Passerine response to roads associated with natural gas extraction in a sagebrush steppe habitat

Natural gas extraction and field development are pervasive throughout the sagebrush steppe of Wyoming. We conducted this study to determine how roads associated with natural gas extraction affect the distribution of breeding songbirds in sagebrush steppe habitat. The study encompassed dirt and paved roads in the Jonah Field II and Pinedale Anticline Project Area in Sublette County, Wyoming. Sites are dominated by Wyoming big sagebrush ( Artemisia tridentata ), and common passerines include sagebrush obligates: Brewer's Sparrows ( Spizella breweri ), Sage Sparrows ( Amphispiza belli ), and Sage Thrashers ( Oreoscoptes montanus ); and non-obligates: Horned Larks ( Eremophila alpestris ) and Vesper Sparrows ( Pooecetes gramineus ). Species relative density was measured using 50-m-radius point counts during spring 1999 and 2000. Four roads with low traffic volumes (700-10 vehicles per day) were surveyed and point counts were centered at variable distances from the road surface such that relative densities were measured 0-600 m from the road's edge. Density of sagebrush obligates, particularly Brewer's and Sage Sparrow, was reduced by 39%-60% within a 100-m buffer around dirt roads with low traffic volumes (700-10 vehicles per day). While a 39%-60% reduction in sagebrush obligates within 100 m of a single road may not be biologically significant, the density of roads created during natural gas development and extraction compounds the effect, and the area of impact can be substantial. Traffic volume alone may not sufficiently explain observed declines adjacent to roads, and sagebrush obligates may also be responding to edge effects, habitat fragmentation, and increases in other passerine species along road corridors. Therefore, declines may persist after traffic associated with extraction subsides and perhaps until roads are fully reclaimed.     

Response of wintering buteos to plague epizootics in prairie dogs

Several species of raptors winter at Rocky Mountain Arsenal National Wildlife Refuge (Refuge) including the Bald Eagle ( Haliaeetus leucocephalus ), Ferruginous Hawk ( Buteo regalis ), Red-tailed Hawk ( Buteo jamaicensis ), and Rough-legged Hawk ( Buteo lagopus ). Raptors were monitored each winter from 1988-89 to 1996-97 using a standardized road survey. Black-tailed prairie dogs ( Cynomys ludovicianus ) form a major component of the prey base for wintering raptors on the Refuge, with 1850 ha of active prairie dog towns mapped in 1988. Prairie dog town areas and population data were determined by mapping active towns and conducting visual counts on study plots to determine population density on an annual basis from 1988 to 1996. Large-scale plague epizootics were documented on the Refuge in 1988-89 and 1994-95, reducing prairie dog towns by 95% and 99%, respectively. A significant relationship was found in the numeric response of Ferruginous Hawks to changes in prairie dog town area ( r 2 = 0.96, P r 2 = 0.97, P r 2 = 0.07, P = 0.486). This contrasted sharply with the responses to prairie dog town area found for Red-tailed ( r 2 = 0.11, P = 0.377) and Roughlegged Hawks ( r 2 = 0.04, P = 0.612).     

Breeding movements and reproductive activities of porcupine in the Great Basin Desert

I assessed movements of North American porcupines ( Erethizon dorsatum ) in the Great Basin of northwestern Nevada in relation to reproductive activities during the late summer and fall periods of 1991 and 1992. Porcupines exhibit a mate-defense polygynous mating system and I hypothesized that (1) competitively dominant males would have larger home ranges than both subordinate males and adult females, and (2) variation in home range size among adult male porcupines would be positively correlated with reproductive success. Results indicated that dominant male porcupines ranged over larger areas (average 95% minimum convex polygon home range = 20.7 ha) than subordinate males (average 95% MCP home range = 2.9 ha) and adult females (average 95% MCP home range = 8.2 ha). Analyses of movements in relation to body size and energetic requirements revealed that home ranges of dominant male porcupines were larger than predicted based on body size (approximately 10.2 ha). Breeding period home ranges of dominant male porcupines encompassed portions of the home ranges of 3 to 10 adult females, and indices of reproductive success based on observations of mate-guarding behaviors suggested a strong positive relationship between home range sizes of male porcupines and mating success. Together these data suggested that larger home ranges among dominant males were related to increased mating opportunities and not increased metabolic requirements associated with larger male body sizes. In the study area, however, female porcupines congregated around small, patchily distributed riparian areas, and dominant males with relatively small home ranges encompassing riparian areas may have gained mating access to multiple females. Finally, analyses of overlap among core home ranges (60% MCP) of adult male and adult female porcupines suggested that both sexes maintained relatively exclusive core home range areas, with males exhibiting significantly less range overlap with other males ( ￣x = 9.4%) than females with other females ( ￣x = 27.1%). It is possible that the small, patchily distributed riparian areas in this desertlike area were such a limited resource that females were unable to maintain exclusive use of their home range areas.     

