Microtus Longicaudus Research Articles

Woody debris structures on large clearcut openings: Oases for small mustelids and prey species?

Restoration structures such as post-harvest woody debris piles on large clearcut openings may provide habitat for many mammal species. Mustelids such as the American marten (Martes americana) and several weasel (Mustela spp.) species are important furbearers in temperate and boreal forests and are negatively affected by clearcutting. We ask if constructed piles of woody debris on large (e.g., 30–50 ha) openings will be used by these mustelids and their small mammal prey species? We tested the hypotheses (H) that (H1) the presence (index of activity patterns) of small mustelids, (H2) abundance, species richness, and species diversity of the forest-floor small mammal community, and (H3) reproduction of the major species: southern red-backed vole (Clethrionomys gapperi), long-tailed vole (Microtus longicaudus), and deer mouse (Peromyscus maniculatus), would be greater on sites with woody debris piles than on sites with dispersed debris. A fourth hypothesis (H4) predicted that the above response variables would be similar across a linear configuration of debris piles on the large openings. Mustelid presence and populations of forest-floor small mammals were sampled on four replicated (n = 4) large (30–50 ha) clearcut sites from 2017 to 2022 in south-central British Columbia, Canada.Mean presence of mustelids was significantly higher (4.5 to 8.0 times) in piles than dispersed sites during the first four post-harvest years, thereby supporting H1. Mean index of mustelid activity per line was similar among pile index-lines across these clearcut openings. Mean abundance of C. gapperi was similar statistically between treatment sites but with numbers 3 to 10 times higher, on average, in the piles than dispersed sites and was likely biologically important. Mean abundance of M. longicaudus was significantly higher (1.2–4.4 times) in the piles than dispersed sites. Mean abundance of P. maniculatus and Sorex spp. were similar between treatment sites. Mean abundance of total small mammals, including the less common species, was significantly higher (1.4–1.9 times) in piles than dispersed sites. Similarly, mean species richness and diversity were both significantly higher in piles than dispersed sites. Mean number of total recruits was higher in piles than dispersed sites for M. longicaudus and P. maniculatus, but most measures of reproductive attributes were similar, thereby providing only partial support for H3. As per support for H4, response variables were similar across a linear array of debris piles on large openings. Our study is the first to measure responses of small mustelids and forest-floor small mammals to constructed piles of woody debris as a means of habitat restoration on relatively large (mean area 40.5 ha) openings created by conventional clearcutting. Piles of debris seem to act as oases for mustelids and their prey species in ecological restoration of cutover forest land.

Long-Term Changes in Abundance and Composition of Forest-Floor Small Mammal Communities in a Landscape with Cumulative Clearcutting

Responses of forest-floor small mammals to clearcutting are species-specific with generalists occupying a range of habitats, and specialists persisting on clearcuts for variable periods. We investigated the responses in abundance and species composition of small mammal communities to cumulative clearcutting of coniferous forests on a landscape that had four independent clearcutting events (Periods 1 to 4) over a 42-year interval from 1979 to 2020 in south-central British Columbia, Canada. We ask if the small mammal communities have changed significantly over these decades owing to removal of old-growth forest by clearcut harvesting. Hypotheses (H) predicted that the small mammal community would (H1) increase in abundance, species richness, and diversity on new clearcuts owing to the availability of early seral post-harvest habitats from cumulative clearcutting; and (H2) have higher mean abundance, species richness, and species diversity in clearcut than uncut forest sites, owing to availability of vegetative food and cover. A third hypothesis (H3) predicted that abundance of (i) early seral vegetation (herbs and shrubs) and (ii) small mammal populations, will be greater in ungrazed clearcut sites than in those grazed by cattle (Bos taurus). Mean total numbers of small mammals on new clearcuts declined in Periods 3 and 4, and hence did not support the abundance part of H1. Much of this decline was owing to low numbers of the long-tailed vole (Microtus longicaudus) and meadow vole (M. pennsylvanicus). Two generalist species: the deer mouse (Peromyscus maniculatus) and northwestern chipmunk (Neotamias amoenus), contributed to high mean species richness and diversity in Periods 2 and 3 before these metrics declined in Period 4, and hence partly supported H1. The similarity in mean total numbers of small mammals in Periods 2 to 4 did not support the abundance prediction of H2 that total numbers would be higher in clearcut than uncut forest sites. Higher mean species richness (Periods 2 and 3) and diversity (Period 3) measurements on clearcut than forest sites, particularly in the early post-harvest years, did support these parts of H2. The vegetation part (i) of H3 was not supported for herbaceous plants but it was for shrubs. The small mammal part (ii) of H3 that populations would be higher in ungrazed than grazed clearcut sites was supported for abundance but not for species richness or diversity. The decline and near disappearance of both species of Microtus was possibly related to the reduction in plant community abundance and structure from grazing (at least for shrubs) and potentially from drought effects associated with climate change. Loss of microtines from these early seral ecosystems may have profound negative effects on various ecological functions and predator communities.

