DOI: 10.5061/dryad.zpc866thw
title: Small mammal capture data from summer and winter in northern Wisconsin, USA

description: Small mammal live trapping data from northern Wisconsin, USA. Data was
 collected from 10 trapping sessions across 5 years. Five trapping sessions
 occurred in the summer and 5 ocurred in the winter. Data was used to
 explore the season variation in small mammal abundance in northern
 Wisconsin. 
description: We established small mammal trapping sites at 9 study sites, 3
 each in northern hardwood forest, eastern hemlock forest, and spruce-larch
 bog. We sampled small mammals in summer (August/September) and winter
 (January/February) from summer 2018 until summer 2022. Sites in
 spruce-larch bogs were discontinued after winter 2020 and replaced with 3
 sites in white cedar swamp beginning in winter 2021 (Scott et al. 2022).
 Sites were &gt;300 m apart to maintain independence.
 <em>Small mammal trapping. </em>—To sample small
 mammals in the subnivium, we used chimney-like structures (“snow
 culverts”) comprised of sections of corrugated black culvert (Jolly et al.
 2022; Scott et al. 2022). Snow culverts allowed continual observer access
 to the subnivium and partial protection from extreme cold for small
 mammals inside traps (Jolly et al. 2022). We placed traps (HB Sherman
 Traps, Inc. LFA) directly on the ground inside the snow culverts and
 baited each with sunflower seeds. At each site, we placed 25 structures in
 a 5 × 5 grid, 10 meters apart (Scott et al. 2022). Prior to the trapping
 season, we baited culverts weekly with sunflower seeds to ensure that
 small mammals located and entered the structures. For additional
 protection from the cold, we wrapped the traps in either foam pouches
 (30.4 × 30.4 cm, Duck Brand Foam Pouches 284867) or polyester quilt
 batting. Additionally, we hung plastic bags with extra bait and nesting
 material at the back of the traps. We left traps open continuously for 9
 consecutive days and checked traps daily beginning at sunrise (Scott et
 al. 2022). We sampled 3 sites at a time, one of each forest
 type. We identified each animal to species and tagged
 each rodent with two unique ear tags (National Band and Tag Co.). We
 marked short-tailed shrews with non-toxic paint pens for within-season
 recapture identification, as ear-tagging was not feasible (Pauli et al.
 2006). We recorded mass (g), right hind foot length (mm), sex, age, and
 reproductive status for each individual. Additionally, we measured right
 ear and tail length of <em>Peromyscus </em>mice for
 identification to species (Stephens et al. 2014). In cases of extreme cold
 (&lt; -20° C), we forewent body measurements and only applied ear tags
 before releasing the animals. We released animals on top of the snow
 adjacent to culverts where they were captured and ensured that each animal
 successfully burrowed back into the snow before moving on. Upon initial
 site set up, we established a single path through the snow to access all
 traps efficiently and reduce compaction of the subnivium.
 During the summer trapping session (August/September), we placed
 25 traps at each site directly on the ground outside of the culvert
 structures. We selected locations near coarse woody debris, out of the
 sun, and covered traps with bark, leaves, and other debris to keep them
 dry and shaded. We baited traps with sunflower seeds and continued to
 place bags of extra seed and nesting material in all traps but did not
 wrap the traps in foam. We followed the same protocols as winter for
 handling and processing all animals. We limited our analysis to the three
 most abundant subnivium-obligate species that we captured across the 9
 seasons: white-footed mice, southern red-backed voles, and northern
 short-tailed shrews (Scott et al. 2022). These species also rely on
 different resources and dietary components. Deer mice (<em>P.
 manicualtus</em>) were excluded from analysis because of low winter
 capture numbers, likely due to both their regional decline and changes in
 their behavior in the winter, such as daily torpor (Pierce and Vogt 1993)
 and increased arboreal activity (Barry et al. 1984). Live capture of small
 mammals followed ASM guidelines (Sikes et al. 2016) and was approved by
 the University of Wisconsin – Madison Institutional Animal Care and Use
 Committee under protocol number A006063-R01 with a state scientific
 collection permit.
description: # Small Mammal Capture Data
 [https://doi.org/10.5061/dryad.zpc866thw](https://doi.org/10.5061/dryad.zpc866thw) ## Description of the data and file structure We established small mammal trapping sites at 9 study sites, 3 each in northern hardwood forest, eastern hemlock forest, and spruce-larch bog . We sampled small mammals in summer (August/September) and winter (January/February) from summer 2018 until summer 2022 . Sites in spruce-larch bogs were discontinued after winter 2020 and replaced with 3 sites in white cedar swamp beginning in winter 2021 (Scott et al. 2022). Sites were &gt;300 m apart to maintain independence. This work was done to explore the seasonal dynamics of subnivium-specialist small mammal species in northern Wisconsin.  ### Files and variables #### File: CaptureMaster\_Metadata.csv **Description:** Metadata file describing the structure of the capture data #### File: CaptureMaster.csv **Description:** All small mammal capture data ##### Variables * SeasonNumber: Season number in chronological order * Season: Season and year of trapping session (e.g., Summer 2021) * Site: Individual site code (e.g., HW1 = Hardwood Site 1) * Session: Nine-day trapping session within the season (out of 3 total sessions) * Observers: Initials of researchers involved with capture * Ear Tag L: Left ear tag (blank cells indicate that animal was not ear tagged and was either not marked or marked in a different way) * Ear Tag R: Right ear tag (blank cells indicate that animal was not ear tagged and was either not marked or marked in a different way) * Capture Date: mm/dd/yyyy * Trap ID: Individual trap code (blank cells indicate that data was not recorded) * Species: Species code (First two letters of genus and specific epithet) * Sex: Sex (M/F/U) * Reprod: Reproductive status (Y/N) * Age: A/J/U * Total Weight (g): Weight of animal + Bag (blank cells indicate that animal was not weighed/measured) * Bag Weight (g): Just weight of bag * Animal Weight (g): Total weight - Bag Weight (blank cells indicate that animal was not weighed/measured) * R HF (mm): Length of right hind foot (blank cells indicate that animal was not weighed/measured) * Tail (mm): Length of tail (blank cells indicate that animal was not weighed/measured) * R Ear (mm): Length of right ear (blank cells indicate that animal was not weighed/measured) * Recap Date 1-8: Date of first recapture (blank cells indicate that animal was not recaptured) * Recap Trap 1-8: Trap in which animal was recaptured (blank cells indicate that animal was not recaptured) * Mortality Date: Date of mortality, if animal dead in trap/during handling (blank cells indicate that mortality did not occur during handling/trapping) * Hair Sample No.: Sample ID if hair sample was collected (blank cell indicates that sample was not taken) * Ear Sample No.: Sample ID if ear punch was collected (blank cell indicates that sample was not taken) * Scat No.: Sample ID if scat was collected (blank cell indicates that sample was not taken) * Blood No.: Sample ID if blood was collected (blank cell indicates that sample was not taken) * Remove: 1 if animal was a recapture of unknown identity or escaped before tagging. Records that cannot be used in abundance estimates. * Notes: Notes * PESPmath: Peromyscus identification equation: -22.333 + (1.040)(ear length) + (0.090)(tail length) - (0.172)(weight) (NA indicates that animal was not a Peromyscus species) * PESP_ID: Identification of Peromyscus from calculation (P. leucopus &lt; 0 &lt; P. maniculatus) (NA indicates that animal was not a Peromyscus species)