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The estimated effect size and 95% confidence intervals on mean abundance across the sampled range of spatiotemporal covariates for Humboldt's flying squirrels, Townsend's chipmunks, deer mice, and western red-backed voles captured in a late-successional forest in the H. J. Andrews Experimental Forest, Oregon, USA, 2011-2016. The horizontal dark area indicates the range of values that do not achieve the a priori biological significance value, where biological significance was the average site-and species-specific temporal change in abundance. Spatial covariates include elevation, canopy openness percentage (Canopy), berry producing plant cover percentage (Berry), and coarse woody debris volume. Temporal covariates include number of days below 08C (Days below 08C), minimum winter temperature (Min. temp.), and the Palmer drought severity index.
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Effective conservation and management of small mammals require knowledge of the population dynamics of co‐occurring species. We estimated the abundances, autocorrelations, and spatiotemporal associations of 4 small‐mammal species from 2011–2016 using live‐trapping mark‐recapture methods on 9 sites across elevation and canopy openness gradients of a...
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Context 1
... which did not indicate overdispersion. Humboldt's flying squirrel mean abundance was positively associated with berry-producing plant cover (b Berry ¼ 1.89, 95% CI ¼ 1.31 to 2.56) and minimum winter temperature (b Min. Temp. ¼ 0.34, 95% CI ¼ 0.04 to 0.65), and negatively associated with elevation (b Elevation ¼ À0.81, 95% CI ¼ À1.23 to À0.47; Fig. 4). Mean abundance of Town- send's chipmunk was positively associated with elevation (b Elevation ¼ 1.00, 95% CI ¼ 0.60 to 1.42), canopy openness (b Canopy ¼ 2.17, 95% CI ¼ 1.26 to 2.99), and minimum winter temperature (b Min. Temp. ¼ 0.22, 95% CI ¼ 0.01 to 0.43), and negatively associated with berry-producing plant cover (b Berry ¼ ...
Context 2
... and negatively associated with minimum winter temperature (b Min. Temp. ¼ À0.87, 95% CI ¼ À1.59 to À0.15) and PDSI (b PDSI ¼ À0.14, 95% CI ¼ À0.24 to À0.06). Few of the effect sizes exceeded our a priori biological significance threshold, and there was no overlap among the target species for associations with biologically meaningful effect sizes (Fig. 4). ...
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Citations
... The abundance of gray squirrel Sciurus carolinensis not only varies between habitats (Fischer et al 1991) but also between urban and forest areas (Williamson 1983, Jarboe et al 2021. Tree squirrel Tamiasciurus hudsonicus abundance also responds to a range of forest conditions (Sullivan et al 2017), and Humboldt's flying squirrel Glaucomys oregonensis and Townsend's chipmunk Neotamias townsendii abundance are associated with canopy openness and berry-producing shrubs (Weldy et al 2019). Red squirrel density varies between urban environments (Kopij 2014), urban and wild habitats (Piqué 1997), the height and maturity of pine forests, and forest species composition (Purroy andRey 1974, García andMateos 2008). ...
We studied the abundance of red squirrels, a medium-sized forest rodent widely distributed throughout the Palearctic, in the cliffs of Maro-Cerro Gordo (south of Spain; Málaga-Granada), a protected space with a great marine influence. We investigated the abundance of squirrels in this area on two scales: 1) home range, as signs per square meter; and 2) landscape, as active nests per 1x1 km UTM grids. We tested the influence of land use and habitat features on the abundance of squirrels. On the home rage scale, there were more indicators of squirrel activity in mature pines located near cliffs and in pines near freshwater channels. The cliffs hosted the best pine forest patches, and despite being very close to the sea, squirrels used them as feeding areas often but not as areas for setting up nests. On the landscape scale, squirrel nests were rarer in grids with more herbaceous crops and were more abundant in grids with longer freshwater streams. These results suggest that the squirrels in this area may have adapted to life in this space and to the marine influence via a differential use of habitat. The squirrels’ use of the best feeding areas implies a saline stress that is counteracted by establishing nests in humid areas away from cliffs.
