnophis ordinoides and that it shares a haplotype with the northernmost sampled Washington population of T. ordinoides. In light of these analyses, we assess the likelihood that the specimen represents a relict population, a recent natural colonization, or a fresh introduction.
Amphibians show strong dependence on environmental variables (water balance, temperature). However, interactions affecting geographic distribution of body size are poorly known. We present an analysis of body size within and between species of an anuran genus using a climatic approach. We studied geographic body size distribution in 23 species of South American redbelly toads (Melanophryniscus) spanning 16° latitude, 22° longitude, and 2,400 m altitude. Body size was analyzed in relation to climatic parameters including temperature, precipitation, seasonality, evapotranspiration, and water balance at interspecific, interpopulational (all populations regardless of species), and intraspecific (populations within species) levels. LogSVL was regressed against climatic principal components scores using simultaneous autoregression. Interspecifically and interpopulationally, temperature and precipitation are the main factors responsible for the observed size clines, larger body sizes being associated with decreasing maximum ambient temperature and water availability. Intraspecific results for two species suggested comparable body-size trends. That temperature affects these size clines is reinforced by the strong positive correlation of logSVL with altitude. Because anurans strongly depend on water for survival and reproduction, it is reasonable that ,besides temperature, larger body size is favored in drier environments, which is supported by the correlation between body size and coefficients of variation of annual rainfall: lower surface : volume ratios in larger species would help conserve water in unpredictable environments. Also, Melanophryniscus has reproductive peculiarities associated with ephemeral aquatic environments: explosive breeding synchronized with rainfall; eggs deposited in several clutches; and rapid tadpole development, which suggest a strong relationship between life history and water balance.
We studied two closely situated (6.4 km distance) coastal populations of the Gopherus berlandieri in Cameron County, Texas. The Yturria Ranch population was monitored from 1972 through 1987, and the Reed Ranch population was monitored from 1977 through 1987. Tortoises were located by searching between grid lines 18.3 m apart that encompassed 3.3 ha on the Yturria Ranch and 2.0 ha on the Reed Ranch. Nine (3.7%) of 244 tortoises marked on the Yturria Ranch and 16 (10.5%) of 151 marked on the Reed Ranch died during the study. Timing of known deaths were distinctly different for the two sites, with nine tortoises found dead on the Yturria Ranch from 1983–87, whereas all known tortoise deaths occurred on the Reed Ranch from 1977–79. Annual survivorship estimates were higher for males and females on the Yturria Ranch, but survivorships at both sites were similar. Abundance of prickly pear (Opuntia engelmannii), on which tortoises feed, on the Yturria Ranch site may have contributed to a higher survivorship by providing high water content biomass during droughts and by providing cover that reduced predation.
Knowledge of the osteology of species of the Leptodactylus melanonotus group is limited. Nevertheless, osteological characters are useful to diagnose species to, to propose phylogenetic relationships, to understand patterns of morphological evolution, and to predict biological function associated with morphology. Here, we describe the whole osteology of Leptodactylus podicipinus; we have special interest in osteological and morphometric characters whose interpopulational and intersexual differences can be related with fossorial habits. Individuals from the Pantanal, Brazil, were compared with L. podicipinus from northern Argentina and central and southern Paraguay by analyzing morphometric and osteological characters. The quantitative data revealed sexual dimorphism in tarsus length in the specimens from the Pantanal. The observed interpopulation osteological differences could not be associated with burrowing habits. Osteologically, L. podicipinus is intermediate between the members of the Leptodactylus fuscus group, which is more specialized for digging, and the generalized L. melanonotus, Leptodactylus latrans, and Leptodactylus pentadactylus groups.
A recent study demonstrated marked variation in cranial shape between a population of Brachycephalus ephippium from Jundiaí in São Paulo state and populations from Atibaia and São Francisco Xavier (São Paulo) and Macaé de Cima in the state of Rio de Janeiro in southeastern Brazil. This result contrasts with earlier work describing differences in cranial shape between the population from Rio de Janeiro and those from São Paulo. Here, we investigate the nature and extent of variation between populations of B. ephippium using two lines of evidence. First, we reevaluate patterns of morphological variation by incorporating semi-landmarks into the quantitative description of cranial shape and by using scanning electron microscopy (SEM) to describe qualitative skeletal features. Second, we assess molecular variation in the mitochondrial genes cytochrome b, 12S rRNA, and 16S rRNA, and the nuclear Rag-1 gene, totaling 3,697 base pairs. Geometric analyses of cranial shape and SEM images of skeletal traits show that the population from Macaé de Cima and the populations from São Paulo differ markedly in morphology and diverge in the cytochrome b, 12S, and 16S rRNA genes by 9.7%, 2.8%, and 4.4%, respectively. Divergence in the nuclear gene Rag-1 is, as expected, much lower (0.6%). These results clearly demonstrate heterogeneity between populations that are all currently diagnosed as B. ephippium and point to the need for further research to ascertain the true diversity currently hidden under the name of B. ephippium.
