Survival in fluctuating bank vole populations: seasonal and yearly variations

Abstract

For most organisms, both within‐year (i.e. seasonal) and between‐year variations in demography are important components in shaping the population dynamic patterns observed on a multiannual scale. These two sources of variation have, however, rarely been studied simultaneously. Most of the recent work on small rodent population dynamics, for example, has focused on between‐year variation. Densities of seed‐ and fruit‐eating rodents, such as the bank vole (Clethrionomys glareolus), are in particular known to have between‐year variation related to seed crop production. Here we report on the analysis of a long‐term (1976–1982) capture‐mark‐recapture (CMR) study of the bank vole in Belgium. The study was done on two grids, an open and a fenced grid. As part of the CMR statistical analysis, we propose a general modelling approach which allows for a detailed understanding of the relative importance of seasonal and between‐year variation in survival. We demonstrate that most of the seasonal variation corresponds to a lower apparent survival in spring compared to the rest of the year. During winter, apparent survival was lower on the open grid than on the fenced grid. Dispersal is therefore concluded to be an important determinant of the seasonal pattern. The between‐year variation in survival is largely attributable to variation in seed crops, and is comparable in magnitude to the seasonal variation.

Impact of Puumala Virus Infection on Maturation and Survival in Bank Voles: A Capture-Mark-Recapture Analysis

“…Nevertheless, the range of survival rates in our study coincides with estimates found in a similar study based on trapping sessions with shorter time intervals. Crespin et al (2002) found a 7-day survival probability of 0.85-0.95, corresponding to a survival probability of 0.52-0.81 for 28 days. We estimated 28-day survival probabilities to be 0.76 and 0.55 for reproductively inactive and reproductively active PUUV IgG antibody-negative voles, respectively.…”

“…Typically, smallmammal biologists distinguish juveniles from older individuals on the basis of body weight (sometimes in combination with pelage characteristics; Prevot-Julliard et al, 1999). We considered as juveniles and excluded all voles weighing #13 g (70 females and 55 males; see also Crespin et al, 2002). No reverse PUUV IgG seroconversions (i.e., potential disappearance of maternal antibodies) were detected in the remaining dataset.…”

“…Females were classified as reproductively active (n5214 observations) if they were obviously pregnant or had a perforated vagina and/or enlarged nipples. Females with nonperforated vaginas and small nipples were classified as reproductively inactive (n5321 observations; Crespin et al, 2002). Some females (68 individuals) lacked one or two of such physiologic criteria and therefore their reproductive activity could not be assessed unambiguously.…”

“…For modeling recapture and survival probabilities, however, temporal and spatial variation was taken into account. Temporal variation was modeled by including season (summer, spring, autumn) and year (2004-06) because both scales have been stressed in previous small-mammal demographic studies (Yoccoz et al, 1998;Crespin et al, 2002). Furthermore, fully time-dependent models (i.e., with five values for each parameter) were run, as 3 yr of data may be insufficient to detect both seasonal and intra-annual variation.…”

Winter climate and plant productivity predict abundances of small herbivores in central Europe

“…However, by comparing the performance of climate and plant indices, our findings do suggest that the causal link between plants and herbivore may be more important to the class of small fossorial herbivores than that of large herbivores. There is ample evidence that variations in food availability are highly related to population dynamics of small temperate and arctic rodents (Laine & Henttonen 1983, Eurola et al 1984, Selås 1997, especially in seed eating forest rodents (Jensen 1982, Pucek et al 1993, Crespin et al 2002, Stenseth et al 2002b). Most importantly, hornbeam and oak seed crops incorporated in autoregressive models to analyse variation in annual numbers of wood mice and bank voles in the Bialowie .…”