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Habitat use and movement patterns of Northern Alligator Lizards (Elgaria coerulea) and Western Skinks (Eumeces skiltonianus) in southeastern British Columbia
Abstract
Many reptiles have different habitat requirements for different activities (e.g., hibernation and nesting/gestation) that may not be satisfied by a single location. Suitable habitat may not only be limited, but also fragmented, making it difficult for animals to move between sites. In this study, we examine habitat use and movement patterns of Northern Alligator Lizards (Elgaria coerulea) and Western Skinks (Eumeces skiltonianus). In particular we determine the characteristics of hibernation and summer sites for both species and the extent of movement in both species, particularly whether migration occurs between summer and winter habitats. We used mark-recapture (PIT-tags and toe-clips) to do this. Both species coexisted at many of the same study sites, although some sites had only one of the species, and individuals were found in approximately the same locations in spring, summer, and fall. Thus, hibernation apparently occurs in the same habitat where lizards are active during the summer and no seasonal migration occurs. In fact, individuals of either species were recaptured on average within 10 m of a previous capture. Both species were rarely found in the open and more often under rocks than in vegetation or under logs; they also remained close to shrubs and forest edges. Roads apparently are not a major hazard for either species because they have high site-fidelity and do not make long-distance movements between hibernation or summer sites. Their requirement for cover means that any disturbance or removal of rocks from their habitats would be detrimental to both species.
... I predict that along with thermal properties, a major factor in selection of a particular refuge habitat is the refuge site's humidity properties and the relative homogeneity of thermal and humidity properties under refuge rocks determined by rock size. to the availability of the resource is resource selection (Johnson 1980 Refuge sites are a particular subclass of microhabitat that serve as refugia or protection for an individual in a species population from the surrounding stochastic environment, and may aid in thermoregulation and in encountering prey items (Downes 1999, Beck and Jennings 2003, Howes and Lougheed 2004 (Avery 1976;Huey 1982;Rutherford and Gregory 2003). The amount of time spent in refuge sites then emphasizes the importance of refuge site selection; some ectotherms spend over 99% of their total time in refuge sites (Beck 1990). ...
... In a study on the refuge site selection of Gila Monsters, Heloderma suspectum, Beck and Jennings (2003) Rutherford and Gregory (2003) note that individuals were recaptured on average within 10m of a previous capture site and individuals did not travel long-distances. Although these reptiles along with the Garter snakes might switch amongst rocks in a local site, the relative area selected provides adequate amounts of refuge sites with conditions flexible enough for species population survival. ...
... citations within). Since his review, there has been an increase in studies on refuge sites demonstrating their importance in the thermal biology, water regulation, dispersion patterns, disturbance patterns, and other biological aspects of ectotherms (e.g., Schlesinger and Shine 1994;Web and Shine 1998;Goldingay and Newell 2000;Whitaker and Shine 2002;Beck and Jennings 2003;Rutherford and Gregory 2003;Howes and Lougheed 2004;Kerr and Bull 2004;Webb et al. 2004). ...
... For example, examining movement patterns enables the identification of key portions of critical habitat for listed species, such as nesting and hibernation sites. Many reptiles necessitate more than one habitat for their activities (food acquisition, aestivation, copulation, nesting, thermoregulation, etc.) and, therefore, movement between various habitats is required (Rutherford and Gregory, 2003). Tracking these movements is critical for two fundamental reasons: (1) the availability of suitable habitat in favourable spatial configurations may be a key factor limiting the distribution and abundance of a species and (2) manipulation of habitat is an important potential tool in conservation and management (Rutherford and Gregory, 2003). ...
... Many reptiles necessitate more than one habitat for their activities (food acquisition, aestivation, copulation, nesting, thermoregulation, etc.) and, therefore, movement between various habitats is required (Rutherford and Gregory, 2003). Tracking these movements is critical for two fundamental reasons: (1) the availability of suitable habitat in favourable spatial configurations may be a key factor limiting the distribution and abundance of a species and (2) manipulation of habitat is an important potential tool in conservation and management (Rutherford and Gregory, 2003). In complement to movement patterns, home ranges enable researchers to estimate the size and shape of the area used by an animal (Burt, 1943), which allows for proper delineation of regions that need to be protected. ...
