Capture Rates Of Small Mammals Research Articles

The influence of weather and moon phase on small mammal activity

Small mammals are commonly surveyed using live trapping but the influence of weather conditions on trap success is largely unknown. This information is required to design and implement more effective field surveys and monitoring. We tested the influence of weather and moon phase on capture rates of small mammals in the Murray Mallee region of semi-arid Australia. We used extensive pitfall trapping data collected at 267 sites, totalling 54 492 trap-nights. We built regression models to explore the relationship between the capture rates of five species and daily meteorological conditions, and across families of mammals, including dasyurids, burramyids and rodents. A relationship common to several taxa was the positive influence of high winds (>20 km h−1) on capture rates. We also identified differences between taxa, with warmer overnight temperatures increasing capture rates of mallee ningaui but decreasing those of Bolam’s mouse. This makes it difficult to determine a single set of ‘optimal’ meteorological conditions for surveying the entire community but points to conditions favourable to individual species and groups. We recommend that surveys undertaken in warmer months encompass a variety of meteorological conditions to increase capture rates and provide a representative sample of the small mammal community present in a landscape.

Do dense layers of invasive plants elevate the foraging intensity of small mammals in temperate deciduous forests? A case study from Pennsylvania, USA

Monospecific stands of invasive plants can dramatically restructure habitat for fauna, thereby elevating population densities or promoting foraging of consumer species who benefit in the altered habitat. For example, dense stands of invasive plants may protect small mammals from predators, which in turn could increase foraging pressure on seeds that small mammals feed upon. We used a before-after, control-impact experimental design to test whether small mammal capture rates were higher and giving-up densities (GUDs) lower beneath dense stands of Berberis thunbergii, an invasive shrub with a rapidly expanding range throughout eastern North America. Our experimental design included three plot categories: 1) plots heavily invaded by B. thunbergii, 2) control plots lacking invasive shrub cover, and 3) invaded plots where we eradicated B. thunbergii midway through the study. Although our overall small mammal capture rate was low, small mammal captures were 65% higher in B. thunbergii invaded habitat relative to control plots and eradication lowered capture rates by 77%. GUDs were also 26% higher within B. thunbergii relative to control plots and eradication decreased GUDs by 65%. Our findings suggest that small mammals perceive dense stands of B. thunbergii as relatively safe foraging habitat. Prior surveys within our study locations revealed dramatically depressed tree seedling densities under B. thunbergii, thus invasive plants may promote intensive foraging by small mammals and reduce recruitment for species with foraged seeds or seedlings.

Small mammals in cornfields and associated peripheral habitats in central Nebraska

In the Great Plains, many native grasslands have been converted to agricultural fields during the last two centuries. Peripheral habitats along edges of crop fields generally consist of linear habitats along roads, with many of these habitats used by native fauna. Our study examined capture rates and species composition of small mammals in cornfields, herbaceous roadside ditches, and wooded shelterbelts in central Nebraska. We captured nine species of small mammals. The Prairie Vole (Microtus ochrogaster) and Western Harvest Mouse (Reithrodontomys megalotis) were captured almost exclusively in roadside ditches, the White-footed Deermouse (Peromyscus leucopus) was captured most often in wooded shelterbelts, and the North American Deermouse (Peromyscus maniculatus) was common to abundant in all three habitats. Capture rates of small mammals were greatest in roadside ditches and least in cornfields. Herbaceous roadside ditches contained the greatest species richness with seven species, whereas shelterbelts and cornfields each had five species. Species composition of rodents differed in shelterbelts comprised solely of eastern red-cedars (Juniperus virginiana) compared to those with a mixture deciduous and coniferous trees. Our study demonstrated that roadside ditches associated with agricultural fields serve as habitats for many prairie species whereas wooded shelterbelts along agricultural fields support both woodland and prairie species in central Nebraska. Cornfields mainly were inhabited by North American Deermice but did not support many other species of small mammals. Although agricultural practices have reduced the quantity of grasslands for prairie species across the region, habitats associated with periphery of fields appear to serve as alternative habitats for small mammals throughout the Great Plains.

