Although a substantial literature has demonstrated that disturbances can strongly influence communities, relatively few studies have examined how multiple disturbances influence community structure. This study examined the long-term response of an arid plant community to combinations of grazing by cattle and repeated fire to determine the effects of these disturbances alone and in combination on individual abundances, species richness, and diversity. Over an 8-year period, more species were affected significantly by fire than by grazing. Total abundance, species richness, and diversity of annuals were highest on plots subjected to both burning and grazing, but few significant interaction effects were observed. Thus, fire and grazing seem to affect this arid plant community independently.

Ski-slope plant communities on Lee Canyon in the Spring Mountains of southern Nevada were surveyed to assess effects of disturbance and environmental factors important in structuring vegetation. Ski runs extended from 2,620 to 2,890 m on the north face of Mount Charleston. Eleven plant communities were identified, including 4 types only on slopes, 1 type only in adjacent forest, and 6 types that occurred on both slopes and in forest. Distance to gravel service roads on the ski runs, soil compaction, ski run width, distance to the forest edge, and gullies were the most important variables in structuring vegetation. Nonnative species were found at all elevations and were frequently dominant. Nonnative species cover and richness were negatively correlated with percent bare area, because the nonnative species vegetated the slopes more densely than the native species. Relative to ski runs in other areas, those on Mount Charleston had high nonnative species invasion and few bare areas; vegetation rarely resembled that of surrounding forests and meadows, except in areas of heavy tree invasion.

We collected 423 species of diurnal butterflies (Rhopalocera) during 250 days of observations from March 1997 through January 2000 in the region of Calakmul, Campeche, Mexico. We present a list of 428 species recorded for Calakmul. This is the first reported list of butterflies for the state of Campeche, and it includes 290 new records for the state, 374 new records for Calakmul, and 1 new record for Mexico: Monca telata. Museum records were found for 5 additional species: Caria melino, Cissia labe, Tmolus echion, Emesis lupina lupina, and Calephelis azteca. The accumulation curve of species estimates that 457 species should be present in Calakmul, which suggests the list presented is 93% complete. We found that medium, tropical, semi-evergreen forest is the richest (371 species); more than a quarter of the butterflies of the Calakmul region were found exclusively in this forest. We also found the southern area slightly more abundant in species (82%) than the northern area (79%). Additionally, a comparison was made of the list generated for Campeche to lists from previous studies for Quintana Roo, Tikal-Guatemala National Park, and Belize. The comparison shows that 70%, 58%, and 54% of the butterfly species in Calakmul also are found in Tikal, Quintana Roo, and Belize, respectively.

Mitochondrial DNA sequences and 5 microsatellite DNA loci were used to assess the genetic structure of Micropterus punctulatus (spotted bass) in the upper Red, Ouachita, and Arkansas river basins. Results for 318 spotted bass from 14 localities indicated that extant populations in East Cache Creek, which potentially supported the nominal subspecies M. punctulatus wichitae, are either introductions or they are weakly divergent native populations. Both mtDNA and micro-satellite DNA indicated that populations of M. punctulatus in the Ouachita River basin are more similar to those in the Arkansas River basin than to those in the Red River basin. This conflicts with a previous Pleistocene model for the aquatic biogeography of the region. Microsatellites showed no evidence of genetic introgression by M. dolomieu; mtDNA was not divergent between the 2 species, possibly because of ancient introgression.

We conducted a mark-recapture study of Siren intermedia in a wetland in southeastern Missouri that is intensively managed for waterfowl. Over a 9-month period, we examined population characteristics, growth rates, and spatial activity. Density and standing crop biomass estimates were 1.35 to 2.17 sirens/m² and 44.9 to 72.2 g/m². Juveniles comprised 39% of the population. Adult males were significantly larger in both total length and mass than adult females. Sirens from our population had relatively low growth rates compared to some populations in other areas. Smaller individuals tended to grow faster than larger individuals. Maximum distance between captures did not differ significantly among juveniles and adult males and females. Home ranges of adults overlapped considerably and were highly variable in size, ranging from 1 to 232 m². Sirens can be the dominant vertebrate in many wetland communities, and their natural history and spatial ecology should be considered in management decisions.

