Prior research has demonstrated that fire can be an important structuring force for plant communities in prairies and grasslands. However, investigations of land-management techniques, such as prescribed fire, often overlook responses of local fauna, particularly the arthropods. In this study, we examined a previously unappreciated, although potentially important, component of fire ecology by asking, does the timing of prescribed burns alter community structure of arthropods? At a site in the Texas Hill Country, we used sweep-net sampling to collected arthropods from experimental plots that had been treated with a summer-burn or winter-burn regime. Summer-burn plots supported >170% more individual arthropods than winter burns. Although overall diversity of arthropods did not significantly differ between treatments, there were significantly more carnivorous arthropods and marginally more herbivorous arthropods after fire in summer relative to fire in winter. Effects of timing were particularly strong for Cicadellidae (leaf hoppers) and Tetragnathidae (long-jawed spiders). Our results demonstrate that timing of prescribed fire can substantially alter composition of resident communities of arthropods. Furthermore, these data highlight the importance of examining composition of the community, in addition to diversity indices, when assessing response of arthropods to land-management techniques.

Understanding consequences of changes in climate and fire regimes for succession in plant communities is critical for conservation planning at broad spatial and temporal scales. We selected two sites that burned in high-severity fire decades ago and studied succession in the woody plant community and its variations across two environmental gradients; elevation and distance from a lower-severity/unburned edge. By overlaying an ordination of data for woody species on the modeled environmental gradient most closely related to variation in communities, we analyzed the interaction of life-history traits of species and landscape heterogeneity at each study site. Species that resprout from surviving roots were widespread across the distance gradient 28 years after the La Mesa fire in New Mexico. Species that reproduce from off-site seed, including Pinus ponderosa, were more prevalent where resprouters (e.g., Quercus) were less important in defining communities. At Saddle Mountain, Arizona, 45 years post-fire, we observed neighborhood interactions across the elevation gradient, for example, where shade-tolerant conifers (e.g., Abies concolor) occurred in understories of Populus tremuloides. At both sites, greater cover of woody plants that reproduce from off-site seed at shorter distances from a lower-severity/unburned edge suggested migration of these species following the model of wave-form succession. In contrast to studies that emphasize undesirable effects when forest transitions to openings and alternative habitats, our research elucidates the need for further consideration of both young forest communities and the persistent species and communities described as landscape scars in conservation plans for forest systems of the southwestern United States.

We observed activity and behavior of Trimerotropis pallidipennis in the field and constructed time-activity budgets during June–July 2003. Grasshoppers began to walk once site temperatures (shaded air temperature 1 cm above soil surface) reached 18.6°C, foraging began once temperatures reached 24.2–31.7°C, and courtship began once temperatures reached 30.3–36.4°C. Mating and oviposition occurred when temperatures reached 30–40°C. Quiescence occurred most often at the lowest and highest site temperature categories (20–25, 25–30, and 45–50°C), and the highest frequency of foraging occurred most often at temperatures of 35–40°C. We observed no clear diurnal patterns for walking in grasshoppers, and found no significant difference between frequency of activities in morning and evening, within the same temperature ranges. Males rested, courted, and groomed significantly more frequently than females, and females foraged significantly more than males. Activity patterns, especially quiescence and foraging, were influenced much more by environmental temperature than by time of day.

Travel by pollen from Zizania texana (Texas wild rice) was studied in outdoor cement raceways at the San Marcos National Fish Hatchery and Technology Center, San Marcos, Texas. We examined effects of panicle density and distance from a pollen source on abundance of pollen. There were significantly more pollen grains on traps when panicle number was >40 than there were with fewer panicles. More pollen was on traps within 0.75 m of panicles releasing pollen. We examined the timing of release of pollen by Z. texana by collecting pollen at 6-h intervals for four consecutive 24-h periods. Pollen also was collected at 1-h intervals for four 24-h periods. More pollen was trapped 2400–0600 h (nighttime), compared with 0600–2400 h (daytime); peak hourly release of pollen was 0200–0500 h.

