Abstract

During the last 25 years the number of European brown hares (EBH) has declined in Germany. In general, population dynamics are mainly influenced by reproductive success due to the number of neonates and postnatal mortality rate. The results of a reproductive assessment performed in 297 wild-caught EBH (160 males, 137 females) did not indicate any kind of reproductive disorders which could be responsible for the dramatic population decline.^1,2 There are no reliable data available regarding the postnatal situation in newborn EBH and the mean survival rate. Information about the exact impact of environmental factors like predators, diseases, climate changes, or type of agriculture of the survival rate of newborn EBH is very difficult to receive for field researchers. It is very laborious to find newborn hares by classic field observation technique at daytime or by searchlight observation at night. These two techniques are characterized by a high potential of disturbance for hares observed. A newly developed thermal imaging system was applied to find and monitor neonates over a time period of at least 14 days. The study was carried out at night in different agricultural areas of the state Northrhein-Westfalia, Germany. The portable infrared thermography camera (Inc. Emerge Vision) equipped with a colour screen (5.4×4.0 cm) and connected to a portable VCR, was successfully applied to detect hares based on their body surface temperature that differed clearly from the environmental temperature. Due to the high-resolution imaging system and the special telephoto lens even small or hidden animals could be identified with high precision over a distance of 1.0 to 100 m. Each detected individual was categorized according to its body size in three different age groups (neonate, juvenile, adult). Thirteen young were detected at different field sites and their activities were closely monitored up to 14 days before they disappeared. The preliminary results of this study indicate a great potential for further application of this system. It offers new opportunities for monitoring life-history of newborn hares and other small mammals.

Literature Cited

1.  Blottner S, Lange A, Goeritz F, Fassbender M, Broich A, Quest M, et al. Untersuchungen zur reproduktiven fitness an lebenden männlichen feldhasen aus unterschiedlichen habitiaten. Z Jagdwiss. 2001;47:84–91.

2.  Goeritz F, Fassbender M, Broich A, Quest M, Lange, Blottner S, et al. Untersuchungen zur reproduktiven fittnes lebender männlicher feldhasen aus unterschiedlichen habitaten. Z Jagdwiss. 2001;47:92–99.