Flourensia cernua seeds have far lower germination than the average recorded for arid-land shrubs of the family Asteraceae. In this study, we investigated whether low germination was due to dormancy effects of embryonic immaturity, the absence of hormones (i.e., gibberelic acid), moisture conditions provided by the germination substrate, or specific conditions of light and temperature. Percent germination increased for seeds between 5 and 8 months and decreased for older seed ages. We observed no increase in germination when gibberelic acid was applied to seeds. Germination was higher on an agar substrate (33.47%) than on a substrate of filter paper with cotton (7.73%), suggesting the advantage of a constant moisture condition. The highest germination percentages were obtained with white and red light, indicating that germination might be favored under conditions of exposed seed or conditions of minimal canopy and litter cover. The highest germination followed a combined pretreatment of heat and cold. These pretreatments probably reproduced thermic conditions encountered by F. cernua seeds under field conditions. Specifically, in nature, these seeds are dispersed during cold, winter months, but germinate later, after passing through the heat of the summer. Percent germination in our experiments rarely surpassed 30%, but is still considered low compared to those reported for other desert species of Asteraceae. We suggest that a dormancy mechanism, other than those considered in this study, accounted for low germination rates in F. cernua; alternatively, reduced germination might have been caused by endogamic depression.

We studied the habitat characteristics of 7 species of montane land snails in the genus Ashmunella in southern New Mexico from July 1999 to September 2000. We compared 9 numeric variables and 4 categorical variables by species. Geographic differences in microhabitat variables exist among these species; however, these differences tend to be obscured when comparing species, because some species are ecological generalists that occupy a wide range of habitat types. Although this study determined that different populations occupy ecologically distinct habitats in a broad range of environmental conditions, it remains unclear whether these factors influence the morphological characters on which past workers assigned species status. Management plans for the conservation of these species should take careful note of demonstrated habitat differences among and within the species.

We sampled the aquatic benthos at 6 remote sites on the Colorado and Green rivers through Canyonlands National Park, Utah, USA. This study provides the first published description of benthic standing mass, invertebrate community composition, and primary carbon source for this portion of the Colorado River system. High suspended sediment concentrations prohibited growth of primary producers. The primary carbon source for benthic invertebrates was terrestrial organic matter. The invertebrate community was composed of 49 taxa, mostly mayflies, caddisflies, and diptera, which were dominated by filterer/collector species. A smaller portion of the community was made up of predatory stoneflies and odonates. Standing mass of invertebrates on cobble substrates within a given site was stable over the multiyear sample period (1993 through 1996) and was comparable with other southwestern streams (overall mean = 0.41 g/m² ash-free dry mass ± 0.01 SE). Invertebrate standing mass at each site was controlled by the availability of primary carbon. Primary carbon availability was controlled by supply to the site and retention within the site. Both aspects might be influenced by anthropogenic alteration of the river basin and discharge patterns upstream of the study site.

Flash floods are a defining feature of desert streams, but flow records are not always available to characterize long-term flood dynamics. In this study, rainfall data spanning 100 years were used as a proxy to quantify long-term flood regimes for southeastern Arizona (USA) streams. The frequency and seasonal timing of severe floods (>50% substrate movement) were highly variable at short temporal scales (days to several years), but clear patterns emerged in the long-term (several years to a century). To explore the ecological effects of flood timing, populations of the caddisfly Phylloicus aeneus (Calamoceratidae) were monitored in 2 streams over 3 years. The timing of individual floods relative to the long-term average strongly affected P. aeneus populations: early and timely floods had little effect on population size in the next year, but late floods significantly reduced population size in the next year. Thus, flood timing might play a role in regulating populations of desert stream organisms.

We conducted laboratory tests to evaluate the effects of an abrupt 10°C decrease in water temperature on ability of age-0 flannelmouth suckers (Catostomus latipinnis) to escape predation by rainbow trout (Oncorhynchus mykiss). Juvenile flannelmouth suckers (58 mm mean total length) were maintained at 20°C and introduced individually, without acclimation, into tanks containing a single adult rainbow trout (246 mm mean total length) at 10 or 20°C. Rainbow trout attacked suckers more often at 20°C, but were more likely to capture them at 10°C. Age-0 flan-nelmouth suckers experience an abrupt temperature decrease when they exit warm tributaries and enter cold hypolimnetic water released from Glen Canyon Dam on the Colorado River. This temperature change might increase susceptibility of young flannelmouth suckers to predation by rainbow trout, which are abundant in the Colorado River in Glen, Marble, and Grand canyons.

