The wood mouse and the rhododendron
The wood mouse Apodemus sylvaticus is found throughout Europe and northern Africa. High fecundity – the young are sexually mature after only two months – and the ease with which it is trapped, tagged and recaptured make this an ideal candidate for the holistic study of an indigenous mammalian population. The EU-funded 'Predicting population dynamics from quantitative traits in Apodemus sylvaticus' (Apodyna) project chose an area of 1.7 hectares of deciduous woodland in the suburbs of London for their survey. Their aims were to collect information on a range of phenotypic or observable characteristics as well as on features related to survival such as ectoparasite frequency. A large number of fleas, for example, will affect the survival rate of the mouse. Apodyna scientists measured and recorded indicators affecting body condition, breeding success, and survival for the 270 mice caught. Behavioural traits such as how they handled on capture and use of space were considered relevant. Project workers devised an ingenious tracking mechanism to study behaviour: data loggers in a weather-proof box. Environmental conditions (biotic as well as abiotic) and weather conditions were also recorded. The ecologists even logged moonlight intensity as this has an effect on predation levels and the rodent's activity. The impact of the mouse population on the environment is significant. The invasive Rhododendron, normally considered a menace, sustained up to five times the density of mouse population as did the native deciduous woodland. Surprisingly, an equally positive effect resulted from the distribution of seeds by the mice from the native trees into the rhododendron plots, but not vice versa. At a population dynamics level, the data on phenotypic characteristics is continuing to be used to calculate effects on demographic rates like reproduction and survival. The interaction of mice and rhododendron will be of particular interest to land managers concerned about the negative impact of this invasive plant.