Relative abundance of the Prairie Long-tailed Weasel (<em>Mustela frenata longicauda</em>) in southwestern Alberta

Prairie Long-tailed Weasels (Mustela frenata longicauda) were live-trapped during fall 2005, 2006, and 2007 at Pine Coulee Reservoir and during fall 2005, 2008, and 2010 at Twin Valley Reservoir in southwestern Alberta. Our objective was to estimate the relative abundance of the Long-tailed Weasel and to estimate the relative abundance of small mammal prey. Body size and capture rates are reported for Long-tailed Weasels, and we report capture rates of small mammals. Annual capture rates for Long-tailed Weasels at Pine Coulee Reservoir were 0.44, 0.41, and 0.50 individuals per 100 corrected trap-nights (0.42, 0.38, and 0.48 individuals/100 trap-nights) in 2005, 2006, and 2007, respectively. No Long-tailed Weasels were captured at Twin Valley Reservoir. The probability of capturing zero Long-tailed Weasels at Twin Valley Reservoir was very low, assuming a true capture probability equivalent to that observed at Pine Coulee Reservoir. Deer Mice (Peromyscus maniculatus) were the most abundant small mammals captured in both project areas. Few shrews (Sorex spp.) and voles (Microtus spp.) were captured in either area.

PREY-MEDIATED EFFECTS OF DROUGHT ON CONDITION AND SURVIVAL OF A TERRESTRIAL SNAKE

Drought can have severe ecological effects and global climate-change theory predicts that droughts are likely to increase in frequency and severity. Therefore, it is important that we broaden our understanding of how drought affects not only individual species, but also multitrophic interactions. Here we document vegetation and small-mammal abundance and associated patterns of Texas ratsnake (Elaphe obsoleta) body condition and survival before, during, and after a drought in central Texas, USA. Vegetation (grass and forbs) height and small-mammal capture rates were two times greater in wet years compared to the drought year. The decline of small mammals (the snakes' principal prey) during the drought was associated with a drop in ratsnake body condition, consistent with reduced food intake. During the drought, snake mortality also increased 24%. Although higher snake mortality was attributable to predation and road mortality rather than being a direct result of starvation, an increase in risk-prone behavior by foraging snakes probably increased their exposure to those other mortality factors. Drought conditions lasted only for 21 months, and vegetation, small-mammal abundance, and snake condition had returned to pre-drought levels within a year. Although estimates of snake population size were not available, it is likely that substantially more than a year was required for the population to return to its previous size.

Comparison of 2 Vegetation-Height Management Practices for Wildlife Control at Airports

Vegetation-height management is a potential method to reduce bird numbers at airports. Based on studies in Europe, researchers recommended vegetation heights around 25 cm; however, preliminary studies in the United States produced confl icting results regarding the effect of tall (18 to >25 cm) vegetation on bird numbers at airports. From 1999 to 2002, we compared birds and other wildlife use of 4 short-vegetation plots (mean maximum height of 15.6 cm ± 5.1 SE and visual obstruction reading of 4.6 ± 3.0 cm) and 4 tall-vegetation plots (mean maximum height of 26.9 ± 8.4 cm and visual obstruction reading of 10.0 ± 5.0 cm) in Ohio. We surveyed bird use of the plots 2 to 3 times/week and observed 6,191 birds in short-vegetation plots and 5,962 birds in tall-vegetation plots. We detected no difference between short-vegetation and tall-vegetation plots in the probability of avian use of the plots when evaluated as a binary response of presence and absence. Small mammal capture rates in 100 adjusted trap nights were 0.0 in short-vegetation plots and 0.3 in tall-vegetation plots. We found no difference in the number of deer observed in the plots during sunset and spotlighting counts. There was slightly greater insect biomass in tall- than in short-vegetation plots. Mowing negatively affected small mammal use. The generalization that tall vegetation (18 to >25 cm) alone would reduce bird use of an airport is not supported by the results of this study. Further research on vegetation density, composition, palatability, and nutritional value is necessary to accommodate airfi eld requirements for habitat that is pleasing to the public and repellent to wildlife.

The responses of small mammals to patches regenerating after fire and rainfall in the Simpson Desert, central Australia

Abstract Patch‐burning is frequently advocated as a management tool to enhance the biodiversity and pasture values of spinifex (Triodia) grasslands. In this study we compare the capture rates of small mammals in habitats regenerating shortly after fire (aged 1–5 years) and in long‐unburnt habitats (aged >25 years). To unravel the effects of temporally and spatially variable rainfall on capture rates, the study was replicated at three locations spaced over 50 km apart that experience different rainfall regimes. Ten species of small mammals were captured over the course of the study, between October 1999 and June 2001. Pseudomys desertor showed a strong preference for long‐unburnt habitats. Notomys alexis, Sminthopsis youngsoni and Sminthopsis hirtipes showed some preferences for regenerating habitats, but these were not consistent throughout the study. Factors indicative of temporal and spatial variation in rainfall, time and site had important effects on capture rates. High rainfalls associated with the La Niña phase of the El Niño/Southern Oscillation in 2000 increased seed production and prompted eruptions of rodent species and the carnivorous Dasycercus cristicauda. The greatest numbers of captures were made at the sites that received the highest rainfalls. We conclude that patch‐burning regimes do not benefit small mammals directly, but are likely to increase the resilience of ‘fire‐sensitive’ species that are dependent on dense spinifex by reducing the extent of wildfires.

