We conducted a 13-yr study of Crotalus pricei in Arizona's Chiricahua Mountains, capturing 306 individual snakes and recapturing snakes on 155 occasions. Juveniles shed and fed more frequently and grew more quickly than adults. Spiny lizard (Sceloporus) scales were found in 78% of fecal samples, making Sceloporus the most common prey item for both juveniles and adults. Males became larger than females at 5 yr of age, a year or two after females reached reproductive size. Although 45% of adult females were gravid, reproduction was not typically biennial and larger snakes were more likely to be gravid than smaller adult snakes. Survival rate (mean ± SE) at our most-studied site was 0.707 ± 0.0334 and detectability was 0.309 ± 0.0386; detectability was positively correlated with number of search hours and negatively correlated with dry weather. Mean population size at this site was 67 snakes, and there was no evidence of a population decline over the course of the study. However, age class structure was skewed toward younger snakes at the site, probably due to illegal collection of snakes for the pet trade.

The Black-tailed Rattlesnake (Crotalus molossus Baird and Girard, 1853) is a wide-ranging species complex with representatives from the southwestern United States through the highlands of central and southern Mexico. The systematics of this group has received little attention and in the past six decades only two taxonomic changes have been proposed (the transfer of C. basiliscus oaxacus to C. molossus and the elevation of C. m. estebanensis to full species). However, a recent revision of the Neotropical Rattlesnakes (C. durissus and C. simus) recovered a polyphyletic C. molossus. We sequenced data from three mitochondrial genes (ATPases 8 and 6, cyt b, and ND4) and three nuclear genes (c-mos, EXPH5, and RAG1) to examine phylogenetic relationships among C. molossus lineages and the closely related species C. basiliscus and C. totonacus. Results recovered strong support for two deeply divergent northern C. molossus lineages that are morphologically distinct. Biogeographical patterns and divergence dates inferred from mitochondrial data suggest the diversification of C. molossus is the result of a Neogene vicariance event associated with uplift of the Sierra Madre Occidental. Population-level analyses suggest that major lineages of C. molossus have been stable since their initial divergence. On the basis of morphological and molecular evidence we resurrect the name Crotalus ornatus Hallowell, 1854 for Black-tailed Rattlesnake populations in the Chihuahuan Desert and central Texas, USA.

We studied growth in snout–vent length (SVL) and body mass of Dusky Pygmy Rattlesnakes (Sistrurus miliarius barbouri) in Volusia County, Florida, with the use of mark–recapture techniques. Between February 1992 and December 2000, we PIT-tagged (Passive Integrated Transponder) 665 individuals of approximately 1 yr of age or greater that were subsequently recaptured at least once. Because snakes can be definitively aged at 1 yr, this resulted in a large sample of snakes of known age that were followed for up to 7 yr. Seventy-five of these individuals PIT tagged at 1 yr were identified from photographs of neonates born in captivity, allowing us to relate adult growth to neonate traits. Our data suggest that Pygmy Rattlesnakes in central Florida exhibit highly variable patterns of growth that are related to a mild climate that allows feeding and growth throughout the year, and to a fluctuating prey base that results in irregular growth patterns often unlike those predicted by typical growth equations such as the von Bertalanffy model. Snakes in our populations were surface-active throughout the year, and snakes with detectable prey in the gut were found in all months. Growth is most rapid in the first year, but growth rates did not differ markedly from other viperids occurring in more temperate areas. In their first year, Pygmy Rattlesnakes in Florida increased their mass over birth on average more than fourfold, and increased SVL 1.8-fold. Growth in both mass and SVL continued throughout life, with no clear indication of an asymptote in size. Multiple regressions of SVL and body mass against age showed a slight but significant effect of sex on both SVL and mass, though these differences were not apparent until snakes were approximately 4 yr. Males and females showed no difference in SVL growth rates or patterns of change in growth rate with age, but females grew faster in body mass than males. Body-mass growth rates did not decline with age in either sex. Rates of increase in SVL in the first year of life differed significantly among years, though these differences were not correlated with estimates of prey (frog) abundance. However, neither body size at birth or first-year growth rates was significantly related to size at 1 yr of age or with growth rates later in life. Inspection of individual growth records and characterization of records into categories defined here showed great variability in patterns of growth, with episodic growth occurring in most individuals, including larger adults. A year-round activity season may decouple feeding and growth in these snakes from the temporal constraints imposed on more northern snakes, resulting in greater variability in individual growth trajectories. Prolonged feeding opportunities may allow snakes with below-average feeding conditions in their first year to compensate for slower initial growth by opportunistic feeding and rapid bouts of growth at any time later in life.