... In a similar situation, urban wildlife that has access to an abundance of food are often decoupled from their predator-prey relationships creating a safer existence for prey (Rodewald et al., 2011). A more complete understanding of this could be acquired through methods such as small mammal trapping in areas proximate and distant from gut piles (Frank et al., 2020;Weldy et al., 2019). ...
... We then estimated small mammal abundance for each trapping session by dividing the number of individuals caught at each site by p specific to Frontiers in Ecology and Evolution 05 frontiersin.org that session (Weldy et al., 2019). Small mammal abundance estimates for each year were calculated as the average abundance over the two trapping sessions. ...
Due to consistent population declines across the continent, grassland birds have become a guild of high conservation and management interest. Despite a large number of studies investigating grassland bird habitat associations, we know relatively little about the mechanisms through which habitat characteristics may impact grassland birds, as these mechanisms are often assumed rather than directly tested. For this study, we estimated whether the effects of habitat structure on breeding Field Sparrows are mediated through changes in predator (snake and raccoon) abundance, alternative prey availability, or arthropod biomass using structural equation models. We found no evidence of nest survival or nest density of Field Sparrows being directly influenced by nest predator abundance, alternative prey, or arthropod biomass, although habitat characteristics associated with increased nest survival were also associated with greater arthropod biomass and reduced predator abundance. We suggest that habitat structure in our study area primarily impacts breeding Field Sparrows through direct means, such as influencing nest concealment or foraging efficiency. Our results also suggest that nest success and nest density are decoupled in our study area, so Field Sparrows may be preferentially selecting nest sites with structural characteristics that do not increase nest survival. Ultimately, our findings from this study indicate that while predator avoidance and food provisioning likely play an important role in determining nest survival for grassland birds, predator abundance and arthropod biomass may not necessarily predict predation risk and foraging efficiency to the extent that is often assumed.
... During this study, we set and maintained 112 baited trail cameras and captured and tracked western spotted skunks (n F = 12, n M = 19) using Tomahawk traps (Models 102 and 103, Tomahawk Live Trap, Hazelhurst, WI) and VHF radio collars (M1545, 16 g; Advanced Telemetry Systems, Isanti, MN). Cameras placed in the HJA were paired with previously established long-term songbird monitoring (Frey et al., 2016) and small mammal monitoring sites (Weldy et al., 2019). ...
There are increasing concerns about the declining population trends of small mammalian carnivores around the world. Their conservation and management are often challenging due to limited knowledge about their ecology and natural history. To address one of these deficiencies for western spotted skunks (Spilogale gracilis), we investigated their diet in the Oregon Cascades of the Pacific Northwest during 2017–2019. We collected 130 spotted skunk scats opportunistically and with detection dog teams and identified prey items using DNA metabarcoding and mechanical sorting. Western spotted skunk diet consisted of invertebrates, such as wasps, millipedes, and gastropods; vertebrates, such as small mammals, amphibians, and birds; and plants, such as Gaultheria, Rubus, and Vaccinium. Diet also consisted of items, such as black‐tailed deer, that were likely scavenged. Comparison in diet by season revealed that spotted skunks consumed more insects during the dry season (June–August), particularly wasps (75% of scats in the dry season), and marginally more mammals during the wet season (September–May). We observed a similar diet in areas with no record of human disturbance and areas with a history of logging at most spatial scales, but scats collected in areas with older forest within a skunk's home range (1‐km buffer) were more likely to contain insects. Western spotted skunks provide food web linkages between aquatic, terrestrial, and arboreal systems and serve functional roles of seed dispersal and scavenging. Due to their diverse diet and prey switching, western spotted skunks may dampen the effects of irruptions of prey, such as wasps, during dry springs and summers. By studying the natural history of western spotted skunks in the Pacific Northwest forests, while they are still abundant, we provide key information necessary to achieve the conservation goal of keeping this common species common.