Censusing bobcats using remote cameras

We estimated bobcat ( Lynx rufus ) density for 3 different locations in northern California using active infrared-triggered cameras. Using differences in pelage pattern as well as other physical characteristics, we identified individual bobcats from photographs, and used mark-recapture techniques to estimate population density. Camera density affected the precision of population estimates. The same population was estimated using camera densities of 0.5, 1, 2, 4, 6, and 8 cameras ? km–2. Higher camera densities resulted in more captures and recaptures of bobcats and, consequently, in more precise density estimates. Similarly, the number of photo-captures and recaptures increased with increasing study duration. Increasing the area sampled resulted in the capture of more individuals but did not increase the percentage of recaptures. While some locations captured multiple bobcat photographs (e.g., 15 at 1 station), these photos tended to be recaptures of the same individual. There were no more than 2 individuals photo-captured at any 1 camera location. Bobcat density varied among habitat types as predicted. We estimated density as 0.27 bobcats ? km –2 ( s = 0.16) overall in an area in the northern Sacramento River Valley and as 0.35 bobcats ? km –2 ( s = 0.56) in a steep and rocky canyon within the area. At a 3rd site in the Coast Range, the estimate was 0.39 bobcats ? km –2 ( s = 1.44). Bobcats were more diurnal where human activity was less common. In addition, photo-capture was significantly higher along roads and trails without an attractant than it was off-trail with an attractant.     

Fertile island development around perennial shrubs across a Mojave Desert chronosequence

Spatial heterogeneity has been examined only recently as a factor in studies of ecosystem processes. The effect of this factor on desert organisms is exemplified in the ""fertile island"" a concentration of essential soil nutrients under perennial shrubs. In this study we examined fertile island patterns in undisturbed desert areas and on abandoned roadways to see at what rate and magnitude these fertile patches reappeared after disturbance. Small-scale examination of patterns of soil P, organic matter, moisture, and bulk density showed that soils beneath Larrea tridentata (DC.) Cov. shrubs on the roads lacked the tight circular gradient in these variables that was characteristic of soils beneath control shrubs, even 88 years after road abandonment. The nature of the initial soil disturbance altered both spatial patterns of soil N and temporal patterns of fertile island development. Fertile island patterns for total soil N, available P, and organic matter were more circular than patterns for bulk density, texture, or pH. We suggest that patterns of soil heterogeneity may develop first for elements that may be limiting to desert shrub growth (N, P, organic matter), followed by spatial development in other less limiting soil factors (bulk density, texture, pH).     

Deer mouse ( Peromyscus maniculatus ) home-range size and fidelity in sage-steppe habitat

Within a species, home-range size can vary due to factors such as sex, mass, age, and breeding condition of individuals as well as habitat type, food availability, population density, and season. The objectives of this study were to estimate home ranges of deer mice ( Peromyscus maniculatus ) in sage-steppe habitat and to test the hypothesis that several factors (sex, mass, reproductive status, and seasonality) affect home-range size. We also tested the hypothesis that deer mice exhibit home-range fidelity over time. Passive integrated transponder (PIT) technology was used to estimate home ranges in June and September 2006. Home-range estimates varied from 360 m 2 to 5868 m 2 (65 individuals, 753 observations). Home-range size increased by approximately 60% from June to September. Besides seasonality, none of the other predictors of home range were informative in explaining the variation in home range. Deer mice recaptured in September (3 months after initial capture) had high fidelity in home-range use (42.1% [SE = 8.4%] overlap with 74.1% [SE = 8.7%] area conserved; n = 9). All animals for which home range was estimated in both seasons retained some fraction of their June home range in September. Results support the use of combined location data collected over long periods, such as weeks or months, to estimate home range for deer mice. The results have implications for deer mouse–pathogen ecology, particularly with respect to modeling transmission of Sin Nombre virus—a pathogen that is directly transmitted by deer mice.     

