Seasonal patterns in habitat use by the harvest mouse (Micromys minutus) and other small mammals in wetlands and associated habitats
Publication Date
July 16, 2019
Creator
Abstract
Small mammals are an important group due to their multiple roles in the ecosystem: they act as prey species for raptors and larger mammals, as predators of invertebrates and seeds and they can also facilitate dispersal for some plants and fungi. They have some very interesting population dynamics as they experience strong fluctuations in numbers. Due to their unusual patterns, most studies have focused on the multiannual cycles observed only in voles and lemmings in the arctic region, while there are fewer studies on the more common annual cycles. Recently there have been studies that suggest that small mammals change habitat preference in different seasons but not much supporting evidence has followed. The harvest mouse (Micromys minutus) is a particularly understudied species because of its small size and scansorial lifestyle, which make it difficult to trap using the conventional live-trapping technique that consists of placing the traps on the ground. There is some evidence of an extreme reduction in the numbers of harvest mice present in the reedbeds in the summer months, but due to the difficulties in monitoring them, it is unknown whether this is caused by mortality or movement to other habitats. A new technique of live-trapping at an elevation has been much more successful than previous methods and therefore it is now possible to monitor this species more effectively.
This study has attempted to monitor the presence of harvest mice and other small mammals by live trapping both on the ground and at an elevation in habitat mosaics in Nottinghamshire. The focal site was surveyed every month from February to October 2018 and additional sites were surveyed either once or twice throughout the study. The four habitat types surveyed were: reedbed, woodland, pasture and arable. The presence of the reedbed is crucial as this habitat is known to have the highest biodiversity of small mammals but has not yet been the focus of many studies. The total sampling effort consisted of 9,887 trap bouts and resulted in 1,446 trapping events, which included harvest mice (N=70), wood mice (N=1,022), bank voles (N=252), field voles (N=9), common shrews (N=86) and pygmy shrews (N=7). The reedbed was the habitat with the most captures and highest biodiversity. Harvest mice were only caught in the reedbed of two sites at the beginning of autumn. Wood mice were the dominant species in all habitats and showed seasonal variation in their habitat preference, as in late spring their numbers decreased in the woodland and the pasture and increased in the arable. Bank voles did not show a clear change in habitat preference throughout the course of the study but experienced a sharp increase in numbers in August, after a long period of very low numbers.
Although this study was not successful at shedding light on the population dynamics and seasonal habitat preference of the harvest mouse, it provided records for this very understudied species and others. It also confirmed the fact that harvest mice prefer the wet areas of the reedbed. The evidence collected seems to support the idea that this species undergoes extreme reductions in numbers for part of the year and then it is able to make a fast recovery. However further research is necessary to prove that this is a repeated trend and not the result of a harsh winter.
Item Type
ethesis
Thesis Type
MRes
Supervisors
Subjects (LC)
Associated Schools / Departments
School of Life Sciences
eprints ID
56355
UoN Repository URI
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Full-text
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Examined
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