The Mojave Desert is one of the driest and hottest deserts in North America. One would expect that birds living in this desert would be specialists adapted to survive such an environment. However, most of the avifauna present in the Mojave Desert range into cooler, more-humid regions. We report observations of horned larks (Eremophila alpestris) using burrows of the desert tortoise (Gopherus agassizii) during summer as refugia from hot above-ground temperatures. We show that horned larks appear selective of the micro-environment they choose and that burrows are the coolest, most-humid, microsites available. By using burrows of desert tortoises, horned larks may reduce evaporative water loss by ≤65% and they may avoid physiological stress, or potentially death. Additional research should investigate the importance of burrows of desert tortoises to other species as it is likely to provide a key microhabitat to many species that reside in the Mojave Desert.

Structure of assemblages of fish at 97 sites using 12 metrics was examined. Of 176 species known from Oklahoma, 118 were collected. Few species had a statewide distribution and most were limited to the eastern one-half of the state. Number of species in a collection was 2–28 with a mean of 15. In four of 12 indices analyzed, means for the Canadian River drainage were significantly lower than those of the Red River drainage. No significant difference existed between drainages of the Arkansas and Red rivers or the Arkansas and Canadian rivers. Comparing groups from west to east showed five of the 12 mean indices for the panhandle group were significantly less than those for the rest of the state. For north to south groups, means for two of the 12 indices for the southern group were significantly larger than means for the rest of the state and significantly larger than 75% of the state for three other indices. Principal-components analysis of standardized means of indices for geographical blocks indicated that areas of the state could be similar in structure of assemblage, although they may contain different species.

We studied the reproductive cycle of Sceloporus dugesii from Pátzcuaro, Michoacán, Mexico. Males and females reached sexual maturity at the same snout–vent length (50 mm). Reproductive activity of both sexes was asynchronous, similar to other species of the torquatus group. Testicular recrudescence was July–August and maximum activity was September–December. Vitellogenesis occurred during early September to late March, with ovulation occurring November–December, and embryonic development was observed December–May. Mean clutch size was 4.4 ± 0.34. Clutch size was not correlated with snout–vent length of females. The reproductive cycle of S. dugesii is similar to other montane species of the torquatus group. Our study showed that S. dugesii shares some reproductive characteristics with its sister species.

The state of Colima in western Mexico is part of the transition zone between the two biogeographic regions of America, the Nearctic and the Neotropical. The state has particularly high mammalian diversity (128 species) and is in the area with the greatest concentration of endemic species in Mexico (25%). As a result, there is intrinsic scientific interest in the study of mammals of Colima. However, the mammalian fauna has received only limited attention to date. There is no published comprehensive inventory of mammals of Colima and only a few detailed reports of the species that occur at any given location within the state have been published. As a contribution to the knowledge of mammals present in Colima, data were compiled on the mammals of Ejido Ranchitos, municipality of Minatitlán, and the species were characterized. We recorded 35 species, 9 monotypic and 26 polytypic, gathering information on natural history and reproductive condition for each. These represent 27.3% of species of mammals known from Colima and 7.4% of the total for Mexico. Eleven species were endemic, comprising 31.4% of species captured for Ejido Ranchitos and 6.5% of the endemic species for Mexico. Nonvolant mammals exhibited three reproductive patterns: continual polyestrous (10 species, 28.6%), seasonal polyestrous (4, 11.4%), and seasonal monoestrous (3, 8.6%). Reproductive patterns for bats were seasonal monoestrous (7 species, 20.0%), asynchronic continual polyestrous (7, 20.0%), bimodal polyestrous (2, 5.7%), continual polyestrous (1, 2.9%), and asynchronic monoestrous (1, 2.9%). Three of the species we examined (Heteromys spectabilis, Neotoma mexicana tenuicauda, and Peromyscus hylocetes) have not been reported previously for Colima. Overall, Ejido Ranchitos supports a diverse fauna of small-sized and medium-sized mammals.