... Movement patterns are a relatively undocumented characteristic for G. infernalis (along with density, territoriality, and home range), but the species is thought to exhibit active or wide foraging habits (Gans and Tinkle 1977, Vitt and Pianka 1994, García Bastida 2013, Yasuda 2015. Studying the movement patterns of G. infernalis is critical to developing management plans, as this can identify required habitat types (i.e., overwintering, mating, and nesting sites) and factors limiting abundance and distribution (Rutherford andGregory 2003, Millar andBlouin-Demers 2011). Only one prior study (García Bastida 2013) has attempted to utilize radiotelemetry to understand the ecological characteristics of G. infernalis; occurring near Monterrey, Nuevo León, Mexico, this study indicated that G. infernalis is primarily terrestrial, as no arboreal activity was described. ...
Texas Alligator Lizards (Gerrhonotus infernalis) range from Central Texas into adjacent northeastern Mexico, and published ecological studies on their terrestrial and arboreal movement patterns are lacking. We used radiotelemetry to assess movements, annual home range, and arboreal activity of G. infernalis at Bamberger Ranch Preserve, Blanco County, Texas, to provide baseline ecological data for populations occurring in the northernmost extent of the species’ range. Movement patterns were influenced by temporal (e.g., seasonal) and behavioral cues (e.g., breeding period), but generally no differences were observed between sexes. Annual home range varied, but males averaged larger 95% MCP (minimum convex polygon) annual home ranges, while females averaged larger 50% MCP core use areas, although we were unable to test for differences due to low sample sizes. Males and females exhibited similar arboreal trends, but arboreal activity did vary by season and diurnal period. Most arboreal activity occurred during the summer and
late spring, with less during the fall and winter months. Gerrhonotus infernalis, on average, inhabited higher perch sites during the evening and morning diurnal periods and lower perch sites during the afternoon periods. These findings provide
novel insights into the ecology of G. infernalis in Central Texas and will aid in future management activities.
... Captures of Western Skinks decreased by over two-thirds during the ten-year monitoring gap, in all three patch sizes (Fig. 6A). The Western Skink is a sedentary habitat generalist that is rarely seen, and they have very small home ranges (Tanner, 1957;Rutherford and Gregory, 2003). It is unknown what drove the decline of skinks over ten years; however, the decreased rainfall may have had the effect of removing vegetative cover as grass and shrubs died out. ...
... In this context, one of the most important factors for the spatial organization of population is how individuals select the resources in the environment (Pianka, 1973;Nogueira et al., 2005;Rocha & Anjos, 2007;Gonçalves-Sousa et al., 2019;Peixoto et al., 2020). However, within their habitats, ani-mals deal with many environmental constraints that directly influence their activity patterns and microhabitat selection (Rutherford & Gregory, 2003;Domenici et al., 2007;Ariano-Sánchez et al., 2020;Ortega et al., 2019). ...
Understanding how different environmental factors influence species occurrence is a key issue to address the study of natural populations. However, there is a lack of knowledge on how local traits influence the microhabitat use of tropical arboreal lizards. Here, we investigated the microhabitat selection of the poorly known lizard Tropidurus lagunablanca (Squamata: Tropiduridae) and evaluated how environmental microhabitat features influence animal's presence. We used a Resource Selection Function approach, in a case/control design where we analyzed the effect of substrate temperature and tree's diameter at breast height (DBH) in the probability of presence of lizards using mixed Conditional Logistic Regression. We found that T. lagunablanca uses trees with DBH from 0.40 m to 4 m and substrate temperatures ranging from 25.9℃ to 42℃. Moreover, we showed that thickness of the trees and substrate temperatures significantly increased the probability of presence of T. lagunablanca individuals, being the probability of presence higher than 50% for trees up to 1.5 m DBH and temperature of substrate up to 37.5℃. Our study probed that T. lagunablanca individuals choose trees non-randomly, selecting thicker and warmer tree trunks. This information advances the knowledge of the spatial ecology of Neotropical arboreal lizards and is relevant for conservation, putting an emphasis on preserving native vegetation in the Pantanal.
... The potential mortality rates are lower in lizards because of the limited use of the roads for their immigration, their relatively high speed and ability to cross roads faster than amphibian and other reptilian species (20) . ...
... The Caribbean Islands make up only 0.15% of the Earth's total land area but rank fifth in biodiversity hotspots based on high concentrations of endemic species threatened by significant habitat loss (Myers et al. 2000;Hedges 2006). As habitat degradation increases on these islands, the ability of wildlife populations to persist decreases due to lack of adequate resources (i.e., food, shelter, hibernation sites, etc.), constraints on movement corridors, and greater risks of exposure to agents of mortality (Brito 2003;Rutherford et al. 2003;Pearson et al. 2005;Daversa et al. 2012). In order to mitigate these negative demographic effects, translocation, defined as the deliberate assisted movement of organisms from one site for release in another (IUCN/SSC 2013) has become an integral technique in wildlife management and conservation (Seddon et al. 2007;Roe et al. 2010). ...