Forest Structure and Vertical Stratification of Small Mammals in a Secondary Atlantic Forest, Southeastern Brazil

This study investigated the differential capture rates of small mammals in different strata of a secondary forest, Minas Gerais State, Brazil. From March through October 1994 mammals were live-trapped at ground, understory and mid-story level. Five species of marsupials and six species of rodents were recorded. Didelphis aurita, Marmosops incanus, Metachirus nudicaudatus, and Oryzomys spp. were captured mostly on the ground, while Caluromys philander, Micoureus demerarae, Rhipidomys mastacalis and Sciurus aestuans were sampled mainly at 5-12 m height. Species richness was correlated with structural complexity of the forests surveyed. On the other hand, a relationship between species richness and habitat heterogeneity was not detected. These results suggest that local saturation of small mammal species, rather than regional species richness, is determined by the level of habitat complexity. The conservation of stratified forests, such as those found at the Parque Estadual do Rio Doce and the other sites in the Rio Doce valley, are therefore essential for the maintenance of local species diversity.

Small Mammal Habitat Associations at Patch and Landscape Scales in Oregon

Abstract To investigate multiscale habitat associations, we examined patterns of capture rates of small mammals in thirty 250–300 ha landscapes in the central Oregon Coast Range. We compared capture rates of 14 species within ≥7 patch types to expected capture rates based on sampling effort. We used landscape level capture rates to test for associations with percent area (composition) and 8 pattern indices at the landscape scale. Capture rates of 10 of 14 small mammal species were higher in conifer and/or mixed large sawtimber patch types. At the landscape scale, capture rates of 6 of 14 species of small mammals were positively associated with the area of patch types. The pattern of patches on the landscape may influence the distribution of 5 small mammal species in this region. We conclude that some small mammals may respond to landscape pattern and/or composition, while other small mammals may not respond to either landscape pattern or composition. Our results suggest that mature forest habitat, patch richness, pattern, and composition are key landscape features that should be considered in management plans, particularly when biodiversity of forest floor mammals is a management objective. FOR. SCI. 48(2):255–264.

Response of Forest Floor Vertebrates to Riparian Hardwood Conversion Along the Bear River, Southwest Washington

Abstract The conversion of riparian red alder (Alnus rubra) forest to conifers for salmon (Oncorhynchus spp.) habitat improvement is controversial. I monitored changes in vegetation, microclimate, and the abundance, distribution, and body condition of small mammals and amphibians during the initial stage of alder conversion. Treatments reduced alder and moss cover [mean standardized effect size (ES) = -2.38 and -1.23, respectively (P = 0.0001)], but increased shrub and forb cover [ES = 0.98 and 0.37, respectively (P = 0.0001)]. Treatment effects on microclimate were neutral to moderate (ES = 0.00 to 0.67, P = 0.2). Effects on pitfall trap capture rates of small mammals were small to moderate (ES = -0.04 to 0.51, P = 0.2) and varied by taxon, and effects on captures of amphibians were small (P = 0.2), but positive (ES = 0.05 to 0.26). Pitfall captures were influenced more by seasonal weather patterns than treatment effects on vegetation. Differences in the density of torrent salamanders (Rhyacotriton kezeri) in streams in conversion and control sites were large (ES = -1.00, P = 0.4) and moderate for giant salamanders [ Dicamptodon spp. (ES = 0.31, P = 0.4)]. Treatment effects on the mass/individual for three species of shrew were small (P = 0.2 to 0.9) and either negative or neutral (ES = -0.21 to 0.00) for juveniles and adults. Effects on the mass of western red-backed salamanders (Plethodon vehiculum) were small for adults (ES = -0.12, P = 0.6) and juveniles (ES = 0.08, P = 0.8). Treatment effect on the mass of red-legged frogs (Rana aurora) was positive ( P = 0.2) for both age classes (adult ES = 0.52, juvenile ES = 0.20). The effect of conversion on the mass of torrent salamanders was positive (adult ES = 1.00, P = 0.002; juvenile ES = 0.25, P = 0.02). Additional research should focus on confirming my results, longer term effects, and additional wildlife species. FOR. SCI. 48(2):299–308.

