Boulder Piles Research Articles

Case Study: Using Soil Survey to Help Predict Sonoran Desert Tortoise Population Distribution and Densities

On the Ground Soils properties can affect the ability of an animal to dig burrows for habitat and survival purposes. The Sonoran (Gopherus morafkai) and Mojave Desert Tortoise (Gopherus agassizii) require burrows that are at least 20 inches deep to help them thermoregulate during the cold of winter and heat of summer. Soils that have characteristics that restrict their “digability” would be expected to limit the population density and distribution of animals such as the Sonoran or the Mojave Desert Tortoise regardless of the amount of forage vegetation being produced. The Sonoran Desert Tortoise in Mohave County, Arizona, and possibly throughout its range may seek “habitats of opportunity” within boulder piles, under exposed bedrock, and in caliche caves due to the limited “digability” of the soils endemic to this part of the Sonoran Desert. The natural availability of thermoregulating burrowing habitat and temperature/precipitation records should be considered when interpreting any fluctuations in Sonora...

Resting-Site Selection of American Minks in East-Central New York

Research related to resting-site selection among native Neovison vison (American Mink) populations in North America is scarce. We radio-tracked 35 American Minks from March 2008-September 2011 along the Hudson River, NY, and its tributaries to evaluate restmg-site characteristics and selection. We located 583 resting sites, consisting primarily of boulder piles and riprap along the Hudson River (35.6%) and bank burrows along tributaries (29.0%). Results of logistic regression analysis revealed that the percentage of shoreline cover with woody debris best predicted resting-site selection <10 m from water and shoreline cover was the most important single-parameter model. Shorelines that provide abundant cover may help to conceal American Mink activity while also providing resting sites that are safe from predators.

Application of a species distribution model to identify and manage bear den habitat in central British Columbia, Canada

Several mammals have adapted to harsh winter conditions by adopting hibernation strategies that enable them to survive periods of unfavourable environmental conditions. At northern latitudes, black and brown bears can be in a state of hibernation for up to seven months. As a result of this prolonged occupation of one small space, bears can be vulnerable to environmental and human caused disturbances. In this study, we developed a predictive model that identifies potential den habitat for black bears that can assist with management planning for industrial land development activities. We identified 40 dens (17 excavated in soil and 23 natural rock cavities) and used fine‐scale information to determine how dens were positioned in forest stands. We found that bears denned in areas on mid to upper slope positions and that soil dens were located mainly in clay‐loam soil complexes while rock cavity dens were either caves or cavities in boulder piles. Den location was distant from portions of the study area with relatively high road density. We then used resource selection functions to predict where bear dens might be located on the landscape. When applied to the GIS data, the averaged coefficients suggested that 3.1% of the study area had a high suitability ranking as den habitat while 9.1%, 14.6%, and 73.2% had mid, low, and limited suitability, respectively. In our study area, habitat for den sites is reasonably predictable and should be considered during the planning of industrial activities.

Granite geomorphology and its geological controls, Serra da Estrela, Portugal

Serra da Estrela is an elevated granite massif in central Portugal, characterized by extensive plateau surfaces incised by deep valleys affected by Quaternary glaciation, bounded by steep fault-generated escarpments. The presence of seven major textural variants of granite provides an opportunity to study the relationships between lithology and relief, whereas DEM analysis helped to show the relationships between lithology and topography objectively. The higher ground is associated with fine- to medium-grained granites and is typified by planar surfaces of low gradient, with occasional angular tors and rock pedestals. Block fields built by angular material are common in the parts that were not previously glaciated. Less elevated parts of the plateau are supported by medium- to coarse-grained granites and show more varied topography, with an abundance of tors, boulder piles, and depressions. Lithological boundaries locally coincide with slope breaks but this is not the rule. In the northern part of the massif a deep topographic basin has evolved in biotite granite, whereas deeply incised valleys follow major fault lines. Geological controls show a hierarchy, in that gross relief reflects the pattern of tectonic uplift and subsidence, whereas lithology and then fracture patterns become more and more important if one focuses on smaller and smaller landforms.

Importance of Native Grassland Habitat for Den-Site Selection of Indian Foxes in a Fragmented Landscape

Fragmentation of native habitats is now a ubiquitous phenomenon affecting wildlife at various scales. We examined selection of den-sites (n = 26) by Indian foxes (Vulpes bengalensis) in a highly modified short-grassland landscape in central India (Jan-May, 2010). At the scale of the home-range, defined by an 800 m circular buffer around den sites, we examined the effect of land-cover edges and roads on selection of sites for denning using a distance-based approach. At the smaller den-area scale, defined by a 25 m x 25 m plot around den and paired available sites, the effect of microhabitat characteristics was examined using discrete-choice models. Indian foxes selected den-sites closer to native grasslands (t = -9.57, P < 0.001) and roads (t = -2.04, P = 0.05) than random at the home-range scale. At the smaller scale, abundance of rodents and higher visibility increased the odds of selection of a site by eight and four times respectively, indicating resource availability and predator avoidance to be important considerations for foxes. Indian foxes largely chose to den in human-made structures, indicated by the proportion of dens found in earthen bunds (0.69) and boulder piles (0.27) in the study area. With agricultural expansion and human modification threatening native short-grassland habitats, their conservation and effective management in human-dominated landscapes will benefit the Indian fox. The presence of some human-made structures within native grasslands would also be beneficial for this den-dependent species. We suggest future studies examine the impact of fragmentation and connectivity of grasslands on survival and reproductive success of the Indian fox.