The Jamaican Boa Chilabothrus subflavus (Boidae) is a Jamaican-protected species whose numbers and distribution have declined during the last century. In order to protect Jamaican Boas, translocation has been recommended as a conservation strategy. From December 2010 to November 2012 a short-distance translocation (SDT) of seven resident female Jamaican Boas in Windsor, Trelawny Parish, Jamaica was conducted to assess the effects of SDT on the survivability, home range size and microhabitat use of translocated individuals. A subset of seven resident (non-translocated) Jamaican Boas radiotracked in Windsor from November 2008 to June 2009 was used for comparison
to SDT snake data. No mortalities or significant differences in home range size were recorded for SDT as compared to resident female Jamaican Boas in Windsor. Visual detectability was higher for resident as compared to SDT snakes, however, both groups utilized arboreal microhabitats in greater proportion to terrestrial locations. Both groups were found in areas characterized by tall, canopy layer trees with vines and epiphytes, but SDT boas utilized larger trees with greater epiphyte densities than resident snakes. Results suggest short-distance translocation has potential as a management strategy for the conservation of Jamaican Boa populations in Jamaica.
... Jochimsen et al. (2004) observed that the road mortality rate of saurians is lower, which is due to their relative high speed and ability to cross roads faster. Furthermore, research indicates that certain species do not migrate seasonally and exhibit high site fidelity within small home ranges, limiting their encounters with roads (Rutherford and Gregory, 2003). An incidental survey conducted over 19,041 kilometers in northern Alabama reported the road deaths of 8 lizards (Dodd et al., 1989). ...
... This finding is similar to that found in China and Vietnam (Huang et al. 2013), indicating that the populations of C. mystaceus in Thailand have had sufficient time to acquire unique haplotypes. Moreover, the lizards, including C. mystaceus, are believed to have limited dispersal abilities (Rutherford and Gregory 2003), which is likely to affect gene flow among populations (Irwin 2002). We also found highly significant genetic differentiation among populations/localities of C. mystaceus, even when at a close distance from one another, with no natural barriers, especially between the northeast populations. ...
The blue-crested lizard, Calotes mystaceus Duméril & Bibron, 1837, is listed as a protected wild animal in Thailand. Its population is likely to be dramatically reduced due to massive hunting in several areas in this country. Basic information on its population genetics is therefore needed to facilitate its conservation. Thus, in this study we investigated the mitochondrial cytochrome c oxidase subunit 1 (CO1) sequence variation of 238 individual C. mystaceus from 42 different geographical localities of the north, west, central, east and northeast regions of Thailand. High genetic diversity and genetic differentiation at the intrapopulation and interpopulation levels was observed. We detected 63 unique haplotypes and 12 common/shared haplotypes. The phylogenetic analysis reveals two major lineages, I and II. These two lineages are separated by mountain ranges, which play an important role as natural barriers blocking gene flow. Our finding reveal at least two cryptic lineages represented in C. mystaceus populations in Thailand. However, a comprehensive investigation of the morphology, biology, ecology and genetic diversity of C. mystaceus in other regions within its area of distribution is needed.
... Ecological studies can provide insights about factors limiting the distribution and abundance of susceptible species. This information is critical for habitat management (Rutherford and Gregory 2003) and enables proper delimitation of regions that need to be protected (Burt 1943, Litzgus andMousseau 2004). More importantly, the persistence of many species depends upon the effectiveness of strategies for conserving biodiversity in human dominated landscapes (Vandermeer and Perfecto 2007). ...
Culebra, which is an archipelago that forms part of the Puerto Rican Bank, has had a limited scope of biological studies, provided the basis for this work. Culebra's terrestrial resources were disturbed since the early 1900's until the 1970's. Since the 1970's, a natural reserve, called the Culebra National Wildlife Refuge, has been managed by the United States Fish and Wildlife Service. The purpose of this research is to update the species list of reptiles and amphibians on the Island as well as to examine how spatial and temporal changes affect the diversity and abundance of its herpetofauna. Twenty species of reptiles and amphibians placed in thirteen families were identified. Two new records for Mount Resaca are Eleutherodactylus coqui Thomas, 1966 and Eleutherodactylus cochranae Grant, 1932. Meanwhile, Anolis pulchellus Duméril and Bibron, 1837 is a new record for the Luis Peña Cay. Mount Resaca has greater species richness, ten more species than the Luis Peña Cay, three species of amphibians and seven species of reptiles. The differences in herpetofaunal biodiversity (e.g. Shannon Wiener, Simpson's Index and Margalef's Index) between Mount Resaca and the Luis Peña Cay were statistically significant. Abiotic factors, such as temperature and humidity, and biotic factors, such as vegetation and the presence of other animal species, possibly influence the relative abundances within these communities.
