The Irish hare (Lepus timidus hibernicus) is an endemic sub-species of mountain hare and is the focus of an All-Ireland Species Action Plan. The Irish Government is required to report the status of Irish hares under the EC Habitats Directive. Quercus undertook a survey for the National Parks and Wildlife Service in order to report on the current and historical status of hares and to formulate recommendations for monitoring.

Historical game bag data suggest that the Irish hare population is likely to have been considerably larger during the mid-19th to early 20th century than at present. Since then, there has been a substantial decline in the number of hares shot per year. Similar hunting data from Britain and Europe are accepted as evidence of the historical decline of hare populations. Game bags show marked fluctuations and multiannual periodicity in Irish hare populations. Intrinsic density dependence and extrinsic climatic effects influence the scale and period of fluctuations. Coursing records mainly reflect changes in practice, but with information on capture effort, they may be suitable for monitoring changes in hare numbers.

Quercus staff and >80 NPWS personnel surveyed 691 1km2 squares across Ireland during 2006 and 2007. To estimate hare densities, novel distance sampling approaches were developed to account for non-uniform distribution of animals with respect to distance from roads. Here, we demonstrate the importance of accounting for this bias when designing and analysing hare surveys.

Assuming that the survey areas were representative and stratifying data analysis by region, the spring density of Irish hares in the Republic of Ireland was estimated to be 3.33 hares/km2 in 2006 and 7.66 hares/km2 in 2007. Multiplying density estimates by land area, the population of Irish hares in the Republic of Ireland was approximately 233,000 hares in early 2006 and 535,000 in early 2007. The scale of this marked and significant change between consecutive years is consistent with historical data and with recent surveys of Northern Ireland. Approximately 50% and 70% of the Irish hare population were found on pastoral farmland in 2006 and 2007 respectively. The bulk of change in population estimates between years was ascribed to an increase in density on pastoral farmland.

No records of brown hares were confirmed during the survey, suggesting that this non native and potentially invasive species is mostly, if not entirely, restricted to Northern Ireland.

We make several recommendations:

1. The aim of future monitoring should be clarified prior to the adoption of a particular survey strategy as there are major implications for cost and analytical complexity;

a. If the main aim is to produce accurate estimates of density, a custom Distance sampling approach similar to that developed here is essential.

b. If the main aim is to establish temporal trends in population change, repeated counts of relative abundance with standardised effort will provide an index of change in numbers over time.

c. Annual counts supplemented with the intermittent collection of distance data could be analysed to establish temporal trends punctuated with reference points of estimated density.

2. A pilot investigation of the use of coursing records supplemented with capture effort data for monitoring hares would contribute to a low cost monitoring strategy.

3. Better understanding of the drivers of population change, particularly on pastoral farmland, is required.