Current hypotheses suggest that many of the biased sex ratios reported for turtle populations are the result of sampling errors, such as improper sex determination, collection bias, and behavioral differences between the sexes. This study was performed to assess whether the observed sex ratio of a population of stinkpots (Sternotherus odoratus) was an artifact of sampling biases. A total of 989 stinkpots (637 males, 352 females) was captured from 1996 through 2000 at Spring Lake, Aquarena Center, Hays County, Texas. The overall sex ratio based on all census techniques was significantly male-biased (1.8M:1F). The sex ratio changed across size classes. Data from a bimonthly trapping experiment from May 1999 through May 2000, in which hoop traps baited with either a food source or a mature female stinkpot, reinforced the view that the observed sex ratio in this population is inherently skewed, and not an artifact of sampling techniques.

Phyllorhynchus have been proposed to eat a wide variety of food items. The leading hypothesis is that the tails of the gecko Coleonyx variegatus are an important food source. We dissected museum specimens of P. decurtatus and P. browni. The diet of P. decurtatus consisted primarily of squamate eggs; few individuals of that species contained the tails of C. variegatus. The diet of P. browni consisted entirely of squamate eggs. We compared the monthly diet patterns between the sexes, as well as between the species.

Declines in loggerhead shrike (Lanius ludovicianus) populations have been associated in part with habitat loss and degradation, including that resulting from urbanization. We monitored the productivity and examined nesting habitat of loggerhead shrikes nesting in an urban environment in Tucson, Arizona. We located 22 breeding pairs in 1997 and 26 breeding pairs in 1998, with a 72% breeding area reoccupancy between years. Mean fledgling numbers were 2.28/nesting attempt and 3.11/successful nest. Although some pairs initially failed and renested, 91% and 73% of shrike pairs successfully fledged young in 1997 and 1998, respectively. Mayfield estimates of nesting success were 78% in 1997 and 65% in 1998. Nest sites were characterized by more trees >3 m in height, taller nest trees than those randomly available, and a greater proportion of bare ground surface than at random sites. Shrike breeding territories had lower proportions of residential and commercial development and greater proportions of open areas with low-growing vegetation than randomly available. Some shrikes nested in school playgrounds, residential front yards, and parking lots, if adjacent open space was available.

Patterns of endemism of terrestrial mammals inhabiting México are analyzed by applying Parsimony Analysis of Endemicity (PAE) to 47 ecoregions. The ecoregions were classified in 2 main groups: ecoregions of the Baja California Peninsula and ecoregions of the rest of the country. We found 27 ecoregions with characteristic taxa, and 5 areas of endemism: Northern High Plateau, Baja California, Chiapas, Isthmus, and Yucatán Peninsula. Groups of ecoregions are basically congruent with other regionalization schemes previously proposed for the country.

Conversion of tropical rain forest to pasture and cropland often leads to a loss of local species. However, information on the role of some isolated elements of the fragmented landscape on maintaining biodiversity is lacking. This study, carried out in human-made pastures in Veracruz, Mexico, demonstrated the year-round presence of frugivorous bats in isolated trees inside pastures and in riparian corridors of vegetation among pastures. During a 1-year study (October 1995 through September 1996), we captured 652 bats belonging to 20 species, representing 56% of the total species recorded for the area. Higher abundance and diversity of bats were recorded for riparian sites than for isolated trees. Of the bats we captured, 82% were frugivorous, 15% insectivorous, 2% nectarivorous-frugivorous, and 2% sanguivorous. Bats visited isolated trees regardless of tree species or phenological state. Abundance decreased with distance from the nearest forest fragment. We discuss how riparian corridors and isolated trees in pastures might contribute to maintaining diversity of frugivorous bats and plants in a fragmented landscape.

We determined the foraging range of Mexican free-tailed bats (Tadarida brasiliensis mexicana) that spend summer in Carlsbad Cavern, Carlsbad Caverns National Park, New Mexico. We captured bats at varying distances and directions from the cavern and attached a radiotransmitter to each. During daylight hours, we entered Carlsbad Cavern to determine if bats with radiotransmitters were present in the maternity roost. The distribution of localities where captured bats returned to Carlsbad Cavern indicated a nightly foraging range of at least 56 km from Carlsbad Cavern. Our data indicated that the colony eventually dispersed in every direction after leaving the cavern each evening and foraged in a space nearly 4,000 km³. This study was the first to document use of water sources on property of Carlsbad Caverns and Guadalupe Mountains national parks, the Lincoln National Forest, and other sites in southeastern New Mexico and western Texas by members of the colony of T. b. mexicana that reside in Carlsbad Cavern.

