Badger Censusing
Wytham woods has over 450 active badger latrine sites and more than 600 active badger holes
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Each evening, volunteers were divided into sub-groups of 3 or 4 people and positioned at a sett to count badgers as they emerged. Every effort was made not to count the same individual badger on multiple occasions as they go back and forth into the sett.
An attempt was made to distinguish cubs from adults on the basis of size and behaviour. Video recordings were made by one group each night as a focus for group discussion later and for teaching about badger behaviour.
“When badger watching one cannot over-state the importance of insect repellent ~ a mosquito will always strike just when you want to be absolutely still!”This methodology broadly follows that of the “Annual Badger Census” at Wytham, which has been conducted in May of almost every year since 1976 and yields both a guide to absolute numbers of badgers and changes in relative abundance year-to-year, as well as sett-by-sett detail. At the annual census as many volunteers are recruited over 3 evenings as possible, usually over 100 people attend, and all of the setts in the woods are covered consecutively.
Badger watching at the sett provided 4 tiers of useful information:
Was the sett active? How many badgers were present? Were there cubs present? What were the badgers doing? In the first instance the veracity of these observational data could be assessed by comparison to our long-term badger trapping records (mark-recapture) which provide us with detailed records of how many badgers live at each sett. The results of the badger watching allow us to calibrate the effectiveness of counting badgers directly in estimating population size.
These data show that only about 64% of the badgers known to be present at a sett are likely to be observed. But nevertheless, in terms of presence/absence of badgers, badgers were seen at all setts known to be active.
Due to crop damage by rabbits on a farm adjoining Wytham Woods it became necessary to install rabbit netting along a 700m stretch of the perimeter fence in the summer of 2000. In order for badgers to keep their access to the fields outside the woods which are important sites when foraging for earthworms, badger gates had to be installed by way of mitigation.
Phase 1: The survey prior to netting installation (June).
Volunteers were broken up into 4 teams of 3 and each team surveyed a section of the existing fence line to see where it had been breached by badgers digging under it to form “runs” as illustrated.
These runs (usually accompanied by a clear badger path coming towards the fence line out of the woods) were marked onto base-maps and marker tape was stuck to the existing fence to indicate to the netting contractors where gates should be located.
Phase 2: Installation and checking (August)
Gates were installed by contractors during August and initially tied open in order for badgers to get used to using them.
Volunteer teams re-surveyed the gates and used sand traps to see if there were badger footprints actively going through the gates. This method, along with general inspection established that several gates needed modification or securing in order to make them more “badger friendly”. This work was implemented by the forestry team at Wytham and the gates not already in use were left open for a further 2 weeks.
Phase 3: Closing the gates (October & December)
Volunteer teams used sand traps to see if badger footprints could be found on both sides of operational badger gates and if the gates were being used in both directions.
The extent of badger gate use benefited enormously from the efforts of the volunteer teams to identify ways to improve the location and operation of the gates and the expertise of the forestry staff in implementing these refinements.
Once closed, gate usage went from 43% of the gates showing footprint activity in October to 76% showing activity in December.
Badger Field Signs: Latrine and Hole Survey
The ability to find and accurately identify badger field signs is important for two reasons:
- The distribution of badger latrine sites tells us where their territory boundaries lie
- The number of setts in an area is a popular method for assessing badger numbers, as was used in the recent National Badger Census.
Volunteers were shown a badger sett and a latrine site and quickly taught what indicators to look for to find more field signs themselves... e.g. bright orange sandy spoil heaps outside active holes They were broken into teams of 3 and each provided with a map and compass. Each team was asked to note down on the map any badger holes or latrines they found.
The volunteers were encouraged to survey using systematic transect methods. Their findings could then be compared to those of the research scientists working in this field.
“The biggest difficulty lay in map reading and knowing where you were when you found something”
In terms of field signs, the bigger the feature the better the chance of volunteer teams finding them. Therefore setts were better than holes which were better than latrines. In particular, a large number of latrines were overlooked, this would be critical if volunteers were to undertake or assist with a bait-marking survey. Volunteers would also tend to underestimate badger setts/holes by over 1/3rd according to these findings, which would dramatically underestimate the badger numbers in an area.
