Papers by Guillermo Woolrich
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On 1 September 2013 at ca. 0917 h, at ejido el Cora, Municipio de San Blas, Nayarit, Mexico (21.4... more On 1 September 2013 at ca. 0917 h, at ejido el Cora, Municipio de San Blas, Nayarit, Mexico (21.433988°N, 105.135329°W, WGS 84; elev. 230 m), we observed an adult B. sigma in an area of tropical dry forest planted with teak trees (Tectona grandis) consuming a young Collie’s Squirrel (Sciurus colliaei). The squirrel had ascended one of the teak trees to a height of ca. 7 m, where it was preyed upon by the snake. The event lasted about 17 min, from the time of capture until the squirrel was swallowed. The B. sigma then descended and sought shelter in a burrow
among some rocks. The S. colliaei might have been distracted by our presence, as we had stopped to photograph the animal and the squirrel perhaps did not see the snake.
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Woolrich-Piña, G. A., P. Ponce Campos, J. Loc-Barragán, J. P. Ramírez-Silva, V. Mata-Silva, J. D. Johnson, E. García Padilla, y L. D. Wilson. 2016. The herpetofauna of Nayarit, Mexico: composition, distribution, and conservation. Mesoamerican Herpetology 3: 376–448. The herpetofauna of Nayarit, Mexico, is composed of 154 species, including 34 anurans, two salama... more The herpetofauna of Nayarit, Mexico, is composed of 154 species, including 34 anurans, two salamanders, one crocodylian, 107 squamates, and 10 turtles. We detail the distribution of these species among the four physiographic regions we recognize. The number of species in these regions ranges from 34 in the Nayarit Islands to 110 in the Trans-Mexican Volcanic Belt. The species occupy from one to four regions (x– = 2.2). The largest number of single-region species is found in the Sierra Madre Occidental. Approximately six of every 10 species are confined to one or two physiographic regions, which is of profound conservation significance. We developed a Coefficient of Biogeographic Resemblance (CBR) matrix in which the number of shared species ranges from 17 to 78. We used these data to construct a UPGMA dendrogram, which indicates that the montane regions of the state, the Sierra Madre Occidental and the Trans-Mexican Volcanic Belt, resemble one another most closely in herpetofaunal content, and in turn they most closely resemble the Coastal Plain in composition; the most distinctive region in the state is the Nayarit Islands. We placed the members of the herpetofauna in four distributional categories, of which the greatest number is composed of the country endemics (88), followed by the non-endemics (61), non-natives (four), and state endemics (one). We identified the principal environmental threats as habitat fragmentation resulting from agriculture and livestock raising, the construction of hydroelectric dams, acceleration of the tourist industry, and global climate change. We assessed the conservation status of the native species by utilizing the SEMARNAT, IUCN, and EVS systems, of which the EVS proved to be the most helpful. The number of species in the three EVS categories increased from low (42) to medium (56), and decreased to high (47). Additionally, we employed the EVS ratings to assess how the species
in the IUCN categories of DD, NE, and LC might be evaluated more accurately. We also used a scheme for determining Relative Herpetofaunal Priority (RHP), a simple means for ascertaining the rank order of a regional herpetofauna dependent on the number of state and national endemic species, as well as the number of EVS species evaluated with high vulnerability. Using these two measures, we found the Trans- Mexican Volcanic Belt to occupy rank order one in both cases, followed by the Sierra Madre Occidental, the Coastal Plain, and the Nayarit Islands. We also discuss the ability of the state’s six protected areas to
protect the members of the herpetofauna. Based on our analyses, we present a set of conclusions and recommendations
for the future protection of the Nayarit herpetofauna.
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Phyllomedusa: Journal of Herpetology, 2012
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Acta …, 2010
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In lizards, the role of gravid oviparous females in controlling the temperature experienced by de... more In lizards, the role of gravid oviparous females in controlling the temperature experienced by developing embryos prior to oviposition has been rarely examined. In particular, relatively little is known about the effect of gravidity on the thermal ecology of female Anolis lizards. Here we examine the thermal ecology of Anolis nebulosus from Nayarit, Mexico, with a particular goal of comparing the thermal ecology of gravid females to that of non-gravid females and males. The thermal efficiency (E) of gravid female A. nebulosus (E=0.782) was higher than in males (E=0.464), and to a lesser extent, non-gravid females (E=0.637), despite no significant differences observed in body, air, operative, or set point temperatures
among males, gravid females, and non-gravid females. Gravid females had smaller differences between body temperatures and set point temperatures (db), but did not differ in the difference between operative temperature and set point temperature (de). Gravid females used sun-shade and shaded microhabitats proportionately more than males and non-gravid females, and rarely used sunny microhabitats.
