DOI: 10.5061/dryad.1zcrjdfwj
title: Effects of multiple types’ ecological factors on the body mass of small rodents in a forest ecosystem

description: The body mass of animals is directly or indirectly affected by multiple
 ecological factors. However, the effects of ecological factors on body
 mass are controversial, and a comprehensive study dealing with diverse
 ecological factors is rare. This study was performed to determine the
 effects of ecological factors on the body mass of small rodents in a
 natural deciduous forest located on Mt. Gariwang, Pyeongchang, and
 Jeongseon, South Korea from May 2019 to October 2020. We classified
 ecological factors into topographic, climatic, cover, and demographic
 factors. Three forest-dwelling small rodent species, striped field mouse
 (Apodemus agrarius), Korean field mouse (A. peninsulae), and red-backed
 vole (Myodes regulus), were captured using the capture-mark-recapture
 method. The findings showed that the body mass of three rodent species was
 not regulated by topographic factors. In addition, a high ambient
 temperature resulted in a heavy body mass for A. agrarius and A.
 peninsulae, and the A. agrarius body mass was negatively affected by
 extreme rainfall. The body mass of each rodent species had a specific
 response to the cover factors: ground vegetation, understory vegetation,
 or downed trees. The three species showed sexual dimorphism and two
 Apodemus species competed with each other. This study reveals that
 ecological factors affecting body mass differ among species. Our findings
 contribute to enhancing the understanding of variation in the body mass of
 animals, particularly small rodents, in response to diverse ecological
 factors.
description: Small rodents were captured
 using Sherman live traps (7.62 Í 8.89 Í 22.86 cm) placed at each of the trapping points
 from May to October 2019 and 2020. We used the capture-mark-recapture
 method to identify captured individuals and estimate population sizes. The
 traps were baited with peanuts, activated during
 three consecutive nights
 in each month, and checked every morning. We marked each captured small
 rodent with an identification (ID) number together with toe clipping or
 ear punching. We recorded the capture place, ID number, species, sex, age
 (adult or juvenile), reproductive condition of each animal, and measured
 their body mass using a spring balance to the nearest 0.1 g (Pesola AG,
 Baar, Switzerland). Thereafter, the captured individuals were immediately
 released at the trapping point at which they were
 captured.  We measured the altitude (meters above sea
 level) and slope gradient as topographic factors at each trapping point
 using a portable GPSMAP (Garmin Ltd., Kansas, USA) and
 a laser measuring tool
 (Forestry Prom Nikon Vision Co., Ltd., Tokyo, Japan),
 respectively. The measured
 slope gradient was standardized using the following formula: standardized
 slope gradient = slope
 gradient / 90 ×
 200%.  The
 temperature during the study period was recorded at hourly intervals using
 three Hobo data loggers (Onset Computer Corporation, Massachusetts, USA)
 placed at 900 m asl, 1,100
 m asl, and 1,300 m asl.
 Precipitation data were collected from the Korea Meteorological
 Administration Weather Data Service. Temperature and precipitation were
 calculated as monthly mean temperature (℃) and monthly total precipitation (mm),
 respectively. Cover factors reflecting microhabitat conditions
 were measured from July to August in 2019 and 2020. We set up a circle
 with a 5.64 m radius centered on each trapping point and surveyed the
 following features: ground vegetation coverage (0–1 m height), understory
 vegetation coverage (1–2 m height), stone coverage (%), tree basal area
 (m<sup>2</sup>/ha), number of standing trees and downed trees
 (n/ha), and volume of downed trees (m<sup>3</sup>/ha). We
 categorized the values of vegetation coverage into the following four
 groups: 0 (coverage = 0%),
 1 (1–33%), 2 (34–66%), and
 3 (&gt; 67%). We estimated the population size of small
 rodents using the Jolly-Seber model with POPAN parameterization.
 Therefore, we made 12 models for the population estimation in total. These
 models included four parameters: <em>φ</em> (apparent
 survival), <em>p</em> (capture
 probability), <em>pent</em> (entry
 probability), <em>N</em> (super population size). The global
 model was as follow: <em>φ</em> (species*time), <em>p</em> (species*time), <em>pent</em> (species*time), <em>N</em> (species). We selected the best models based on the Akaike information criterion with corrections for small samples (AICc).
description: Excel is required to open the data files.