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GPS-collars on mouflon: space utilization among European wild sheep in the Harz Mountains (1996-2001)  

by Environmental Studies

Methods and goals
Few investigations on the ranges of European wild sheep have been conducted as yet in the Federal Republic of Germany. A possible reason for this may be the exceptionally shy habits of this species.  Up to the present time the migrations and use of territory of these animals have only been studied within the framework of re-introductions of the species. In these studies the localization of the animals was determined by observations of marked animals (earmarks, collars). The goal of the presented study was to investigate in regular time intervals over an entire year the spatial and temporal behaviour of European wild sheep in one of the oldest free living populations. From the data obtained the locations and sizes of the ranges were to be calculated, graphically depicted, and the seasonal distribution of the animals in their habitats analyzed. For this purpose 9 wild sheep in the management area East Harz were outfitted with GPS collars. 

The GPS collars were programmed to determine the localities of the sheep 2-4 times per day over the course of one year. The investigation area is situated in the eastern Harz in the the vicinity of Harzgerode (red rectangle in Fig. 1):

Fig: 1:  Location of the investigation area in the Harz

The region is hilly, altitudes varying between 320m and 520m above sealevel.  The forest is mainly composed of closed spruce stands (44%), followed by beech (28%), and oak (11%), which forests are only occassionally interspersed with wet meadows in the valleys. 

The animals were caught in two corrals 8 km distant from each other. The GPS collars were fitted individually, age and neck circumference documented, and the animals additionally provided with ear marks.

The localization points of the telemetrized animals are presented in the form of an overview map in Fig. 2. The localization points for each animal is a different colour symbol for each.  Since a total of 4509 position points are depicted, the point symbols overlap each other especially in the much frequented areas.  Each of the telemetrized animals used only one range throughout the year. One to several day migrations outside of their home ranges occasionally occurred. The greatest distance between two subsequent localizations was 3.8 km for rams as well as for ewes. The greatest range extension of 6.3 km east-west direction was observed for one ewe.

Fig. 2: Overview map of the localization points of all telemetrized European wild sheep

The wild sheep showed different patterns of range utilization.  Fig. 2 clearly shows that the ranges of the wild sheep from the same corral largely overlap.  Each of the telemetrized animals used only one range very intensively throughout the year.  A few sheep went on one to several day migrations. Ram Nr. 63 undertook an especially long journey of 2 weeks directly after being supplied with the GPS collar  in March 2000, before returning to his home range. State and federal roads were regularly crossed by the wild sheep if these were within their ranges as, for example, for Ram Nr. 2. 

During the lambing season in April two of the telemetrized ewes moved for 2 weeks to a quiet , remote valley on the eastern border of their ranges. In Fig. 3 all localization points of ewe Nr. 53 are presented (green symbols), whereby all position points during the lambing season  from 8 - 22 April, 2000 are distinguished by red symbols. The reduction of spatial activity to two small areas is clearly evident. The more distant localizations(red symbols)were determineda few days before the ewes gave birth.

Fig. 3:  Localization points of ewe Nr. 53 connected in chronological order

All telemetrized wild sheepdid not use their ranges uniformly, definite intensively used areas within these ranges can be clearly recognized. These intensively used areas are home bases to which the animals regularly return with varying priorities. The Kernel Method (Worton 1989) is particularly suited to the presentation andquantitative determination of  such activity densities within the ranges. This method mathematically converts the position coordinates into lines or areaswith varying probabilities of use and presents these graphically. For ram Nr. 32 the use intensities in 10% intervals were calculated with the Kernel Method and the respective areas marked with a different colour (Fig.4).


Fig. 4:  Utilization intensity of the range of ram Nr. 32

The range was used with varying intensities depending on the season or period of day. Rape and winter wheat fields were only used for grazing from November to March and then only at night. The remaining time of the year the animal stayed in closed forest. The size of the ranges of the investigated wild sheep varied between 549 and 1090 ha.Two of the animals which had originally come from a reserve preferred smaller ranges of 107 ha (ewe) and 412 ha (ram). 


orton, B.J.: 1989:  Kernel methods for estimating the utilisation distribution in home range studies.  Ecology 70 (1): 164-168

Our especial thanks to Dr H. Piegert Forest District Manager of the Forest District Thale for his constructive cooperation.  He provided this research project with great support and assisted in outfitting some of the wild sheep with GPS collars.