... However, it is not permanent since lizards shed their skin. Permanent marking techniques that can be used in lizards are PIT tags (Godfrey et al. 2006;Rutherford and Gregory 2003), sewing beads in the base of the tail (Fisher and Muth 1989;Halloy and Robles 2002), branding (Hitchmough et al. 2012;Stamps 1977) and, most commonly, toe-clipping (e.g., Allsop et al. 2006;Calsbeek and Cox 2010;Chapple and Keogh 2005;Haenel et al. 2003;Sinervo et al. 2001). In toe-clipping a unique combination of digits is removed from the lizard. ...
... They are all moderately robust and short-limbed relative to intergirdle length. These lizards commonly use cover of rocks, presumably for predator avoidance, thermoregulation, and food-acquisition (Fellers and Drost, 1991;Mautz, 1993;Rutherford and Gregory, 2003). Where heavy herbaceous cover or thorny thickets are available, however, these lizards can be heard and sometimes seen moving slowly about. ...
Introduction, The four basic tasks, EPM, FAM, and habitat One useful theoretical focus in evolutionary ecology is that an animal has four basic, autecological tasks: (1) find, acquire and utilize food; (2) avoid, evade, and deter predators; (3) cope with abiotic stresses and avoid abiotic extremes; and (4) acquire mates and reproduce. An integrative understanding would require knowing the relative influence of each of these tasks on the ecology of an individual, on the population, and on the evolution of higher taxa. In addition, it would be important to identify and understand how behavioral traits (ethotypes), physiological traits (physiotypes), and morphological traits (morphotypes) of animals are adapted to each of the four basic autecological tasks (Fig. 15.1). I refer to the sum of these traits as the EPM (the ethophysiomorph or ethophysiomorphotype). Among the four basic autecological tasks, food acquisition and utilization may be the primary, albeit sometimes indirect, cause for salient features of ethotypes, physiotypes, and morphotypes (and thus EPMs) of lizards and other animals (Anderson and Karasov, 1988). The classic, general vertebrate mode of food acquisition as mobile, ectothermic predators on invertebrates continues to dominate in lizards (basal level in Fig. 15.1), and many features of lizards appear to be related to the basic autecological task of food acquisition (Pianka and Vitt, 2003). The set of physiological, behavioral, and morphological characteristics (the EPM) that are integrally involved in the search, detection, capture, and eating of food, may be considered an adaptive syndrome (Eckhardt, 1979) that I refer to as the “food acquisition mode,” FAM. An adaptive syndrome is a coordinated set of characteristics (adaptive traits) associated with an issue of overriding importance (a core adaptation) to an organism (Eckhardt, 1979). é Cambridge University Press 2007.
... The D max for amphibians are from a summary (166 articles, 90 species) compiled by Alex Smith and Green (Alex Smith and Green, 2005) and we estimated typical body masses of each species from field guides and the literature. The D max and typical body mass values for reptiles were taken from a variety of studies (Noble and Clausen, 1936;Hirth et al., 1969;Brown and Parker, 1976;Wiewandt, 1977;Werner, 1983;Larsen, 1987;Brown and Brooks, 1994;Madsen and Shine, 1996;Plummer, 1997;Pough et al., 1998;Hokit et al., 1999;Blouin-Demers and Weatherhead, 2002;Middendorf et al., 2005;Marshall et al., 2006;Keogh et al., 2007;Dubey et al., 2008;Rutherford and Gregory, 2003;Templeton et al., 2011;Warner and Shine, 2008;Welsh et al., 2010). The D max and typical body mass values for birds and mammals were taken from Sutherland et al. (Sutherland et al., 2000). ...
