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Standard techniques for inventory and monitoring
... rare or common; small-or large-bodied), habitat characteristics (e.g. rocky outcrops or plains; dense or sparse vegetation), and the temporal and/or geographic scope of the study (Foster, 2012). Because many of these factors influence cost, one should consider in advance if there are sufficient funds, personnel, and equipment for the study. ...
... The technique entails non-random or random searches by one or more observer(s) for individuals of one or more species within a selected area. Researchers or managers can modify the methodology easily to answer simple or more complex questions, such as to confirm presence or absence of a target species, or to estimate abundance and trends in abundance over time or space (Foster, 2012). By collecting more than locality data during surveys (see Table 14.1), the method can also provide information on population characteristics (e.g. ...
... VESs to estimate relative abundance can be time-, distance-, or area-constrained, and the results can be expressed as either individuals per person-hour, per distance, or per unit area (Fasham and Mustoe, 2005;Foster, 2012). For example, if four observers participate in a five-hour survey and find 12 turtles, sampling effort would amount to 20 person-hours and relative abundance to 0.6 individuals per person-hour. ...
... Se pueden utilizar distintos tipos de trampas para capturar vivas a las serpientes, como las trampas de caída, solas o acompañadas de cercos de desvío, y las trampas de embudo (Foster, 2012). Asimismo, aunque se ha recomendado el uso de trampas de pegamento (Mengak, 2004), es muy común que las serpientes mueran adheridas a las trampas, además, estas trampas no son selectivas y muchos otros animales podrían adherirse y morir, por lo que no se recomienda su uso. ...
... Debido a que los intervalos de alimentación de las serpientes son muy espaciados e irregulares, el uso de trampas con cebos no funciona tan bien como con los mamíferos y las aves (Klauber, 1982). Además, las trampas de caída deben ser lo suficientemente grandes para evitar que las serpientes que hayan caído en la trampa escapen y deben colocarse en grandes cantidades (Foster, 2012), por lo tanto, su uso puede resultar caro y laborioso y no asegura el control total de las serpientes alrededor de una casa; por consiguiente, es una práctica poco viable para la mayoría de las comunidades rurales o periurbanas de México. ...
El conflicto entre los humanos y las serpientes ha existido desde el principio de la humanidad y, aunque el
temor y la aversión hacia estos animales podrían tener una explicación evolutiva y pueden estar justificados
por la presencia de especies venenosas y mortales para el hombre, que causan miles de muertes al año, la
percepción social, los medios de comunicación, los mitos e incluso la religión acrecientan y alimentan el temor
hacia estos animales, por lo que en muchos lugares el sacrificio intencionado de serpientes es una práctica
común. Esta situación también ocurre en México, un país megadiverso que acoge a la mayor diversidad de
serpientes de todo el mundo y en el que también existe una problemática seria a causa de las mordeduras
de serpientes. Aquí presentamos una revisión de este conflicto desde distintas perspectivas, para tratar de
entenderlo, proponer posibles soluciones para mitigarlo y contribuir a la conservación de las serpientes
... Two different and complementary sampling methods were used. Visual encounter surveys without time constraints (VES) were used to sample areas where no pitfall traps were placed, inside the forest and close to water bodies ( Figure 1) aiming to cover the largest area possible (Foster 2012). All pitfall traps were installed in straight line with buckets of 30 liter and five-meter drift fences between each bucket, at specific sites (Foster 2012). ...
... Visual encounter surveys without time constraints (VES) were used to sample areas where no pitfall traps were placed, inside the forest and close to water bodies ( Figure 1) aiming to cover the largest area possible (Foster 2012). All pitfall traps were installed in straight line with buckets of 30 liter and five-meter drift fences between each bucket, at specific sites (Foster 2012). Sampling efforts were distinct in each expedition. ...
The northern most portion of Atlantic Forest is currently considered as the most vulnerable and threatened in this ecoregion, while also harboring the ecoregion’s least studied biota. Herein we present results of a herpetofaunistic survey in Refúgio de Vida Silvestre (Wildlife Refuge) Matas de Água Azul (RVSMAA), in the mountain range Serra do Mascarenhas, northeastern state of Pernambuco, Brazil, one of the largest forest remnants in the northern Atlantic Forest. The sampling was carried out in four expeditions using methods of visual searching and pitfall traps. A total of 43 species of amphibians and 40 species of reptiles were registered, including anurans, caecilians, lizards, snakes and chelonians. The richness recorded represented 56% of amphibians and 20% of reptiles registered in the Atlantic Forest north of the São Francisco River. The RVSMAA holds a high diversity of amphibians and reptiles, representing one of the highest levels of richness in the northern Atlantic Forest. The record of seven species included in some of the threatened species lists reinforces the importance of the area for the conservation of the Atlantic Forest herpetofauna and adds relevant information to our knowledge of northern Atlantic Forest biodiversity and aids in its assessment of conservation.
... Transect surveys that rely on visual encounters (hereafter referred to as visual surveys) are commonly used to estimate the distribution of organisms within a landscape (Foster 2012). With relatively low cost and effort, such surveys allow sampling over geographically extensive areas and enable scientists to model population characteristics at large spatial scales ( MacKenzie et al. 2006, Glisson et al. 2017). ...
... Additional field tests would be necessary to distinguish between these competing hypotheses to explain the higher CPUE for snakes encountered on edge transects. Importantly, edge surveys are frequently used to inventory herpetofauna, especially in densely vegetated habitats (Foster 2012). Habitat suitability estimates that incorporate such surveys may be extremely biased if edge detections are not parameterized differently from interior habitat detections. ...
Abstract Transect surveys are frequently used to estimate distribution and abundance of species across a landscape, yet a proportion of individuals present will be missed because either they were out of view and unavailable for detection or they were available but not detected because the surveyors missed them. These situations lead to availability and perception bias, respectively, and can result in misleading estimates of abundance and habitat use. In this study, we examined potential biases of visual surveys used for the brown tree snake (Boiga irregularis), a cryptic invasive snake responsible for the extirpation of at least 15 vertebrates on Guam. We simultaneously executed visual surveys and radiotelemetry in a low‐density population of brown tree snakes with two goals in mind: to assess the efficacy of visual surveys in detecting subjects at low densities and to identify sources of perception and availability bias in such surveys. Results indicated that with considerable effort, visual surveys can predict the presence of this cryptic reptile even at low densities (0.4 animals/ha) but perform poorly at predicting areas of high use resulting in inaccurate estimates of relative habitat importance. Telemetered snakes used densely foliated plants including Pandanus tectorius and ferns (epiphytic and terrestrial species) for nearly half of their time, yet
... We used two collection methods: Pitfall Traps (PFT) (Cechin and Martins 2000;Foster 2012) and Time Constrained Search (TCS) (Martins and Oliveira 1999). Specimens recorded through Incidental Encounters (IE), run over on roads (Road) and collected by third parties (CTP) were also considered. ...