Timing of sexual activity by males and females is a critical aspect of mating systems. We analyzed whether reproduction in western Mexican whiptail lizards, Aspidoscelis costata, on a tropical Pacific island in Mexico is seasonal or continuous, and whether it is linked to certain meteorological factors. Macroscopic and microscopic analyses of monthly samples of gonads showed that reproductive cycles of males and females were seasonal (February–September) and significantly associated with day length. Necropsies did not evidence an overlap between successive reproductive events in females. However, our observations of free-ranging females showed that 35% of them were accompanied by males >1 time/season, with intervals between accompaniments of 14–31 days. In addition, observations of captive females and males revealed that accompaniment lasted 2–5 days, seemingly coincided with female receptivity and was broken 8–12 days before egg-laying. Repeated accompaniment by males suggests females have successive reproductive events within a season.

We report nesting success for a population of ground-nesting black-bellied whistling ducks (Dendrocygna autumnalis) for the summers of 2003 and 2004 at a hypersaline lake in southern Texas, and a population decline of 71% between 2002 and 2003. We attribute the population decline to a change in ecology of the lake, specifically, an increase in salinity from cessation of inflow of fresh water in 2000. The increased salinity led to high mortality in ducklings and brood failure due to sodium toxicity. We compared nest success, nest habitat, and nest predation to other reported populations of black-bellied whistling ducks in the northern area of their range.

Males of the tarantula hawk wasp Hemipepsis ustulata defend individual trees and shrubs on mountaintops in central Arizona where they wait for arrival of sexually receptive females. Each spring, a new generation of males comes to prominent hilltops to compete for mating territories. In 4 of 5 years during 1997–2007, in which the same Arizonan peaktop was censused regularly, behavior of males was similar with respect to such things as total number of plants occupied by territorial males, average number of days in which site-faithful males returned to their territories, and mean maximum days of residency at those select sites that attracted at least one male for a period of ≥2 weeks. Territories that regularly attracted males in one year did so in other years as well; territories that were infrequently occupied in one year were defended only occasionally, if at all, in other years. Even in the year (1998) when an unusually large number of plants were selected as perch territories by male wasps, preferred sites (those most consistently occupied over the flight season) remained the same as in the more typical years. Perhaps because the position and relative conspicuousness of the slow-growing mature trees and shrubs on hilltops remains the same from year to year, perch preferences of males also remain constant over long periods.

We used scalation, color pattern, and scanning electron microscopy of scale microdermatoglyphics to evaluate the hypothesis that an unusual rattlesnake specimen, from Wise Co., Texas, represents a natural hybrid between Crotalus atrox and C. horridus. The specimen demonstrates particular features of scalation and color pattern that are characteristic of either, but not both, parental species. With respect to microstructure of scales, the specimen exhibits a phenotype intermediate between the putative parental species. Based on this evidence, we tentatively consider the specimen to represent the first reported natural hybrid between C. atrox and C. horridus.

In this paper, we provide a description of six excavated burrow systems of Gunnison's prairie dog (Cynomys gunnisoni) in northern Arizona. These data plus other data from the literature on structure of the burrow system of Gunnison's prairie dogs, black-tailed prairie dogs (C. ludovicianus), white-tailed prairie dogs (C. leucurus), and Utah prairie dogs (C. parvidens) were used to compare species. Our excavations reveal that burrow systems of Gunnison's prairie dog vary from simple to complex structures, with >50% of burrow systems having multiple aboveground entrances. There was no significant difference among species in total length of burrow. Burrow systems of black-tailed prairie dogs were significantly deeper than burrow systems of Gunnison's prairie dog. On average, burrow systems of Utah and Gunnison's prairie dogs had more aboveground entrances than black-tailed or white-tailed prairie dogs. Overall, the burrow systems for all species were similar in structure, complexity, and underground connectivity.

Previous studies of oviposition sites of Corydalus cornutus have been restricted to large lotic systems. Attempts were made to correlate parameters of streams and oviposition sites in a small stream from early to late summer 2004 in Walker Co., Texas. Height of egg mass above surface of water, depth of water below egg mass, distance of oviposition to nearest shore, width of stream, distance to previous riffle, distance to next riffle, and velocity of water were measured to determine preference of sites for oviposition. At two study sites on a stream containing riffled areas, 94 egg masses were examined to determine their position. Significant correlations existed between width of stream and height of oviposition above water.