A taxonomic study on the South American dwarf boas of the genus Tropidophis revealed the existence of two new species in the Atlantic Forest biome. As a result, we recognize five mainland species, three in the Atlantic Forest and two in northwestern South America. Based on general distribution and morphological orientation, the type locality of T. paucisquamis is restricted to Estação Biológica de Boracéia (EBB), municipality of Salesópolis, state of São Paulo, Brazil; furthermore, a lectotype for T. taczanowskyi is designated. We provide data on the hemipenial morphology of two South American Tropidophis, showing that the quadrifurcate condition described for West Indian taxa also occurs in mainland congeners. The distributions of the three Atlantic Forest species are congruent with patterns of diversification of other vertebrate taxa associated with cold climates prevalent at high elevations. Refugial isolation and riverine barriers may account for such speciation events.

Patterns of burrow size, tortoise size, home range size and overlap, movement distances, and mating rates were compared among six sites that differed in density of Gopher Tortoises. Burrow sizes differed among sites because tortoise size distributions differed among sites, but this was due principally to the unusually small size of animals on the Conecuh National Forest. A linear relationship between tortoise density and burrow density was documented from the six sites, suggesting that tortoises, on average, created 2.5 burrows per site or that the burrow-to-tortoise conversion factor for our sites was 0.40. The average distance from a burrow to its nearest three neighbors was greater for low-density sites than for high-density sites, indicating that animals probably were more isolated from each other on sites with low tortoise densities. Tortoise home ranges were larger in males than females, a feature documented in other studies of tortoise movements. Home range sizes were greatest for densities of approximately 0.4 tortoises/ha and decreased in size above and below this density. This suggests that animals moved to visit close neighbors in areas of high density, expanded movements to maintain contact with neighbors that became more widely dispersed as density decreased, and then restricted movements to a few close neighbors as density reached extremely low levels. Home range overlap increased linearly with increasing density, suggesting that opportunities for social interactions decreased with decreasing density. When tortoises moved between burrows, males moved longer distances than females and tortoises of both sexes moved shorter distances on high-density sites than did tortoises on low-density sites, suggesting greater movement costs for males than females and for tortoises on low-density sites. Males traveled up to 500 m to visit female burrows, but most movements were < 80 m. Median movement distances of males to visit females were negatively correlated with burrow density, suggesting that cost of male movements to find mates increased as population density decreased. Based upon patterns of 95% confidence limits, rates of mountings of female tortoises approached zero when females occupied burrows approximately 200 m from neighboring burrows. If burrows were uniformly distributed 200 m apart, then reproductive failure would be a statistically supportable outcome at a density of 0.3 burrows/ha (0.12 tortoises/ha). These values are similar to the values of 0.4 tortoises/ha (1.0 burrows/ha) that our data suggest is the density at which social structure associated with movements within home ranges are altered.

Species diversity in skinks in the genus Brachymeles recently has undergone a state of flux, with numerous taxonomic discoveries over the past few years. Newly available, robust data sets from morphological data and molecular sequences have revealed that taxonomic diversity within this unique group of lizards is substantially underestimated. In this third recent monographic revision of a major Brachymeles clade, we review the medium-sized, pentadactyl species of the Brachymeles gracilis Complex (now known to include B. pathfinderi) and describe three new species in this unique clade of endemic Philippine lizards. For more than three decades B. gracilis has been recognized as a single polytypic, “widespread” species. The species' wide geographic range has persisted as a result of weak sampling, morphologically similar body sizes, scale pigmentation, and patterns of scalation among populations. However, previous authors have noted morphological variation between populations on different islands, as well as in geographically different subregions across the large southern island of Mindanao in the Philippines. Our new data build on these observations and extend them to inference of species boundaries. We evaluate both morphological and genetic data to define species limits in B. gracilis and its close relatives, and our data indicate that the “widespread” species B. gracilis is actually a complex of at least six distinct lineages. In order to clarify the status of B. suluensis (a species collected only once, in 1918) we redescribe this enigmatic taxon. Phylogenetic analyses of available B. gracilis sampling reveal that some of these lineages are not each others' closest relatives, but are all genetically distinct. All but two of the taxa we define possess allopatric geographic ranges and differ from their congeners by numerous diagnostic characters of external morphology, and therefore should be recognized as full species in accordance with any lineage-based species concept. Over the past 3 yr, the species diversity of the genus Brachymeles has increased by 125%.

We studied scutellation and morphometrics in the gymnophthalmid lizards of the genus Alopoglossus. Six species are recognized: Alopoglossus angulatus, A. atriventris, A. buckleyi, A. copii, A. festae, and A. lehmanni. We place the nominal species Alopoglossus andeanus Ruibal in the synonymy of A. angulatus. We provide detailed descriptions and head scalation illustrations of each species, an identification key, and a distribution map.

Se estudia la folidosis y morfometría de las lagartijas gymnophthalmidas del género Alopoglossus. Se reconocen un total de seis especies: Alopoglossus angulatus, A. atriventris, A. buckleyi, A. copii, A. festae y A. lehmanni. La especie nominal Alopoglossus andeanus Ruibal es considerada como sinónimo de A. angulatus. Se provee ilustraciones de la escamación de las cabezas, claves de identificación y un mapa de distribución.