Population fluctuations of long-tailed voles (Microtus longicaudus) in managed forests: site-specific disturbances or a long-term pattern?

Abstract We investigated population responses of Microtus longicaudus to cumulative clear-cutting of coniferous forests and to enhanced understory vegetation in young, fertilized pine stands near Summerland, British Columbia, Canada. We explored if there was a threshold level of habitat quality arising from a given forest disturbance for M. longicaudus to increase to high population levels and potentially fluctuate in abundance over time. Secondly, we asked if these outbreaks were site-specific or part of a long-term pattern. We tested three hypotheses (H) that populations of M. longicaudus would increase in abundance and potentially fluctuate owing to (H1) the availability of early seral postharvest habitats associated with cumulative clear-cut harvesting; (H2) woody debris piles on clear-cuts; and (H3) have higher mean abundance, reproduction, and survival in fertilized forest sites with enhanced understory vegetation. Mean annual and peak abundances of M. longicaudus were significantly different across the four Periods of cumulative forest harvesting with numbers being highest in the first two Periods. Thus, H1, that long-tailed voles would increase in abundance on new clear-cuts, was partially supported for the first two Periods but not in the later Periods. Constant cattle (Bos taurus) grazing during summer periods over the four decades may have reduced vegetative productivity for voles and damped out population responses on these clear-cut sites, at least in the last two Periods. Woody debris piles on clear-cuts may have increased abundance and generated a population fluctuation, thereby supporting H2. Enhanced abundance of understory vegetation had no effect on mean abundance, reproduction, or survival of M. longicaudus, and hence did not support H3. We conclude that it is site-specific disturbances, particularly in forest management, that generate occasional outbreaks of M. longicaudus, and there does not appear to be any long-term pattern to these discordant fluctuations.

Small mammal relative abundance within riparian ecosystems of the Blue Mountains

There is a growing interest and investment in restoring riparian areas in the Pacific Northwest to protect biodiversity and water quality, and to restore quality habitat for threatened fish species. However, these management activities change vegetation conditions and potentially impact terrestrial species in these ecosystems. Our objective was to estimate associations between small mammals and 4 broad cover types—conifers, shrubs, grasses, and forbs—in riparian areas within the Blue Mountains of northeast Oregon, USA. We estimated abundances and spatial association for 10 small mammal species using a multispecies hierarchical abundance model and mark-recapture data collected on 36 sites from 2014 to 2017. We predicted that forest-associated species would be more abundant with greater conifer cover, that increases in shrub cover would favor most species, and that increases in grass and forb cover would favor grassland-associated species. Yellow-pine chipmunks (Tamias amoenus) were positively associated with conifer cover, while long-tailed voles (Microtus longicaudus) and montane voles (Microtus montanus) were negatively associated with conifer cover. Associations with shrub cover were positive for bushy-tailed woodrats (Neotoma cinerea), deer mice (Peromyscus maniculatus), and yellow-pine chipmunks, but negative for montane voles. Bushy-tailed woodrats and montane voles were negatively associated with grass cover. This study is the first to characterize the riparian small mammal communities in this region and provides insights on the effects of restoration activities on riparian ecosystems in dry interior forests and grasslands. We suggest that riparian plantings, a ubiquitous restoration practice, will increase the relative abundances for some, but not all, small mammal species. We also demonstrate use of a new multi-species abundance model that can be a powerful tool for analyzing mark-recapture data because it allowed us to extend the scope of our analysis to data poor species by pooling information with data rich species.