Vagility is the inherent power of movement by individuals. Vagility and the available duration of movement determine the dispersal distance individuals can move to interbreed which affects the fine-scale genetic structure of vertebrate populations. Vagility and variation in population genetic structure are normally explained by geographic variation and not by the inherent power of movement by individuals. We present a new, quantitative definition for physiological vagility that incorporates aerobic capacity, body size, body temperature, and the metabolic cost of transport, variables that are independent of the physical environment. Physiological vagility is the speed at which an animal can move sustainably based on these parameters. This meta-analysis tests whether this definition of physiological vagility correlates with empirical data for maximal dispersal distances and measured microsatellite genetic differentiation with distance ((FST/1-FST)/ ln km) for amphibians, reptiles, birds and mammals utilizing three locomotor modes (running, flying, swimming). Maximal dispersal distance and physiological vagility increased with body mass for amphibians, reptiles and mammals utilizing terrestrial movement. The relative slopes of these relationships indicate that larger individuals require longer movement durations to achieve maximal dispersal distances. Both physiological vagility and maximal dispersal distance were independent of body mass for flying vertebrates. Genetic differentiation with distance was greatest for terrestrial locomotion, with amphibians showing the greatest mean and variance in differentiation. Flying birds, flying mammals, and swimming marine mammals showed the least differentiation. Mean physiological vagility of different groups (class and locomotor mode) accounted for 98% of the mean variation in genetic differentiation with distance in each group. Genetic differentiation with distance was not related to body mass. The physiological capacity for movement (physiological vagility) quantitatively predicts genetic isolation by distance in the vertebrates examined.
... pieces of natural and artificial ground cover, and caught the specimens by hand. This technique has proven effective for the capture of prairie skinks Mullen 2006;Cairns 2007;Dransfield 2008;Rutherford 2007), and other small lizard species Goode et al. 2003;Rutherford and Gregory 2003;Howes and Loughheed 2004;Du et al. 2006;Tocher 2006). All individuals were marked by toe clipping and placed in one of the following sex/age classes: adult female, adult male or juvenile. ...
... Our results suggest that the patterns in C. versicolor are consistent with the isolation-by-distance model [65], in which gene flow decreases with increasing geographical distance because of limited dispersal. We have few data on dispersal distance in C. versicolor, but it is believed that lizards have limited dispersal abilities [66,67], which can affect gene flow among populations [68]. ...
The Oriental garden lizard (Calotes versicolor) is one of the few non-gekkonid lizards that are geographically widespread in the tropics. We investigated its population dynamics on Hainan Island and the adjacent mainland of China and Vietnam, focusing on the impact of cyclic upheaval and submergence of land bridges during the Pleistocene. Our Bayesian phylogenetic analysis reveals two mitochondrial lineages, A and B, which are estimated to have coalesced about 0.26 million years ago (95% credibility interval: 0.05-0.61 million years ago). Lineage A contains individuals mainly from central and southern Wuzhi Mountain on Hainan Island, whereas lineage B mainly comprises individuals from other sites on the island plus the adjacent mainland. The estimated coalescence times within lineages A (0.05 million years ago) and B (0.13 million years ago) fall within a period of cyclical land-bridge formation and disappearance in the Pleistocene. A spatial analysis of molecular variance identified two distinct population groupings: I, primarily containing lineage A, and II, mainly consisting of lineage B. However, haplotypes from lineages A and B occur sympatrically, suggesting that gene flow is ongoing. Neither Wuzhi Mountain nor Qiongzhou Strait and Gulf of Tonkin act as barriers to gene flow among C. versicolor populations. Analyses of the data using mismatch distributions and extended Bayesian skyline plots provide evidence of a relatively stable population size through time for Group I, and moderate population expansions and contractions during the end of the Pleistocene for Group II. We conclude that the phylogeographical patterns of C. versicolor are the combined product of Pleistocene sea-level oscillations and nonphysical barriers to gene flow.
... In the observation area, the only hibernacula used by T. merianae (n56) were in human-made constructions. It is possible that due to the absence of rocks in the studied area, T. merianae uses the cement of human-made construction, in place of its natural heat source (rocks), for thermoregulation and thermal protection (Rutherford and Gregory 2003). This hypothesis is reinforced by the fact that individuals that use hibernacula in natural cavities emerged later (42 days after the first individual; mean563.67¡7.53 ...
The emergence period and winter aggregations of a population of Tupinambis merianae from southern Brazil as well as some behavioural aspects from its post‐emergence period are examined. Fifty‐six individuals were captured and marked in 64 days (640 h) of field study. Most of the hibernacula identified were beneath human constructions. The first individuals emerged in August and the last active ones were observed in April. The population's emergence shows a protandric pattern, where males emerge before females, both in adults and juveniles. After emerging, males basked in aggregations of up to 13 individuals, in which individuals changed positions following audible resonant signals emitted by the lizards. Sibilated sounds were emitted in stress situations or in agonistic interactions. Future studies are necessary to elucidate behaviour patterns of the species in the natural environment, mainly related to the utilization of sound communication.