During a 2-year study, we documented eight species of bats using bridges in the lower Rio Grande Valley of New Mexico. Of 17 bridges surveyed, 15 (88%) contained day-roosting bats and ≥8 bridges (47%) contained maternity colonies with one or more species, including the Arizona myotis (Myotis occultus), Yuma myotis (Myotis yumanensis), and Brazilian free-tailed bat (Tadarida brasiliensis). The pallid bat (Antrozous pallidus), big brown bat (Eptesicus fuscus), silver-haired bat (Lasionycteris noctivagans), California myotis (Myotis californicus), and fringed myotis (Myotis thysanodes) roosted infrequently in bridges. Use of bridges by day-roosting bats differed seasonally, with most individuals occupying bridges April–October. During November–March, relatively few individuals of only three species (L. noctivagans, M. yumanensis, and T. brasiliensis) occupied bridges. Individuals roosted at many sites in bridges, but 99.9% roosted in narrow cracks and crevices. A total of 36,629 day-roosting bats was counted, with 99.8% observed in bridges constructed from timbers and 0.2% observed in I-beam bridges constructed from concrete, metal, or both. Paucity of bats in I-beam bridges reflected lack of narrow spaces. Our study demonstrates that some bridges represent important roosting sites for bats in southern New Mexico. Bridges throughout the southwestern United States likely serve similar life-history functions for bats and should be managed as a resource, especially those occupied by maternity colonies or large numbers of individuals.

Understanding how mining operations influence use of habitat and movements by bighorn sheep (Ovis canadensis) is critical to long-term management of populations that inhabit areas in and around mining operations. We studied responses of a population of desert bighorn sheep to a surface-mining operation in the Silver Bell Mountains, Pima County, Arizona. We incorporated two study periods with different levels of activity at the mine: closure (1993–1995) and operation (2003–2005). We captured and radiocollared ≥22 bighorn sheep in each period and monitored size of home ranges, size of core areas, and use of the mine. Home ranges and core areas of adult males during the breeding season were larger during closure than during operation. During the non-breeding season, there was evidence that home ranges of adult males were larger during closure compared to when the mine was in operation. Core areas of adult males were similar in size during the non-breeding season of both periods. During the breeding season, adult males used the mine more while the mine was in operation than during closure. During the non-breeding season, however, adult males did not use the mine more during either period. Home ranges and core areas of females were not different in size during both seasons and periods of closure and operation of the mine. During both seasons, females used the mine more during operation than during closure. Overall, the population of desert bighorn sheep used an active mine more than it did when the mine was closed.

Vegetational development in areas covered by volcanic ash from the Paricutin Volcano shows striking differences among types of plant cover at the time of the eruption. Forests affected by deposition of ash recovered soon after the eruption (1943–1952), but areas lacking vegetation at the time of the eruption today lack a closed canopy. We tested the effect of adding organic matter, straw, and a combination of organic matter and straw on recruitment of seedlings in a sand deposit formed in agricultural fields covered by ash from the Paricutin Volcano in Michoacán, Mexico. Number of seedlings varied significantly among treatments. At the end of the rainy season, plots with organic matter showed the highest number of seedlings (154 ± 20 seedlings/m²) followed by plots with organic matter and straw (82 ± 7 seedlings/m²), plots with straw (68 ± 14 seedlings/m²), and control plots (21 ± 13 seedlings/m²). In contrast, plots with organic matter and straw accumulated significantly more biomass (61.7 ± 10.8 g/m²) than organic-matter plots (14.5 ± 3.1 g/m²) or mulched plots (9.9 ± 3.1 g/m²). Clustering of experimental plots indicated that species composition of seedlings differed between plots with organic matter and straw, and plots with straw or organic matter. Our results suggest that the nature of organic matter that accumulates in soil can have a significant effect on composition of the seedling community, and support Eggler's hypothesis that lack of organic matter prevents development of vegetation in sandy substrates of volcanic origin.

Wild turkeys (Meleagris gallopavo) occur intermittently throughout Trans-Pecos, Texas. In the lower desert of the Trans-Pecos, turkeys are associated strongly with the limited riparian habitat where roosting habitat is found. We initiated a study to document microhabitat characteristics of roost sites in the Trans-Pecos region of Texas. We measured microhabitat characteristics (canopy cover, density of stand, visual obstruction, understory herbaceous cover, height of tree, diameter at breast height (dbh), height-to-lowest live branch, slope, and aspect) at 15 winter roosts and 15 random sites in three habitats in the Trans-Pecos region: ponderosa pine (Pinus ponderosa), live oak (Quercus virginiana), and sugar hackberry (Celtis laevigata). All roost sites were <1 km from riparian corridors and located in riparian regions. Among the three habitats, large diameters and height of trees were a prerequisite for roost trees in live oak and sugar hackberry habitat, where live oaks used as roost trees were larger (mean dbh  =  57.78 cm) than non-roosting trees (mean dbh  =  39.13 cm). Roost trees in live oak habitat had a greater height than trees in random sites (13.58 and 11.28 m, respectively). Sugar hackberries used as roost trees had larger dbh, height, height-to-lowest live branch, and canopy cover than nonroost trees in random sites. Due to the sparse density of trees, we recommend that riparian corridors with potential roosting habitat be protected throughout the Trans-Pecos. In addition, exotic species (e.g., Tamarix) should be controlled and native riparian habitats should be preserved.