Mesopredators (e.g., raccoon Procyon lotor, Virginia opossum Didelphis virginiana, striped skunk Mephitis mephitis) have received considerable attention because of links to population declines in birds via increased nest predation, especially in landscapes fragmented by anthropogenic forces. Relationships of abundance of mesopredators to size of habitat patches have received less attention than relationships to other metrics of fragmentation, particularly edge characteristics. We tested the hypothesis that relative abundance of mesopredators (e.g., raccoons and Virginia opossums) was related negatively to size of forest patch. We delineated 15 patches of oak (Quercus) forest ranging from 0.2 to 55.3 ha within a grassland-woodland mosaic in the cross-timbers ecoregion of Oklahoma. Scent stations and live traps within these patches were used to index relative abundance of mesopredators in summers 2003 and 2004. Both indices of relative abundance were related weakly and negatively to area of forest patch. However, rate of capture and visitation to scent station were not correlated consistently throughout the study. Our results suggested that the two methods to index abundance provided separate information on functional and numerical responses to size of patch. Our evidence that mesopredators within the cross timbers were more likely to be in smaller patches of oak forest may have implications to success of avian nesting in these patches.

Los Terreros Creek, a reservoir-fragmented tributary in the upper Lerma River system of central Mexico, was sampled at four localities in wet (2001) and dry (2002) seasons to evaluate spatial and temporal patterns of fish assemblages, the conservation status of native fishes, and prevalence of exotic species. Two of five species present were non-native; the common carp (Cyprinus carpio) and the shortfin silverside (Chirostoma humboldtianum). Fish assemblages formed a strong gradient largely separating the lentic, reservoir-impacted, locality (downstream-most site) from the remaining lotic sites. The two most-upstream sites were not distinguishable based on structure of fish assemblages. Three of five species showed significant spatial variation in abundance. The Aztec shiner (Aztecula sallaei) occurred only at the lotic sites and the two species of silversides (Chirostoma) occurred only at the lentic site. Temporal trends in assemblages were less evident, but assemblages in the dry season had lower mean species-richness and mean abundance values. Analysis of distance matrices based on assemblages, site-specific environmental conditions, and spatial structure indicated that a strong, spatially structured environmental gradient was significantly associated with fish assemblages in the wet season, but not assemblages in the dry season. Los Terreros Creek still supports an assemblage of native fish that is typical for the upper Lerma River system. However, this relict system remains threatened by anthropogenic activities including changes in land use and further introduction of exotic species.

Adult black-bellied whistling ducks (Dendrocygna autumnalis) were observed leaving islands with recently hatched young in a South Texas hypersaline lake during summer 2003. We counted 216 ducklings from 20 broods attempting to make their first swim to the mainland, presumably heading for suitable rearing habitat. Of these, 144 (67%) either died in the water or on the salt-encrusted shoreline within minutes to a few hours of first entering the water. An additional 35 carcasses from unobserved broods were found. Nine carcasses of ducklings were necropsied and they had levels of sodium in the brain above the lethal threshold concentration for sodium poisoning. From our surveillance efforts, we documented a decrease in maximum number of adult black-bellied whistling ducks observed on the islands from 489 in 2002 to 138 in 2003.

The razorback sucker (Xyrauchen texanus), an endangered big-river fish of the Colorado River basin, has demonstrated no sustainable recruitment in 4 decades, despite presence of spawning adults and larvae. Lack of adequate recruitment has been attributed to several factors, including predation by nonnative fishes. Substantial funding and effort has been expended on mechanically removing nonnative game fishes, typically targeting large predators. As a result, abundance of larger predators has declined, but the abundance of small nonnative fishes has increased in some areas. We conducted laboratory experiments to determine if small nonnative fishes would consume larval razorback suckers. We tested adults of three small species (threadfin shad, Dorosoma petenense; red shiner, Cyprinella lutrensis; fathead minnow, Pimephales promelas) and juveniles of six larger species (common carp, Cyprinus carpio; yellow bullhead, Ameiurus natalis; channel catfish, Ictalurus punctatus; rainbow trout, Oncorhynchus mykiss; green sunfish, Lepomis cyanellus; bluegill, L. macrochirus). These nonnative fishes span a broad ecological range and are abundant within the historical range of the razorback sucker. All nine species fed on larval razorback suckers (total length, 9–16 mm). Our results suggest that predation by small nonnative fishes could be responsible for limiting recovery of this endangered species.