We collected data on diet and population ecology of painted turtles (Chrysemys picta) at 2 high-elevation sites in southwestern Colorado during 1996 and 2000. Painted turtles from both sites fit previously reported patterns of delayed maturity and increased body size for C. picta at more northerly latitudes. Minimum body size at sexual maturity was similar at both sites for males (93 to 95 mm plastron length) and females (165 to 177 mm plastron length). Males appeared to reach sexual maturity at 2 to 3 years of age, whereas the onset of sexual maturity in females was delayed until 7 to 8 years of age. Average adult female body size (183 mm) exceeded any previously reported values for this latitude and might reflect an adaptive response to cooler climates and shorter growing seasons. Our analysis of dietary data indicated that painted turtles from these sites did not exhibit the same degree of carnivory (53.8% and 71.7% animal material) compared to more northerly populations of C. picta.

The black toad, Bufo exsul, has one of the most restricted ranges of all anuran amphibians. Its habitat is located almost entirely on land owned by Deep Springs College within Deep Springs Valley, Inyo County, California. Although abundant within its habitat, it is listed as threatened by the California Department of Fish and Game, primarily because of the small size of its range. Many aspects of its natural history remain unknown, making scientifically based conservation difficult. Potential threats to the black toad population might include the unquantified effects of cattle grazing, well-intentioned but non-scientifically based conservation efforts, changes in water availability, and other factors that have been implicated in the decline of amphibians worldwide. A census performed in part of the range of the toad in 1978 estimated a population size of 7,897 to 9,744 toads. We censused this population in 1999 and estimated 8,419 toads, with a 95% confidence interval of 5,624 to 16,740. The current population size is consistent with previous studies; however, continued monitoring is required to detect future changes. We summarize observations on changes in the sex ratios, average body size, and habitat conditions, and we recommend future research that might effectively guide conservation efforts.

We used 4 analyses to examine latitudinal patterns in geographical range sizes of New World woodpeckers and to test for the occurrence of Rapoport's rule, which predicts an increase in size of geographical ranges of species with increasing latitude. Although details of results varied among analyses, general patterns were the same. Smallest average range sizes occurred near 20°N, increasing in average size at more northerly (25°N to 60°N) and southerly (15°N to 0°) latitudes. Trends were less obvious within the southern hemisphere, but generally, species had larger average range sizes between 0° and 30°S than at higher latitudes. Therefore, although there is a positive latitudinal gradient for a portion of the northern hemisphere, data in general do not support Rapoport's rule.

Wing, bill, and mass measurements of eastern (Otus asio) and western (O. kennicottii) screech-owls identify them, their subspecies, and sexes. The eastern screech-owl is the more massive, shorter winged, and longer billed. Females of both species are larger than males. Subspecies follow Marshall (1967), except that O. a. naevius and O. k. macfarlanei are reinstated, and O. k. cardonensis is synonymized with O. k. xantusi. Body size is clinal from large in the north to small in the south in both species. Increasing sexual dimorphism in bill length correlated with decline in mass might reflect increased subdivision of the food niche related to increased competition in more dense populations and among more coexisting insectivorous owls southward. Eastern and western screech-owls coexist in southeastern Colorado, west-central and Trans-Pecos Texas, and northern Chihuahua and Coahuila, where their bill-length differences are 2.3 times greater than among allopatric populations. Interspecific competition is suggested by such character displacement, habitat segregation, and vocal mimicry. The 2 species seem to have mostly separate evolutionary histories, although occasional hybridization indicates continuing speciation.

We used remote cinematography to evaluate the interactions between feral honey bees (Apis mellifera) and desert bighorn sheep (Ovis canadensis) at an artificial water source (guzzler) in Anza-Borrego Desert State Park in southern California from July through September 1995. Honey bees, determined by molecular analysis to be non-Africanized (i.e., not A. m. scutellata), were present at the guzzler collecting water from dawn to dusk whenever bighorn sheep were videotaped. Bighorn sheep exhibited behavioral responses (violent head shaking, rapid withdrawal from the water source, and temporary refusal to drink) to honey bees during 62% (66 of 107) of their visits to the guzzler. Bighorn sheep spent significantly (P < 0.001) more time at the guzzler when their visits were interrupted by honey bees than when they were not interrupted. We concluded that honey bees altered the behavior of bighorn sheep and that honey bees and bighorn sheep were competing for water resources at the guzzler.

While much is known about the behavioral ecology of some species of pupfish (Cyprinodon), virtually nothing is known about the reproductive and territorial behavior of the Comanche Springs pupfish (C. elegans). Using SCUBA and underwater videography, observations were made of the reproductive and territorial behavior of C. elegans in the source pool of San Solomon Spring, Balmorhea State Park, Texas. We constructed time budgets of territorial males and manipulated territorial landmarks. Cyprinodon elegans exhibited courtship and agonistic behaviors, including territorial disputes similar to other Cyprinodon species. Additionally, C. elegans used visual cues as a means for identifying territory, as do other species of Cyprinodon.