A small, late Quaternary deposit of degraded bat guano in Arkenstone Cave, Colossal Cave Mountain Park, Pima County, Arizona, yielded thousands of fossil bat bones. The bones primarily represent an attritional accumulation of dead bats beneath a maternity colony of Myotis thysanodes, a species that no longer roosts at the elevation of the cave. Rarer bones in the deposit represent a smaller species of Myotis and the extinct vampire Desmodus stocki. Due to leaching in the alkaline cave environment, the bones could not be dated by radiocarbon, but the fossils probably date to the late Pleistocene. Myotis thysanodes, a species that frequently forages in the desert but typically day-roosts at higher elevations in pygmy conifer woodland or higher vegetative zones, is consistent with the occurrence of conifer woodland at similar elevations in nearby mountain ranges in the late Pleistocene. This is the first record of D. stocki in what is now the Sonoran Desert and the second locality of occurrence for the species in Arizona.

We describe population estimates, survival rates, and aspects of hibernation for a population of Zapus hudsonius preblei along a 3.7-km section of South Boulder Creek and 2 associated outflow ditches in Boulder County, Colorado. Mark-recapture analysis was used on 352 marked jumping mice with 722 captures from 6 paired sites along the creek and 2 sites on ditches. Linear population density estimates ranged from 22.7 ± 7.9 to 79.5 ± 33.3 animals/km of stream-reach for the 6 sites combined along South Boulder Creek, and from 33.9 ± 1.6 to 85.6 ± 30.3 animals/km along the occupied ditches. This study highlights the potential importance of irrigation ditches as suitable habitat for Z. h. preblei. Estimated over-winter survival rate for both sexes combined was 54.1 ± 18.8%, summer survival rate was 16.2 ± 9.6%, and combined annual survival rate was 8.8 ± 6.0%. We suggest that good hibernation habitat is important for these populations to offset low summer survival. First emergence from hibernation was 19 May 1999, the only year trapping was conducted during the emergence period. Males preceded females. Adults were captured in June with low post-hibernation weights and reached weights that would enable them to enter hibernation by the third week in August. Juveniles captured after mid September were considered to be offspring from second litters. By mid October in both years, no jumping mice were captured, and we infer that they had all entered hibernation.

The low number of records and specimens of red foxes (Vulpes vulpes) for Arizona and Utah through the 1960s prompted us to collect verified records of the species from the Navajo Nation in northeastern Arizona and southeastern Utah. We compiled and verified 80 visual observations of 88 live and dead foxes, and 21 specimens, from the study area between 1979 and 2001. We also compiled 686 supplemental records of foxes reportedly trapped by permitted fur-trappers within the same area and time period. This work verified that the red fox was common to this region despite the low number of records prior to the 1960s and that northeastern Arizona should be included in distribution maps for the species. We analyzed temporal and spatial distributions of fox records and determined the vegetation types and elevational range of records within the study area. Numbers of trapped foxes (and trappers) peaked during the mid 1980s, but the number of observations has remained relatively constant. Foxes occupied a 1,100-m range of elevations and were observed in equal numbers in 3 vegetation types that comprise 95% of the study area. Seventeen of the 21 specimens were measured for 15 standard cranial measurements. A thorough literature review and museum search revealed 8 specimens previously documented elsewhere.

Biting insects impose costs on hosts, including decreased feeding or resting time as the result of disturbance, blood loss, and disease transmission. Insect-repelling behaviors, such as ear-flicking, head-shaking, stamping, and grouping, have evolved in many ungulate species to minimize these costs. We studied female desert bighorn sheep (Ovis canadensis mexicana) at Red Rock Wildlife Area, New Mexico, during the summers of 1999 and 2000. We tested the predictions that: 1) bighorn sheep will increase insect-defense behavior when biting insects are more abundant, and 2) close aggregation of sheep will decrease the per capita insect harassment by means of a dilution effect. Numbers of midges and other biting insects increased in association with rising temperature and decreased with increasing wind speed. Ewes performed between 0 and 78 ear-flicks/min, and >5,000 ear-flicks over the course of a 12-h day. As predicted, the rate of ear-flicking was positively correlated with counts of biting insects, indicating that ear-flicking was a direct response to the irritation of attacking insects. We also found a negative correlation between the number of sheep clustered together within 1 body length and ear-flicking rate, suggesting that insect harassment is diluted when bighorn sheep bunch together. Bighorn sheep generally bedded on upper slopes and rocky outcrops exposed to gusts of wind. These results indicate that ear-flicking, grouping, and microhabitat choice might be important strategies for reducing the costs of biting insects in desert bighorn sheep.