We studied reproduction and sexual dimorphism of Aspidoscelis gularis from an arid environment in Guadalcázar, San Luis Potosí, Mexico. Males reached sexual maturity at a larger snout-vent length (55. 2 mm) than females (52. 4 mm). Males and females were similar in size, but males had larger heads and longer hindlimbs than females. Reproductive activity of both sexes was synchronous, similar to other species of the genus Aspidoscelis. Testicular recrudescence occurred February–March and maximum activity was March–October, and regression was in November. Vitellogenesis occurred February–September, with ovulation and fertilization occurring in June. Mean size of clutch of oviductal eggs was 3.0 ± 0.32. Size of clutch was not related to snout-vent length. Proximal factors influenced timing and intensity of reproduction in A. gularis.

We studied natural history and ecology of Thamnophis rufipunctatus at San Francisco Hot Springs, Catron County, New Mexico. Gee minnow traps were more effective at sampling adults than opportunistic captures. Females were larger than males in snout–vent length and mass, but males had longer tails. Although females were larger, rates of growth for juvenile males and females were similar. In 1996, the population was ca. 7.2 adult snakes/ha; however, we did not detect snakes in subsequent visits. Thamnophis rufipunctatus was most likely to be captured at sites with steep riverbed slope and large rocks of uniform size. Diet was exclusively fish, of which a large proportion was the introduced Gambusia affinis. This population of T. rufipunctatus was one of the most robust in the United States and it has completely disappeared in <10 years.

We surveyed mercury concentrations of aquatic macroinvertebrates collected from fishless ponds on the Lyndon B. Johnson National Grassland, Wise County, Texas. Macroinvertebrates representing eight taxonomic groups were collected from 13 ponds in June 2006. Significant differences in concentrations of mercury were detected among taxonomic groups, with the omnivore Hydrophilidae and the predator Notonectidae containing lowest and highest concentrations of mercury, respectively. We also detected significant differences in concentrations of mercury in macroinvertebrates among ponds. Concentrations of mercury of some macroinvertebrates were above recommended thresholds for consumption by birds. Our study suggests that fishless ponds can produce large populations of mercury-contaminated macroinvertebrates that could be harmful to aquatic and terrestrial consumers.

We examined contents of alimentary canal from pond-reared Rio Grande silvery minnows (Hybognathus amarus; n  =  183) to determine frequency of occurrence for foods consumed among small (9–20 mm), medium (21–35 mm), and large fish (36–75 mm). Among 183 fish, 19% (n  =  34) of alimentary canals were empty. Of those with food items (n  =  149), insects were the most common and were present in 66% of fish, followed by formulated feed (60%), diatoms (40%), cladocerans (36%), rotifers (35%), filamentous algae (32%), bryozoan statoblasts (19%), copepods (11%), protozoa (9%), plant material (9%), ostracods (6%), detritus (5%), and sand (4%). Among size groups, small and medium fish consumed a greater variety of foods than large fish. Information on contents of alimentary canal of pond-reared Rio Grande silvery minnows will aid in refining culture techniques for this federally listed endangered species.

The Mexican gray wolf (Canis lupus baileyi) was extirpated from Arizona and New Mexico in the 1970s. In 1998, Mexican gray wolves were translocated into the east-central Arizona portion of the Blue Range Wolf Recovery Area. One measure of success of the translocation is the ability of the Mexican gray wolf to capture native prey. Our objectives were to determine diet of wolves during summers 2005 and 2006, and contrast diet in areas that were grazed by livestock seasonally to areas grazed annually. We collected scats, identified contents from hair and bone fragments, and estimated diet by calculating percentage biomass of prey consumed. Elk (Cervus elaphus) comprised 80.3% of diet of the Mexican gray wolf. Other prey included domestic cattle (16.8%), deer (Odocoileus; <1%), squirrels (<1%), other rodents (2%), and lagomorphs (<1%). In areas of year-around grazing, 21% more livestock were consumed, compared to areas grazed seasonally.