... In this study we did not consider the urban area, although we have seen boas in the city. The local distribution of a species may be determined mainly by prey and shelter availability (Andrewartha and Birch 1974; Huey et al. 1989; Madsen and Shine 1996; Jepsen et al. 2002; Brito 2003; Rutherford and Gregory 2003 ). This serpent, however , is a generalist predator (Greene 1997; Sironi et al. 2000; Gonzá lez-Baca 2006), The asterisk represents the vegetation type where there were significant differences (p < 0.05); thus, the number of expected individuals is not within the Bonferroni interval estimated for that particular vegetation type and potential sites for shelter are abundant on Cozumel, so boas are capable of finding food and establishing themselves throughout the island. ...
Species introductions are among the most pervasive types of disturbance, seriously affecting island biota and ecosystem dynamics. The management of introduced generalist species, which may live in a wide range of environmental conditions, can be particularly difficult and is a major challenge for the conservation of native insular species. Boa constrictor was introduced onto Cozumel Island, Mexico, in 1971. The introduction of this generalist predator has affected negatively the native species (many of them endemic to the island) on which the boa feed. It is important to determine temporal variation in boa abundance, the areas of the island in which boas live, and the vegetation types they use in order to develop management strategies to reduce boa pressure on the native biota. We used nocturnal road transect sampling and occasional boa encounters during field work, to estimate boa distribution, abundance and habitat use, taking into account its spatiotemporal patterns on Cozumel Island. This study confirms that Boa constrictor is well established, widespread, and abundant on the island. Our results show that boas are distributed throughout Cozumel, in all vegetation types and geographical regions. Overall, there were 0.11 ± 0.03 boa/10 km road transect. There were no significant spatiotemporal differences in boa activity (time of day) and abundance (monthly, seasonally, by vegetation types or regions of the island). According to the habitat use analysis, there were, however, fewer boas than expected in the subdeciduous tropical forest we sampled and in the central-northern region of the island, which coincide with areas inhabited by humans. There were more boas in areas uninhabited by humans, and there was a tendency towards a greater proportion of dead boas in inhabited areas and live boas in uninhabited areas. Cozumel boas are habitat generalists, which are affected by human induced mortality in inhabited areas. There is a vast area uninhabited by humans, with natural vegetation, on the island where boas have suitable habitats available for their continuous existence on Cozumel. This situation, and the adaptability of the boa, makes the control or eradication of this introduced species a critical conservation challenge.
... In this study we did not consider the urban area, although we have seen boas in the city. The local distribution of a species may be determined mainly by prey and shelter availability (Andrewartha and Birch 1974; Huey et al. 1989; Madsen and Shine 1996; Jepsen et al. 2002; Brito 2003; Rutherford and Gregory 2003 ). This serpent, however , is a generalist predator (Greene 1997; Sironi et al. 2000; Gonzá lez-Baca 2006), The asterisk represents the vegetation type where there were significant differences (p < 0.05); thus, the number of expected individuals is not within the Bonferroni interval estimated for that particular vegetation type and potential sites for shelter are abundant on Cozumel, so boas are capable of finding food and establishing themselves throughout the island. ...
Species introductions are among the most pervasive types of disturbance, seriously affecting island biota and ecosystem dynamics. The management of introduced generalist species, which may live in a wide range of environmental conditions, can be particularly difficult and is a major challenge for the conservation of native insular species. Boa constrictor was introduced onto Cozumel Island, Mexico, in 1971. The introduction of this generalist predator has affected negatively the native species (many of them endemic to the island) on which the boa feed. It is important to determine temporal variation in boa abundance, the areas of the island in which boas live, and the vegetation types they use in order to develop management strategies to reduce boa pressure on the native biota. We used nocturnal road transect sampling and occasional boa encounters during field work, to estimate boa distribution, abundance and habitat use, taking into account its spatiotemporal patterns on Cozumel Island. This study confirms that Boa constrictor is well established, widespread, and abundant on the island. Our results show that boas are distributed throughout Cozumel, in all vegetation types and geographical regions. Overall, there were 0.11 ± 0.03 boa/10 km road transect. There were no significant spatiotemporal differences in boa activity (time of day) and abundance (monthly, seasonally, by vegetation types or regions of the island). According to the habitat use analysis, there were, however, fewer boas than expected in the subdeciduous tropical forest we sampled and in the central-northern region of the island, which coincide with areas inhabited by humans. There were more boas in areas uninhabited by humans, and there was a tendency towards a greater proportion of dead boas in inhabited areas and live boas in uninhabited areas. Cozumel boas are habitat generalists, which are affected by human induced mortality in inhabited areas. There is a vast area uninhabited by humans, with natural vegetation, on the island where boas have suitable habitats available for their continuous existence on Cozumel. This situation, and the adaptability of the boa, makes the control or eradication of this introduced species a critical conservation challenge.
