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1

Influence of pitfall versus Longworth livetraps, bait addition, and drift fences on trap success and mortality of shrews

100%
Stromgren E. J., Sullivan T. P.
Acta Theriologica
|
2014
|
tom 59
|
nr 1
Pitfall trapping is believed to be the most efficient method for capturing shrews (Sorex spp.); however, Longworth live-traps have been used successfully in North America and Great Britain. Due to high metabolic rates, previous attempts to livetrap shrews have been faced with very high (exceeding 95 % in some circumstances) mortality rates. Here we report the results of two experiments attempting to integrate successful livetrapping of shrews into standard rodent trapping protocols. In Experiment 1 we compared efficiency of pitfall and Longworth live-traps operated with drift fences on 1-ha trapping grids for capturing vagrant shrews (Sorex vagrans) on agricultural set-asides in Delta, British Columbia, Canada. A total of 100 trap stations, on each of three trapping grids, were equipped with a 3-m-long drift fence and randomly assigned either one pitfall at the centre of each fence, or two Longworth traps, one at each end of the fence. In addition, we randomly selected 50 % of trap stations and provided 6 g of mealworms (Tenebrio molitor) larvae as bait. In response to high mortality rates, we varied the frequency of trap checks, with intervals of 12–14 h (long), 6–9 h (medium) and 3–4 h (short). Contrary to our predictions, Longworth traps captured significantly more shrews than pitfall traps. We observed the highest mean mortality rates in traps without mealworms, checked at long intervals. Shrews in mealworm-baited traps checked at short intervals experienced no mortality. Mortality rates in mealworm-baited traps checked at short and medium intervals were similar (t = −1.33, P = 0.20, Bonferroni-corrected alpha = 0.004). In Experiment 2, we attempted to determine the relative gains in efficiency when using drift fences in conjunction with Longworth and pitfall traps. However, due to small sample size, we were unable to detect significant differences. A trapping protocol using Longworth traps in conjunction with drift fences, provided with mealworms as food, and checked at a maximum interval of 8 h should be sufficient to effectively include shrews in rodent livetrapping studies.
2

Population dynamics of meadow voles (Microtus pennsylvanicus) and long-tailed (M. longicaudus) and their relationship to downed wood in early successional forest habitats

80%
Craig V. J., Klenner W., Feller M. C., Sullivan T. P.
Acta Theriologica
|
2015
|
tom 60
|
nr 1
Forest habitats after harvesting or wildfire disturbance are usually dominated by early successional vegetation for up to 5–10 years, as well as downed wood or coarse woody debris (CWD). Abundance of Microtus voles is often highest in these sites with sufficient plant cover being crucial for population increases. The role of CWD for voles is less clear. We tested the hypotheses (H) that (H1) abundance and reproduction of meadow vole (Microtus pennsylvanicus) and long-tailed vole (Microtus longicaudus) populations would be higher on sites with greater amounts of downed wood and that (H2) this relationship would be stronger on sites with sparse vegetation cover. There were two study areas: a dry Douglas-fir (Pseudotsuga menziesii)–lodgepole pine (Pinus contorta) forest and a high-elevation Engelmann spruce (Picea engelmannii)–subalpine fir (Abies lasiocarpa) forest in southern British Columbia, Canada. We monitored the responses of meadow voles and long-tailed voles to three levels of downed wood over a 4-year period in replicated clear-cut sites at each area. Amount of downed wood did not positively influence meadow or long-tailed vole population dynamics, and hence, H1 was not supported. Variability in meadow vole numbers and vegetation precluded a test of H2 for this microtine. In dry forests, abundance of meadow voles on clear-cuts was related to the availability of cover and vertical structure provided by herbs and grasses. Vegetation cover was sparse in the high-elevation clear-cuts and long-tailed voles did seem to be positively affected by the number of pieces of CWD, but not by volume, and hence H2 appeared to be partly supported. In high-elevation or otherwise slow-growing areas, and in areas with long-tailed voles, downed wood left after harvest may provide some cover and structure.
3

Long-term responses in population dynamics and diversity of small mammals in riparian and upland habitats within an agricultural landscape

80%
Sullivan T. P., Sullivan D. S., Sullivan J. H.
Acta Theriologica
|
2014
|
tom 59
|
nr 2
Riparian zones in agricultural landscapes provide linear non-crop habitats for a variety of plant and mammal species, and hence are an important component of biodiversity. To date, variable responses of abundance, species richness, and species diversity of small mammals have been recorded in riparian and upland habitats. To address this variability, we provide a detailed analysis of seasonal changes in abundance and diversity of terrestrial small-mammal communities over a 7-year period within an agricultural landscape in south-central British Columbia, Canada. We tested the hypotheses (H) that abundance, species richness, and species diversity of communities of small mammals (H1), and demographic parameters of reproduction, recruitment, and survival of the major species: deer mouse (Peromyscus maniculatus) and montane vole (Microtus montanus) (H2), would be higher in riparian than upland habitats. Mean total abundance of small mammals was higher in summer and winter, and species richness higher in summer, in riparian than hedgerow habitats. Winter population data supported the total and species abundance patterns for small mammals, but species richness was similar, and diversity lower, in riparian than hedgerow sites during winter periods. Deer mice were the dominant species in terms of abundance and reproductive output for pregnancies and recruitment, but not survival, in riparian sites. Montane voles were similar in abundance and demographic parameters in the two habitats. House mice (Mus musculus) preferred hedgerows and wandering shrews (Sorex vagrans) riparian sites. Demographic parameters for deer mice and montane voles indicated that both riparian and hedgerow sites were “source” rather than “sink” habitats, and likely contribute to maintenance of mammal diversity in agricultural landscapes.
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