Desert mule deer (Odocoileus hemionus eremicus) and Texas white-tailed deer (O. virginianus texanus) are sympatric in west-central Texas. During winter, spring, and summer 1999 and 2000, we recorded locations of sympatric mule and white-tailed deer to determine habitat-use differences between species. We measured 379 mule deer and white-tailed deer locations for biotic and abiotic landscape parameters. Slope and percent shrub cover explained most variation in distributions of the 2 species. Locations of bedded deer were the most discriminated behavior type for all models. Density of shrubs and slope were the most important variables used to describe habitat preference by either deer species. Mean shrub cover used by mule and white-tailed deer at bed sites was 37.7% and 53.9%, respectively. Mean percent slopes used by mule and white-tailed deer for bed sites were 9.2 and 2.9, respectively. To a lesser extent, the same habitat parameters discriminated locations between deer species for moving and browsing for 1999 and 2000. If land managers want to maintain both deer species, several land management actions might be necessary. For mule deer on relatively steep slopes, managers should maintain lower percent woody cover and encourage native forb growth. For white-tailed deer in lower drainages, managers should maintain >50% woody species cover and encourage intermittent grass growth in the remaining areas.

Frequency of interspecific hybridization between mule deer and white-tailed deer was investigated using ribosomal DNA and nucleotide sequences from the mitochondrial cytochrome b gene. Two of 15 individuals (collected by hunters) from northwestern Texas (Kent County) were identified as hybrids based on the ribosomal DNA marker. Sequence data from the cytochrome b gene indicated that 1 individual was the result of mating between a mule deer doe and a white-tailed deer buck, whereas the second individual resulted from mating between a white-tailed deer doe and a mule deer buck. These results indicate that hybridization between mule deer and white-tailed deer is not restricted to the Trans-Pecos region of Texas. Given the low levels of genetic divergence and frequency of hybridization, the validity of recognizing mule deer and white-tailed deer as distinct species is discussed. It is concluded that without the morphological and behavioral differences these 2 taxa could be considered subspecies rather than distinct species.

The seasonality of 10 of the most abundant species of macromycetes was studied at 3 sites in west-central Mexico. Collections over 20 years from the Instituto de Botánica of the Universidad de Guadalajara database were used for this study. Two of the sites were pine-oak forests: Mazamitla (70 collections) and Tapalpa (68 collections). The third consisted of an ecotone between subtropical cloud forest and pine-oak forest: Nevado de Colima (91 collections). The 3 sites are close to the tropical region and have a rainy season between late May and October. The development and abundance of fruit bodies were related to the climate and the vegetation of each site. Differences were found at 3 scales for both fructification time and abundance: between sites, between species, and within species at different sites.

We report collections of threatened loach minnow, Tiaroga cobitis, from 2 Gila River basin (Arizona) streams, one representing a rediscovery and the other a new record. The species had been taken in 1950 from Eagle Creek, but it was not seen again until 1994–1997 and, despite repeated attempts, has not been detected since. It likely persists in adjacent, unsampled areas. A new distribution record is reported for loach minnow captured in 1996 from North Fork of East Fork Black River. This last population has been resampled repeatedly and seems stable. Genetic analysis confirms the uniqueness of these and most other known populations, and we recommend protection and conservation of loach minnow in these 2 streams.

We describe the tadpole of the recently described hylid frog Hyla xera and report information regarding the distribution and natural history of this species endemic to the Tehuacán-Cuicatlán Valley in Oaxaca and Puebla, Mexico. This species was previously known only from the type locality near Zapotitlán Salinas, Puebla, south of Tehuacan, Puebla. With our work, its range is now extended, adding 6 localities in Puebla and 4 in Oaxaca. Adults take refuge in arboreal bromeliads and breed in streams in the rainy season from May to August.

