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We examined influence of type of nest, olfactory attributes of nests, and size of egg on rates of predation of artificial ground nests in a tallgrass prairie site in Oklahoma during 1998–1999. Our objective was to investigate the role that odors of nests might play in predation of artificial grassland nests. In the first experiment, using eggs of the house sparrow (Passer domesticus) as bait, rates of predation on artificial reed nests purchased commercially were compared to artificial grass nests constructed from on-site vegetation. Rate of predation did not differ between type of nest. A second experiment tested effects of the odor of nests that mimicked presence of an incubating female. Artificial nests baited with eggs of the house sparrow were used with one-half being lined with 25–35 feathers from an adult house sparrow, and half being allocated no feathers. Overall depredation did not differ between these types of nest. In a third experiment, which tested effects of novel odors on predation, artificial nests were baited with either painted or unpainted eggs of the house sparrow. Nests with both types of eggs were depredated heavily (70–75% losses). A final experiment tested effects of size of egg by comparing predation among nests baited with eggs of the house sparrow, northern bobwhite (Colinus virginianus), or domestic chicken (Gallus gallus). Nests with eggs of the house sparrow (smaller eggs) were preyed upon significantly more (75% cumulative losses) than nests with either eggs of the northern bobwhite or domestic chicken (both with 5% cumulative losses). Although our observed rates of predation on artificial nests were similar to those from studies of predation of both artificial and natural ground nests, our results indicated that odors associated with artificial nests were unimportant relative to size of egg with respect to predation at this grassland site.
We studied seasonal variation in size and fidelity of home range in a population of eastern side-blotched lizards, Uta stejnegeri, in southern Coahuila, Mexico. Field work was carried out during the active seasons of 2002–2004. Home ranges during breeding and non-breeding seasons were larger for males than females and were reduced in both sexes during non-breeding months (autumn). There was greater intersexual overlap of home range during summer and less in autumn. Intrasexually, males had more overlap in home range than females (particularly during summer), which could be related to their large home ranges during that season. Fidelity to home range from one season to the next in a given year was similar in males and females. Although males had greater length and mass than females, neither measure correlated with size of home range. Density of adult lizards was negatively correlated with size of home range during the reproductive period. During non-reproductive months, density of all age classes combined was negatively correlated with size of home range. Our results indicate that home range sizes of U. stejnegeri vary considerably over the year and diverse factors are involved.
Two unmanaged sites (blackland prairie and deciduous woodland) in Walker County, southeastern Texas, were sampled monthly from February 2000 through January 2001 to determine effects of temperature and moisture on activity and population density of earthworms. The blackland-prairie grassland site supported an endemic earthworm fauna of two species of Diplocardia. A population of Diplocardia invecta was most numerous in the deep clay soil of this grassland site. The deciduous-woodland site supported a population of the exotic species Amynthas corticis (syn. Amynthas diffringens). This epigeic earthworm occurred in an isolated patch of disturbed, sedimentary clay soil in an otherwise sandy area. All observed D. invecta demonstrated seasonal vertical migration, but were quiescent from June to October. All observed A. corticis remained seasonally in the upper 10 cm of woodland soil, but were not observed during July, September, or October. Soil temperature and moisture at depths where earthworms occurred did not differ between the two sites from February through May and from November through January. Juvenile, adult, and total monthly population densities of both D. invecta and A. corticis varied due both to seasonal attrition and reproduction.
Species in the pleurocerid genus Elimia are important components of freshwater systems in the eastern United States, but little is known about their natural history. Using dual-simultaneous linear regression and principal components analyses, we show patterns of morphological change in two populations of E. comalensis from the Edwards Plateau, Texas. Both populations had similar rates of change for all shell measurements analyzed, and both showed similar decreases in growth as total length of shell increased. However, the size at which growth slowed was different between populations, and small shells tended to have a consistent shape, while larger shells were more variable.