Our results suggest that gravid A. nebulosus are using a different and more efficient thermoregulatory strategy than other adults in the population. Such efficient thermoregulation is possibly related to females attempting to provide a thermal environment that is conducive to the development of embryos in eggs prior to oviposition.
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Numerous studies have explored environmental factors that drive the distributions of anuran larva... more Numerous studies have explored environmental factors that drive the distributions of anuran larvae. However, the causal links between physical or chemical factors and tadpole distributions often remain untested. The Río Salado is an intermittent, naturally saline river in Puebla, Mexico, that is increasingly being impacted by removal of water for commercial salt production. Using tadpoles of Exerodonta xera (Hylidae; Puebla Treefrog) and Incilius occidentalis (Bufonidae; Pine Toad), we experimentally examined the hypothesis that the distribution of tadpoles along the Río Salado results from the effects of salinity on tadpole survivorship, growth, and metamorphosis. We also examined the effect of tadpole density and the interaction of tadpole density and salinity, because pool size likely affects tadpole density. Increased salinity did not affect survivorship in I. occidentalis but reduced survivorship in E. xera by approximately 20% at both 0.4 parts per thousand (ppt) (0.4 g
L-1) and 0.8 ppt (0.8 g L-1). Higher salinities delayed metamorphosis by up to 9 wk in E. xera and by 3 or 4 d in I. occidentalis. Tadpole density had a nonlinear effect on survivorship in E. xera, and higher densities delayed metamorphosis in I. occidentalis. There were no significant
interactions between salinity and tadpole density in either species. Our results suggest that even though they can be found in pools averaging 0.8 ppt, tadpoles may not emerge from such pools because of delayed metamorphosis at salinities around 0.8 ppt. Decreasing pool volume and
increasing tadpole density may further delay emergence of I. occidentalis. The removal of water from the Rı´o Salado to produce salt may threaten amphibians that use the river for breeding.
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Ambystoma altamiranoi is an endangered endemic salamander
found in the Transvolcanic Belt of Mexi... more Ambystoma altamiranoi is an endangered endemic salamander
found in the Transvolcanic Belt of Mexico. Unfortunately, relatively little is known about its ecology. Here we report on the diet of larval A. altamiranoi from a population in Llano de los Axolotes, Sierra de las Cruces, State of México, Mexico. Empty stomachs were found in 13.3% of individuals.
Ostracods and gastropods dominated the diet of A. altamiranoi, together accounting for 89.9% of prey items consumed. The remainder of the diet consisted primarily of insects. Our observations suggest that the diet of A. altamiranoi is relatively narrow and that resources may be limited (relatively
high frequency of empty stomachs), suggesting that factors that could impact the availability of ostracods and gastropods might have serious consequences for these endangered salamanders
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Mexico’s Late Neogene mammal faunas are largely known from localities in the Trans-Mexican Volcan... more Mexico’s Late Neogene mammal faunas are largely known from localities in the Trans-Mexican Volcanic Belt; those from other morphotectonic provinces are few and far apart. Thus, the discovery of Late Miocene vertebrates in western Sierra Madre Oriental at San Luis Potosı´, the Paso del A´ guila local fauna, significantly adds to this meager record. The assemblage was collected from the floodplain facies of the San Nicola´ s Formation, a 1100-m thick, dominantly fluviolacustrine and calcilithitic, 158–208 NE dipping sequence preserved in the Peotillos-Tolentino Graben, between 22811’–22819’ N and 100830’– 1008398 W. It includes remains of cf. Trachemys, a small to medium-sized emydid chelonian, a large camelid, a small cervid and a new species of the equini Pliohippus s.s., comparable in size, cranial morphology and odontographic characters to the Clarendonian-Early Hemphillian horses of the Pliohippus clade. Ar-Ar dates from ash-fall tuffs seemingly above and below the fossiliferous strata, bracket the age between 12.33 and 7.41 Ma (i.e., late Middle to Late Miocene), that is, within the Late
Clarendonian-Early Hemphillian NALMA interval, making this fauna the first in Mexico from this age. The Paso del A´ guila local fauna is at least partly correlative with the Hemphillian local faunas from the TMVB and adjacent areas (e.g., Rancho El Ocote, Guanajuato and Tecolotla´ n, Jalisco), the Central Plateau (e.g.,
Arroyo Los Fragmentos, Zacatecas), and the Sierra Madre Occidental (e.g., Yepo´mera). Elsewhere, it is broadly correlative with the Late Clarendonian-Early Hemphillian faunas from the California Coast Ranges (e.g., North Tejon Hills, Ricardo and Dove Springs in the Mohave Desert), and the Gulf Coast Plain,
Florida (McGehee Farm and Mixon). The Paso del A´ guila local fauna was part of a subtropical savannah and pine-oak forest (with a well-developed understory) biome that thrived on a climate regime much more humid than today.
