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1 September 2005 Home ranges of mountain hares Lepus timidus in boreal forests of Finland
Kaarina Kauhala, Matti Hiltunen, Thea Salonen
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Abstract

Home ranges of mountain hares Lepus timidus were studied in boreal forests in Finland and compared to those on the British Isles and in Sweden. During 1998–2001 we radio-tracked 22 hares. Mean yearly home range size was 206 ha. Home ranges were largest in late winter-spring (mean: 202 ha) and smallest in autumn (mean: 71 ha). Home ranges were rather stationary, and only minor shifts in home range locations occurred between seasons. The hares used, however, partly different core areas in different seasons. Home ranges were much larger in the boreal forests of Finland, where the climate is cold, than in the moorlands and grasslands of the British Isles, where the climate is much milder. Home ranges in Finland were similar in size to those in the boreal forests of Sweden. In Finland and Sweden, winters are harsh, the growing season for plants short and the field layer vegetation is covered by snow from November until late April. The large home ranges in the boreal forests are probably mainly due to the low food availability in this environment.

In Europe, the natural distribution of the mountain hare Lepus timidus covers Fennoscandia, the Baltic states, northeast Poland, Belarus and northern Russia. The species also occurs in Scotland, Ireland and the Alps as a glacial relict (Sulkava 1999). Mountain hares live in various habitats, including heather moor, alpine grassland, pastures, shrublands, bogs, tundra and boreal and mixed forests (Angerbjörn & Flux 1995). In Finland, the mountain hare lives in rather unproductive boreal forest and bogs, where the climate is harsh, winters are long and the snow cover thick, and the growing season is short. Furthermore, most young deciduous trees are cleared from the heavily managed forests.

Home ranges of the mountain hare have been studied in heather moorland in the uplands of Scotland (L. t. scoticus; Flux 1970, Hewson 1965, Hewson & Hinge 1990, Hulbert et al. 1996a) and in the lowland pastures and grasslands of Ireland (L. t. hibernicus; Wolfe & Hayden 1996). Only few home range studies of the mountain hare L. t. timidus have been done in the boreal forests of northern Europe, i.e. the main distribution area of the species in Europe (Seiskari 1957, Olsson 1997, Dahl & Willebrand in press). Knowledge of home ranges is, however, essential for understanding the habitat use of hares. Information about the habitat use is needed, e.g. when planning forestry and game management.

Our radio-tracking study is part of a larger project planned to evaluate the population biology of the mountain hare in Finland, and to obtain knowledge that can be applied in forest and game management. The aim of our paper was to examine the home ranges of mountain hares in different seasons in a managed boreal forest in Finland. Habitat use within home ranges is presented in another paper. We also compare the results of home range sizes with results published from the British Isles and Sweden.

Material and methods

Study areas

Mountain hares were radio-tracked in two areas in Finland during 1998–2001: around Evo Game Research Station, southern Finland (61°14′N, 25°10′E) and near the city of Oulu (Sanginjoki), northern Finland (65°01′N, 25°50′E). The southern area covers 20 km2 and is mainly coniferous and mixed forest with clear-cuts, small swamps and small lakes and streams. Much of the area is unproductive barren heath. The northern area covers 15 km2 and mainly consists of mixed forest and pine heath with some small lakes. Forests in both study areas are managed, and there are also clear-cuts and plantations. Many small timber roads run through both areas, facilitating radio-tracking. Hare hunting was not allowed in the northern area during the study, but hares were occasionally hunted in the southern area.

Mean yearly temperature is 3.4°C in the southern and 2.1°C in the northern study area ( www.worldclimate.com). The coldest month is January with the average temperature of −9.3°C in the southern and −11.8°C in the northern area. The warmest month is July with a mean temperature of 15.7°C in both areas. The permanent snow cover lasts from late November or December until late April in the southern area and from late November until late April in the northern area. The growing season for plants starts in the beginning of May and ends during the second week of October in the southern area. In the northern area, the growing season lasts from the first week of May to the first week of October. Thus, the length of the growing season is about 162 days in the southern area and 150 days in the northern area (Finnish Meteorological Institute 2004).

Temperature data are also given for Scotland, Ireland and Sweden ( www.worldclimate.com; see Table 4). The annual mean temperature and the mean temperatures for late winter-spring (March–April) and autumn (October–November) are here considered as rough estimates of the plant growing season, because the temperatures in spring and autumn mainly determine the onset and end of the growing season. For instance in Finland, there is a strong positive correlation between the annual mean temperature and the length of the growing season (r = 0.97, P = 0.002, N = 6). The length of the growing season is one factor, among others, affecting primary production.

Radio-tracking

Mountain hares were captured in March and April using baited wire traps. The hares were ear-tagged and fitted with transmitter collars (Televilt, 230 MHz, weight 52 g). Transmitter life was about one year. Hares were also sexed and weighed. Because hares were captured in March and April, all of them were > 6 months old. After capturing, the hares were released within few hours. We radio-tracked 11 hares (eight males and three females) in Evo between March 1998 and December 2000, and 11 (six males and five females) in Oulu between March 1999 and April 2001.

Hares were located from a vehicle with a Yagi-type antenna with five elements that could be lifted up to 4 m above ground. Bearings were taken from at least two points. The angles between the bearings were as near to 90° as possible and the time interval < 5 minutes. The distance between the transmitter and receiver was < 1 km. Data were collected in two ways: 1) using ‘the point method’: hares were located several times a week at different times of day and night, and 2) using ‘intensive tracking nights’: hares were located at 15-minute intervals during whole nights (from 17:00 to about 09:00) until the hares settled at their day lairs.

Home range calculations

When testing mean location error, one person walked in the woods with a GPS-instrument and a radio transmitter (made for hares) imitating hare movements, and others located that person every 15 minutes in a way similar to the way used to locate hares. The test revealed that the home range sizes calculated on the basis of true (GPS) locations and radio-fixes did not differ significantly (P = 0.459;