Habitat Use by Small Mammals in Coastal Marshes of Southwestern Louisiana

A short-term study based on snap-trap capture rates of small mammals in the marsh and levee system in southwestern Louisiana was conducted in the winter-spring period. Marsh rice rats (Oryzomys palustris) dominated marsh habitats and rice rats and fulvous harvest mice (Reithrodontomys fulvescens) were co-dominants on levees. Least shrews (Cryptotis parva) and house mice (Mus musculus) were also taken. Although rice rat capture rate in marshes was twice that from levees, the difference was not significant (p=0.1428). When found on levees, rice rats preferred portions of levees adjacent to marshes and canals (p<0.0001). We found few differences in rice rat capture rates from marsh and levee habitats, although capture rates from fresh marsh and adjacent levees were select levee ridges over the marsh and canal edges (0.1≥p≥0.05). The abundance of harvest mice on levees adjacent to intermediate marshes exceeded all other levee habitats. For reasons as yet unexplained, intermediate marshes and adjacent levees had the highest small mammal abundance and species richness. Conversely, fresh marshes and their adjacent levees had the lowest abundance and variety of small mammals.

Pitfalls and Snap Traps for Sampling Small Mammals and Herpetofauna

Experiments were conducted to compare the efficiency of drift-fence pitfalls with three types of snap traps for sampling small mammals and to determine the usefulness of pitfalls for sampling herpetofauna. During winter 1984, small mammal capture rates were lower in pitfalls and Victor rat traps than in Victor mouse traps (P<0.01). During summer and autumn 1984, capture rates in pitfalls were greater than in Victor mouse traps (P<0.01). During winter and summer 1985, capture rates of pitfalls and Museum Specials were similar. Pitfalls with drift fences also captured 220 individual reptiles and amphibians. INTRODUCTION Some form of trapping is often used to sample the members of a local fauna. Most authors agree that a combination of trapping methods yields the most complete data on community composition and reduces biases associated with various traps (Getz, 1961; Smith et al., 1971; Weiner and Smith, 1972). Boonstra and Rodd (1984) and others have compared conventional live traps with pitfalls for a single species of small mammal. However, we know of no studies comparing the effectiveness of snap traps and pitfalls for a large assemblage of species. We compare three snap trap types and pitfalls with drift fences as methods for collecting small mammals, and examine the effectiveness of pitfalls for sampling herpetofauna. STUDY AREAS Data were collected from Abbeville, Edgefield, Greenwood, McCormick and Saluda counties in the Piedmont Plateau Region of western South Carolina. Twenty-eight sites within young (0-21 years old), even-aged loblolly pine (Pinus taeda) stands were sampled. Criteria for site selection included seed-tree or plantation regeneration, chop-and-burn site preparation and access (Smith, 1962). Stands previously thinned or with a recent history of fire were not selected. Study sites were located on the Long Cane Division of the Sumter National Forest and lands owned by International Paper Company. Average tree age was 6.6 years (SE = 1.2 years) and tree density was 3078 pines/ha (SE = 489.0 pines/ha). Average annual temperature and precipitation in the study counties was 16.7 C and 150 cm (NOAA, 1983), respectively. Stand size varied from 4-200 ha and averaged 58.1 ha (SE = 9.95 ha). MATERIALS AND METHODS Trap locations were determined by drawing grid lines on a map of each study site and randomly selecting five lines. Pitfalls were arbitrarily placed in the center of the trap lines and equidistant from the nearest two lines. Field placement of lines and pitfalls was achieved by using a compass and pacing from the stand boundary or road intersection. By preselecting trap locations, we reduced any bias associated with subjective placement of trap lines and pitfalls. Pitfall traps. -We used pitfalls with drift fences to sample small terrestrial vertebrates. A single cross-shaped array with four fence sections was used on each site (Campbell and Christman, 1982). All fences were constructed of 5-m sections of aluminum flashing placed in a ditch 8-12 cm deep. All sections of fence were 15 m apart. Sites were randomly assigned a fence height of either 25.4 cm or 50.8 cm. A 19-liter plastic bucket was buried flush with the ground at either end of each fence section. 'Present address: Division of Life Sciences, Ferrum College, Ferrum, Va. 24088.