Soil loosening processes following the abandonment of two arid western Nevada townsites

Soil compaction was measured at four sites within two abandoned mining camps in the western Great Basin Desert, Nevada. Bulk density and macroporosity values were generated from soil samples collected in areas of different land use intensities in camps that had been abandoned for approximately 70 years. Results show that significant differences remain in bulk density values between abandoned roads and undisturbed areas in both towns, and that the areas around foundation peripheries are still significantly more compacted in one town. There were no significant differences between land use groups as measured by macroporosity. Estimated soil recovery, based on a linear model using bulk density values, suggests that approximately 100 to 130 years are necessary for complete loosening to occur for abandoned roads, and that 100 or fewer years are necessary for complete amelioration of the foundation periphery areas. The wetter townsite, with more freeze-thaw days, finer-grained soils, and greater plant cover, had shorter recovery estimates. These finding suggest that the results of human-use impacts in arid areas may still be apparent long after disturbances cease.     

Pocket gophers ( Thomomys talpoides ) in successional stages of spruce-fir forest in Idaho

This study examined (1) the relative abundance of the pocket gopher ( Thomomys talpoides ) in four successive stages (1–10, 11–39, 40–79, and 80+ years following disturbance) of spruce-fir forest; (2) the relationship between number of gopher sign (mounds and earth plugs) with gopher density; and (3) a method of sampling pocket gopher populations using a 500 by 4 m strip transect. The number of gopher mounds was significantly correlated with the number of earth plugs. Data were pooled and a categorical log linear analysis used to test for significant differences in pocket gopher sign between the four successive stages. The 1–10 and the 80+ -year-old sites had significantly more gopher sign than the 11–39 and the 40–79 year-old sites. No significant differences were found between the 11–39 and the 40–79-year-old sites, or between the 1–10 and the 80+ -year-old sites. The difference in population densities may be due to understory vegetation differences between the successional stages. There was a significant correlation between amount of gopher sign and gophers caught in each of the study sites. This indicates that counts of pocket gopher sign may be used to estimate pocket gopher density. The strip transect is recommended as the most appropriate method when sampling heterogeneous habitats or when there is cause to suspect gopher populations may be aggregated within the area rather than spaced randomly or regularly.     

Population structure of Tachypleus tridentatus (Chelicerata: Merostomata) at a nursery beach in Puerto Princesa City,Palawan, Philippines

This study aimed to determine the population structure of juvenile Tachypleus tridentatus, one of two species of horseshoe crabs found in Palawan, at Aventura Beach, Puerto Princesa City, Palawan. Surveys to assess the population in terms of size, density, size‐frequency, age structure, sex ratio and distribution were conducted from June to October 2002. The habitat was mapped and physical/chemical parameters taken to further describe it. The position of population members was plotted on the map. Individuals were measured, marked, sexed and released. Prosoma width was measured for living individuals and exuviae. Postembryonic stages were identified based on histograms with different interval size. The normal distribution of the animals per instar stage was tested with the Kolmogorov–Smirnov test. After the 5‐month survey a total of 125 juveniles was recorded and 40% of them were recaptured. Population size was estimated to be 150 individuals. Seven postembryonic stages were identified based on their prosoma width. Male: female ratio was 1:1.8 and the age of the first five postembryonic stages ranged from 5.4 months to 17.6 months. The population density was 1.47 individuals per?100?m². The majority of the animals of all postembryonic stages were found between 0 and 50?m from the mean high tide level. Further studies on the population structure of T. tridentatus with regards to the adult population are seen as a necessity.     