During colder months in temperate regions, non-migratory bats are suspected to remain relatively inactive during hibernation. I examined activity of bats November–March in a region of North America with moderate winter temperatures. Bats were captured in nets over water and along flyways in southern and central New Mexico. In 47 nights, I captured 401 individuals representing 12 species. Captures for 10 species represent records of bats previously unknown outside roosts during colder months in New Mexico. The western pipistrelle (Pipistrellus hesperus), silver-haired bat (Lasionycteris noctivagans), California myotis (Myotis californicus), pallid bat (Antrozous pallidus), and Brazilian free-tailed bat (Tadarida brasiliensis) were captured frequently, whereas the western small-footed myotis (M. ciliolabrum), Townsend's big-eared bat (Corynorhinus townsendii), big brown bat (Eptesicus fuscus), Allen's big-eared bat (Idionycteris phyllotis), hoary bat (Lasiurus cinereus), fringed myotis (M. thysanodes), and Arizona myotis (M. occultus) were captured infrequently. Except for A. pallidus, I documented many individuals of the commonly captured species feeding November–March, and I also saw many individuals drinking during those months. Body masses of most species were lowest in March. During the study, activity of bats was positively, but not significantly, correlated with ambient air temperature at dusk. In this region of North America, many individuals of several species do not hibernate for the entire winter nor do they migrate from the region.
Mixed conifer of southwestern Colorado is poorly understood in comparison to other common forests in this area, in part due to its compositional complexity. We identified four stand types in warm-dry, mixed-conifer forests; Abies concolor (white fir), Pinus ponderosa (ponderosa pine), Pseudotsuga menziesii (Douglas-fir), and Populus tremuloides (aspen). We examined how composition and abundance of understory varied across these four types, and assessed the correlation between biotic and abiotic variables and understory vegetation. Composition of understory community differed significantly among stand types, with aspen plots having the most distinct understory plant community. Total plant cover was significantly higher in aspen, and shrub richness was significantly higher in the Douglas-fir stand type. On average, for all stand types combined, shrubs dominated the understory cover (11.35%), followed by forbs (7.89%), and graminoids (4.34%). Multivariate multiple regression showed that several topographic site factors (distance to drainage, slope, and aspect) and characteristics of stands (white fir/ha, ponderosa pine/ha and basal area, and basal area of aspen) explained variability in the understory community. Univariate regression showed that variation in annual species richness and Simpson's diversity index were partially explained by stand type and site. Our findings illustrate the necessity to not simplify forest dynamics for all western forest types or even within one forest type (warm-dry mixed conifer) for a general region. Implementation of forest management should be based on site-specific knowledge within localized geographic regions to restore or preserve semi-natural communities within a range of natural variability.
Distribution of the swift fox (Vulpes velox) has declined dramatically since the 1800s, and suggested causes of this decline are habitat fragmentation and transformation due to agricultural expansion. However, impacts of fragmentation and human-altered habitats on swift foxes still are not well understood. To better understand what effects these factors have on diets of swift foxes, scats were collected in northwestern Texas at two study sites, one of continuous native prairie and one representing fragmented native prairie interspersed with agricultural and fields in the Conservation Reserve Program. Leporids, a potential food source, were surveyed seasonally on both sites. Diets of swift foxes differed between sites; insects were consumed more on continuous prairie, whereas mammals, birds, and crops were consumed more on fragmented prairie. Size of populations of leporids were 2–3 times higher on fragmented prairie, and swift foxes responded by consuming more leporids on fragmented (11.1% frequency occurrence) than continuous (3.8%) prairie. Dietary diversity was greater on fragmented prairie during both years of the study. Differences in diets between sites suggested that the swift fox is an adaptable and opportunistic feeder, able to exploit a variety of food resources, probably in relation to availability of food. We suggest that compared to continuous native prairie, fragmented prairie can offer swift foxes a more diverse prey base, at least within the mosaic of native prairie, agricultural, and fields that are in the Conservation Reserve Program.