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We report on the reproductive cycles of male and female X. rectocollaris from the Tehuacan Valley... more We report on the reproductive cycles of male and female X. rectocollaris from the Tehuacan Valley, Puebla, Mexico. Testis volume peaked in May. The smallest female with enlarged follicles was 69 mm SVL, which is the smallest size at
maturity yet observed in Xenosaurus. Maximum follicular volume varied among months, with small peaks in April and July, and a large peak in September. Embryos were largest in July. These cycles are generally similar to those observed in previously studied Xenosaurus.
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We studied sexual dimorphism, reproduction, thermal ecology, and diet of Xenosaurus rectocollaris... more We studied sexual dimorphism, reproduction, thermal ecology, and diet of Xenosaurus rectocollaris in Tehuacan Valley, Puebla, Mexico. Females were significantly larger than males, but there was no significant sexual dimorphism in size of head or length of femur. Mean size of litter was 2.6 – 0.3 (range, 1–4) and size of litter was not related to size of female. Mean body temperature was 23.28C. Pregnant females had higher body
temperatures than non-pregnant females. Adult coleopterans dominated the diet. Ecological traits of this population were within the range previously observed in Xenosaurus.
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There are currently eight described species in the lizard genus Xenosaurus. However, given their ... more There are currently eight described species in the lizard genus Xenosaurus. However, given their restricted habitat use (primarily limited to crevices or holes in rocks) and the limited ability to disperse among isolated populations, it is likely that more species of Xenosaurus await discovery and description.
Herein we describe a new species of Xenosaurus from the Sierra Madre Oriental in the State of Hidalgo, Mexico. This new species differs from previously described species in lacking a neck band and in having two pale lines that angle up from the jaws and extend parasagittally along the neck.
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We report on the temperature relationships of three Mexican species of Phrynosoma (P. braconnieri... more We report on the temperature relationships of three Mexican species of Phrynosoma (P. braconnieri, P. orbiculare, and
P. taurus). Mean body temperature (Tb) was 32.72°C for P. braconnieri, 32.54°C for P. orbiculare, and 33.39°C for P. taurus. In P. braconnieri and P. taurus, Tb was not correlated with air or substrate temperatures, whereas in P. orbiculare Tb was positively correlated with them. Body size did not affect Tb in any of the species. Females had higher Tbs than males in P. orbiculare, males had higher Tbs than females in P. braconnieri, and males and females had similar Tbs in P. taurus. Most of the Phyrnosoma observed in our study were found in sunny microhabitats, although several were found in shaded microhabitats.
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The distribution and abundance of organisms within a pond or lake can reflect the result of a var... more The distribution and abundance of organisms within a pond or lake can reflect the result of a variety of factors. We examined the abundance of the endemic fish, Poblana Alchichica, in Lago de Alchichica, Puebla, Mexico, as well as how the abundance varied among months. Dissolved oxygen, temperature, and salinity varied among months. The abundance of Poblana Alchichica peaked in December and February. For the months when fish were observed, their abundances were positively related to dissolved oxygen concentration and were generally not related to temperature. Our results provide evidence that there is substantial seasonal variation in the abundances of Poblana Alchichica and that within months, their distributions are likely driven by dissolved oxygen than either temperature or salinity.
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Papers by Guillermo Woolrich
among some rocks. The S. colliaei might have been distracted by our presence, as we had stopped to photograph the animal and the squirrel perhaps did not see the snake.
in the IUCN categories of DD, NE, and LC might be evaluated more accurately. We also used a scheme for determining Relative Herpetofaunal Priority (RHP), a simple means for ascertaining the rank order of a regional herpetofauna dependent on the number of state and national endemic species, as well as the number of EVS species evaluated with high vulnerability. Using these two measures, we found the Trans- Mexican Volcanic Belt to occupy rank order one in both cases, followed by the Sierra Madre Occidental, the Coastal Plain, and the Nayarit Islands. We also discuss the ability of the state’s six protected areas to
protect the members of the herpetofauna. Based on our analyses, we present a set of conclusions and recommendations
for the future protection of the Nayarit herpetofauna.
among males, gravid females, and non-gravid females. Gravid females had smaller differences between body temperatures and set point temperatures (db), but did not differ in the difference between operative temperature and set point temperature (de). Gravid females used sun-shade and shaded microhabitats proportionately more than males and non-gravid females, and rarely used sunny microhabitats.