... The combined use of these methods aided in the compilation of a representative sample for the region, considering that they are complementary methods and access different faunas (Ávila-Pires et al. 2007;Maschio et al. 2009;Foster 2012). ...
We present the first lizard species list for the municipality of Juruti, state of Pará, Brazil. The list was drawn up as a result of data obtained from specimens deposited in the Herpetological Collection of the Museu Paraense Emílio Goeldi and from inventories conducted in 2008-2011. Sampling methods included pitfall traps with drift fences and time constrained searches. We considered the data collected by other researchers, incidental encounters and records of dead individuals on the road. We recorded 33 species, 26 genera and ten families. Norops tandai was the most abundant species. Compared with the other regions of Amazonia, the region of Juruti presented a large number of lizards. However, further studies with an increase in the sampling effort, could prove this area to be richer in lizards than that observed so far.
... We used two collection methods: Pitfall Traps (PFT) (Cechin and Martins 2000;Foster 2012) and Time Constrained Search (TCS) (Martins and Oliveira 1999). Specimens recorded through Incidental Encounters (IE), run over on roads (Road) and collected by third parties (CTP) were also considered. ...
... The combined use of these methods aided in the compilation of a representative sample for the region, considering that they are complementary methods and access different faunas (Ávila-Pires et al. 2007;Maschio et al. 2009;Foster 2012). ...
We present the first lizard species list for the municipality of Juruti, state of Pará, Brazil. The list was drawn up as a result of data obtained from specimens deposited in the Herpetological Collection of the Museu Paraense Emílio Goeldi and from inventories conducted in 2008-2011. Sampling methods included pitfall traps with drift fences and time constrained searches. We considered the data collected by other researchers, incidental encounters and records of dead individuals on the road. We recorded 33 species, 26 genera and ten families. Norops tandai was the most abundant species. Compared with the other regions of Amazonia, the region of Juruti presented a large number of lizards. However, further studies with an increase in the sampling effort, could prove this area to be richer in lizards than that observed so far.
... Systematic strip-and line-transect surveys are popular, statistically robust methods for estimating abundance of organisms, including cetaceans and ice-associated pinnipeds (Buckland et al., 2001;Williams et al., 2002;Elphick, 2008;Foster, 2012;Hammond et al., 2021). However, survey-derived abundance estimates can be biased when animals that are visible to observers are not seen (perception bias), or when they are unavailable to be counted because they are concealed by vegetation, boulders, other animals or turbid waters (availability bias) (Caughley, 1974;Marsh and Sinclair, 1989;Buckland et al., 2004;Brack et al., 2019). ...
Abundance estimation of wildlife populations is frequently derived from systematic survey data. Accuracy and precision of estimates, however, depend on the number of replicate surveys, and on adjustments made for animals unavailable to (availability bias), or available but undetected (perception bias) by observers. This study offers a comprehensive analysis of the relative influence of methodological, environmental and behavioral factors on availability bias estimates from photographic and visual aerial surveys of a small cetacean with a highly clumped distribution, the beluga (Delphinapterus leucas). It also estimates the effect of the number of surveys on accuracy and precision of abundance estimates, using 28 replicate visual surveys flown within a 16—29 day window depending on survey year. Availability bias was estimated using detailed dive data from 27 beluga from the St. Lawrence Estuary, Canada, and applied to systematic visual and photographic aerial surveys of this population, flown using various survey platforms. Dive and surface interval durations varied among individuals, and averaged (weighted) 176.6 s (weighted s.e. = 12.6 s) and 51.6 s (weighted s.e. = 4.5 s), respectively. Dive time and instantaneous availability, but not surface time, were affected by local turbidity, seafloor depth, whale behavior (i.e., whether beluga were likely in transit or not), and latent processes that were habitat-specific. Overall, adjustments of availability for these effects remained minor compared to effects from survey design (photographic or visual) and type of platform, and observer search patterns. For instance, mean availability varied from 0.33—0.38 among photographic surveys depending on sightings distribution across the study area, but exceeded 0.40 for all visual surveys. Availability also varied considerably depending on whether observers searched within 0-90° (0.42—0.60) or 170° (0.70—0.80). Simulation-based power analysis indicates a large benefit associated with conducting more than 1 or 2 survey reps, but a declining benefit of conducting > 5—10 survey reps. An increase in sample size from 2, to 5, and 10 reps decreased the CV from 30, to 19 and 13%, respectively, and increased the probability of the abundance estimate being within 15% of true abundance from 0.42, to 0.59 and 0.69 in species like beluga.
... Two individuals conducted each survey accumulating 3,388 person-hours. We used Visual Encounter Surveys (Foster 2011), and we captured and measured all observed snakes recording all the microhabitats where snakes were seen. We made all measurements in situ immediately after capture and released the specimens shortly thereafter. ...
Understanding the variation of morphological traits in a population is essential to comprehend their ecological interactions and their role in the ecosystem in a given geographic region. Here, we evaluated the sexual dimorphism of the Blunt-headed Tree Snake (Imantodes cenchoa) in Los Tuxtlas, Veracruz, Mexico, using data from 263 specimens sampled between 2013-2019. We found 164 adults, 74 juveniles, and 25 hatchlings. Adults were sexually dimorphic where females are larger than males in head length (t = 5.42, df = 138.94, P < 0.001) and width (t = 4.42, df = 142.79, P < 0.001), and weight (t = 2.00, df = 131.52, P < 0.001). Our findings do not match reports from other populations within the broad geographic distribution of the species along México and Central and South America. These differences can be better attributed to differential effects of sexual selection between populations, rather than to an effect of the sampling method used. We expect our results may trigger research comparing sexual dimorphism among broadly distributed populations of tropical snakes.