Mogollon voles (Microtus mogollonensis) live in grassy areas primarily in ponderosa pine (Pinus ponderosa) forests. We evaluated effectiveness of measuring visual evidence of Mogollon voles to monitor their populations. We used presence of five types of visual evidence and a combined measure (Index of Visual Evidence) to examine relationships between rate of capture of voles, presence, and visual evidence. We conducted our study in six meadows in ponderosa pine forests in northern Arizona, comparing evidence of presence of voles and rate of capture in an area with high density to an area with low density of voles in each meadow. We used linear regression to determine associations between visual evidence of voles and rate of capture, and we used logistic regression to investigate which visual evidence of voles were best predictors of presence. Relative abundance of voles was correlated with all types of visual evidence of voles. Relative density of fresh feces was the best predictor of rate of capture, but the Index of Visual Evidence was the best predictor of presence of voles. To monitor Mogollon voles, resource managers could use the Index of Visual Evidence, or search for fresh fecal material on runways.
Effects of unpredictable, variable rainfall in arid systems on diets of adults and lambs of desert bighorn sheep (Ovis canadensis) are poorly understood. We determined associations based on analysis of feces between amounts of rainfall and composition and similarity (overlap and diversity) of diets of adults and lambs, and relationships between diets of adults and lambs, in the Sonoran Desert of central Arizona during 1999–2003. Drought occurred in 2 of 3 years during sampling of feces of adults, and in 1 of 3 years during sampling of feces of lambs. Composition and diversity of diets of adults were comparable during years of drought and normal rainfall, except that diets were not correlated between years when severe drought (31% of long-term average rainfall) followed normal rainfall. Composition and diversity of diets of lambs also were independent of amounts of rainfall, but dietary overlap between and within age groups was greater during years of increasing rainfall compared to previous years. We hypothesized that amounts of rainfall moderately influenced diets of adults and lambs of desert bighorn sheep, but diets generally were closely linked among years and between age classes, and associations tended to persist independently of amounts of rainfall. Improved quality of diets and higher production, particularly of forbs, were more important proximate factors than composition of diets in affecting differences in nutritional status of adults and lambs between drier and wetter years. Furthermore, selection of forage by lambs likely is learned, at least in part, through associations, particularly with their mothers, prior to weaning.
The California Channel Islands, USA, and Pacific Baja California Peninsula Islands, Mexico (hereafter referred to as the California islands), are known for their high levels of biodiversity and globally important colonies of seabirds. We document the history, impacts, and management of non-native mammals and summarize the current status of native, non-volant mammals on the California islands. Of the 26 species of native mammals on the California islands, including 6 species and 41 subspecies that are endemic, ≥10 populations have suffered extirpation or global extinction. All recent extirpations and extinctions resulted directly from non-native mammalian predators or indirectly via habitat degradation by non-native herbivores. In light of the devastating effects non-native mammals have had on the native insular biotas of the California islands, a variety of organizations have collaborated to eradicate 44 populations of non-native mammals from 19 California islands. Documentation of impacts of non-native mammals and timely implementation of successful eradication efforts are essential to the conservation of these and other insular ecosystems.
We conducted a rigorous monitoring program to develop appropriate conservation plans for swift foxes (Vulpes velox). We set 20 cage traps on 51 grids to estimate rates of occupancy in eastern Colorado. Every 50th grid was selected systematically with a randomly selected starting grid from a list of 2,566 grids ranked by percentage of shortgrass prairie. We trapped 31 August 2004–12 February 2005, with each grid trapped 3 nights. Upon capture, we marked individual foxes with a unique identifier, and determined gender prior to release. We centered a 6.4 by 8.0 km-rectangle over each grid trapped and calculated percentage of shortgrass prairie using a GIS. We caught 136 swift foxes on 40 grids, including 12 recaptures; 71% of captures were in grids with >50% shortgrass prairie. We estimated the proportion of 4.8 by 6.4 km-grids in eastern Colorado occupied by swift foxes to be ψ ˆ = 0.711 (SE = 0.069, 95% CI 0.576–0.846), with no evidence of a decline from the 1995–1997 surveys.
