Tick burden in neonatal roe deer (Capreolus capreolus): the role of age, weight, hind foot length, and vegetation and habitat on bed sites

Abstract: This thesis deal with tick burden on roe deer (Capreolus capreolus) fawns, in relation to age, weight, hind foot length, and as well as to vegetation and habitat on bed sites. Roe deer fawns (N = 25) were captured from May 27 to June 27. Samples of ticks were collected and tick burden were estimated. Of all sampled ticks the nymphs and adults were Ixodes ricinus, while the larvae were not identified. 4.4 % of the sampled ticks were larvae, 55.0 % nymphs, 26.8 % adult females, and 13.8 % adult males. The average tick burden were rather small (14 ticks per fawn), with individual variation from 0 to 80 ticks per fawn. Tick burden were positively correlated with age, weight and hind foot length. However, tick burden did not have any effect on weight gain or growth rate. There was a significant difference in tick burden on roe deer neonatal in the heavier weight group between vegetation types, where the fawns that had been captured in short grass, herbs, blueberry shrubs, and moss in closed habitats had a higher tick burden than fawns that was captured in high grass and herbs in open habitats. This was consistent with the result from sampling ticks on cloth drags, where the highest amount of ticks was found among short grass, herbs and moss with a mean of 69.1 ticks/100m², followed by blueberry shrubs and moss with 44.9 ticks/100m² and high grass and herbs with a mean of 6.6 ticks/100m². The highest prevalence of I. ricinus was found on roe deer fawns that were more frequently located in coniferous forest, while the lowest prevalence was found on the fawns that were more frequently located in farmlands. The analysis of the collected ticks’ shows that the presence of nymph, adult female, and adult male ticks on roe deer fawns is dependent of the habitats the fawn has been in, but that presence of larvae is independent of habitat. Adult tick burden was higher on fawns captured in closed habitats then on fawns in open habitats. Overall, the tick burden was relatively low and did not have any visible effect on the roe deer fawns during this study period. Since age and tick burden was positively correlated, we cannot reject the risk that tick burden will reach a level that might have a negative effect on weight gain and/or growth rate as the fawns’ ages. To examine this further, the fawns should therefore be followed for a longer period of time.