... Sampling herpetofauna in tallgrass environments can be difficult due to the cryptic nature of reptiles and amphibians (Fitch, 1987;Szaro et al., 1988). Visual sampling is a common method for sampling snake species (Foster, 2012), however, small, cryptic, or camouflaged species are often difficult to detect in areas of thick vegetation due to their slender bodies (Turner, 1977;Ward et al., 2017). One efficient form of sampling includes the use of coverboards constructed out of sheets of various heat conducting materials, such as metal, wood, rubber, or asphalt roofing (Fitch, 1987;Engelstoft and Ovaska, 2000). ...
We assessed habitat use and preference with respect to artificial coverboards for the snake community of a restored tallgrass prairie. Coverboards offer herpetofauna protection from predators and space to thermoregulate their body temperature. These covers also create microhabitats that differ from their surrounding habitat. We placed plywood and metal coverboards along a transect that crossed from prairie floodplain into upland prairie. Coverboards were checked over a three-week period during the fall season, during morning, afternoon, and dusk. Snake species were identified and counted, and ambient temperatures and humidity were checked under each coverboard. We found four snake species across the habitat gradient, common gartersnake (Thamnophis sirtalis), plains gartersnake (T. radix), Dekay’s brownsnake (Storeria dekayi), and Western foxsnake (Pantherophis ramspotti). Species richness was greatest in the floodplain habitat and microhabitat associated with metal coverboards. The floodplain habitat was also the habitat predominantly used by common gartersnake and Dekay’s brownsnake. Dekay’s brownsnakes, furthermore, preferred utilizing metal coverboards over wood. The composition of snake species we observed suggests that the restoration efforts on this tallgrass prairie system have attracted some grassland snake species, but the possibility of a greater snake community remains. Our data suggest that using metal coverboards during the cooler active seasons, such as fall and spring, will increase capture success and more efficiently sample snake communities. Studies such as ours to better understand habitat and coverboard use will result in more efficient sampling of herpetofauna for conservation and monitoring efforts.
... La unidad de muestro fueron parcelas de 1000 m 2 en un diseño estratificado (Foster, 2011). Fueron ubicadas siete parcelas en cada hábitat, lo más regular posible de acuerdo a la accesibilidad a los sitios y con distancias entre ellas de 50 a 200 m, excepto dos parcelas en la zona urbana que fue necesario colocarlas a una distancia de 30 m (Fig. 1). ...
La conservación de la importante riqueza herpetofaunística de México está fuertemente amenazada por la antropización, que ha causado alteración en más de la mitad del país, por lo que la herpetofauna debe ser evaluada en estos ambientes antropizados. Este trabajo evaluó la riqueza y composición de la herpetofauna en tres ambientes con diferentes niveles de alteración de un paisaje rural de la Sierra Madre Oriental en San Luis Potosí, México. Las hipótesis planteadas fueron que el matorral submontano como ambiente más natural presentaría mayor riqueza de especies que los ambientes antropizados (urbano y agrícola), y que la composición de especies es diferente entre dichos ambientes. El diseño de muestreo fue estratificado por ambiente, en cada uno fueron muestreadas siete parcelas en cuatro ocasiones durante temporada de lluvia del 2015. La completitud del muestreo fue calculada, y la riqueza, diversidad y composición de especies fueron comparadas. Durante el estudio fueron registradas 12 especies, cinco de ellas con estatus de conservación o endémicas a México. El ambiente con mayor riqueza fue el matorral submontano, que además presentó todas las especies con estatus de conservación y endémicas. El ambiente urbano presentó menor riqueza de reptiles, pero mayor de anfibios. Una riqueza y abundancia menores fueron presentadas en el ambiente agrícola. La composición de especies fue diferente entre ambientes, si bien hay importantes diferencias entre las parcelas de cada ambiente. Estos resultados muestran que se cumplieron las hipótesis planteadas, y que es importante realizar acciones de manejo principalmente alrededor del cuerpo de agua y en la zona de cultivos.
... Two individuals conducted each survey accumulating 3,388 person-hours. We used Visual Encounter Surveys (Foster 2011), and we captured and measured all observed snakes recording all the microhabitats where snakes were seen. We made all measurements in situ immediately after capture and released the specimens shortly thereafter. ...
Understanding the variation of morphological traits in a population is essential to comprehend their ecological interactions and their role in the ecosystem in a given geographic region. Here, we evaluated the sexual dimorphism of the Blunt-headed Tree Snake (Imantodes cenchoa) in Los Tuxtlas, Veracruz, Mexico, using data from 263 specimens sampled between 2013-2019. We found 164 adults, 74 juveniles, and 25 hatchlings. Adults were sexually dimorphic where females are larger than males in head length (t = 5.42, df = 138.94, P < 0.001) and width (t = 4.42, df = 142.79, P < 0.001), and weight (t = 2.00, df = 131.52, P < 0.001). Our findings do not match reports from other populations within the broad geographic distribution of the species along México and Central and South America. These differences can be better attributed to differential effects of sexual selection between populations, rather than to an effect of the sampling method used. We expect our results may trigger research comparing sexual dimorphism among broadly distributed populations of tropical snakes.
... possible changes in fly activity due to strong wind or heavy rain), we surveyed sites 3-8 on 2 nights each, with a gap of 2 days before site revisiting sites. At these sites, we ran audio-visual surveys (Foster, 2012) along a 100 m transect in addition to collecting dipterans for iDNA surveys. Because the primary targets of our iDNA surveys were frogs, we focussed only on frogs during transect surveys. ...
Well‐informed biodiversity conservation practice can often be precluded by poor species detectability. For example, populations being missed during surveys can lead to them being omitted from species lists or area management plans. iDNA (invertebrate‐derived DNA) is a recently developed set of techniques for improving the detectability of elusive vertebrates by exploiting their associated invertebrates. Parasitic and scavenging invertebrates can be readily collected, and their gut contents DNA barcoded to detect local vertebrate diversity. However, most iDNA surveys have targeted mammals and have been carried out in tropical areas and/or rainforests. We carried out iDNA surveys targeting frogs in temperate dry sclerophyll forests in south‐eastern Australia. We set mosquito traps broadcasting recorded frog calls with the aim of collecting frog‐biting flies, which are attracted to frog calls. We collected 156 fly specimens, although none were of frog‐biting species, and no frogs were detected via iDNA, despite many being observed in the field. However, two mammal and one reptile species were detected via iDNA: the feral cat ( Felis catus : Felidae), domestic dog or dingo ( Canis lupus : Canidae) and the threatened Rosenberg's monitor ( Varanus rosenbergi : Varanidae). Vertebrate‐sampling flies are likely highly abundant in the area since they were collected apparently incidentally in traps lacking appropriate attractants; a promising result for further surveys is different attractants are employed. This study is one of the few in which an invasive species has been detected through iDNA, and highlights its potential for improved detectability of threatened species outside of the tropics and early detection of invasive species.