Anaxyrus melancholicus Tschudi, 1845, has been referred to as a nomen dubium by various authors. In this note, a holotype of A. melancholicus Tschudi is designated and referred to the synonymy of the Mexican species Bufo compactilis Wiegmann.

To study possible intergradation between Aspidoscelis tigris munda (west) and A. t. tigris (east) through Walker Pass, a low-elevation corridor in the southern Sierra Nevada, California, I collected 90 individuals of A. tigris from 26 May through 2 June 1994 from a 24-km transect with 3 evenly spaced sampling sites representing populations on the summit (1,555 m), west slope (1,098 m), and east slope (1,014 m). The central (summit) population lacked phenotypic intermediacy in body size (larger), color (greater melanism), and multivariate morphological variation (means of first canonical variate: summit > west > east). In addition, egg clutches were present only in females from the summit population. Stepwise regression of snout-vent length (SVL) on 6 environmental variables revealed that body size was related positively only to winter precipitation. Dominant vegetation of the 3 sampling sites substantiates the presence of a pronounced rain shadow at Walker Pass. It is likely that the phenotypic and reproductive differences among the 3 populations are related to the greater amount of critical winter precipitation at the summit of the pass.

Four syntopic assemblages of parthenogenetic lizards were compared for differences in body size at which reproductive maturity is attained and mean clutch size: 1) Aspidoscelis flagellicauda and A. exsanguis from the vicinity of San Francisco Hot Springs (type locality of A. flagellicauda), Catron and Grant counties, New Mexico; 2) A. flagellicauda and A. sonorae from the vicinity of Oracle, Pinal County, Arizona (type locality of A. sonorae); 3) A. sonorae (3 color pattern classes) from the vicinity of Cochise Stronghold, Cochise County, Arizona; and 4) A. sonorae (2 color pattern classes) from the vicinity of Parker Canyon Lake, Cochise County, Arizona. Reproduction begins at a smaller body size in A. exsanguis (61 mm SVL) than in A. flagellicauda (70 mm SVL). This results in a higher population density in A. exsanguis, despite the larger mean clutch size in A. flagellicauda (3.7 vs. 3.3 eggs). Aspidoscelis sonorae and A. flagellicauda, although morphologically distinguishable, were not significantly different in size at reproductive maturity or mean clutch size, which was also true for the color pattern classes of A. sonorae.

A population of the parthenogenetic teiid lizard, Aspidoscelis tesselata, was recently discovered in the vicinity of Benavides, Chihuahua, México. This population is located in the general area where A. tesselata originated, as a parthenogenetically competent F₁ hybrid, from hybridization between A. tigris marmorata and A. gularis septemvittata. Subsequent to its origin, A. tesselata utilized habitats associated with the Rio Grande and Pecos River drainages to expand its range into New Mexico. We used a canonical variate analysis of samples from Chihuahua, México, and the Rio Grande and Pecos River distribution corridors in southern New Mexico to determine the pattern of morphological variation among the 4 populations. The 2 populations from New Mexico were divergent, both from the Chihuahuan populations (which were morphologically similar) and from each other. A male specimen, collected with A. tesselata in the Benavides vicinity, was identified as a putative A. tesselata × A. tigris marmorata hybrid.

We describe a new subspecies of Sceloporus merriami from extreme southeastern Chihuahua and adjacent Coahuila. We discuss the derivation of the 7 subspecies now known of S. merriami.

Micrurus pachecogili is a rare coralsnake that inhabits the desert region around Zapotitlán Salinas in southern Puebla, Mexico. The original description of this species was based on 2 specimens. We report on morphological variation, sexual dimorphism, and distribution based on 4 additional specimens. Males have 218–223 ventrals, 43–48 subcaudals, and 24–30 black body rings; females have 235–242 ventrals, 37–39 subcaudals, and 29–30 black body rings. This new material was collected at localities within the Zapotitlán Basin. The coralsnake most similar to M. pachecogili seems to be M. nebularis, which is restricted to pine-oak forest near Ixtlán de Juárez in central Oaxaca. Micrurus nebularis is easily distinguished in having fewer ventrals (203–208 in males and 218–223 in females).