Diverse Genotypes and Species of Cryptosporidium in Wild Rodent Species from the West Coast of the USA and Implications for Raw Produce Safety and Microbial Water Quality.

Cryptosporidium spp. are protozoan parasites that infect perhaps all vertebrate animals, with a subset of species and genotypes that function as food- and waterborne pathogens. The objective of this work was to collate the Cryptosporidium species and genotypes from common wild rodents on the west coast of the USA and update the information regarding the zoonotic potential of Cryptosporidium from these ubiquitous wild species. Representative sequences of the 18S rRNA gene for a unique set of Cryptosporidium isolates obtained from deer mice, house mice, mountain beavers, yellow-bellied marmot, long-tailed vole, California ground squirrels, Belding’s ground squirrels, and a golden-mantled ground squirrel in GenBank were selected for phylogenetic analysis. Phylogenetic and BLAST analysis indicated that 4 (18%) of the 22 unique Cryptosporidium sequences from these wild rodent species were 99.75% to 100% identical to known zoonotic species (C. parvum, C. ubiquitum, C. xiaoi), suggesting that a minority of these representative Cryptosporidium isolates could have a public health impact through food and waterborne routes of human exposure. These zoonotic isolates were shed by deer mice and a yellow-bellied marmot from California, and from a mountain beaver trapped in Oregon. In addition, the group of unique Cryptosporidium isolates from deer mice and ground dwelling squirrels exhibited considerable DNA diversity, with multiple isolates appearing to be either host-limited or distributed throughout the various clades within the phylogenetic tree representing the various Cryptosporidium species from host mammals. These results indicate that only a subset of the unique Cryptosporidium genotypes and species obtained from wild rodents on the US west coast are of public health concern; nevertheless, given the geographic ubiquity of many of these host species and often high density at critical locations like municipal watersheds or produce production fields, prudent pest control practices are warranted to minimize the risks of water- and foodborne transmission to humans.

Resource selection of a montane endemic: Sex-specific differences in white-bellied voles (Microtus longicaudus leucophaeus).

Resources that an individual selects contrasted against what is available can provide valuable information regarding species-specific behavior and ecological relationships. Small mammals represent excellent study organisms to assess such relationships. Isolated populations that exist on the edge of a species' distribution often exhibit behavioral adaptations to the extremes experienced by a species and can provide meaningful insight into the resource requirements of the species. We deployed radio transmitters in a peripheral population of the long-tailed vole (Microtus longicaudus) during the mating season. We developed models of resource selection at multiple scales (within home range and patch). We found voles generally selected areas close to water and roads and consisting of high understory vegetation primarily composed of grasses. Resource selection varied between sexes suggesting different resource needs during the breeding season. The differential resource needs of voles might be a result of the energetic requirements for reproduction and are representative of a promiscuous or polygynous mating system.

Synthetic mustelid semiochemicals depress survival of long-tailed vole (Microtus longicaudus) populations and feeding damage

Microtus and Myodes continue to be major pests in agricultural and forest production in many temperate and boreal ecosystems of North America and Eurasia. However, voles may also be keystone species because of their predator-prey dynamics and feeding linkages in many networks. As an alternative to rodenticides, exploration continues for a suitable fear-based method to reduce vole damage to crops. This study tested the hypotheses (H) that a “neat” formulation of synthetic anal-gland compounds of the short-tailed weasel (Mustela erminea L.) would reduce (H1) abundance, reproduction, survival, body mass, and movement of long-tailed vole (Microtus longicaudus Merriam) populations; and (H2) feeding damage to coniferous seedlings by voles in forest plantations. Vole populations were live-trapped on replicate sites from May 2005 to June 2006 during a peak year in abundance near Golden, British Columbia, Canada. Synthetic weasel odour was continually present on treatment sites from June 2005 to June 2006. Overwinter mortality to planted coniferous seedlings from vole feeding was measured on all sites in May–June 2006.Synthetic weasel odour compounds did not reduce mean abundance of M. longicaudus but, in fact, resulted in significantly higher numbers of voles in the treatment sites owing to a major pulse of transient (single capture) animals. Mean number of successful pregnancies and total recruits were also higher in treatment than control sites, but early juvenile survival, movements, and body mass were all similar between control and weasel-odour sites. However, mean Jolly-Seber 28-day total survival rates were higher (2.9–3.9 times) on control than treatment sites for both male and female voles during the overwinter-spring 2005–06 period. Much of the reduced survival was due to transient animals which tended to have a higher proportion of adults to juveniles in treatment than control sites. Some degree of disruption presumably occurred on the treatment sites perhaps owing to increased breeding intensity by females in the face of perceived predation or the presence of various mammalian predators attracted to the weasel odour and preying upon voles. This disruption may be linked to the use of synthetic weasel odour in suitable release devices that maintain the odour even in high quality habitats for voles. Despite the difference in abundance, voles seemed to feed less on plantation trees in the treatment than control sites. If this population disruption is real, we suggest that large-scale (e.g., 10+ ha) application of synthetic weasel odour in areas requiring crop protection from voles would be a worthwhile endeavour. This prediction is particularly germane for M. longicaudus where weasel odour treatment might be able to disrupt substantially their one population fluctuation on newly clearcut sites.