... For the ESEC de Murici, expeditions were carried out every two months of 3 to 4 consecutive days by EMXF, ST and collaborators between the years 1994 to 1996. The sampling effort was entirely employed using the active search method, totaling 1,450 hours/person (Foster 2012 ...
Currently the Atlantic Forest hotspot has less than 11% of its original coverage. However approximately 300 species of reptiles are known to inhabit this ecoregion, of which 34% are endemic. The creation of protected areas represents a strategy for preserving ecosystems and managing land use, and for attaining the proper management of these protected areas, information on local biodiversity is essential. Herein we provide the first list of reptile species for the Estação Ecológica and Área de Proteção Ambiental de Murici, two overlapping protected areas located in the state of Alagoas, one of the most important sets of forest remnants for the conservation of the Atlantic Forest in the northeast of Brazil. The species list was constructed based on expeditions and occasional encounters in the area between 1994 and 2022. A total of 89 reptile species were obtained during the 28 years of collection, being two species of Crocodylia, three species of Testudines and 84 species of Squamata. This richness is by far one of the greatest ever documented for the Atlantic Forest. Additionally, two species registered in the area are considered threatened according to the national list (Amerotyphlops paucisquamus and Bothrops muriciensis) and six are defined as data deficient for the assessment of their conservation status. Three species are recorded for the first time in the Atlantic Forest north of the São Francisco River: Dipsas indica, Trilepida salgueiroi and Cercophis auratus. We claim that the species list provided here will serve as a starting point for further studies in this rich reptile “hotspot” within the Atlantic Forest.
... We opportunistically captured amphibians and reptiles through visual detection within each segment, searching different habitats (native vegetation, crop fields, and urban areas) and microhabitats (trunks, rocks, bodies of water, cracks, among others) in which these organisms are known to occur (Casas-Andreu et al. 1991;Foster 2011). We captured, photographed, and identified the specimens at the species level using the taxonomic keys for amphibians and reptiles of Queretaro (Dixon and Lemos-Espinal 2010). ...
The spatial patterns of herpetofaunal diversity through elevational gradients have been little studied and therefore many aspects of their composition, arrangement, and functioning are unknown, especially in the mountainous areas of central Mexico. The Sierra Madre Oriental of Querétaro shows high environmental diversity in a small area with a range of vegetation, climate, and topography. This is reflected in the high vertebrate diversity, especially among amphibians and reptiles. We described and compared the diversity of amphibians and reptiles along an elevational gradient ranging from 1,028-3,100 m above sea level. Within seven segments along this gradient, we carried out systematic searches in microhabitats suitable for amphibians and reptiles. We conducted visual searches for a total of 680 person-hours during the rainy season of 2014 (July and August) and the dry season of 2015 (January, February, and March). We identified nine amphibian and 20 reptile species. Of these species, 41.1% are listed under some category of protection under Mexican law and 65.5% are endemic to Mexico. The communities above and below 1,900 m differed in their species composition with more species recorded at higher elevations; this change was associated with climatic and vegetation turnover. We found a significant nonlinear relationship between species richness and elevation with differences in community structure by elevation. Due to the high percentage of protected and endemic species and the dramatic turnover in community structure identified, we agree with proposals recommending the integration of the study area into a system of protected mountainous areas.
... Two persons checked both, transects and traps, three times a day, accumulating a sampling effort of 192 person-hours for transects and 2754 trap-hours for pitfall traps. We performed intensive visual encounter surveys along transects in the most frequent microhabitats for herpetofauna (under logs and tree stumps, rocks, ponds, and pools; Jiménez-Velázquez & Sandoval 2010;Foster 2011). Traps remained open during the night and until noon of the next day, paying special attention to provide shelter from weather and potential predators in each trap. ...
Due to its topographic and climatic diversity, the state of Querétaro presents high levels of amphibian and reptile richness, abundance, and endemism. However, this information must be updated constantly as regions with previously little to no information are further explored, using sampling methods that allow efficient recording of biological diversity. The objective of this study was to compare herpetofaunistic diversity among three different vegetation types (oak-forest, grassland, and secondary vegetation) using two sampling methods (pitfall traps and transects). We recorded thirteen species: five amphibians, and eight reptiles. We found differences in dominance between herpetofaunal groups, with amphibians showing higher values of relative abundance in oak forest and grassland for both sampling methods. Transects showed a higher effective number of species for q0, q1, and q2, for both, amphibians and reptiles. The oak forest and secondary vegetation possess comparable similarity percentages and did not show significant differences. We observed significant differences between the grassland and secondary vegetation. We ARTÍCULO CIENTÍFICO Tepos-Ramírez et al.-Herpetofauna of La Barreta-116-125 https://doi.
... Los muestreos se complementaron con transectos de encuentros visuales diurnos y nocturnos a pie (Foster, 2012), de 1 a 1.5 km de longitud en los distintos hábitats, realizados por 3-4 personas, entre 10:00-13:00 h y 20:00-22:00 h respectivamente. También se tomaron en cuenta los registros incidentales de organismos que se encontraron muertos o atropellados en caminos de acceso. ...
The Estero Punta Banda in Bahia Todos Santos, Baja California, is a coastal wetland of international importance considered a RAMSAR site and a priority area for biodiversity conservation. However, no formal studies have been carried out on the richness and diversity of amphibians and reptiles at this site, focused on knowing their richness and diversity. We selected five sampling sites on coastal dunes, crop fields, and riparian areas. Arrays of pitfall traps with drift fences were implemented, as well as diurnal and nocturnal visual encounter surveys. The herpetofauna of Estero Punta Banda is composed of 15 species of amphibians and reptiles, belonging to 13 genera and 10 families. The best-represented families were Phrynosomatidae and Colubridae, with the lizards Uta stansburiana, Aspidoscelis hyperythrus, and Sceloporus zosteromus being the most abundant. Ten species previously recorded in scientific collections were not observed in the field, it is possible that the alteration of habitat and threats in the area are causing the extirpation of species. We suggest carrying out actions to control exotic plant species, and avoid the spread of the urban area to prevent the loss of biodiversity at this site.