Marmota Caligata (Rodentia: Sciuridae)

Abstract Marmota caligata (Eschscholtz, 1829), a large ground squirrel commonly called the hoary marmot, is 1 of 15 species of extant marmots. It is distributed in western North America from Alaska and Canada south to Washington and Montana and is found at elevations ranging from sea level to 2,500 m. M. caligata prefers alpine and subalpine boulder piles and talus slopes surrounded by meadows. The species is listed as “Least Concern” by the International Union for Conservation of Nature and Natural Resources, although populations of Montague Island and Glacier Bay are of conservation concern by the State of Alaska.

Rock hyrax (Procavia capensis) den site selection: preference for artificial sites

Context Objective assessments of habitat requirements for endangered species are often lacking when planning management strategies, and inappropriate landscape manipulation can sometimes turn an endangered species into a pest. Recent expansive population growth of the rock hyrax Procavia capensis in northern Israel has been attributed largely to the proliferation of man-made boulder piles on the fringes of new residential developments. Aims The hyrax is a protected species, but when in proximity to residential areas it can be a garden pest and is medically important as a reservoir of cutaneous leishmaniasis. Management should thus consider preservation of hyrax populations in combination with minimising pest potential. We examined the hypothesis that hyraxes prefer artificial boulder piles to natural outcrop crevices as den sites. Methods We surveyed all 57 potential den sites in a 1 × 1 km area around a village in northern Israel, and conducted logistic regression to examine the correlation of hyrax presence with site type (pile or crevice), size, distance from the village, distance from other den sites and network centrality within the den site network. We used the Aikaike information criterion (AIC) to compare logistic models. Key results Occupancy was well predicted by site type, site size, and distance from other sites, explaining 59% of the variation in the logistic regression. These three predictors were selected both by considering the combination of predictors that gave the lowest AIC value, and also by the stepwise logistic algorithm. Conclusions and implications Hyrax den site preference, and in particular preference for boulder piles over natural crevices, should be integrated into managing this species simultaneously for conservation and pest control in the face of continuing residential encroachment on natural areas.

Monitoring and evaluating rockfish conservation areas in British Columbia

Baseline data for rockfish abundance and substrate associations were documented for newly established rockfish conservation areas (RCAs) in Howe Sound using a multilevel occupancy model, which is new to fisheries science. In 2005, a series of roaming video dives was conducted. Videotapes were scored, minute by minute, according to substrate type, revealing a strong association of rockfish with piled boulders as preferred habitat. Paired divers sighted about twice as many rockfish as were documented on videotape in the same areas (same dates). In 2006, 69 dives were conducted at 11 randomly selected RCA sites and 12 random control sites (three dives per site). Of the factors investigated, only the percentage of boulder coverage predicted rockfish abundance. In 2007–2008, side-scan sonar was deployed for locating boulder piles to streamline efficiency of dive surveys. A combination of telemetry and underwater surveys in randomly selected areas should enable unbiased, noninvasive evaluation of the effectiveness of RCAs in rebuilding populations of inshore rockfish species on the Pacific coast of Canada.

Stability of nest range, home range and movement of the northern bettong (Bettongia tropica) following moderate-intensity fire in a tropical woodland, north-eastern Queensland

Nest use, home-range characteristics and nightly movements by the northern bettong (Bettongia tropica) were examined before and after a low- to moderate-intensity fire in sclerophyll woodland in north-eastern Australia using radio-telemetry. In all, 23 animals were radio-tracked at three-month intervals between February 1995 and May 1996. During November 1995 a low-intensity experimental fire burned the entire home range of most animals. The northern bettong appeared fairly catholic in choice of nest site, with a variety of nest locations and nesting materials used. Prior to the fire, nests were generally located in areas of dense cover, such as the skirts of grass trees (46%) or grass close to a log (29%). After fire removed most ground cover in the nesting areas of most animals, bettongs used remaining shelter such as boulder piles (45%), recently fallen trees (8%) and patches of unburnt vegetation (21%). Nest areas (10.1 ha) of males were significantly larger than those of females (5.4 ha). Home ranges of both sexes were large (59 ha) and most ranges lacked distinct core areas, suggesting that bettongs used all parts of their home ranges equally. High mean rates of nightly movement by the northern bettong indicated that large distances were moved within home ranges during nightly foraging. No significant fire-related changes were detected in home-range size, home-range location, nest-area location or mean rates of nightly movement, suggesting that the northern bettong is well adapted to the low- and medium-intensity fires that characterise its habitat.