Long-term functionality of woody debris structures for forest-floor small mammals on clearcuts

Restoration practices are much needed on clearcut openings in commercial forest landscapes where some mammal species have declined in abundance from a loss of preferred food, cover, and other components of stand structure. Retention of excess woody debris in piles and windrows provides habitat for forest-floor small mammals and some of their predators such as small mustelids. However, it is unknown if these retention habitats are used over longer periods (>10 years) as new forests grow and develop on harvested sites, or do they become unoccupied? We tested the hypotheses (H) that (H1) abundance, species richness, and diversity of the forest-floor small mammal community, and (H2) reproduction and survival of the southern red-backed vole (Myodes gapperi), long-tailed vole (Microtus longicaudus), and deer mouse (Peromyscus maniculatus) would decline on sites with woody debris structures, compared with sites of dispersed woody debris or uncut forest, up to 12 years post-construction in south-central British Columbia, Canada.Woody debris structures provided habitat on new clearcuts for M. gapperi at comparable or higher abundance than in uncut forest and 5.0 to 7.6 times higher than on dispersed sites in the first 5-year period. Although numbers declined after the initial three years, populations of M. gapperi in debris structures recovered to earlier abundance levels at 11–12 years post-construction. Mean abundance of M. longicaudus was consistently higher (2.8 to 3.5 times) in piles and windrows than in sites with dispersed woody debris over the first 5-year period. Populations of M. longicaudus were high in all three treatment sites at 11 years post-construction reaching mean annual peak numbers of 24, 42, and 36 voles per ha in the dispersed, piles, and windrow sites, respectively. Mean abundance of P. maniculatus was similar among treatment sites and consistent over time. Mean abundance of total small mammals was consistently higher (1.8 to 2.4 times) in piles and windrows than dispersed or forest sites in the first 5-year period and this pattern was continued at 11–12 years post-construction. At 11 years post-construction, all treatment sites had the highest peak numbers per ha in the study: dispersed (40.3), piles (64.1), windrows (56.1), and forest (29.0). Our results did not support H1 as abundance, species richness, and diversity were increased or maintained in the debris structures over the 12-year period. Reproduction and survival followed the pattern of abundance for the major species, and hence H2 was not supported. Our study is the first to measure long-term (up to 12 years) responses of forest-floor small mammals to constructed piles and windrows of woody debris as a means of habitat retention on clearcuts. These mammalian species, particularly voles, may then serve as prey for marten and other mustelids. This relationship provides further support for piles and windrows to act as baseline trophic structures in ecological restoration of cutover forest land.

Living on the edge: Exploring the role of coastal refugia in the Alexander Archipelago of Alaska.