Our results suggest that gravid A. nebulosus are using a different and more efficient thermoregulatory strategy than other adults in the population. Such efficient thermoregulation is possibly related to females attempting to provide a thermal environment that is conducive to the development of embryos in eggs prior to oviposition.
L-1) and 0.8 ppt (0.8 g L-1). Higher salinities delayed metamorphosis by up to 9 wk in E. xera and by 3 or 4 d in I. occidentalis. Tadpole density had a nonlinear effect on survivorship in E. xera, and higher densities delayed metamorphosis in I. occidentalis. There were no significant
interactions between salinity and tadpole density in either species. Our results suggest that even though they can be found in pools averaging 0.8 ppt, tadpoles may not emerge from such pools because of delayed metamorphosis at salinities around 0.8 ppt. Decreasing pool volume and
increasing tadpole density may further delay emergence of I. occidentalis. The removal of water from the Rı´o Salado to produce salt may threaten amphibians that use the river for breeding.
found in the Transvolcanic Belt of Mexico. Unfortunately, relatively little is known about its ecology. Here we report on the diet of larval A. altamiranoi from a population in Llano de los Axolotes, Sierra de las Cruces, State of México, Mexico. Empty stomachs were found in 13.3% of individuals.
Ostracods and gastropods dominated the diet of A. altamiranoi, together accounting for 89.9% of prey items consumed. The remainder of the diet consisted primarily of insects. Our observations suggest that the diet of A. altamiranoi is relatively narrow and that resources may be limited (relatively
high frequency of empty stomachs), suggesting that factors that could impact the availability of ostracods and gastropods might have serious consequences for these endangered salamanders
Clarendonian-Early Hemphillian NALMA interval, making this fauna the first in Mexico from this age. The Paso del A´ guila local fauna is at least partly correlative with the Hemphillian local faunas from the TMVB and adjacent areas (e.g., Rancho El Ocote, Guanajuato and Tecolotla´ n, Jalisco), the Central Plateau (e.g.,
Arroyo Los Fragmentos, Zacatecas), and the Sierra Madre Occidental (e.g., Yepo´mera). Elsewhere, it is broadly correlative with the Late Clarendonian-Early Hemphillian faunas from the California Coast Ranges (e.g., North Tejon Hills, Ricardo and Dove Springs in the Mohave Desert), and the Gulf Coast Plain,
Florida (McGehee Farm and Mixon). The Paso del A´ guila local fauna was part of a subtropical savannah and pine-oak forest (with a well-developed understory) biome that thrived on a climate regime much more humid than today.
maturity yet observed in Xenosaurus. Maximum follicular volume varied among months, with small peaks in April and July, and a large peak in September. Embryos were largest in July. These cycles are generally similar to those observed in previously studied Xenosaurus.
temperatures than non-pregnant females. Adult coleopterans dominated the diet. Ecological traits of this population were within the range previously observed in Xenosaurus.
Herein we describe a new species of Xenosaurus from the Sierra Madre Oriental in the State of Hidalgo, Mexico. This new species differs from previously described species in lacking a neck band and in having two pale lines that angle up from the jaws and extend parasagittally along the neck.
P. taurus). Mean body temperature (Tb) was 32.72°C for P. braconnieri, 32.54°C for P. orbiculare, and 33.39°C for P. taurus. In P. braconnieri and P. taurus, Tb was not correlated with air or substrate temperatures, whereas in P. orbiculare Tb was positively correlated with them. Body size did not affect Tb in any of the species. Females had higher Tbs than males in P. orbiculare, males had higher Tbs than females in P. braconnieri, and males and females had similar Tbs in P. taurus. Most of the Phyrnosoma observed in our study were found in sunny microhabitats, although several were found in shaded microhabitats.
among some rocks. The S. colliaei might have been distracted by our presence, as we had stopped to photograph the animal and the squirrel perhaps did not see the snake.