Estimates of abundance commonly are used for assessing quality of wildlife habitat. However, disparities between abundance and fitness parameters make the utility of abundance for predicting quality of habitat questionable. We used survival of rodents and rates of capture to assess quality of habitat in greasewood scrub and sandhill prairie habitats at the United States Army Pueblo Chemical Depot, Pueblo, Colorado. Only the Ord's kangaroo rat (Dipodomys ordii) and the North American deermouse (Peromyscus maniculatus) were captured and recaptured enough to warrant statistical analysis. Apparent survival was modeled using temporal and seasonal patterns, vegetation cover, type of habitat, abundance of sympatric rodents, and abundance of grasshoppers. The most parsimonious models for survival of Ord's kangaroo rat incorporated abundance of bare ground at trapping sites, while the most parsimonious models for survival of North American deermice included amount of shrub cover at trapping sites. Although rates of capture for Ord's kangaroo rats and deermice were different between habitats, rates of survival did not differ between habitats. Suggestions that particular xeric-shrub habitats provide better quality of habitat for deermice and kangaroo rats should be framed using the relationship between rates of survival and abundance, instead of relying on abundance or rates of capture.
On a hilltop in central Arizona, males of the wasp, Astata boharti, exhibit fidelity to certain perch sites on the ground, while males of Astata occidentalis return to perch sites on the outer twigs of the limbs of trees and shrubs. As is true for other members of the genus, males of both species fly out from and then back to their perches, sometimes in response to passing insects. Both species are present during the late morning to early afternoon in September, when temperatures are still high in the Sonoran Desert. Although during this study, males of neither species were seen interacting with females, their behavior is convergent with that of a variety of other species of insects known to possess a mating system in which males wait for females to come to them at perch sites on hilltops. Hilltopping behavior has been previously documented for only a few crabronid wasps.
Capture techniques are an important consideration for studies involving endangered or threatened species. Mortality or serious injury can cause an unfavorable reaction from the public and bias results. Safe and selective capture of jaguars (Panthera onca) depends on such factors as environmental conditions in the study area, accessibility, avoidance of nontarget animals, budget, time, mobility, and skills and training of the capture team. In consideration of these factors, trained cat hounds were chosen as a capture method for a study of jaguars in the Chaco of Paraguay. During winter months of June and July 2002 through 2006, representing 5 capture periods, 15 jaguars were captured and fitted with GPS-VHF collars during 92 days of hunting. Four of these 15 jaguars were recaptured and refitted with new collars. No jaguar was killed or injured during capture or recapture, and no nontarget animal, including jaguar kittens, was chased, captured, or harassed. Post-capture monitoring via telemetry indicated that 14 jaguars moved 1–5 km from capture site the following day, with Jaguar 2 moving 12 km the day after capture. Six collared jaguars were captured on camera 24 times. Camera-trap photos gave visual support that the collared jaguars remained in good physical condition.
The Mediterranean gecko (Hemidactylus turcicus) is an introduced nocturnal lizard that often can be seen on and around buildings in the southern United States and in its native Old World range. However, little is known about the factors that determine its selection of microhabitat, except that it does not actively thermoregulate. For example, geckos may forage near lights due to presence of higher concentrations of flying insects or they may select darker sites near refugia to avoid predators. This study investigates the influence of ambient light level (irradiance) and distance to a refuge on selection of microhabitat. During their normal activity period, 54 geckos were hand captured. Snout–vent length, mass, sex, irradiance, and distance to the nearest refuge (crack, crevice, or hole) were determined for each lizard at the time and place of capture. Juvenile geckos tended to be in areas with higher irradiance and farther from refugia than adults. All adults generally selected sites closer to refugia. Adult male and female geckos did not differ significantly in selection of microsites. Thus, we suggest that adult lizards, especially territorial males, exclude juveniles from sites closer to refugia, which are typically of lower irradiance.
I studied diet and life-history attributes of a population of the Texas river cooter (Pseudemys texana) in the South Llano River, a southern tributary of the Colorado drainage in southcentral Texas. Turtles were primarily herbivorous, consistent with other reports of diets of Pseudemys spp. Volumes of samples from flushing stomachs did not show the expected 3∶1 log-log correlation with length of plastron, suggesting that the technique may vary in reliability as a function of body size. Length of plastron ranged from 78 to 161 mm in adult males and from 213 to 241 mm in adult females. Four clutches averaged 8.4 eggs, which averaged 41.9 mm in length and 26.9 mm in width. Compared to congeners, P. texana is small-bodied with large eggs and a high degree of sexual dimorphism in size. Data from other populations of P. texana suggest that the turtles in the South Llano are exceptionally small-bodied.