Swift fox response to prescribed fire in shortgrass steppe

Swift foxes ( Vulpes velox ) are shortgrass specialists and as a result are heavily dependent upon grassland disturbance regimes to maintain high-quality habitat. To better understand this relationship, we monitored the movement and spatial ecology of resident swift foxes before and after a 2005 prescribed burn in southeastern Colorado. We hypothesized that foxes would shift home ranges into and increase foraging activity within the prescribed burn area. Foxes did appear to alter their space-use patterns in response to the burn, although the response was constrained by territoriality. Foxes whose core-use areas overlapped the burn increased their use of the burn area for foraging and denning, but we did not observe shifts of individual home ranges to encompass more of the burned area. Foxes whose coreuse areas did not overlap the burn did not alter their space use or change home range boundaries in response to the burn. Because we observed only positive or neutral responses to prescribed burning, we recommend this tool as an appropriate method to maintain high-quality swift fox habitat.     

Home ranges and aspects of the natural history of the Black-masked Finch Coryphaspiza melanotis (Gray, 1840) (Aves,Thraupidae) in central Cerrado,Brazil

ABSTRACT

In the Cerrado, native grasslands have been dramatically lost, leading to an alarming decline in populations of bird species that require these vegetation physiognomies. Species such as the Black-masked Finch Coryphaspiza melanotis (Gray, 1840) are vulnerable to extinction and remain poorly studied. The objective of this study was to examine home ranges of the Black-masked Finch at the Parque Nacional da Chapada dos Veadeiros, central Brazil. Ten males were studied in a patch of shrubby grassland (campo sujo) between February and December 2008. The mean sizes of home ranges were 4.47 ± 1.49 ha (Minimum Convex Polygon) and 3.48 ± 1.44 ha (Kernel 95%), and this varied significantly between seasons. Home ranges were significantly larger in the non-breeding dry season than during other periods, and significantly smaller in the breeding season than during other periods. Core areas (Kernel 50%) had a mean of 0.46 ± 0.26 ha. A large overlap of home ranges was observed. The home ranges of all banded males overlapped those of at least three co-specifics, and most had an area overlap of more than 50%. A nest containing an egg and a nestling was found in November. Small and largely overlapped home ranges can be considered as positive for the conservation of the Black-masked Finch. This is because both small grassland fragments and conservation units can substantially contribute to the conservation of its populations through the Cerrado extension.     

Brood habitat use by Sage Grouse in Oregon

Habitat use by Sage Grouse ( Centrocercus urophasianus hens with broods was examined at Jackass Creek and Hart Mountain, Oregon, from 1989 through 1991. Sage Grouse hens initially selected low sagebrush ( Artemisia spp.) cover types during early brood-rearing, big sagebrush cover types later in the brood-rearing period, and ultimately concentrated use in and near lakebeds and meadows. Areas used by Sage Grouse broods typically had greater forb frequency than did random sites. Hens at Jackass Creek selected sites with forb cover similar to that generally available at Hart Mountain, but home ranges were larger at Jackass Creek because of lower availability of suitable brood-rearing habitat. Differences in habitat use by broods on the two areas were reflected in dietary differences; at Hart Mountain, chicks primarily ate forbs and insects, whereas at Jackass Creek most of the diet was sagebrush. Larger home ranges, differences in diets, and differences in availability of forb-rich habitats possibly were related to differences in abundance and productivity between areas.     

Movements and home ranges of San Joaquin kit foxes ( Vulpes macrotis mutica ) relative to oil-field development

We examined the effect of oil-field development on movements and patterns of spatial use of San Joaquin kit foxes ( Vulpes macrotis mutica ) on the Naval Petroleum Reserves in California (NPRC) in the San Joaquin Valley. To do this, we compared movements and home ranges of kit foxes from June 1984 to September 1985 in areas developed for petroleum production (30% of native habitat lost to production facilities) and areas with little development (3%). Distances traveled nightly by kit foxes did not differ between levels of petroleum development or between sexes ( P > 0.2). Mean length of nightly movements during breeding (14.6 km) was longer than during pup-rearing (10.7 km) and pup-dispersal (9.4 km) periods ( P = 0.01). Mean size of home ranges was 4.6 ± 0.4 ( s￣x ) km 2 ( n = 21) and did not differ between levels of petroleum development and sexes ( P > 0.2). Overlap of home ranges of foxes from the same social group (78 ± 4.3%) was greater than that of same-sex foxes (35 ± 7.8%) and males and females of different social groups (32 ± 8.0%, P P > 0.4). Despite extensive overlap of home ranges, kit foxes on NPRC maintained relatively exclusive core areas, particularly adjacent foxes of the same sex. Future studies should examine which levels of habitat conversion impact spatial use of kit foxes.     

