Movement, Activity and Distribution of the Small Rodents Clethrionomys glareolus and Apodemus sylvaticus in Woodland

Publication Type:Journal Article
Year of Publication:1964
Authors:Kikkawa, J
Journal:Journal of Animal Ecology
Volume:33
Date Published:1964
ISBN Number:00218790
Keywords:Apodemus sylvaticus
Abstract:

1. Movement, activity and distribution of populations of bank voles (Clethrionomys glareolus) and wood mice (Apodemus sylvaticus) in Wytham Woods, Berkshire, were studied from October 1955 to February 1957 to assess the errors in population estimates that may arise from the use of live-trapping (`capture-recapture') techniques. 2. Trapping both inside and outside an isolated woodland of about 5 acres (2 ha), revealed that dispersal into and out of the woodland was limited in the vole but occurred comparatively freely in the mouse. Females were more resident than males and males were drawn to traps from larger areas than were females. Consequently, the sex ratio obtained with traps spaced too widely may be biased and the estimate of population parameters subject to error if the data for both sexes are combined. Population estimates based on recaptures `between trappings' and on recaptures `within trappings' were not appreciably different when the sample size was large. 3. By tracing two voles with a Geiger-Müller counter, changes of home site were detected within the home range revealed by trapping. Analysis of movements from the trapping results showed that in both voles and mice movement was greater for males than females and greater in summer than in winter. Wide trap spacing affected population estimates. 4. Trap spacing, size of the trapping area, trapping periodicity and number of captures all influence estimates of the size of home range. In the present study the trap-revealed range was more reliable in voles than in mice, since many mice were revealed as wanderers and were excluded from the calculation. For mice, it was considered important to know the proportion of the population showing wandering and dispersal movements according to age, sex, season, habitat and density, rather than to obtain the average range size. 5. Field observations suggested the existence of a social hierarchy among some voles visiting the same trap. Behaviour towards the trap was different between dominant and subordinate animals, which would prevent random catches. Mice did not reveal this social order. 6. Distribution of voles in woodland was closely associated with ground cover and as the amount of cover diminished towards winter the distribution of voles became restricted. Mice did not show such seasonal change of distribution. 7. In both voles and mice estimates of population size calculated without overnight trapping results were generally lower than those obtained from all data. Fewer juveniles were represented in the smaller samples and biased the estimates. 8. Individual differences in activity rhythm, exploratory drive, experience and social position produce different reactions to traps. In the vole, trapping bias caused by differential trap response was associated with large population size, restricted movement and less interest in traps. In the mouse, it was associated with large population size and much interest in traps, resulting in severe competition for them.

URL:http://www.jstor.org/stable/2631
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