... There were a number of species for which we had very few detections that may be due to extremely low occupancy rates. However, many of these species, such as larger snakes, are not efficiently sampled with methods we used and alternative methods, such as larger pitfall traps, would likely improve detection rates (Dodd, 2016;Foster, 2012;Jones, 1986). ...
Population monitoring is fundamental for informing management decisions aimed at reducing the rapid rate of global biodiversity decline. Herpetofauna are experiencing declines worldwide and include species that are challenging to monitor. Raw counts and associated metrics such as richness indices are common for monitoring populations of herpetofauna; however, these methods are susceptible to bias as they fail to account for varying detection probabilities. Our goal was to develop a program for efficiently monitoring herpetofauna in southern Texas. Our objectives were to (1) estimate detection probabilities in an occupancy modeling framework using trap arrays for a diverse group of herpetofauna and (2) to evaluate the relative effectiveness of funnel traps, pitfall traps, and cover boards. We collected data with 36 arrays at 2 study sites in 2015 and 2016, for 2105 array-days resulting in 4839 detections of 51 species. We modeled occupancy for 21 species and found support for the hypothesis that detection probability varied over our sampling duration for 10 species and with rainfall for 10 species. For herpetofauna in our study, we found 14 and 12 species were most efficiently captured with funnel traps and pitfall traps, respectively, and no species were most efficiently captured with cover boards. Our results show that using methods that do not account for variations in detection probability are highly subject to bias unless the likelihood of false absences is minimized with exceptionally long capture durations. For monitoring herpetofauna in southern Texas, we recommend using arrays with funnel and pitfall traps and an analytical method such as occupancy modeling that accounts for variation in detection.
... Tortoises, Indotestudo elongata (Blyth 1854) (Fig. 1), and four Tricarinate Hill Turtles, Melanochelys tricarinata (Blyth 1856) (Fig. 2), during Visual Encounter Surveys (VES) (Foster et al. 2012;Hofmeyr and Henen 2016) along existing trails of the Forestry Campus Complex (FCC), Hetauda, Makwanpur, Nepal (Fig. 3). We also searched diligently for these species in various microhabitats around the periphery of the study site (~97 ha) (Pradhan et al. 2020). ...
... To determine the detectability of C. triseriatus, we performed monthly visits to each study site during 2012 and 2013 (24 visits to each one) and captured individuals of C. triseriatus. At each visit, five observers simultaneously walked five linear transects from 0900 to 1300 hours using the visual encounter survey (VES) technique (Foster, 2012). Each transect was approximately 800 m long and separated by 200 to 300 m. ...
Published by the British Herpetological Society Human activities have caused several changes in biotic communities all over the world. Some species maintain viable populations in altered environments through different adaptations, however, knowledge in this regard is scarce for certain taxa, including reptiles. We analysed the detectability and habitat selection of the rattlesnake Crotalus triseriatus to contribute to our knowledge about how this species responds to anthropogenic landscape change. Rattlesnakes were monitored for two years in two anthropized landscapes using visual encounter surveys. We analysed detectability in relation to climatic factors and human activity, and habitat selection was analysed in native and non-native vegetation. Our study shows that detectability of C. triseriatus is differentially affected in anthropized landscapes; human activity may be determinant in landscapes such as agricultural fields, whilst climatic factors may be determinant in landscapes where people are less active such as the protected areas within urban parks. The analyses of habitat selection shows that native vegetation is crucial for the persistence of C. triseriatus in the studied landscapes. Several strategies may allow rattlesnakes to persist in different anthropized landscapes; nonetheless, native habitat remnants should be protected in anthropized areas to conserve wildlife.
... Metodología Avifauna El principal método utilizado para la observación de aves corresponde a los recorridos de observación o Visual Encounter Surveys (VES) (Foster, 2012) dentro de la zona de influencia del proyecto, en horarios previamente establecidos. Para aves, las observaciones se hicieron entre las 06:00 y las 11:00 horas y entre las 16:30 y las 18:30 horas (las especies observadas fuera de este horario se registraron dentro del muestreo, incluyendo las observadas en la noche). ...
... VISUAL encounter surveys, often done on foot, are a standard method for surveying reptiles and amphibians (Hutchens and DePerno 2009;Foster et al. 2012). Detection might be hampered by target organisms being small, cryptic, motionless, and/or occupying a habitat that might obscure them from the surveyor's vantage point. ...
... Visual encounter surveys are an important and widely used animal sampling tool, providing the data necessary to monitor populations and quantify the impacts of environmental change (Foster et al. 2012). Unfortunately, detections and counts may depend on a wide variety of factors besides size and/or density of the focal population. ...
Context
Visual encounter surveying is a standard animal inventory method, modifications of which (e.g. distance sampling and repeated count surveys) are used for modelling population density. However, a variety of factors may bias visual survey counts.
Aims
The aim of the present study was to evaluate three observer-related biases: (1) whether fatigue compromises detection rate as a survey occasion progresses; (2) whether long-term fatigue or boredom compromise detection rates over the course of a survey period; and (3) whether observers exhibit biases in detection rates of different animal taxa.
Methods
We analysed >2.3 × 10⁴ observations of lizards and small mammals from nocturnal pedestrian visual encounter surveys, each 4 h in duration, conducted by a pool of 29 observers, each of whom surveyed for up to 31 nights.
Key results
Detections of sleeping (diurnal) emerald tree skinks (Lamprolepis smaragdina) exhibited a small but statistically verified decline as the evening progressed, whereas detections of sleeping (diurnal) green anoles (Anolis carolinensis) increased as the evening progressed. Detections of nocturnal geckos (several species pooled) showed a weak and non-significant declining trend. Small mammal sightings (rats, shrews and mice pooled) declined strongly over the course of an evening. The participants saw greater or equal numbers of animals the more nights they surveyed. Most participants exhibited statistically significant, and often strong, taxonomic detection bias compared with the pool of peer observers. The skills of some observers appeared to be consistently above average; others consistently below average.