... Flying squirrels have been characterized as a potentially K-selected species with "slow" traits (Bielby et al., 2007), leading to survival that is higher than for similar sized mammals (Smith, 2007;Villa et al., 1999) and that varies little across time (Lehmkuhl et al., 2006). However, other demographic characteristics such as abundance (Weldy et al., 2019), sex ratio (Rosenberg & Anthony, 1992), and recruitment (Weldy et al., 2020) vary substantially across time. Much less is known about chipmunk demography, but they have been characterized as an r-selected species with "fast" traits (Bielby et al., 2007). ...
... We felt that this assumption was met on our study sites, which were randomly placed within a large, continuous, old latesuccessional forest where site edges did not reflect biological edges. Furthermore, Carey (1995) suggested that there was no evidence that the densities of flying squirrels and chipmunks were misleading indicators of habitat suitability, and Weldy et al. (2019) found no evidence for marginal or sink habitat on our study sites. ...
... Future studies could continue to explore the movement ecology of small mammals by incorporating study designs suitable for directly estimating movement parameters (i.e., multistate mark-recapture or telemetry) and evaluating the effects of spatiotemporal predictors on movement probabilities, or by linking temporal variation in movement rates to studies of population cycling (Fryxell et al., 1998;Weldy et al., 2019). A PPEN D I X 1 ...
Age-and sex-specific survival estimates are crucial to understanding important life history characteristics, and variation in these estimates can be a key driver of population dynamics. When estimating survival using Cormack-Jolly-Seber (CJS) models, emigration is typically unknown but confounded with apparent survival. Consequently, especially for populations or age classes with high dispersal rates, apparent survival estimates are often biased low and temporal patterns in survival might be masked when site fidelity varies temporally. We used 9 years of annual mark-recapture data to estimate age-, sex-, and time-specific apparent survival of Humboldt's flying squirrels (Glaucomys oregonensis) and Townsend's chipmunks (Neotamias townsendii). For Humboldt's flying squirrels, these estimates support a small body of research investigating potential variation in survival among age and sex classes, but age-and sex-specific survival has not been evaluated for Townsend's chipmunks. We also quantified the effects of age-and sex-specific emigration on confounded estimates of apparent survival. Our estimates of juvenile flying squirrel survival were high relative to other small mammal species and estimates for both species were variable among years. We found survival differed moderately among age and sex classes for Humboldt's flying squirrels, but little among age and sex classes for Townsend's chipmunks, and that the degree to which emigration confounded apparent survival estimates varied substantially among years. Our results demonstrate that emigration can influence commonly used estimates of apparent survival. Unadjusted estimates confounded the interpretation of differences in survival between age and sex classes and masked potential temporal patterns in survival because the magnitude of adjustment varied among years. We conclude that apparent survival estimators are robust during some time periods; however, when emigration rates vary in time, the effects of emigration should be carefully considered and accounted for.
... Glaucomys volans is found in eastern North America from southern Quebec to Florida as well as in isolated populations in Mesoamerica (Dolan and Carter 1977;Kerhoulas and Arbogast 2010). Glaucomys sabrinus' range covers most of Canada and Alaska with some populations extending into the contiguous United States (Wells-Gosling and Heaney 1984). The third species, G. oregonensis, resides along the Pacific Coast of British Columbia and the United States (Washington, Oregon, and California) and was only revealed to be a reproductively isolated, distinct species of flying squirrel in 2017 (Arbogast et al. 2017). ...
... While we did not detect a recent bottleneck in G. o. californicus, which is reassuring, there are no other local populations available should genetic rescue or intervention need to be implemented in the future. So, we recommend persistent vigilance and long-term monitoring of the population as small mammals are prone to boom-bust population cycles (Weldy et al. 2019). If flying squirrels are intended to be reintroduced to the San Jacinto habitat, the genetic data recovered here suggest that individuals with the G. o. lascivus nuclear profile plus the mitochondrial haplotype most common in G. o. californicus (medium green in Fig. 3) best represent that historical population. ...