Although islands are of long‐standing interest to biologists, only a handful of studies have investigated the role of climatic history in shaping evolutionary diversification in high‐latitude archipelagos. In this study of the Alexander Archipelago (AA) of Southeast Alaska, we address the impact of glacial cycles on geographic genetic structure for three mammals co‐distributed along the North Pacific Coast. We examined variation in mitochondrial and nuclear loci for long‐tailed voles (Microtus longicaudus), northwestern deermice (Peromyscus keeni), and dusky shrews (Sorex monticola), and then tested hypotheses derived from Species Distribution Models, reconstructions of paleoshorelines, and island area and isolation. In all three species, we identified paleoendemic clades that likely originated in coastal refugia, a finding consistent with other paleoendemic lineages identified in the region such as ermine. Although there is spatial concordance at the regional level for endemism, finer scale spatial and temporal patterns are less clearly defined. Demographic expansion across the region for these distinctive clades is also evident and highlights the dynamic history of Late Quaternary contraction and expansion that characterizes high‐latitude species.

Population fluctuations and tree damage by red-backed voles (Myodes gapperi) after clearcutting of coniferous forest

ABSTRACTAlthough Eurasian species of Myodes voles are indeed pest species in forestry, it is not clear if the southern red-backed vole (Myodes gapperi), a closed-canopy species in western North America, also feeds on tree seedlings. Thus, we tested the hypotheses (H) that (H1) abundance of M. gapperi would dominate the vole population immediately post-clearcutting and then disappear, and (H2) while at high densities, incidence of mortality from feeding damage to newly planted tree seedlings by M. gapperi would be comparable to that reported for long-tailed voles (Microtus longicaudus). We live-trapped both species of voles, and measured feeding damage to planted trees, on seven replicate sites for the first 2 years after clearcutting near Golden, British Columbia, Canada. Population changes of M. gapperi and M. longicaudus were essentially the converse of one another in the first 2 years post-harvest. Red-backed voles were the dominant species in the first year and long-tailed voles were prominent in the second year. M. gapperi did not persist on these cutover sites and was at, or near, extirpation after 2 years post-harvest, and hence H1 seemed to be supported. The range of tree mortality by red-backed voles was near the overall mean percentage tree mortality (33.9 ± 4.8%) by M. longicaudus, and hence H2 seemed to be supported. If new plantations have to survive relatively high numbers of two vole species and their feeding damage up to 4–5 years after harvest, then it may be worthwhile to delay planting until vole numbers have declined.

Long-tailed vole (Microtus longicaudus) population outbreaks and refugia after clearcutting of coniferous forests: The search for fluctuations and hotspots

AbSTRACT Some species of Microtus voles exhibit multi-annual population fluctuations with peak numbers every 3–5 years, and these periods may be interspersed with annual fluctuations in abundance. Populations of long-tailed voles (M. longicaudus Merriam) increase during the first 3–4 years after clearcutting of coniferous forests, and it is during this population outbreak that voles may feed on newly planted tree seedlings. It is unclear if M. longicaudus has multi-annual population fluctuations similar to other Microtus species, and we do not know the location of refuge habitats during low years of abundance. We describe changes in abundance of M. longicaudus during the first 5–10 years after clearcut harvesting near Golden, British Columbia, Canada, and evaluated four hypotheses (H) that long-tailed voles will (H1) have peak populations at 3–4 years post-harvest, decline to low numbers, with outbreak populations appearing again on newly clearcut sites; (H2) occur at very low ( Long-tailed vole populations increased in abundance on newly clearcut sites and reached independent peak numbers (62, 96, and 134/ha) at 3–4 years post-harvest in three different areas and time periods, thus supporting H1. Long-tailed voles were consistently at very low numbers in uncut forest, and hence this habitat did not provide a refuge or source area for voles, thereby supporting H2. We had some evidence to support H3 that long-tailed voles seemed to persist at low numbers (

Mammalian responses to windrows of woody debris on clearcuts: Abundance and diversity of forest-floor small mammals and presence of small mustelids