Model of breeding habitat of the Mountain Plover ( Charadrius montanus ) in western Wyoming

To aid the conservation and management of Mountain Plovers ( Charadrius montanus ), we developed a spatially explicit model of breeding habitat for the shrub-steppe of western Wyoming. Points of Mountain Plover presence and absence were determined by field surveys conducted May through June 1999. At each point we measured topographic slope and a cover type suitability index related to vegetation height and density. Logistic regression revealed a strong negative relationship between presence and slope, and a weaker and positive relationship between presence and cover index. A multiple logistic regression model using slope and cover index to predict presence successfully classified 87% of the points in an independent data set covering much of western Wyoming. The spatial expression of this model will help managers target future surveys and identify currently unsuitable habitat that could be improved via vegetation management. Patches of suitable breeding habitat of the Mountain Plover in western Wyoming are probably functions of poor soil, low precipitation, and wind scour, and thus are likely rather persistent in space and time. Combined with the relatively large proportion of publicly owned land here, this may make conservation and recovery of the Mountain Plover easier in western Wyoming than in the more dynamic and privately controlled Great Plains.     

Comparison of two roadside survey procedures for dwarf mistletoes on the Sawtooth National Forest, Idaho

Two roadside surveys were conducted for dwarf mistletoes parasitizing lodgepole pine and Douglas-fir on the Sawtooth National Forest, Idaho. One survey used variable-radius plots located less than 150 m from roads. The 2nd survey used variable-radius plots established at 200-m intervals along 1600-m transects run perpendicular to the same roads. Estimates of the incidence (percentage of trees infected and percentage of plots infested) and severity (average dwarf mistletoe rating) for both lodgepole pine and Douglas-fir dwarf mistletoes were not significantly different for the 2 survey methods. These findings are further evidence that roadside-plot surveys and transect-plot surveys conducted away from roads provide similar estimates of the incidence of dwarf mistletoes for large forested areas.     

Habitat use and selection and home ranges of Merriam's Wild Turkey in Oregon

Habitat use and selection by Merriam's Wild Turkeys ( Meleagris gallopavo merriami ) in Wasco County, Oregon, was studied during 1981-82. This turkey population selectively used forested cover types (such as ponderosa pine-Douglas-fir-oak, ponderosa pine-oak) characterized by a variety of structural features, species, and age classes. The population used single species forested cover types (oak, ponderosa pine) less than expected, used nonforested cover types in proportion to their availability, and avoided forested cover types with structure simplified by logging activities. The four age and sex classes had large seasonal home ranges (￣x = 1,615 ha); the smallest home ranges were exhibited by adult males in winter and the largest were shown by subadult males in fall. In most instances, turkeys used cover types as they were available. We suggest that structural complexity of vegetation, both within and among cover types, is an important component of habitat for Merriam's Wild Turkeys that should be considered in the evaluation of potential release sites and in habitat management plans.     

Abundance and condition indices of coyotes on Hart Mountain National Antelope Refuge, Oregon