Breeding Phenology of the Lowland Leopard Frog (Rana yavapaiensis): Implications for Conservation and Ecology

Breeding Phenology of the Lowland Leopard Frog (Rana yavapaiensis): Implications for Conservation and Ecology

Taxonomy of Rock-wallabies, Petrogale (Marsupialia: Macropodidae). II. An Historical Review.

The indigenous Australian genus Petrogale (rock-wallabies) consists of small to medium sized macropodids that are found throughout mainland Australia. As their name implies, rock-wallabies live in rocky habitats, preferring steep rocky slopes, cliffs, gorges, rocky outcrops and boulder piles (Sharman and Maynes 1983a). Many rock-wallaby species are distinctively marked, brightly coloured and are amongst the most beautiful of all macropods. Although well known to Aboriginal Australians for (at least) tens of thousands of years, rock-wallabies were only "discovered" by European explorers and naturalists in the early 19th century. Considerable variation in size, pelage characteristics and skull morphology has lead to the formal scientific description of 26 taxa in the last 170 years. The history of the scientific "discovery" of Petrogale in Australia and their subsequent taxonomy is long and fascinating. It is a story dominated by uncertainty and considerable speculation surrounding the inter-relationships of many taxa. It is in this historical context of confusion and contradiction that the current comprehensive genetic studies of rock- wallabies have both their significance and their genesis.

Natural History of Two Beach Hoppers of the Genus Orchestoidea (Crustacea: Amphipoda) with Reference to their Complemental Distribution

Natural History of Two Beach Hoppers of the Genus Orchestoidea (Crustacea: Amphipoda) with Reference to their Complemental Distribution

Hirstiella pyriformis sp. n. (Acari, Pterygosomidae), a New Parasite of Lizards from Baja California

Hirstiella pyriformis sp. n. is found on a number of lizards of the genus Sauromalus. It appears to be generally distributed on islands in the Gulf of California, and also on the mainland of Baja California. Ecological conditions under which the mite and its hosts live are described briefly. Lewis and Wagner (1964) recently showed that a mite parasite of Sauromalus varius Dickerson, 1919 is a vector of a hemogregarine of that lizard. Bonorris and Ball (1955) described Schellackia occidentalis from Sceloporus occidentalis and Uta stansburiana and showed that these lizards become infected by ingestion of the mite Geckobiella texana (Banks) 1904. The mite serves as a passive vector of the hemogregarine; no developmental stage is passed in the mite. Cunliffe (1949) described Hirstiella pelaezi and intimated that it might be the vector of a disease of lizards. Evidently this is the Hirstiella sp. referred to by Pelaez and Barrera (1948) as a potential, but unproved, vector of Plasmodium mexicanum Thompson and Huff, 1944, a parasite of Sceloporus ferariperezi and S. microlepidotus in Mexico. Thus, transmission of blood Sporozoa from one lizard host to another by Pterygosomidae is emerging as a phenomenon which should be examined more fully. The present paper describes a new species of Hirstiella which Lewis and Wagner (1964) implicated as the vector of the hemogregarine of Sauromalus varius. The specimens on which the following description is based were collected in a laboratory colony of S. varius at Loma Linda University in February 1963. The lizards had been collected in May 1962 on San Esteban Island in the Gulf of California. Since mites taken from the lizards at the time of collection belonged to the same species, there is no reasonable doubt about either the host or the locality from which the type Received for publication 2 August 1963. material was originally obtained. Specimens collected from Sauromalus obesus at Las Arrastras, on the mainland of Baja California, also agreed with the material described here. The genus Sauromalus (chuckwalla lizards) is confined to the southwestern United States and northwestern Mexico. At present seven species are recognized. Sauromalus obesus (including three subspecies) is geographically the most widespread of the group, occurring in Baja California, California, Nevada, Arizona, and Sonora. The other six species are quite restricted in their distributions, occurring in isolated populations on Baja California and several islands in the Gulf of California. It is interesting to note that mites taken from precinctive populations of chuckwallas on Angel de la Guarda I. and from San Esteban I. are not morphologically distinguishable from those collected on the mainland. It would thus appear that the mite parasite has not changed morphologically, while precinctive populations of the host have changed rather markedly. Chuckwallas are vegetarian lizards usually found frequenting dry washes and rocky outcroppings. Near Las Arrastras, in Baja California Norte, Sauromalus obesus was quite abundant on rocks during the early morning hours in May 1962. This region affords excellent protection for lizards due to the fact that many of the rocks and boulders have fractured extensively, resulting in numerous cracks and crevices. S. hispidus inhabits burrows along dry washes, boulder piles, and former gas pockets (vesicles) in volcanic rocks. A burrow some 6 ft in length was excavated in consolidated soil and gravel on southeastern Angel