A list of 13 noteworthy bird species records from the state of Tamaulipas, México, is presented. Two records (Agamia agami and Aquila chrysaetos) are new for the state, and the remaining 11 extend significantly their distributional range.

Flight speeds of Davy's naked-backed bat (Pteronotus davyi), Wagner's mustached bat (P. personatus), Parnell's mustached bat (P. parnellii), and Peter's leaf-chinned bat (Mormoops megalophylla) were studied in Colima, Mexico, during January 2000. Bats were assessed in a simulated cave passage cleared in a dense thorn forest. Rates of travel over a known distance were measured using stopwatches. Individual flight speeds varied from 7.4 (female P. davyi) to 30.6 km/h (male M. megalophylla); mean flight speeds ranged from 11.3 (male P. davyi) to 19.1 km/h (female P. parnellii). There was a positive correlation between mean forearm length and mean flight speed. Larger bats flew faster than smaller ones. Results of this investigation provide the first report of flight speed for female P. davyi (13.1 km/h) and extend our knowledge concerning the flight speeds of other taxa studied.

During a survey of the biota of part of Kisatchie National Forest, Louisiana, 3 specimens of Myotis septentrionalis were collected and are the first records of the species from Louisiana. Two males and 1 female were collected on 3 nights. The female is the earliest record (10 May) of lactation for M. septentrionalis. Caves known in Louisiana are 55 to 87 km from the Winn Parish collection site, but use of these caves by M. septentrionalis has not been documented. Based on the discovery of M. septentrionalis in Louisiana, it is necessary to reevaluate the southern boundary of the distribution of this species.

Previous studies have documented the presence of the prairie vole (Microtus ochrogaster) in the extreme northern panhandle of Texas and north-central Oklahoma, and specimens have been collected from the Oklahoma Panhandle region. In July 2000, 2 prairie voles were captured in Carson County, Texas, 80 km south of the previously reported southern range. Additionally, barn owl (Tyto alba) pellets collected from the northern Texas Panhandle and western Oklahoma Panhandle contained prairie vole remains. These remains represent the first records of the prairie vole in Cimarron County, Oklahoma, and Dallam and Sherman counties, Texas, and a new western limit for the prairie vole in Texas and Oklahoma. The specimens collected likely represent a recent southwestern range expansion of the prairie vole in the shortgrass prairies of the Texas and Oklahoma panhandles.

We identified species of fleas found in New Mexico on kit foxes (Vulpes macrotis), swift foxes (V. velox), red foxes (V. vulpes), and gray foxes (Urocyon cinereoargenteus). Pulex irritans and P. simulans were the fleas found most commonly. All species found, except 2, are known to carry plague, and we found fleas on foxes throughout New Mexico capable of carrying plague, which occurs in every county of New Mexico. Thus, every fox in New Mexico should be considered a potential carrier of plague.

We report observations and quantification of white nosed coatis (Nasua narica) using century plants (Agave palmeri) as a novel food source in Arizona. After observing a female coati eating in century plants, we inspected all flowering century plants in areas of coati activity for presence of scratch marks. Use of agaves by coatis was relatively common. Coatis climbed plants with large diameter at breast height relative to unscratched plants, but did not preferentially use agaves based on height or number of flower aggregations. Agaves in areas of high coati activity were more likely to possess scratch marks. Flowering agaves contain nectar, pollen, and arthropod species, all of which likely provide nutrition. The opportunistic foraging and willingness of coatis to experiment with unique food sources might partially explain the expansive distribution of the species under a wide variety of ecological conditions.

The Sonoran pronghorn (Antilocapra americana sonoriensis), a subspecies in danger of extinction, inhabits an area of the Barry M. Goldwater Range (BMGR) in southwestern Arizona. Since 1941, BMGR has been a training site for military pilots. We evaluated whether this subspecies of pronghorn used areas, as defined by noise levels produced by military aircraft, in proportion to their availability. Radiocollar-equipped pronghorn were monitored during September 1994 to August 1998, and their locations were recorded on a map of sound levels. In general, pronghorn used areas with lower levels of noise (<45 decibels [dB]) more than expected and areas with higher levels (≥55 dB) less than expected. More intensive monitoring, habitat influences, and additional measurements of noise in the area, could produce a clearer picture of the factors that determine areas of use within the BMGR by Sonoran pronghorn.