The San Bernardino flying squirrel (Glaucomys oregonensis californicus) is thought to be the southernmost population of the Humboldt’s flying squirrel (G. oregonensis) and is restricted to the San Bernardino and San Jacinto Mountains in California. However, recent surveys indicate they have been extirpated from the latter locality. In this study, we characterized the intraspecific genetic structure and diversity of G. oregonensis. We amplified and sequenced at least 300 bp of the mitochondrial cytochrome-b gene and 11 nuclear microsatellites to provide baseline genetic data for this species and subspecies, investigate G. oregonensis genetic structure with a focus on the subspecies distributed in California, and finally evaluate the genetic diversity within G. o. californicus. Population and phylogenetic analyses were performed on a total of 147 samples (tissue, hair, and museum specimen) using the Illumina high-throughput sequencing (HTS) platform, thereby bioinformatically coding microsatellite alleles using established pipelines. Our results indicate reduced genetic diversity in G. o. californicus and highlight genetic distinctiveness of the San Jacinto population. In addition, the differences in genetic diversity between the mitochondrial and nuclear markers suggest sex-biased dispersal and historic separation of the species in multiple refugia followed by more recent gene flow among subpopulations in northern California. This study contributes valuable information toward understanding the genetic variation within G. oregonensis, provides information for future conservation decisions for G. o. californicus, and has novel implications for HTS genotyping-by-sequencing.
... During analysis these datasets are often reduced to a subset of the total captured species that has suitably high numbers of individual captures and recaptures. For example, Weldy et al. (2019) reported analysis for the four most commonly captured species from a total of 21 captured species, because data for the remaining 17 species were too sparse to independently estimate capture probability. In contrast, we were able to obtain reasonably precise estimates of group-specific abundance for 10 of 20 captured species, including Columbian ground squirrels, bushy-tailed woodrats, northern flying squirrels, and western jumping mice which are largely understudied in this region, by using our contemporary modelling framework. ...
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 long-icaudus) 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.
... Following methods outlined in Weldy et al. (2019), we implemented a sequential model selection strategy in Program Mark to estimate p and c for each trapping round using Akaike's Information Criterion corrected for small sample sizes (AIC c - Burnham and Anderson 2002). First, we considered a priori recapture probability model structures while maintaining a capture model structure that varied by time (trap night). ...
Extensive habitat loss and degradation have transformed the grasslands of North America into one of the continent’s most vulnerable ecosystems and have greatly imperiled the plants and animals that depend on them. Small mammal communities play a pivotal role in maintaining the health and function of grasslands, and managing small mammal populations is an important, though overlooked, part of grassland restoration and management. We identified habitat variables in restored tallgrass prairie patches that were most strongly associated with variation in small mammal abundance and community composition, with the goal of aiding management efforts to manipulate small mammal populations. We found that small mammal abundance at the local vegetation scale was negatively related both to litter depth and plant diversity. At the landscape scale, small mammal abundance was positively associated with the amount of water surrounding a patch, and negatively associated with the amount of grassland surrounding a patch. Variation in small mammal community composition largely was governed by differences in habitat structure at the landscape scale, rather than differences in vegetation structure at the local scale. We suggested that managers interested in influencing small mammal abundance in grasslands employ tools such as prescribed fire to decrease litter depth if increased small mammal abundance is desired, or increase plant diversity by sowing a high diversity of seeds to depress small mammal abundance.
... By the end of the study, this resulted in patterns of deer mouse densities among treatments similar to those found for chipmunks. In contrast to chipmunks, we did not find a relationship between deer mouse density and structural complexity, although deer mice are positively associated with downed wood (Manning and Edge, 2004) and shrub cover (Weldy et al., 2019) in Pacific Northwest forests. Deer mice abundance typically increases at forest edges (Bayne and Hobson, 1998) and in small patches (Robinson et al. 1992) so the observed lower densities in larger upland patches may relate to lower levels of edge compared to several small patches. ...