Conclusions
Data on sleeping lizards suggest that neither short-term nor long-term observer fatigue is of much concern for 4-h visual searches. On the contrary, differences among observers in taxonomic bias and overall detection skills pose a problem for data interpretation.
Implications
By comparing temporal detection patterns of immobile (e.g. sleeping) with actively moving animal taxa, sampling biases attributable to searcher fatigue versus the animals’ circadian rhythm can be disentangled and, if need be, statistically corrected for. Observer skill differences and observer-specific taxonomic biases may hamper efforts to statistically evaluate survey results, unless explicitly included as covariates in population models.
... To increase the set of truly sampled species and to obtain a more accurate estimation of the total richness, biodiversity students can combine (i.e., add up) data obtained with different sampling methods. This practice is known as a structured inventory ( Gotelli and Ellison, 2013) and it has frequently been applied in biodiversity studies (for instance, see King and Porter, 2005;Coddington et al., 2009;Gotelli et al., 2011, or Castro et al., 2017Jenkins et al., 2003;Hutchens and DePerno, 2009;Sung et al., 2011;Foster, 2012, or Carpio et al., 2015, for amphibians and reptiles; or Pech Canche et al., 2011, for bats). Nevertheless, because of systematic biases in favor of or against certain activity periods, animal behaviors or body sizes ( Hutchens and DePerno, 2009), the different sampling methods applied in a structured inventory can differ in their probability to capture different species ( Yoccoz et al., 2001). ...
Many sampling methods allow the study of species richness and diversity in biological communities, but it is not known whether a single method can determine both the number and diversity of species in an unbiased and efficient way. Here we assess whether the least biased and most efficient method to determine reptile species richness in a Mexican dry scrubland is also the best method to estimate species diversity. The local assemblage was composed of 10 species, with the Mexican mud turtle (Kinosterton integrum) and the Jalapa spiny lizard (Sceloropus jalapae) being the dominant ones. Microhabitat surveys (MHS) were the most accurate and the most efficient method to estimate species richness, but they over–estimated species diversity (+67.1%) as much as the other sampling methods, i.e., transect surveys and pitfall–trap stations, under–estimated it (–59%). Our study shows that the best sampling method to determine the number of species in local assemblages may not be the best method to study species diversity. Although combining different sampling methods can increase the project costs in terms of time, effort and money, the use of structured inventories is recommended for the analysis of species diversity.
... We conducted field sampling during May and June 2014. Reptiles were surveyed using line transects at the 16 study plots, as this is a widely followed method for measuring the population structure of terrestrial reptiles (Nomani et al., 2008; Foster, 2012). Within each plot, the transect had a ''U'' shape, with both sides of the path separated from each other at least 25 m, thus minimizing the possibility of data pseudoreplication (double counting of the same individual) according to the vagility of Iberian reptiles (review in Salvador, 2014). ...
... Neste período foram realizadas nove visitas a campo, perfazendo um total de 35 dias de amostragem, com cada ponto amostral sendo visitado somente uma vez. Para os anuros em fase adulta, os corpos d'água foram amostrados durante o período noturno utilizando-se os métodos de "amostragem por encontro visual" (Crump & Scott Junior 1994) e "transectos auditivos" (Zimmerman 1994 ...
The Cerrado is the second largest biome in Brazil and is considered one of most important among the biodiversity hotspots. In this biome can be found about 150 anurans species, from which 30% are endemic. However, there are many Cerrado areas that have little information gathered about the anuran biodiversity. Thus, in this study we present the result of an inventory of anurans species from the southwest region of Goiás State (Central Brazil). In this region, we sampled 45 water bodies, located near soybean and sugar-cane cultures, pastures and natural vegetation, from November/2007 to February/2008 and from November/2008 to March/2009. Altogether, adults and tadpoles of 36 species were registered, with the majority of species registered in association to open areas. The rarefied curve of species richness show an asymptote formation, which indicates that the chance to add species to the inventory is low, even with additional habitats sampling. Therefore, our results reveal high species richness in the present sampled region, which represented almost one fourth of all species found in Cerrado.
... O inventário da herpetofauna foi realizado entre setembro de 2007 e março de 2008, em sete etapas de campo mensais de cinco dias cada, totalizando 35 dias de amostragem. Foram utilizados três métodos complementares de amostragem ativa: procura auditiva, procura visual e encontro ocasional (Crump & Scott Junior 1994, Sawaya 2004. A procura auditiva (PA) e visual (PV) consistiu em censos realizados no período noturno por duas pessoas, em transectos previamente definidos. ...
Despite its great extension and biodiversity, there are still sampling gaps in the Cerrado. This region has shown drastic changes due to the conversion of natural areas into pastures and plantations. In the last four decades, around 88.5% of the Cerrado areas in the state of São Paulo were supressed. Only 0.8% of Cerrado original cover in the state (14%) remain as pristine habitats. We present the species composition, abundance and use of habitat of amphibians and reptiles recorded at Estação Ecológica de Assis, a remnant of Cerrado in the state of São Paulo. The survey was conducted between September 2007 and March 2008 during seven monthly field trips of five days each, totaling 35 sampling days. Surveys were conducted using pitfall traps (AIQ), incidental encounters (EO), auditory encounters (PA), and visual encounters (PV). In addition to the field samples, we included records of species occurring on the municipality of Assis, obtained at the main scientific collections of amphibians and reptiles in the state of São Paulo. We recorded 27 amphibian species, belonging to 13 genera and six families (Bufonidae, Cycloramphidae, Hylidae, Leiuperidae, Leptodactylidae, and Microhylidae), and 53 reptile species belonging to 38 genera and 13 families (Amphisbaenidae, Anguidae, Gekkonidae, Gymnophthalmidae,
Polychrotidae, Scincidae, Teiidae, Anomalepididae, Boidae, Colubridae, Dipsadidae, Elapidae, and Viperidae). This survey is an important contribution to the knowledge about these assemblages in the highly threatened Cerrado of the state of São Paulo. Remnants such as the Estação Ecológica de Assis are extremely important for the conservation of amphibians and reptiles in the state and in the Cerrado region.
