Research


How do patch size, isolation and patch proximity to the city edge affect wood mice (Apodemus sylvaticus) in an urban area?

A completed 12 month MSc by research by Alex Baldwin.


Introduction

Urban areas are becoming increasingly larger as the human population continues to grow. The process of urbanisation leads to a number of dramatic alterations in the environment. These changes mainly involve spatial reduction, fragmentation and the introduction of barriers such as roadways. Because of these large scale changes it is inevitable that the wildlife living in the altered environment is affected. Previous studies have shown that small mammal species (mice, voles and shrews) are present in urban areas but the extent to which they are affected by urbanisation remains unclear. It is valuable to know about the effects of urbanisation on small mammals as they are an important taxonomic group. Not only are they important prey items for carnivores (eg: the red fox Vulpes vulpes) and raptors, but they also play an important role in seed dispersal. So if small mammal populations are being altered then almost certainly many other species will be affected as a result. Knowledge of what is affecting small mammal species could be valuable for future conservation efforts with regards to urban wildlife.

Aims

Wood mice (Apodemus sylvaticus) appear to be the most ubiquitous and persistent small mammal species in urban areas and are the main study species in this project, which has three main aims: (i) to compare the relative population densities of wood mice on patches of different sizes which may provide knowledge on a minimum patch size for supporting a viable population, (ii) to investigate the effects of isolation on relative wood mouse population density, and (iii) discover if there is significant variation between population densities on patches at different distances from the city edge.

A final aim of the project will be to compare the relative population densities of wood mice with those of another small mammal species. Bank voles (Clethrionomys glareolus) have been shown to be another persistent small mammal species in urban areas. Bank voles are more specific in their habitat requirements than wood mice and there is evidence that they depend more on ground cover than wood mice. Because of their persistence in urban areas, if samples are adequate I will compare the population densities of bank voles with those of wood mice to see how one species may affect the other. Any shrews (Sorex spp.) detected will also be recorded, and may provide additional species comparisons.

Methods

To census patches for small mammals in urban areas, it is not sensible to use Longworth live traps due to a high risk of theft or vandalism. In addition, live trapping is labour intensive and results are often poor in terms of return for effort. An alternative method of censusing was performed using a standardised grid of hair tubes. Hair tube censusing is not a perfect method of detecting small mammal presence, yet they appear to be a more sensitive method than live trapping. This method will allow comparisons in abundance to be made between patches. Whilst hair tube censusing does not provide data for absolute densities of species on certain patches, it can provide an index of abundance that corresponds with estimates derived from live trapping. Relative densities will be determined by identifying species from hairs left in the hair tubes. Statistical analysis will be performed using a general linear model.

Contact details

Alex Baldwin
School of Biological Sciences
University of Bristol
Woodland Road
Bristol BS8 1UG, U.K.

Tel: 0117 9287593
Email: Alex Baldwin