In a 1983 survey of 50 spring-runs in northwestern Arkansas, Etheostoma cragini and E. microperca were each represented by only 5 populations. In summer and autumn 1997, we surveyed localities with historically documented populations and several additional spring-runs for presence of E. cragini and E. microperca to assess the current status of these species in Arkansas. Additionally, we documented local habitat attributes of each sample locality. We estimated population size of persistent populations in our surveys by mark-recapture method. Two populations of E. cragini had 546 (±214) and 79 (±60) individuals, and 2 populations of E. microperca had 1,341 (±349) and 129 (±56) individuals. Both darters inhabited small spring-run habitats with sand and silt substrate and some aquatic vegetation. These species are at risk of extirpation in Arkansas and should be considered for protection.

The Oklahoma salamander, Eurycea tynerensis, is an endemic species restricted to the superficial currents that exist in mountain streams of the Ozarks in Oklahoma, Missouri, and Arkansas. The results of our study show a close relationship between the salamander and the presence of rocks from the Ordovician/Silurian period. The small interstitial spaces created by the structure of this type of rock provide ideal habitat for the development of this neotenic species.

Summer activity and nesting biology of Plethodon angusticlavius is poorly known. On 7 July 1999, 6 brooding females were discovered in a small cave in the Arkansas Ozarks. The salamanders were monitored during the summers of 1999 and 2000 to determine nesting behavior, oviposition date, clutch size, egg development, and hatching date. We documented the first report of egg deposition by P. angusticlavius and confirmed speculations on the reproductive habits and nesting behavior of an endemic Ozark salamander.

Information on the feeding habits of a paedomorphic population of Ambystoma ordinarium is presented. Caddisfly larvae composed the greatest portion of the diet in numbers and frequency of occurrence, but grasshoppers were the most abundant item by volume. Smaller paedomorphs selected large numbers of small prey, whereas the largest size class fed on fewer but larger prey.

We report the results of standardized surveys to determine the effects of wildfires on desert tortoises (Gopherus agassizii) and their habitats in the northeastern Mojave Desert and northeastern Sonoran Desert. Portions of 6 burned areas (118 to 1,750 ha) were examined for signs of mortality of vertebrates. Direct effects of fire in desert habitats included animal mortality and loss of vegetation cover. A range of 0 to 7 tortoises was encountered during surveys, and live tortoises were found on all transects. In addition to desert tortoises, only small (<1 kg) mammals and reptiles (11 taxa) were found dead on the study areas. We hypothesize that indirect effects of fire on desert habitats might result in changes in the composition of diets and loss of vegetation cover, resulting in an increase in predation and loss of protection from temperature extremes. These changes in habitat also might cause changes in vertebrate communities in burned areas.

Colorado Division of Wildlife currently considers the Texas horned lizard a species of special concern. From May 1995 to October 1997, Texas horned lizards were captured or collected during the active season from 6 counties in Colorado to document abundance and distribution of the species. We captured or collected 290 Texas horned lizards (170 alive and 120 dead on road). In Colorado, average snoutvent length (SVL) for adult males was not significantly different from females; the largest male and female lizards measured 84.9 mm SVL and 90.4 mm SVL, respectively. The sex ratio of adult males to adult females is 1M:1.4F. Results of distribution and habitat analysis indicated that the Texas horned lizard in Colorado is locally common in arid shortgrass and sand-sage prairie lacking ground litter. Activity of the Texas horned lizard in Colorado is diurnal in spring and fall and bimodal (almost crepuscular) in the summer. Texas horned lizards in Colorado apparently breed in May and June, and hatchlings emerge in late August to mid-September. Mortality due to vehicle traffic seems high, but because the Texas horned lizard occurs in remote areas, the Colorado population in general seems to be relatively stable.

We studied diets of 3 species of lizards in the genus Xenosaurus (X. grandis, X. newmanorum, X. platyceps) from México. In general, the 3 species ate a diversity of prey, but the most important prey were insects (particularly Coleoptera and Orthoptera). Mammal remains and plant material were found in the diet of X. newmanorum.

We studied 2 populations of Sceloporus ochoteranae to determine if there were differences in body size, sexual dimorphism, and clutch size. Males were larger and had larger heads than females. Sceloporus ochoteranae from the Cañón del Zopilote (elevation 600 m) were smaller, had narrower heads and longer femurs, and had smaller clutches than those from Acatlan (elevation 1,250 m).

