Abstract
The harvest mouse (Micromys minutus) is understudied compared to other small mammals as a result of its small size and scansorial habits. This study in wetlands dominated by common reed (Phragmites australis) compared nest census, a commonly used technique to confirm presence/absence and monitor populations, with live-trapping using Longworths and a home-made alternative trap (the Jordan trap) set both on the ground and in the stalk zone (∼1 m from ground or water level). Nests were found at only two of the four study sites, which may have suggested an absence of the species. However, harvest mice were caught in traps at all sites. All 108 captures of 39 individuals were made in aerial traps in the stalk zone with none caught in ground traps. Generalised linear mixed model (GLMM) also showed that significantly more captures were made in Longworth traps compared to the Jordan trap, although the efficiency of the latter increased after modification. There were also significant differences in capture rate between sites and season and a preference for higher reed quality as described by PCA in the wetter areas of the reed-beds studied. We conclude that live-trapping is preferable to nest census as a population monitoring technique and that future studies of harvest mice, especially in tall wetland vegetation, should use Longworth traps and/or cheaper home-made alternatives set in the stalk zone.
Highlights
The harvest mouse (Micromys minutus) is the smallest rodent in Europe with an average adult weight of 6–7 g
Harvest mice were recorded at all sites, with a total of 108 captures of 39 individuals made over the 1751 trap night effort
Harvest mice were significantly more likely to be caught in Longworth traps compared to Jordan traps (X2(1) = 29.172, P < 0.001), but there was no significant interaction between trap type and elevation (X2(1) = 0.0022, P = 0.963) or trap type and site (X2(3) = 4.960, P = 0.175)
Summary
The harvest mouse (Micromys minutus) is the smallest rodent in Europe with an average adult weight of 6–7 g. Small size and a partly prehensile tail are adaptations to a scansorial lifestyle in the stalk zones of vegetation (Harris 1979). This specific habitat preference makes it difficult to detect using conventional live-trapping techniques, which tend to place traps at ground level Riordan et al 2007; Poulton and Turner 2009), and it is understudied in comparison with other small mammals in the UK. As nests can often be missed (Poulton and Turner 2009), the method may only weakly predict population size (Riordan et al 2009) and does not provide detailed ecological information (Hare 2005).
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