... Another advantage of favouring structural rich microhabitats is the larger amount of vegetation cover that effectively protects P. lineoocellata from predators (Castilla & Bauwens, 1991; Bentley, Catterball & Smith, 2000; Norbury, 2001). This is further supported by a study on Northern Alligator Lizards (Elgaria coerulea) and Western Skinks (Eumeces skilonianus) where the removal of cover was detrimental to both species (Rutherford & Gregory, 2003). Nevertheless, as discussed above, the increase in daily movement activities in degraded habitats results also in a higher predation risk (Huey & Pianka, 1981; Polis, 1988; Wymann & Whiting, 2002 ). ...
Although the effects of grazing-induced savannah degradation on animal diversity are well documented, knowledge of how they affect space use or responding behaviour remains poor. In this study, we analysed space use of the spotted sand lizard (Pedioplanis l. lineoocellata) in degraded versus nondegraded habitats of southern Kalahari savannah habitats. Lizards were radio tracked, daily movement distances recorded and home range sizes calculated. In degraded Kalahari savannah habitats where plant diversity and perennial grass cover are low but shrub cover high, P. lineoocellata moves larger distances (40.88 ± 6.42 m versus 27.43 ± 5.08 m) and occupies larger home ranges (646.64 ± 244.84 m2 versus 209.15 ± 109.84 m2) than in nondegraded habitats (high plant diversity, high perennial grass cover and low shrub cover). We assume that this increase in daily movement distances and home range sizes is a behavioural plasticity to limited food resources in degraded savannah habitats. Although P. lineoocellata is able to adjust to resource-poor savannah habitats, the increase in the lizard's movement activities is likely to result in a higher predation risk. This is supported by the lower availability of protective vegetation i.e. perennial grass cover. Hence, we conclude that despite behavioural plasticity of P. lineoocellata, overgrazing has a severe negative impact on the space use of P. lineoocellata. © 2009 The Authors. Journal compilation
... One question that arises is why the mtDNA boundary persists even when there are no obvious barriers to gene exchange. The most probable explanation is that skinks have low dispersal capabilities and strong female philopatry (Rutherford & Gregory 2003). Both theoretical and organismal examples have demonstrated that shortdistance dispersal can lead to a pattern of isolation by distance when data are averaged over a large number of markers, while maintaining deep phylogeographic breaks in any individual marker (such as mtDNA; Avise 2000; Wake & Jockusch 2000;Irwin 2002;Irwin et al. 2005). ...
Speciation is generally viewed as an irreversible process, although habitat alterations can erase reproductive barriers if divergence between ecologically differentiated species is recent. Reversed speciation might also occur if geographical contact is established between species that have evolved the same reproductive isolating barrier in parallel. Here, we demonstrate a loss of intrinsic reproductive isolation in a clade of scincid lizards as a result of parallel body size evolution, which has allowed for gene flow where large-bodied lineages are in secondary contact. An mtDNA phylogeny confirms the monophyly of the Plestiodon skiltonianus species complex, but rejects that of two size-differentiated ecomorphs. Mate compatibility experiments show that the high degree of body size divergence imposes a strong reproductive barrier between the two morphs; however, the strength of the barrier is greatly diminished between parallel-evolved forms. Since two large-bodied lineages are in geographical contact in the Sierra Nevada Mountains of California, we were also able to test for postzygotic isolation under natural conditions. Analyses of amplified fragment length polymorphisms show that extensive gene exchange is occurring across the contact zone, resulting in an overall pattern consistent with isolation by distance. These results provide evidence of reversed speciation between clades that diverged from a common ancestor more than 12Myr ago.
The Northern Prairie Skink (Plestiodon septentrionalis) is listed as endangered and very little is known about habitat use in this semi-fossorial lizard. Much of the research to date has occurred on provincial park lands and federal military lands. This project aimed to define Prairie Skink habitat characteristics on exurban private land, which is defined as low-density rural residential developments, 5 to 20 acres (2 to 8 ha) in size. Prairie Skink presence data were collected using visual encounter surveys in three habitat types found on eight exurban properties in southwestern Manitoba: mowed lawn, gardens–flower beds, and native prairie. At each capture site, and at three other randomly selected sites within 10 m of each capture site, we recorded percent cover of grasses, forbs, small shrubs, bare ground, litter, and cover material. To measure thermal habitat characteristics we placed iButton® temperature loggers in each of the three habitat types. Prairie Skinks were found most commonly in native prairie and were significantly more likely to be found in areas with more artificial cover material. The number of Prairie Skink captures increased significantly as cover abundance per acre increased. Vegetation height was the most important factor moderating temperature among the habitat types. Cover may also be important on properties with minimal heterogeneity in the vegetation structure. Suitable Prairie Skink habitat exists on exurban land, specifically remnant prairie and with an abundance of artificial cover material. This type of habitat could become more important as habitat conversion continues throughout the Prairie Skink's range.