We collected two specimens of Reithrodontomys megalotis on Magdalena Island on the Pacific Ocean side of Baja California Sur. They represent the first insular record of the species in Mexico. These records extend the distribution range of the species about 450 km south of the southernmost record of R. megalotis in Baja California. In addition, three previously unpublished localities in mainland Baja California are reported.
One of two (50%) cave myotis, Myotis velifer, and one of five (20%) pallid bats, Antrozous pallidus, from Terrell Co., Texas, were infected with lecithodendrid trematodes, Acanthatrium alicataiMacy, 1940. A total of 22 specimens was collected from the small intestines of these two species of bats. This study documents two new host records and a new locality for this parasite. This also represents the second occurrence of the species since the original description >65 years ago. In addition, three nematodes (Seuratum cancellatum) and a coccidian (Eimeria antrozoi) were found in one (20%) of the A. pallidus. A summary of endoparasites of both species of bats is presented.
We studied the ecology of a population of the spiny lizard, Sceloporus jarrovii, located in the central Chihuahuan Desert. We compared the ecology of this population to that of other populations of S. jarrovii. Males were larger in snout–vent length, width of head, length of head, and length of femur than females. Mean size of clutch was 5.7. Overall sex ratio did not different from 1:1. However, the sex ratio was 1:2 in spring and summer, and 2:1 in autumn (reproductive period). All lizards were associated with crevices. Size of crevice (thickness) did not increase with snout–vent length of lizards. Mean body temperature was 31.6°C. Body temperature was related to air and substrate temperature. Of the four characteristics of crevices measured, only thickness of crevice was related to body temperature.
We found alligator snapping turtle (Macrochelys temminckii) carcasses in association with northern river otters (Lontra canadensis) at two sites in Oklahoma in summer 2006. Both specimens of turtles were juveniles, and at least one had been hatched and head-started in captivity prior to being released. This specimen was part of a radiotelemetry study at Sequoyah National Wildlife Refuge in east-central Oklahoma. The second carcass was found while investigating recent sightings of northern river otters at Tishomingo National Wildlife Refuge in southern Oklahoma. With the exception of cannibalism observed in a study of diet of adult alligator snapping turtles, these are the first reports of specific incidences of likely postembryonic predation of alligator snapping turtles.
An ecologically based classification system, when accompanied by digitized maps of biotic communities, has been shown to be useful for plotting and assessing affinities of plants and animals in the southwestern United States and northwestern Mexico. Because these maps show ecological relationships of plants and animals with their environment, maps of biotic communities can be especially informative when delineating and describing affinities of habitats. We have expanded the classification system and prepared a digitized, ecologically based, color map of the biotic communities of North America to assess distributions of organisms on a continental as well as regional scale. As such, this map also can be used as a sample frame to design and stratify surveys of animals.
Lizards that use perches may respond positively to structural features added to the landscape. Here, I describe preliminary observations of side-blotched lizards (Uta stansburiana) using dung piles of cattle as perches in an area where cattle were recently introduced in northwestern Utah. During timed surveys along transects, 89% of lizards were located on top of dung piles versus 11% on the ground. Dung piles might be used by lizards for basking or for feeding if invertebrate prey are attracted to dung. However, based on field observations, the best explanation for this behavior is that elevated positions atop dung piles enhance visibility for detection of prey while potentially reducing heat load. These findings support the notion that adding structural elements to the environment might improve habitat quality for certain lizards.
We present the geographic range expansion of Peromyscus schmidlyi to the north (430 km). The two new localities represent the first record for the state of Sonora. These records show that P. schmidlyi may be present throughout the Sierra Madre Occidental. P. schmidlyi could have a similar range to the other endemic species of this region, such as Spermophilus madrensis, Sciurus nayaritensis, and Nelsonia neotomodon.