We used two mitochondrial and eight nuclear microsatellite gene loci to compare genetic diversity and genetic affinities of white suckers (Catostomus commersonii) introduced into the Rio Grande of northern New Mexico to putative source populations in the Pecos and Canadian rivers of northeastern New Mexico. Estimates of genetic diversity based on allelic identity were similar among localities from all three drainages, whereas samples of non-native white suckers from the Rio Grande exhibited greater genealogical diversity. We attributed increased genetic diversity in the Rio Grande to separate introductions from ≥2 genetically distinct source populations, only one of which appeared to be from either the Pecos River or the Canadian River. There also was a divergent haplotype in the Pecos River, consistent with the introduction of a non-native lineage into this native population.

Parasites represent an element within natural systems that can elucidate interactions between their hosts and the environment. We collected and examined ectoparasites (80 samples) and fecal samples for endoparasites (81 samples) from 82 swift foxes (Vulpes velox) captured or collected in the Oklahoma Panhandle during summer and winter 2003–2004 and summer and autumn 2004. Six taxa of external parasites and nine taxa of internal parasites were identified. Overall prevalence of swift foxes infested with external parasites was 99% (range, 1–90% by individual parasite), which included four species of fleas and two species of ticks. Overall prevalence of swift foxes infected with internal parasites was 68% (range, 4–35% by species of parasite), including six nematodes, one cestode, one protozoan, and one mite. We observed two new external parasites not previously recorded for swift foxes, Spilopsyllus inaequalis and Dermacentor variabilis. More males than females were infected with Toxocara. Our results were similar to previously published reports of parasites from swift foxes in southeastern Colorado, northwestern Texas, eastern New Mexico, and the Oklahoma Panhandle, suggesting that this canid might be infected with a similar community of parasites across its range in the southwestern United States.

Allen's big-eared bat (Idionycteris phyllotis) inhabits much of the southwestern USA, but has not been documented in Colorado. We recorded echolocation calls consistent with I. phyllotis near La Sal Creek, Montrose County, Colorado. Based on characteristics of echolocation calls and flight behavior, we conclude that the echolocation calls described here were emitted by I. phyllotis and that they represent the first documentation of this species in Colorado.

During an 18-month sampling effort along the Río Sabinas in Coahuila, Mexico (December 2004–August 2006), we observed eight confirmed and three potentially new breeding records, nine new non-breeding records, and eight rare records of birds for Coahuila. We also identified the Río Sabinas as a potential new breeding site in the state for five species. These data illustrate the considerable conservation value of this understudied area in northern Mexico.

We present a list of noteworthy distributional records for 12 species of birds in the Mexican state of Guerrero. One (Dendroica striata) is new for the state, and the remaining either significantly expand their known geographic and seasonal distribution or add information about their presence in the state.

The silver redhorse Moxostoma anisurum is listed as threatened and considered critically imperiled (S1) in Arkansas by the Nature Conservancy. Only 12 records comprising 23 specimens of this species from five rivers are known from the state. A recent record is from the Strawberry River in Lawrence County during 2007; it and other records in Arkansas are reviewed. In 2007, 26 species of fish were collected with the silver redhorse, including the first vouchered specimens of the pealip redhorse Moxostoma pisolabrum and the pallid shiner Hybopsis amnis from the Strawberry River.

Acquiring water is a challenge for desert animals, and organisms inhabiting arid regions have evolved morphological, physiological, and behavioral traits to maintain an appropriate water balance. On four occasions, I observed rain-harvesting or observed behaviors suggestive of rain harvesting in a population of speckled rattlesnakes (Crotalus mitchellii) in the Mojave Desert of southwestern North America. Snakes collected rainwater on the surface of their bodies and subsequently drank it. Speckled rattlesnakes also drank rainwater that accumulated in structural features of their habitat (e.g., surface of rocks). My observations suggest that C. mitchellii may engage in rain-harvesting when thermal conditions are not optimal (i.e., during cold temperatures). For instance, rattlesnakes presumably emerge from hibernation to take advantage of rainwater.

Stomach contents of Nerodia fasciata and Nerodia rhombifer from Louisiana and Texas were examined by either palpation or dissection. Recovered prey included one new prey item (Siren intermedia) for N. fasciata and one (Arius felis) for N. rhombifer. Prey:predator ratios of mass and total size of meals are reported.

We report an incident from southeastern Arizona of an adult western screech-owl (Megascops kennicottii) entangled in Coulter spiderling (Boerhaavia coulteri), a native forb. Boerhaavia thrives in open areas, such as heavily grazed rangeland and other anthropogenically disturbed land. Rapid urban development may create favorable conditions for proliferation of Boerhaavia and promote avian entanglements.