Parthenogenetic reproduction has not precluded the genesis of extensive genetic variation in the whiptail lizard, Cnemidophorus tesselatus. In Conchas Lake State Park, San Miguel County, New Mexico, the population of C. tesselatus includes pattern class C, with 4 allozyme variants, and pattern class D, with 3 allozyme variants. In 1988, we obtained a lizard in the park, described herein, with a unique color pattern and unusual meristic characters, which indicate that occasional females of C. tesselatus continue to be capable of producing neonates phenotypically different from the mother.

This article reports the first record of white-faced ibis (Plegadis chihi) nesting in Arizona and describes observations during the nesting period. On 21 June 2000, a colony of approximately 75 nests was discovered on an island of bulrush (Scirpus) in Cibola Lake, a backwater of the Colorado River within Cibola National Wildlife Refuge in southwestern Arizona. Based on date of first hatching, egg laying began about 15 June 2000. Ibis nests were monitored weekly. Overall, nesting success in this colony was low, with a fledging rate of slightly less than 1 young per pair.

We examined 56 fecal pellets from under a maternity colony of big free-tailed bats (Nyctinomops macrotis) in the Jemez Mountains of northern New Mexico. The most important food items, listed in order of decreasing percent volume, were Cicadellidae, leafhoppers (26.7% volume, 58.9% frequency); Ichneumonidae, Ichneumon wasps (19.3% volume, 35.7% frequency); and Lepidoptera, moths (17.2% volume, 82.1% frequency). Overall, the most important orders as prey consumed, listed by decreasing percent volume, were Homoptera (27.6% volume, 62.5% frequency), Hymenoptera (19.5% volume, 37.5% frequency), Lepidoptera (17.2% volume, 82.1% frequency), Hemiptera (11.7% volume, 37.5% frequency), and Diptera (10.6% volume, 50.0% frequency). Our study documents an unusually varied diet, as previous studies indicated that these bats fed almost exclusively on moths.

From 1993 to 1995, wild mammals were collected to update the inventory of mammals for the State of Durango, Mexico. New records were obtained for the following species: river otter or water dog (Lontra longicaudis), ocelot (Leopardus pardalis), margay (Leopardus wiedii), jaguarundi (Herpailurus yagouaroundi), and banner-tailed kangaroo rat (Dipodomys spectabilis). With these new records, the species list of mammals for Durango, México, increased to 134.

We report 7 species of free-tailed bats (Family Molossidae) from a single locality in the state of Durango, México. Three (Molossops greenhalli, Molossus molossus, Nyctinomops laticaudatus) are recorded for the first time in the state, whereas the remaining 4 (Eumops perotis, Molossus ater, Nyctinomops macrotis, Tadarida brasiliensis) represent considerable range extensions. The high diversity of bats found in the San Juan de Camarones region evinces its priority for protection and conservation efforts.

Desert bighorn sheep (Ovis canadensis) are known for their climbing skills in rugged and steep terrain. Occasionally sheep die from climbing accidents. Between 1979 and 1995, the Arizona Game and Fish Department reintroduced desert bighorn sheep to areas within their historic distribution: northwest, southwest, southeast, and central Arizona. Because at least half of reintroduced sheep (n = 412) were fitted with radiocollars and monitored monthly, we documented mortalities by climbing accidents. None of 54 mortalities in the southeastern region and 53 mortalities in the southwestern region was identified as climbing accidents. However, climbing accidents caused 5 of 42 sheep mortalities in the northwestern region and 4 out of 54 mortalities in the central region. Most climbing accidents (7 out of 9) happened <9 months after sheep were translocated. Our data suggest that translocated desert bighorn sheep can be vulnerable to climbing accidents due to lack of familiarity with local terrain. Differential vulnerability between regions might be related to differences in substrate, ruggedness of terrain, or both at release sites. Additionally, sheep translocated from less rugged terrain might be more likely to fall in new areas than sheep translocated from more rugged terrain.

Rocky Mountain elk (Cervus elaphus nelsoni) bearing malformed antlers have been observed in northern Arizona during the last 10 years. We collected measurements from 28 skulls of bulls bearing abnormal antlers from the Hualapai Indian Reservation in northwestern Arizona. Most abnormalities were unilateral. Deformed antlers were smaller and had fewer points than normal ones, and originated from deformed pedicles. The abnormal pedicles tended to be larger, and varied in orientation and location relative to normal pedicles. Some males lacked pedicles on 1 side, and the deformed antlers originated directly from the frontal bones. Similar antler and pedicle abnormalities have been documented in other elk populations in northern Arizona. The appearance of the abnormal pedicles was consistent with fracture and subsequent repair of the bones. Such damage might be incurred during sparring among males, and multiple factors might predispose the pedicles to injury.