Does handling reduce the winter body mass of the European hare?

Winter body mass of the European hare Lepus europaeus Pallas 1778 was analyzed with a special focus on changes induced by handling. Data were obtained from large scale translocation (net catchments) during 1960-1980 in Poland. The influence of handling was compared using the mass of first-time captured and repeatedly-captured hares, and, in case of repeated capture, individuals' mass changes were investigated. The average body mass ranged from 2.1 kg to 5.0 kg. Generally, fewer factors influenced the hare's body mass than expected. Body mass was related to age and winter precipitation, while the date of catching, sex and temperature did not have an effect. Body mass of first-captured hares were significantly higher than the re-captured ones (3.99 +/- 0.42 vs. 3.88 +/- 0.48, mean +/- SD). Body mass change between captures was related to the date of the first capture, and the duration between the first capture and re-capture. Following the initial capture, a slight (2.8 +/- 2.6), but significant decrease in body weight occurred. Thus, the handling of hares should be used with caution during studies or management of the species.