... iduais (Valente 2006). O clima é tropical quente e úmido, apresentando duas estações bem definidas, sendo uma seca de abril a setembro e outra chuvosa de outubro a março (Miner 1989). Os corpos d'água amostrados incluíam brejos, poças permanentes e temporárias, localizados próximos a plantações de soja, cana-de-açúcar, pastagem ou vegetação nativa.Crump & Scott Junior 1994) e " transectos auditivos " (Zimmerman 1994). Para melhor padronização dos dados, os corpos d'água foram percorridos http://www.biotaneotropica.org.br Biota Neotrop., vol. 11, no. 3 ...
The Cerrado is the second largest biome in Brazil and is considered one of most important among the biodiversity hotspots. In this biome can be found about 150 anurans species, from which 30% are endemic.
However, there are many Cerrado areas that have little information gathered about the anuran biodiversity. Thus, in this study we present the result of an inventory of anurans species from the southwest region of Goiás State (Central Brazil). In this region, we sampled 45 water bodies, located near soybean and sugar-cane cultures, pastures and natural vegetation, from November/2007 to February/2008 and from November/2008 to March/2009. Altogether, adults and tadpoles of 36 species were registered, with the majority of species registered in association to open areas. The rarefied curve of species richness show an asymptote formation, which indicates that the chance to add species to the inventory is low, even with additional habitats sampling. Therefore, our results reveal high species richness in the present sampled region, which represented almost one fourth of all species found in Cerrado.
... iduais (Valente 2006). O clima é tropical quente e úmido, apresentando duas estações bem definidas, sendo uma seca de abril a setembro e outra chuvosa de outubro a março (Miner 1989). Os corpos d'água amostrados incluíam brejos, poças permanentes e temporárias, localizados próximos a plantações de soja, cana-de-açúcar, pastagem ou vegetação nativa.Crump & Scott Junior 1994) e " transectos auditivos " (Zimmerman 1994). Para melhor padronização dos dados, os corpos d'água foram percorridos http://www.biotaneotropica.org.br Biota Neotrop., vol. 11, no. 3 ...
Biota Neotropica is an electronic, peer-reviewed journal edited by the Program BIOTA/FAPESP: The Virtual Institute of Biodiversity. This journal's aim is to disseminate the results of original research work, associated or not to the program, concerned with characterization, conservation and sustainable use of biodiversity within the Neotropical region. Biota Neotropica é uma revista do Programa BIOTA/FAPESP -O Instituto Virtual da Biodiversidade, que publica resultados de pesquisa original, vinculada ou não ao programa, que abordem a temática caracterização, conservação e uso sustentável da biodiversidade na região Neotropical.
La disminución de la biodiversidad global implica la necesidad de estudiar el estado del ecosistema, no solo en sitios conservados sino también en paisajes con uso de suelo diversificado y en territorio bajo aprovechamiento. Con base en los esfuerzos que se realizan a nivel nacional para la colecta de datos biológicos en Perú y México, así como en diferentes referentes internacionales y a partir de la generación, implementación y análisis de protocolos de monitoreo de la biodiversidad en áreas de manejo forestal en ambos países, se elaboró, mediante un proceso lógico-participativo, un protocolo unificado de monitoreo de la biodiversidad en áreas bajo aprovechamiento, capaz de generar información en tres escalas de aproximación territorial y de emplearse en diferentes condiciones ecológicas. Las cuatro etapas para el desarrollo de las actividades fueron realizadas por un equipo de trabajo conformado por dos bloques con funciones complementarias: A) Análisis situacional y desarrollo metodológico, B) Implementación en campo de protocolos iniciales por país, análisis y diseño de protocolo unificado. Se obtuvieron coberturas de muestra que van de 0,039 a 0,984 con el protocolo “transecto, punto, parcela” TPP (Perú) y de 0,937 a 0,996 con el “método transecto, punto” MTP (México), de acuerdo a las cuales se realizaron ajustes y redistribución de técnicas de muestreo en los grupos biológicos involucrados para delinear el protocolo unificado para el monitoreo de la biodiversidad (TPU). El diseño espacial unificado es un transecto lineal de 1 000 m, el cual dependiendo de la fisiografía puede cambiar de dirección (entre 45° a 90°). Se propone la estandarización en la toma de datos biológicos a nivel predial, ecosistema y paisaje mediante el citado diseño, el cual es capaz de articularse con trabajos de instituciones ambientales nacionales. El proceso desarrollado puede replicarse en otros países para fomentar una mayor estandarización.
Crotalus ravus es una serpiente de cascabel considerada especie prioritaria. Sin embargo, la zona donde se registró por primera vez en Hidalgo, México, tiene un bajo esfuerzo de muestreo, por lo que actualizar la información sobre su distribución en Hidalgo tiene relevancia biológica y para su conservación. En el presente trabajo se documentan nuevos registros de C. ravus en el sureste de Hidalgo, en los municipios de Almoloya de Juárez, Apan, Cuautepec de Hinojosa, Emiliano Zapata, Singuilucan, Tlanalapa y Zempoala. Los nuevos registros amplían la distribución de la especie 18.3 km al noroeste, 25.52 km al noreste, 13.34 km al suroeste y 25.9 km al sureste de los primeros registros en el estado. La mayoría de los registros se ubican en la zona conocida como la Altiplanicie Pulquera, un área de intensa actividad agrícola, donde pese a ello, C. ravus prospera en las bardas de rocas e hileras de magueyes que rodean o dividen las zonas de cultivo.
Two dimensions of the ecological niche (diet and habitat) of a snake assemblage from an endemic rich area in east-central Argentina, the Sierras de Ventania mountain chain, were analyzed. Field data collection was performed in 15-week study periods between 2010 and 2014. Snakes were hand-captured using transect surveys. Field observations on diet were analyzed together with stomach content data from museum specimens. Our results supported the partitioning of the snake assemblage by both habitat use and diet into at least three functional groups: species restricted to microhabitats under rocks and with a diet composed exclusively of ants (Epictia australis); species found mostly in stream microhabitats and feeding mainly upon anurans (Erythrolamprus poecilogyrus and Lygophis elegantissimus); and species found mostly in grassland microhabitats, with specialized diets of terrestrial prey items (Philodryas patagoniensis and Bothrops alternatus). Consistent with previous work, diet was more important than habitat in explaining ecological niche partitioning of this snake assemblage. Our results showed that high overlap values of microhabitat use were compensated by low overlap values of the trophic niche dimension, thus matching the traditional complementary niches hypothesis.