We investigated the taxonomic status of the Indian forms of the Dendrelaphis pictus (Gmelin, 1789) group on the basis of multivariate analyses of morphological data taken from 176 museum specimens and two living specimens. A geographically isolated form from the Western Ghats, southwest India, is described as a new species. The subspecies Dendrelaphis pictus andamanensis (Anderson, 1871), an endemic from the Andaman Islands, is given specific status. Finally, the population of D. pictus from Indochina and northeast India, although superficially homogeneous, is shown to be comprised of two morphologically distinct forms. These forms are distributed parapatrically with a transition near the northern and northwestern borders of Indochina. The two forms are considered to represent distinct evolutionary lineages. The name Dendrelaphis proarchos (Wall, 1909) is revalidated to represent the northwestern form. The southeastern form is referred to as D. pictus (Gmelin, 1789). Whether intergradation between D. pictus and D. proarchos occurs at the contact zone is not clear.
A new species of Mastigodryas is described based on 10 specimens collected on the Upper regions of the Negro and Branco River basins, in the States of Amazonas and Roraima, Brazil, and in the northernmost portion of Guyana. Apparently this species is associated with the open areas of the Amazonian region known as “lavrados,” “campos,” and “savannas.” The new species is characterized by the presence of eight supralabials; five dorsal stripes situated on the anterior portion of the body that fade or disappear on the posterior half of the body and exhibit a reddish unicolor pattern; and a hemipenis with an enlarged spine situated on the left side of the sulcus spermaticus. The new species is similar to Mastigodryas pleei and, herein, included in the pleei group, along with M. pleei, Mastigodryas amarali, and Mastigodryas bruesi.
Bokermannohyla is one of the five genera included in the recently recognized tribe Cophomantini, of the hylid frog subfamily Hylinae. Although karyotypic diversity is relatively well known in two genera of Cophomantini, Aplastodiscus and Hypsiboas, in Bokermannohyla chromosome data are restricted to only two of its 28 species. In this paper, we describe the karyotypes of 12 species of Bokermannohyla using standard staining, Ag-NOR, C-banding, DAPI, CMA3, and BrdU incorporation. The 12 species share a similar diploid karyotype with 2n = 24 biarmed chromosomes; most observed differences involved the NOR-bearing chromosomes (and the NOR position within these chromosomes) and C-banding patterns. The overall similarity of these karyotypes with those of Aplastodiscus and Hypsiboas widens the notion of remarkable morphological homogeneity among Cophomantini karyotypes. The results obtained thus far are promising for comparative studies on the genus Bokermannohyla and, in a wider sense, will allow a better understanding of karyotype differentiation and chromosomal evolution in Cophomantini.
Núñez (2004) examined the syntypes of Liolaemus pictus major Boulenger in the British Museum of Natural History and concluded, without supporting data, that this taxon is a senior synonym of Liolaemus capillitas Hulse. We show that the evidence does not support Núñez's (2004) proposal. We first document the complex taxonomic history of L. p. major, the lack of a precise or even definitive type locality, and the implications of the latter on subsequent checklists and research. Second, we note differences between Boulenger's (1885) type description of L. p. major and Hulse's (1979) type description of L. capillitas. Third, we show that the syntypes of L. p. major photographed by Núñez (2004) do not exhibit the character states of L. capillitas. We conclude that L. capillitas is not a synonym of L. p. major. Based on the available evidence, the syntypes of L. p. major are probably assignable to Liolaemus elongatus from populations occurring in Patagonia (southern Argentina or adjacent Chile). However, the precise identity of the syntypes requires additional study and perhaps a type locality restriction or redefinition of L. elongatus, which is itself in a state of flux.
Invasive species are a major threat to biodiversity and economic interests, with many introductions resulting from actions of people involved in pet and ornamental plant businesses. Invasive species eventually end up in the care of the general public, with most costs born by society rather than businesses or owners: a classic economic externality. Although standard economic instruments used to address externalities are useful, they require considerable extension in this case. Simple taxation of the trade has been suggested and can reduce the volume of trade, but taxes do little to discipline the riskiest actors in the market. Using reptiles and amphibians as our focus, we provide an outline for a mechanism addressing invasive species issues, focusing primarily on the local level. We propose to collect funds from the trade and apply them specifically to support (1) a national resource center offering information and training; (2) programs to professionalize local education and response teams, focusing on pet store owners, hobbyist organizations, and first responders; (3) an incentive program to encourage pet stores to take back unwanted animals; (4) a tracking system for identifying and penalizing owners of newly released animals; and (5) a rapid-response system to address newly reported invasives. Participation by local entities helps them avoid uniform policies from the national level that are typically both more onerous and less effective. To provide an additional incentive for the industry at large to participate in the process, the level of taxation could decrease as problems diminish.