Retention forestry, the practice of maintaining stand legacies in harvested forests, is used to create more complex forest structure and positive biodiversity outcomes in managed forests. However, the relative effectiveness of different retention strategies at increasing forest structural complexity and populations of dependent wildlife species is not well understood. We used an experimental study to evaluate changes in the population density of three small mammal species in response to different size and location (riparian or upland) of retention tree patches within harvested forests in the Pacific Northwest, USA. We further assessed whether small mammal density varied in relation to differences in structural complexity within retention patches among experimental retention stands. Within stands, deer mice (Peromyscus spp.) population density did not differ between retention and harvested areas (β = − 0.05, SE = 0.06), Townsend's chipmunk (Neotamias townsendii) density was higher in retention compared to clearcut areas (β = 1.61, SE = 0.10), and creeping vole (Microtus oregoni) density was highest in clearcut areas (β = − 0.68, SE = 0.10). At the stand-scale, deer mouse density and chipmunk density were lowest in stands with large upland patches of retention (mean = 83, SD = 28 trees) and highest in stands with multiple small patches of upland retention (mean = 8, SD = 2 trees). Creeping vole density followed the opposite pattern, highest in stands with large upland patches and lowest in stands with multiple small patches. Densities of each species were intermediate in stands where at least a portion of the retention trees were connected to forested riparian buffers. Relating the density of each species to structural complexity within stands revealed that Townsend's chipmunk density increased with increasing retention tree blowdown (β = 0.39, SE = 0.08), a proxy for downed wood resources, whereas creeping vole density decreased (β = − 0.51, SE = 0.12), and deer mice density did not change consistently (β = 0.00, SE = 0.08). Furthermore, retention tree mortality was highest in the experimental treatment with several small patches and lowest in the treatment with a single large patch. Our results demonstrate that adopting dispersed retention patch patterns increases the abundance of small mammals in managed, early-seral forests in the Pacific Northwest. This relationship is at least partly mediated through higher levels of structural complexity within small retention patches caused by increased retention tree blowdown compared to larger patches.
... Habitat structures, such as vegetation type and cover have been found to have a large impact on the community structure and population dynamics of rodents (Ecke et al. 2002, Carrilho et al. 2017, Weldy et al. 2019, Chidodo et al. 2020, Ssuuna et al. 2020, Welegerima et al. 2020). This effect is mainly because vegetation type and cover determine the availability of resources which affects both the abundance and diversity of rodent species (Ecke et al. 2002, Ssuuna et al. 2020, Welegerima et al. 2020. ...
The Uluguru Mountains, which are part of the Eastern Arc Mountains, is a hotspot for diversity
and an important area for the conservation of biodiversity in Tanzania but faces increasing disturbance due
to anthropogenic activities leading to a high rate of forest degradation and fragmentation. Changes in habitat
structure have caused significant changes in the faunal assemblage of the region. However, information
on these effects in the Uluguru Mountains is currently lacking. We conducted a survey of the small rodent
assemblage on the Uluguru Mountains in three different habitats: forest, fallow, and cultivated land along
two elevation gradients: 900-1,400 and 1,500-2,000 m a.s.l. Additionally, we recorded the habitat structure for
each transect by looking at grass cover, tree density, and shrub density. Generalised linear mixed models were
used to examine the effects of habitat structure on both species richness as well as abundance. Our results
revealed that, even while species richness remained similar over the whole study area, the species composition
significantly changed depending on habitat structure. This finding arose particularly from changes in the
numbers of Praomys delectorum and Mastomys natalensis, with the latter more abundant in cultivated and fallow
land but not in forest, where P. delectorum is more abundant. This outcome may indicate that an increase in
forest degradation and expansion of agriculture could have an impact on rodent assemblage and potentially
on their population dynamics.
