Analysis of the usefulness of transect counts in monitoring local brown hare populations: Description of monitoring in 12 test areas and detailed analysis of the results from Bertembos

In 2001, INBO engaged in a project with a number of local game management units (GMUs) to evaluate the practicality and feasibility of a census method to determine long-term trends in spring population numbers of brown hare (Lepus europaeus) in Flanders.

Brown hare is an important game species in Flanders, hunted in almost every GMU. In recent years, however, bag sizes for the species have gradually declined. In addition, brown hare is a species that is characterised by large annual fluctuations in population size. It is therefore important for GMUs to gain insight into population numbers, preferably prior to the hunting season, as a basis to determine the annual bag. When GMUs were set up in Flanders, reports on annual spring population estimates per GMU were made mandatory for several game species, including brown hare.

Although transect counts using spotlights have shown to be an appropriate and feasible method for long‐term monitoring of hare populations, an evaluation of their use in Flanders was undertaken in collaboration with several GMUs before making this method mandatory. The data gathered in the different GMUs show that there is sufficient manpower and willingness in Flanders to collect long‐term data of high quality.

Brown hare counts in Flanders are generally performed from January to March, and the results are consistent throughout the entire period. However, it is still preferable to limit the spread of the counts in time and select a shorter consistent annual count period. At least four annual counts are necessary and it is very important that all of them are performed in each year. As the method was also found to be very sensitive to the use of shorter routes (< approx. 300 m), a minimum length of 800 m per route is recommended. To ensure sufficient spatial distribution and capture the variation between the different zones in a given area, it is also recommended that the length of the different separate routes should not be too great (a maximum of 1.5 to 2 km). It is very important that all routes are accessible at all times and can therefore be included in almost every count throughout the entire monitoring period.

As a rule of thumb for the design of a monitoring scheme for hares using transect counts, we recommend a density of 1 route of approx. 1 km per 100 ha of survey area. Using this rule, it is expected that an average difference of four hares between two years per km transect will be identifiable as statistically significant. When these guidelines are adhered to, the quality of the data could be significantly increased with less effort than is currently made by the various GMUs.