in the IUCN categories of DD, NE, and LC might be evaluated more accurately. We also used a scheme for determining Relative Herpetofaunal Priority (RHP), a simple means for ascertaining the rank order of a regional herpetofauna dependent on the number of state and national endemic species, as well as the number of EVS species evaluated with high vulnerability. Using these two measures, we found the Trans- Mexican Volcanic Belt to occupy rank order one in both cases, followed by the Sierra Madre Occidental, the Coastal Plain, and the Nayarit Islands. We also discuss the ability of the state’s six protected areas to
protect the members of the herpetofauna. Based on our analyses, we present a set of conclusions and recommendations
for the future protection of the Nayarit herpetofauna.
among males, gravid females, and non-gravid females. Gravid females had smaller differences between body temperatures and set point temperatures (db), but did not differ in the difference between operative temperature and set point temperature (de). Gravid females used sun-shade and shaded microhabitats proportionately more than males and non-gravid females, and rarely used sunny microhabitats.
Our results suggest that gravid A. nebulosus are using a different and more efficient thermoregulatory strategy than other adults in the population. Such efficient thermoregulation is possibly related to females attempting to provide a thermal environment that is conducive to the development of embryos in eggs prior to oviposition.
L-1) and 0.8 ppt (0.8 g L-1). Higher salinities delayed metamorphosis by up to 9 wk in E. xera and by 3 or 4 d in I. occidentalis. Tadpole density had a nonlinear effect on survivorship in E. xera, and higher densities delayed metamorphosis in I. occidentalis. There were no significant
interactions between salinity and tadpole density in either species. Our results suggest that even though they can be found in pools averaging 0.8 ppt, tadpoles may not emerge from such pools because of delayed metamorphosis at salinities around 0.8 ppt. Decreasing pool volume and
increasing tadpole density may further delay emergence of I. occidentalis. The removal of water from the Rı´o Salado to produce salt may threaten amphibians that use the river for breeding.
found in the Transvolcanic Belt of Mexico. Unfortunately, relatively little is known about its ecology. Here we report on the diet of larval A. altamiranoi from a population in Llano de los Axolotes, Sierra de las Cruces, State of México, Mexico. Empty stomachs were found in 13.3% of individuals.
Ostracods and gastropods dominated the diet of A. altamiranoi, together accounting for 89.9% of prey items consumed. The remainder of the diet consisted primarily of insects. Our observations suggest that the diet of A. altamiranoi is relatively narrow and that resources may be limited (relatively
high frequency of empty stomachs), suggesting that factors that could impact the availability of ostracods and gastropods might have serious consequences for these endangered salamanders
Clarendonian-Early Hemphillian NALMA interval, making this fauna the first in Mexico from this age. The Paso del A´ guila local fauna is at least partly correlative with the Hemphillian local faunas from the TMVB and adjacent areas (e.g., Rancho El Ocote, Guanajuato and Tecolotla´ n, Jalisco), the Central Plateau (e.g.,
Arroyo Los Fragmentos, Zacatecas), and the Sierra Madre Occidental (e.g., Yepo´mera). Elsewhere, it is broadly correlative with the Late Clarendonian-Early Hemphillian faunas from the California Coast Ranges (e.g., North Tejon Hills, Ricardo and Dove Springs in the Mohave Desert), and the Gulf Coast Plain,
Florida (McGehee Farm and Mixon). The Paso del A´ guila local fauna was part of a subtropical savannah and pine-oak forest (with a well-developed understory) biome that thrived on a climate regime much more humid than today.
maturity yet observed in Xenosaurus. Maximum follicular volume varied among months, with small peaks in April and July, and a large peak in September. Embryos were largest in July. These cycles are generally similar to those observed in previously studied Xenosaurus.
temperatures than non-pregnant females. Adult coleopterans dominated the diet. Ecological traits of this population were within the range previously observed in Xenosaurus.
Herein we describe a new species of Xenosaurus from the Sierra Madre Oriental in the State of Hidalgo, Mexico. This new species differs from previously described species in lacking a neck band and in having two pale lines that angle up from the jaws and extend parasagittally along the neck.
P. taurus). Mean body temperature (Tb) was 32.72°C for P. braconnieri, 32.54°C for P. orbiculare, and 33.39°C for P. taurus. In P. braconnieri and P. taurus, Tb was not correlated with air or substrate temperatures, whereas in P. orbiculare Tb was positively correlated with them. Body size did not affect Tb in any of the species. Females had higher Tbs than males in P. orbiculare, males had higher Tbs than females in P. braconnieri, and males and females had similar Tbs in P. taurus. Most of the Phyrnosoma observed in our study were found in sunny microhabitats, although several were found in shaded microhabitats.