The Brazilian free-tailed bat (Tadarida brasiliensis) generally is considered a migratory species in western North America. Throughout the southwestern United States, however, winter records are known from many scattered locations. Here I report on T. brasiliensis exiting and entering a cave in southern New Mexico from November to March. I observed that a winter colony of Brazilian free-tailed bats at Carlsbad Cavern was comprised of males and females of different ages, and in February and March, I documented that numbers of individuals inhabiting the cavern were much higher than previously reported. Nearly all individuals returning to the cavern fed in November, about one-half fed in January and February, and none fed in early December and late March. I suspect that individuals wintering in the cavern consume insects during all colder months in the region, and lack of observations of bats feeding in December and March only reflect extremely windy conditions on nights of sampling. From December to March, body masses of individuals declined about 15%. Although this study adds to our understanding of the natural history of T. brasiliensis in winter, why some individuals remain in such northerly areas and do not migrate farther south is not yet understood.

Little is known about the Arizona gray squirrel (Sciurus arizonensis), which is endemic to mid-elevation riparian habitats in Arizona, New Mexico, and Sonora. In New Mexico, previous compilations of specimen records were restricted to the San Francisco River drainage in western Catron County. We compiled information on museum specimens, literature records, and observations by credible persons to document the distribution and habitats of S. arizonensis in New Mexico. Sciurus arizonensis is broadly distributed throughout the southern Mogollon Plateau region of Catron, Grant, and Sierra counties, including the San Francisco, Gila, Mimbres, and Rio Grande river drainages. All records were closely associated with riparian areas and most were from broadleaf riparian habitats. Sciurus arizonensis was observed to interact with other tree squirrels, including the Abert's squirrel (Sciurus aberti) and red squirrel (Tamiasciurus hudsonicus). We conclude that there has been neither a recent range expansion nor a range decline of this species in New Mexico.

Measurements taken on the skull of a bear shot in northern Sonora, Mexico, in 1976 revealed that the skull is from a brown bear (Ursus arctos). The skull appears to be that of a juvenile (sex unknown) and, to our knowledge, represents only the fourth confirmed record of a brown bear from Sonora, although anecdotal accounts exist from the mid-1800s to early 1900s. The present record also establishes that brown bears, considered extirpated from Mexico since the 1960s, were present in Sonora within the past 30 years.

We examined several aspects of the biology of Procinura aemula, including diet, sexual dimorphism, and clutch size, from Chínipas, Chihuahua, Mexico. Diet of P. aemula was composed entirely of invertebrates. Orthopterans and crickets were the majority of the diet, both numerically and volumetrically. Prey size was significantly related to snake size (snout–vent length, head size). There was no sexual dimorphism in snout–vent length or head size. Mean clutch size was 4.6 eggs. Clutch size tended to increase with snout–vent length of females, but the trend was not statistically significant.

We report on ecological interactions between the Gila monster (Heloderma suspectum) and the desert tortoise (Gopherus agassizii) in the Mojave Desert of southern Nevada. Eggs of desert tortoises are an important source of food for Gila monsters, and although tortoises are not always successful, they vigorously defend their nests from predation by Gila monsters. Shelters were co-occupied by these two species only during the nesting season for desert tortoises, and Gila monsters occupied shelters almost exclusively with female tortoises, probably because these shelters were nesting sites.

Among sympatric populations of lineages I, III, and VI of Tubifex tubifex, lineage VI recently was shown to exhibit resistance to Myxobolus cerebralis, the causative agent of whirling disease in salmonids. Determining the genetic differentiation exhibited among T. tubifex from different habitats and among lineages is key to understanding the etiology of whirling disease. This study examined genetic divergence within two lineages (III and VI) of T. tubifex from shallow and deep habitats in a tailwater at Navajo Dam in the San Juan River, New Mexico. Starch-gel electrophoresis was used to delineate alleles of T. tubifex from deep and shallow habitats. Cellulose-acetate electrophoreses was used to delineate alleles of lineages III and VI of T. tubifex. Of the seven allozymes analyzed, leucine aminopeptidase (LAP) differentiated between lineages III and VI. The LAP allele ‘A’ was exhibited only within lineage III whereas both alleles ‘A’ and ‘B’ were exhibited within lineage VI. Furthermore, lineages III and VI exhibited a genetic distance of 0.124, but were more similar to each other than to T. tubifex from the Great Lakes. Genetic divergence between lineages III and VI of T. tubifex, when coupled with differences in resistance to M. cerebralis, provide support to the hypothesis that populations of T. tubifex are members of a cryptic-species complex.