Forest harvesting often leaves excess woody debris on the forest floor that could provide habitat for small mammals and mustelid predators. A windrow or series of piles constructed from woody debris may connect patches of mature forest and riparian areas to allow small mammals and some of their predators to use clearcut openings. We tested two hypotheses (H) that woody debris arranged in windrows connecting reserves of uncut forest, on newly clearcut sites, would increase (H1) abundance of the major vole species and total abundance, species richness, and species diversity of the forest-floor small mammal community, and (H2) presence of small mustelids in response to abundance of small mammal prey; compared with sites of dispersed woody debris or uncut forest. We measured abundance and diversity of small mammals and the presence of small mustelids (American marten, Martes americana; short-tailed weasel, Mustela erminea; long-tailed weasel, M. frenata) from 2012 to 2016 in replicated treatments of woody debris in windrow and dispersed sites compared with uncut forest sites at two study areas near Elkhart and Golden in south-central British Columbia, Canada.At Elkhart, mean abundance of total voles and total small mammals per index-line were higher in the windrow than dispersed sites, and higher or similar to forest sites. At Golden, mean abundance of total voles was similar, but the dispersed and windrow sites had higher numbers of total small mammals than the forest sites. Mean species richness and diversity were highest in the windrow sites at both study areas. Thus, the predictions of H1 were supported, except for total voles at Golden. Mean abundance of the southern red-backed vole (Myodes gapperi), a principal prey species for mustelids, was higher in windrow than dispersed sites, and similar or lower than forest sites. M. gapperi, along with the long-tailed vole (Microtus longicaudus) dominated the overall vole population in windrows at Elkhart. M. longicaudus dominated the windrows and dispersed sites at Golden. Deer mice (Peromyscus maniculatus) and northwestern chipmunks (Neotamias amoenus) were at similar numbers in dispersed and windrow sites, but shrews (Sorex spp.) showed a positive response to windrows. Overall mean presence by marten and small weasels were, on average, 3.3–4.8 times higher in windrow than dispersed sites, and higher or similar to forest sites, which supported H2. Our study is the first to connect windrows to patches and larger units of uncut forest and to cover a 5-year period since harvest. Responses in mean total abundance, species richness, and diversity of small mammals in windrows were maintained throughout the 5-year period. This consistent result was likely related to the connectivity between windrows and uncut forests. Strategic management of post-harvest woody debris in a network of windrows or piles will help to maintain abundance and diversity of forest mammals, both predator and prey species, on clearcuts.

Phylogeographic structure in long-tailed voles (Rodentia: Arvicolinae) belies the complex Pleistocene history of isolation, divergence, and recolonization of Northwest North America's fauna.

Quaternary climate fluctuations restructured biodiversity across North American high latitudes through repeated episodes of range contraction, population isolation and divergence, and subsequent expansion. Identifying how species responded to changing environmental conditions not only allows us to explore the mode and tempo of evolution in northern taxa, but also provides a basis for forecasting future biotic response across the highly variable topography of western North America. Using a multilocus approach under a Bayesian coalescent framework, we investigated the phylogeography of a wide‐ranging mammal, the long‐tailed vole, Microtus longicaudus. We focused on populations along the North Pacific Coast to refine our understanding of diversification by exploring the potentially compounding roles of multiple glacial refugia and more recent fragmentation of an extensive coastal archipelago. Through a combination of genetic data and species distribution models (SDMs), we found that historical climate variability influenced contemporary genetic structure, with multiple isolated locations of persistence (refugia) producing multiple divergent lineages (Beringian or northern, southeast Alaska or coastal, and southern or continental) during glacial advances. These vole lineages all occur along the North Pacific Coast where the confluence of numerous independent lineages in other species has produced overlapping zones of secondary contact, collectively a suture zone. Finally, we detected high levels of neoendemism due to complex island geography that developed in the last 10,000 years with the rising sea levels of the Holocene.

Wildfire, clearcutting, and vole populations: Balancing forest crop protection and biodiversity

