Winter Mammal Monitoring Project

Project Summary

Coverage

Surveys were undertaken along transects in randomly selected 1-km squares throughout the UK. Over the three field seasons 1,121 different sites were surveyed on at least one occasion, with 1,043 sites surveyed for sightings, 890 sites surveyed for field signs. 612 sites were surveyed for both sightings and field signs. Overall, 907 volunteers took part in the Winter Mammal Monitoring project, each surveying at least one square, but some carrying out six different surveys.

Species Recorded

Sightings

A total of 43 species or species groups was recorded during the WMM sightings survey. This drops to 29 species when species groups, domestic animals, feral cats and free-roaming dogs are excluded. Eleven of these species were seen on at least ten sites. Rabbit was by far the most widespread species recorded, followed by grey squirrel, brown hare, roe deer and fox.

Figure 1: Proportion of sites within which the 14 most common species sightings
were recorded in each year

Field Signs

11 types of field sign were recorded. However, three of these were dropped after first year, two because they were non-specific (deer slots and squirrel dreys) and one due to low rates of detection (hazelnuts chewed by dormice). Not all sites were searched for each field sign, either because the habitat was not suitable or because the volunteer decided not to search for a particular sign.

Figure 2: Proportion of sites within which each major sign was recorded each year

Key findings

The minimum detectable change (MDC) is the percentage change in mammal abundance that can be detected by surveying varying numbers of sites. This allows us to assess the scale of monitoring needed to detect long-term changes in mammal abundance and calculate whether the data collected during the WMM would be sufficient to detect these changes. By these calculations it should be possible to detect changes in abundance, using sightings or field signs, of 25 – 50% in ten of the monitored species.

Table of species that can be monitored by WMM

Field signs provide significantly more information than sightings data, although a smaller range of species can be reliably monitored using this method (mole, fox, badger, field vole, rabbit, brown rat and harvest mice). Sightings are therefore important for the other species.

For each species, recorded in sufficient numbers, we assessed the influence of the recording protocols (e.g. survey duration, habitat type, etc.) and these results are described in detail in the full downloadable report.

Value of Winter Mammal Monitoring

The BTO/JNCC/RSPB Breeding Bird Survey also records mammal sightings, using a similar method to the Winter Mammal Monitoring project. There are three main differences between the surveys:

1. Timing of the surveys

Winter Mammal Monitoring records mammal information during the winter (October – April), whereas the Breeding Bird Survey is carried out during the summer (April – July).

2. Recording methods

BBS volunteers record mammal sightings and signs on either of their two visits to the square each year and record a range of indirect evidence including field signs, sightings of dead animals and information from landowners. Winter Mammal Monitoring, however, records sightings of live animals on one visit, and field signs, for a key set of target species, on another visit. Detailed instructions on the identification of mammal field signs were provided to volunteers.

3. Recording methods

In the WMM protocol, observers record the presence of mammals (both sightings and field signs) in each section of the transect, hence providing a semi-quantitative measure of abundance (or presence) that makes it easier to detect change.

Value of sightings data

Good for a wider range of species not reliably detected using field signs. Rabbits and brown hares were seen on significantly more sites during the summer BBS than during WMM surveys. However, fallow deer were seen more frequently on WMM sites than on BBS sites.

Counts provide reliable data for trend analysis. Moreover, for many species, counts undertaken during the winter may provide amore accurate estimate of the adult population, with less influence from variation in productivity between years.

Value of field signs data

More frequently encountered - field signs were detected on 52% of WMM sites, but only on 10% of BBS sites. Rabbit burrows, brown rat burrows, fox scats and mole diggings were detected more frequently during the winter than the summer, although this is probably due to the more dedicated effort to search for field signs during WMM surveys.

Greater range of species - the WMM methodology provides data on species detected by field signs that are seldom detected by BBS or by sightings on WMM, such as field vole.

Thank you

We would like to say a big thank you to all of the volunteers who took part in our Winter Mammal Monitoring project (winters 2001/02, 2002/03 and 2003/04) and helped to make the survey such a great success.

Thank you also to all the landowners who gave permission for our volunteers to carry out the project on their land.

Funding

Winter Mammal Monitoring is a joint project of The Mammal Society and the British Trust for Ornithology (BTO) funded by the Department for Environment, Food and Rural Affairs (DEFRA). The BTO and the Mammal Society are very grateful to DEFRA for their support of this project.
Future funding for this project has not yet been secured, but proposals to continue Winter Mammal Monitoring are currently being considered by DEFRA and the statutory conservation organisations.
The BBS and the Winter Mammal Monitoring Project are part of the Tracking Mammals Partnership; a collaborative initiative, involving 23 organisations with a variety of interests in UK mammals, which aims to improve the quality, quantity and dissemination of information on the status of mammal species in the UK.