U.S. Fish and Wildlife Service staff at Hart Mountain National Antelope Refuge (HMNAR), southeastern Oregon, documented high pronghorn ( Antilocapra americana ) fawn mortality, subsequent low fawn recruitment, and declining pronghorn numbers from 1996 to 1999. Coyote ( Canis latrans ) predation was the primary cause, accounting for 60-85% of fawn mortalities each year, and fawns were not physiologically predisposed to predation. Therefore, we investigated certain coyote population parameters (age structure, survival, density, physiology) to evaluate how or if these factors influence coyote predation rates on pronghorn fawns. We captured 11 coyotes (5 male and 6 female) in December 1998. Age of captured animals ranged from 1.7 to 10.7 yrs (￣x = 5.0 years), and all coyotes appeared healthy upon capture. There were no known mortalities through December 1999. We estimated pre-whelping (December through February 1997-1999) density from howling surveys conducted within HMNAR to be 0.40-0.53 km -2 . Compared to other published studies, we found significant ( P ≤ 0.05) differences in selected blood parameters (e.g., blood urea nitrogen, total protein, white blood cell counts), indicating coyote nutrition may be marginal to deficient during winter at HMNAR. A high percentage of coyotes (91%) tested positive for serum-neutralizing antibodies to canine parvovirus. We judged that parasite ( Toxascaris spp., Alaria spp., Sarcocystis spp., and Isospora spp.) prevalence and intensity were not high enough to influence coyote condition. Based on our data, the coyote population at HMNAR is old aged, at a relatively high density, and stable, but their nutrition may be marginal to deficient during winter. Presently, we are unable to draw direct conclusions relating the parameters we sampled with predation rates by this unexploited coyote population.     

An extant, indigenous tortoise population in Baja California Sur, Mexico, with the description of a new species of Xerobates (Testudines: Testudinidae)

An extant, indigenous desert tortoise population is reported from the cape region of Baja California Sur, Mexico. This population is described and figured as a new species, Xerobates lepidocephalus , distinct from all other North American tortoises including Xerobates agassizii , X. berlandieri , Gopherus flavomarginatus , and G. polyphemus . Xerobates lepidocephalus , or the scaly-headed tortoise, whose range is known only from an extremely small area in the gulf-drainage mountains just south of La Paz, appears to be a peninsular relict whose closest living relative is probably X. agassizii . However, carpal bone affinities connote a close relationship between X. lepidocephalus and the Oligoeene species X. laticunea from Wyoming and Colorado, suggesting that the former species may be one of the more primitive contemporary tortoises of the Xerobates lineage. Such evidence indicates that X. lepidocephalus is not of vicariant origin resulting from the formation of the cape of Baja California. Scaly-headed tortoises likely ranged, and may yet be discovered, in other medium-elevation mountain ranges of the cape.     

Population structure and reproductive biology of the fiddler crab Uca urvillei (Brachyura: Ocypodidae) in Maputo Bay (south Mozambique)

Although fiddler crabs are among the main faunal components in mangrove habitats, few studies have described the population structure and reproduction of tropical species. Such information is important for understanding their life cycle and ecology. In this study, the population structure and reproduction of Uca urvillei were studied at Costa do Sol, a tropical mangrove forest in Maputo Bay, southern Mozambique. Ten 1.0‐m² squares were sampled during low tide periods, between January and December 2003. The population is characterized by normal size distributions, which are slightly skewed to the left. Males on average are larger than females. Males were more abundant than females and the monthly sex ratios were male‐biased. Juveniles were found year‐round but were less common in June and December. Both gonadosomatic index and frequency of ovigerous females showed that Uca urvillei breeds continuously with peaks in summer and a strong decrease in winter. Egg number was proportional to female size.     

Pogonomyrmex ewyheei nest site density and size on a minimally impacted site in central Oregon

Little is known about the basic characteristics of the western harvester ant ( Pogonomyrmex owyheei ) in the absence of anthropogenic disturbances. We examined the role of P. owyheei as an agent of disturbance in an area of semiarid vegetation in central Oregon known as the Horse Ridge Research Natural Area (HRRNA) that has been largely free of livestock grazing and other significant anthropogenic influences for over 23 yr. We determined density and size characteristics of nest sites and estimate total area cleared by P. owyheei activities on HRRNA. From random sampling of twenty-five 0.04-ha plots we found a mean nest density/standard error of 1.6(± 0.16) nests/0.04 ha. Mean area cleared per nest site was 4.8 m 2 , which results in an estimated barren area of 46,080 m 2 on the 240-ha HRRNA. Comparing our findings to others on P. owyheei and P. occidentalis , we found nest density and mean cleared area to be in the middle range of reported observations under a variety of land-use influences. The literature suggests that moderate disturbance may increase nest site density, but little relationship exists between disturbance history and mean size of nest sites.