Early successional forest habitats that develop after wildfire may provide ideal conditions for population build-ups and subsequent fluctuations by Microtus voles. Regeneration of burned-over forest land may be hindered by consumption of planted trees by voles. A high abundance of voles, occurring in the second growing season after a wildfire, may result in serious feeding damage to seedlings leading to major plantation failures. A wildfire occurred near Golden, British Columbia, Canada in the spring of 2011 and may have initiated the successional conditions to generate a vole population outbreak with consequent feeding damage to tree seedlings. We tested the hypotheses (H) that (H1) abundance of herbaceous plants (grasses and forbs) will be greater, and (H2) abundance of voles and incidence of feeding damage to tree seedlings will be higher, in burned than unburned (control) sites. Microtus voles and other forest-floor small mammals were live-trapped for four years (2011–2014) in replicated sites of a wildfire (burned plantation), control (unburned) plantation, and a new control clearcut. Abundance of total herbs and grasses, incidence of feeding damage, and mortality to tree seedlings by voles were measured in all sites. Mean abundance of total herbs and grasses were similar among treatments during the post-wildfire period. Mean annual peak numbers of Microtus in clearcut sites ranged from 18 to 30 per index-line. Annual peak numbers in the burned and control plantation sites ranged from 5 to 8 voles per index-line and were essentially stable at these numbers. Vole populations in the control and burned plantation sites were dominated by the meadow vole (Microtus pennsylvanicus Ord), and those in the clearcut sites by the long-tailed vole (Microtus longicaudus Merriam). Mean mortality of trees was significantly higher in the control clearcut sites at 30% compared with 13% in the burned plantation sites. These results did not support either H1 or H2. Wildfire, at least in this case, did not generate high populations of voles and significant damage to tree seedlings. Mean abundance of total small mammals was similar in burned and control plantation sites, but less than in clearcut sites. Populations of the deer mouse (Peromyscus maniculatus Wagner) increased after wildfire and those of the southern red-backed vole (Myodes gapperi Vigors) declined. Populations of the northwestern chipmunk (Neotamias amoenus J.A. Allen) and Sorex spp. did not show a clear preference for any of the treatments. Disturbance by clearcutting or wildfire seemed to reduce species richness and diversity, but all eight species of small mammals were present in each of the treatments.

Swimming Long-tailed Vole (<i>Microtus longicaudus</i>) Killed by an Osprey (<i>Pandion haliaetus</i>)

Osprey (Pandion haliaetus) are piscivores, and observations of them preying on non-fish species are rare. I observed an Osprey preying on a Long-tailed Vole (Microtus longicaudus) that was swimming in the Sikanni Chief River in northeastern British Columbia. This is one of few reports of an Osprey preying on a small mammal, and it provides further evidence that Osprey may prey on such species as the opportunity arises. This observation also points to the apparent vulnerability of small rodents to novel predators while they are swimming.

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

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.

Asymmetrical Competition between Microtus montanus and Microtus longicaudus in the Greater Yellowstone Ecosystem

Stable coexistence of ecologically similar species is often a complicated phenomenon involving a synergy of biotic and abiotic factors. We investigated competitive interactions and small scale division of space in the closely related vole species Microtus montanus and Microtus longicaudus, which co- occur across the Greater Yellowstone Ecosystem (GYE) in the Rocky Mountains. We directly manipulated in situ populations of these species in two habitat types over three consecutive years. We confirmed previously described habitat associations of the study species: M. montanus was most abundant in open grassy meadows; M. longicaudus was most abundant in ecotonal areas with greater woody vegetation cover. Additionally, removal experiments conducted in both habitat types revealed a habitat-dependent competitive interaction between species: M. montanus excluded M. longicaudus from resource-rich meadows; M. longicaudus was limited to patchy ecotonal habitats that M. montanus was not observed to colonize. We did not observe an effect of the experimental treatment on either species' body mass. The outcome of the asymmetric competition between these species is influenced by local environmental conditions and enables their coexistence in the GYE.

Identifying CaliforniaMicrotusspecies using geometric morphometrics documents Quaternary geographic range contractions

Paleontology can provide a deep-time dimension to observations about recent reactions of small mammals to climate change. Obtaining this perspective for voles (Microtus), a common and important constituent of North American mammal communities, has been difficult because species identification based on their dental remains is problematic. Here I demonstrate that geometric morphometrics and discriminant analyses can use commonly fossilized dental features to identify the 5 extant species of Microtus in California: M. californicus (California vole), M. longicaudus (long-tailed vole), M. montanus (montane vole), M. oregoni (Oregon vole), and M. townsendii (Townsend’s vole). Analyses of landmarks on the lower 1st molar (m1) provide more accurate identification than those of the 3rd upper molar (M3), and it is important to use jackknife misidentification metrics to assess the precision of discriminant analyses. Addition of semilandmark curves on m1 does not improve accuracy. The utility of these techniques is demonstrated by identifying Microtus specimens from 2 California fossil localities, Pacheco 2 and Prune Avenue, which provides the first evidence for extralimital presence of M. longicaudus at both localities. The presence of M. longicaudus at these low-elevation sites indicates that pronounced geographic range shifts in this species that have been observed in California over the last 100 years also occurred during previous climate changes. Eventually it might be possible to ascertain whether current range shifts are exceeding those that typified responses to past climate changes.