El estudio de las lagartijas (Reptilia: Squamata) es de gran interés para los investigadores de todo el mundo, principalmente porque han sido buenos modelos para estudios biológicos (morfología, ecología, comportamiento, fisiología, entre otros). Este estudio se enfocó en hacer un análisis cuantitativo de las publicaciones científicas que analizan las comunidades de lagartijas y las características de sus hábitats. Se realizó la búsqueda electrónica de artículos sobre los estudios de las comunidades de lagartijas y los atributos del hábitat que se consideran en su estudio. Este trabajo se basó en las publicaciones (1980 al 2015) registradas en la base de datos ISI Web of Knowledge a nivel mundial. Un total de 47 artículos fueron encontrados para este periodo. La mayor parte (68%) se realizaron con datos obtenidos en las regiones tropicales del planeta. Brasil fue el país que concentró el mayor número de artículos (15 de 47). Los resultados mostraron que el 55.31% de los artículos se publicaron en dos revistas. El método predominante de muestreo utilizado fue el de búsquedas visuales en sitios determinados (48.94%). La riqueza y abundancia de especies fueron los atributos estructurales de las comunidades de lagartijas más comúnmente citados en los artículos (51.06%). El estrato arbóreo fue la variable más citada en la caracterización del hábitat (19 artículos de 47 artículos). En general, fueron cuatro los métodos estadísticos utilizados con mayor frecuencia en los artículos: Análisis de Varianza (Anova) (16 artículos), Análisis de Correlación (14 artículos), Escalamiento Multidimensional No Métrico (11 artículos) y Análisis de Regresión (10 artículos). Se discuten los resultados encontrados.
A study is presented on the diversity and richness of the herpetofauna of the Usumacinta basin, based on 8,808 records from scientific collections, faunistic databases of the Comisión Nacional para el Conocimiento y Uso de la Biodiversidad, bibliographical references review, and field survey (2014-2015) for 3 study zones (Selva, Lagunas, and Costa) in the basin. For the study region, 42 species of amphibians and 110 species of reptiles were reported. The Selva zone was the richest in species, with 136, followed by Lagunas with 108 herpetozoos and Costa with a richness of 66 species. Values of effective number of species (qD) indicate differences between the study zones, showing Lagunas (¹D = 20.98 ± 3.35) the highest value, followed by Costa (¹D = 16.01 ± 2.35) and Selva (¹D = 11.63 ± 1.64). The diversity and composition of three functional guilds (anurans, turtles and crocodiles) were analyzed. Selva and Lagunas are the most important zones based on their high richness and diversity of amphibians and reptiles. © 2018 Universidad Nacional Autonoma de Mexico. All rights reserved..
The upstream of Gadjah Wong River is located north on the foothill of Mount Merapi and the downstream is on the south, fused with Opak River in the Bantul Regency. The research was aimed to acquire data about the diversity of snakes and lizards (Reptilia: Squamata) along the Gadjah Wong River in the Daerah Istimewa Yogyakarta. The snakes and lizards diversity data were collected using VES (Visual Encounter Survey) along the riverbank. Sampling area generally divided into three parts, i.e., upstream, midstream, and downstream. Species diversity of snakes and lizards in the Gadjah Wong River consists of nine snakes’ species (suborder Serpentes), and eight lizards’ species (suborder Lacertilia). Based on the species diversity recorded it can be concluded that the Gadjah Wong River, especially the upstream and midstream part is a decent habitat for some lizards and snakes.
Keywords: lizards, snakes, the Gadjah Wong River Yogyakarta
Despite the taxonomic, behavioral, and lifestyle diversity among reptile species, behavioral consistency in reptiles has not been examined to the extent that it has been in fish, birds, and mammals. Careful use of terms such as individuality, temperament, personality, and behavioral syndromes is needed as they carry overlapping connotations and varying dangers of being applied in an anthropomorphic fashion. The majority of research on such phenomena in reptiles has utilized snakes and lizards. Studies on antipredator behavior in natricine snakes, primarily in the genus Thamnophis, has produced strong evidence of individual consistency of behavior over time, some evidence for consistency across situations, clear evidence for a heritable basis for individual differences in antipredator behavior, and limited evidence linking individual variation with fitness-related outcomes. Research in lizards has mirrored findings reported for other vertebrates, focusing on one or more of five traits: shyness–boldness, exploration-avoidance, activity, sociability, conspecific aggression, and possible relationships among them. We review the methodology and statistical analyses used to study these traits in lizards and the relationships of these traits to morphology, reproduction, hormones, fitness, life history, and other factors. The common lizard (Zootoca vivipara) has become a model species, for example, in studies assessing the pace-of-life hypothesis, with results differing from those found in other vertebrates. Studies on turtles and crocodilians are also presented that further illustrate the comparative and methodological value of reptilian studies.
The herpetofauna of São Paulo State, Brazil, can be characterized as the most well-known in the country. However, despite the large number of studies in this area, there are still many sampling gaps within biomes such as the Atlantic Forest that are considered global conservation priorities due to the high rate of endemism and human disturbance. As a result of political and historical pressure, this biome has been reduced to less than 12% of its original extent and, despite its importance for global biodiversity conservation, only a small percentage of its original vegetation cover (1%) has some form of legal protection. This is the case of the Parque Estadual Turístico do Alto Ribeira (PETAR) which, together with the Parque Estadual de Intervales, Parque Estadual Carlos Botelho and Mosaico de Unidades de Conservação de Jacupiranga, forms of an ombrophilous forest continuum of 360 thousand ha in the south of São Paulo State. This study presents a list of amphibians and reptiles from the PETAR, with information on the local distribution and habitat use of the species. The survey was conducted from October to December 2009, completing a total of 15 sampling days using four complementary methods of active sampling: visual encounters, auditory encounters, searches by car and incidental encounters. We recorded a total of 91 species belonging to 53 genera and 24 families. This high diversity can be attributed to the existence of a wide variety of habitats and microhabitats in this region, such as the various aquatic sites used by many species of anuran amphibians. Moreover, the PETAR features a large altitudinal gradient (80 - 1,160 m elevation) that gives a large climatic, geological and hydrological heterogeneity to the area. This inventory is an important contribution to the expansion of knowledge about these assemblages in the Atlantic Forest to the south of Serra de Paranapiacaba mountain range, and provides support for the conservation of these groups in São Paulo State.
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