Balanced dispersal or source–sink–do both models describe wood mice in farmed landscapes?

Abstract

W. 2004. Balanced dispersal or source Á/sink Á/ do both models describe wood mice in farmed landscapes? Á/ Oikos 106: 536 Á/550.To test two models of how wood mouse Apodemus sylvaticus populations in different patches might interact, we estimated parameters from capture-mark-recapture data in four habitats (set-aside, crop, boundary and woodlot) at two sites in arable farmland. In the source Á/sink model, populations in 'source' patches have fitness/1, while in 'sink' patches fitness isB/1; dispersal is constrained so there is a net flow of individuals from sources to sinks. In the balanced dispersal model, patches may vary in quality and carrying capacity, but there are no sinks and no constraints on dispersal; fitness is equal across patches. Our results broadly support balanced dispersal. Patches close together were more likely to exchange individuals than those far apart, there was no evidence of density-dependent dispersal and little evidence for directionality of movement. Overall population growth rates were similar in all patches (range: 0.99 Á/1.05). Times when no animals were known to be alive occurred in some patches and could be attributed to stochastic events. On one crop patch, however, extinction followed high abundance, and coincided with poor recruitment, suggesting sink dynamics. Recruitment rates were highest in boundary and crop, but surprisingly, the proportion of individuals in reproductive condition, timing of breeding and pregnancy rates did not vary between habitats. Apparent survival rates were lowest in crop, although recapture rates were high. While female body size in December did not vary between habitats, males on setaside were smaller than elsewhere. In general, the balanced dispersal model best described arable wood mouse populations, but dynamics on one patch suggested an 'attractive' sink. Our results demonstrate that more than one model for dispersal dynamics between populations may apply within the same landscape, for the same species.

Traditional and diversified crops in South Moravia (Czech Republic): Habitat preferences of common vole and mice species

“…We did not observe population growth of wood mice in any crop, while there was a decrease of mice abundance in rape. This finding was surprising such as the crops should be the habitat with the high recruitment rate of wood mice (Tattersall et al 2004). More than a half of the captured females were gravid, so the decrease could not be caused by the absence of reproduction.…”

Effect of land-use on small mammal abundance and diversity in a forest–farmland mosaic landscape in south-eastern Norway

“…In addition, the abundance increased in the northern sub-area (P < 0.001) and was higher when the neighboring habitats were meadows (P = 0.026), abandoned meadows (P = 0.002), crops (P = 0.004) or old forests (P = 0.003), but not clear-cuts (P < 0.001). The wood mouse, on the contrary, was more abundant in the southern sub-area (P = 0.054) and decreased as the season progressed (P = 0.011), as the species typically exhibit annual population cycles with lowest densities in summer (Tattersall et al, 2004). As expected, wood mice were also positively affected by the proximity of meadows (P = 0.060) and cultivated fields (P = 0.078), and were correlated positively to crops (ÀPC2, P = 0.032) and negatively to older successional stages (+PC1, P = 0.007).…”

“…This seems to be the case for agro-ecosystems in south-eastern Norway, which are embedded in a matrix of forested areas and semi-natural grasslands and still have the potential to attract generalist species. However, these artificial ecosystems are unable to sustain entire small mammal communities year round (Todd et al, 2000;Tattersall et al, 2004). Only one species -the wood mouse -reached high summer densities in this habitat type (see also Hansson, 2002;Tattersall et al, 2002Tattersall et al, , 2004, but its marked association with field margins reflected a clear need for ecological complexity at the landscape scale (see also Hansson, 1994;Bayne and Hobson, 1998).…”

“…However, these artificial ecosystems are unable to sustain entire small mammal communities year round (Todd et al, 2000;Tattersall et al, 2004). Only one species -the wood mouse -reached high summer densities in this habitat type (see also Hansson, 2002;Tattersall et al, 2002Tattersall et al, , 2004, but its marked association with field margins reflected a clear need for ecological complexity at the landscape scale (see also Hansson, 1994;Bayne and Hobson, 1998). It is difficult to establish whether the sporadic presence of species other than wood mice in cultivated fields could be interpreted as a spill-over effect from meadows and abandoned meadows, which sometimes -but not necessarily -were close to agricultural areas.…”

Population level risk assessment: practical considerations for evaluation of population models from a risk assessor's perspective

“…One option could be to protect animals in their typical habitats, e.g. to protect wood mice in landscapes with forests, fields and hedges, the habitats where they typically occur [66]; and hares in open landscapes predominated by large fields [67]. That would imply that wood mice would not be considered in risk assessments for landscapes with a low proportion of forests or hedges.…”