In order to investigate the movement and home range of the Mongolian racerunner, Eremias argus in Taeanhaean National Park, we conducted a capture-recapture study between May 2008 to June 2009. We captured 164 individuals and recaptured 28 individuals. The moved distance of E. argus during the study period was 20.9 ± 52.1 m (male 44.8 ± 110.2 m, female 14.1 ± 12.3 m), and the home range of four lizards were estimated as 4 m2, 7 m2, 34 m2 and 84m2 (31.5 ± 37.8 m2), respectively.
Understanding the spatial ecology of species at risk is essential for conservation because this information forms the base from which management and recovery plans are delineated. We studied microhabitat selection and evaluated the effect of reproductive class on daily movement patterns, home ranges, and seasonal activity of Blanding's Turtles in the St. Lawrence Islands National Park, Ontario, Canada. We also consider the potential conservation/management ramifications of differences in habitat use between the reproductive classes. We monitored 38 Blanding's Turtles (20 males, 13 gravid females, and 5 nongravid females) from April 2008 to August 2009 via radiotelemetry. Reproductive class did not have a significant effect on the mean daily movement of turtles in May, July, and August. In June, however, gravid females moved significantly more (mean = 400 ± 49 m per day) than males (mean = 194 ± 22 m per day). Reproductive class also had a significant effect on turtle home-range size, although high individual variation was observed (range = 1.6–40.6 ha). Gravid females had significantly larger home ranges (mean = 20.3 ± 3.5 ha) did than both males (mean = 8.2 ± 1.8 ha) and nongravid females (mean = 7.3 ± 3.2 ha). At the microhabitat scale, Blanding's Turtles selected colder water with more submerged and floating vegetation and avoided open water. Our results highlight the importance of stratifying field observations and spatial data by reproductive class and time and including terrestrial habitat in home-range analyses of Blanding's Turtles.
Gerrhonotus coeruleus is a viviparous lizard that ranges into high latitudes and altitudes in western North America. Females in a population on the N coast of California (Mendocino Co.) reach sexual maturity in 32 months and produce a single litter each season. Relatively low clutch sizes (X̄ = 3.8 ± 0.2) contribute to low fecundity. Annual survivorship was approximately 73% for adults and 54% for juvenile lizards. Female survivorship exceeded male survivorship during 1974 and mean female size (87.7 ± 1.0 mm) was significantly larger than mean male size (83.6 ± 1.2 mm) the following year. Growth of females in a second coastal population (Monterey Co.) was more rapid and these lizards were larger at sexual maturity than Mendocino County females. Females in a montane population (El Dorado Co., Calif.) reached reproductive maturity when larger and older (44 months) than females in either coastal population although they attain a size in 32 months equal to Mendocino County females at the same age. Litter size, newborn size and relative clutch mass were significantly higher in the El Dorado County population. The evolution of delayed maturity and larger adult size in this species may result from selection for both larger litters and larger young.
We used pitfall traps and time-constrained searches to sample amphibians and reptiles and to describe their habitats in oak woodlands at three areas in California. We captured 766 individuals representing 15 species during pitfall trapping and 333 animals representing 15 species during the time-constrained searches. A total of 19 species were sampled. Across all study areas, several positive relationships were found between animal abundance and the cover of specific tree species. At Tejon Ranch, two salamanders - Batrachoseps nigriventris and Ensatina eschscholtzii croceater - were associated with canyon live oak (Quercus chrysolepis) and two lizards - Sceloporus occidentalis and Eumeces gilberti - were associated with California black oak (Q. kelloggii). At San Joaquin, B. nigriventris was associated with foothill pine (Pinus sabiniana), as was B. attenuatus at Sierra Foothill. Generally, salamanders were found in live oak woodlands on north-facing slopes at Tejon Ranch, or on north-facing woodlands dominated by foothill pine and interior live oak (Q. wislizenii) at Sierra Foothill and San Joaquin. In contrast, lizards used more xeric and open habitats dominated by California black oak, blue oak (Q. douglasii), and valley oak (Q. lobata). As would be expected for terrestrial and fossorial animals, litter depth, the development of grasses and forbs, and cover by downed woody debris and rocks were important in the habitat models. At Sierra Foothill and San Joaquin, these latter variables, in addition to slope, were of primary importance in the habitat models.