Woody debris, voles, and trees: Influence of habitat structures (piles and windrows) on long-tailed vole populations and feeding damage

Coarse woody debris (CWD) has many ecological functions ranging from conservation of biodiversity to long-term ecosystem productivity. Wildlife habitat, in particular, has been the focus of CWD investigations aimed at maintaining mammal species in managed forests. Piles and windrows of post-harvest woody debris could be designed to provide connectivity and habitat across clearcut openings for a wide array of mammalian species. Populations of microtines, such as the long-tailed vole ( Microtus longicaudus), occur in early successional post-harvest habitats with vegetative and CWD cover, and may be potential pests feeding on newly planted trees. The role of CWD as habitat structures that attract voles and perhaps their predators may be part of a predator/prey pest-control scenario. Thus, we tested three hypotheses (H) that woody debris arranged in large piles and windrows, at a real-world scale, would increase (H 1) the abundance, reproduction, and survival of long-tailed voles; (H 2) the relative abundance of small weasels ( Mustela spp.), and (H 3) the incidence of feeding damage by voles to planted seedlings, compared with a dispersed (conventional) treatment on clearcut sites. Long-tailed voles were intensively live-trapped from 2007 to 2009 in replicated woody debris treatments of dispersed, piles, and windrows near Summerland in south-central British Columbia, Canada. Mean abundance of long-tailed voles was significantly higher (6.4–8.0 times) in treatment sites with piles and windrows than in the dispersed CWD treatment. Patterns in reproduction, recruitment, and survival generally followed those of abundance. There was a curvilinear regression relationship ( r = 0.72; P < 0.01) between mean abundance of long-tailed voles and mean volume of CWD per ha across the dispersed, piles, and windrow treatments. A range of 400–600 m 3/ha of CWD in piles or windrows was required as habitat for viable populations of long-tailed voles on these clearcuts, at least during this 3-year period. Winter snow tracking data indicated that there was significantly more weasel activity in the treatment sites with piles than those with dispersed CWD, and similar activity in the dispersed and windrow sites. The predictions of H 1 and H 2 were supported. The incidence of feeding damage (<10%) by voles to planted seedlings was similar among treatment sites, and hence H 3 was not supported. Based on the results of our 3-year study, woody debris structures do not appear to create conditions for buildup of Microtus populations to “pest status” such that newly planted trees are at risk from feeding damage.

A report on late Quaternary vertebrate fossil assemblages from the eastern San Francisco Bay region, California

Here we report on vertebrate fossil assemblages from two late Quaternary localities in the eastern San Francisco Bay region, Pacheco 1 and Pacheco 2. At least six species of extinct mammalian megaherbivores are known from Pacheco 1. The probable occurrence of Megalonyx jeffersonii suggests a late Pleistocene age for the assemblage. Pacheco 2 has yielded a minimum of 20 species of mammals, and provides the first unambiguous Quaternary fossil record of Urocyon, Procyon, Antrozous, Eptesicus, Lasiurus, Sorex ornatus, Tamias, and Microtus longicaudus from the San Francisco Bay region. While a radiocarbon date of 405 ± 45 RCYBP has been obtained for a single bone sample from Pacheco 2, the possibility that much of the assemblage is considerably older than this date is suggested by (1) the substantial loss of collagen in all other samples for which radiocarbon dating was unsuccessfully attempted and (2) the occurrence of Microtus longicaudus approximately 160 km to the west of, and 600 m lower in elevation than, its present range limit. The taphonomic data and limited stratigraphic information for the two localities suggest deposition of bones within a riparian system. Multiple lines of evidence including the taxonomic composition and the relative abundance of skeletal elements point to the original accumulation of most, if not all, of the small vertebrate remains at Pacheco 2 by owls. Based on taxonomic composition, Pacheco 1 appears to have been located in a mosaic of grassland and woodland habitats, and Pacheco 2 in moist woodland with dense underbrush and a body of freshwater.