First description of spatial and temporal patterns of river crossings by European roe deer Capreolus capreolus (Mammalia: Cervidae): characteristics and possible reasons

Abstract Crossing water bodies (like lakes or rivers) by European roe deer Capreolus capreolus Linnaeus, 1758 is a known phenomenon. However, there is scarce information about the reasons for and patterns of this activity. We analysed 4-year localization data of 13 Global Positioning System-Global System for Mobile Communications (GPS-GSM) collared roe deer living in the floodplain forests of the river Tisza in the Hungarian Great Plain in order to describe such behaviour. Initially, we assumed that this river may represent a barrier for roe deer and we studied the frequency of river crossing occasions, between and within the studied animals. Our questions were: (1) Does the Tisza River act as a barrier to the movements of roe deer? (2) Are there any seasonal or daily variations in the crossing patterns? (3) Is there any difference between males and females regarding the water crossing patterns? (4) Does the water level or the increase in human presence (disturbance by hunting) have any impact on crossings? According to our data, 10 of the 13 individuals crossed the river at least twice, and eight of them did so several times or regularly. The periods spent on the different sides of the river varied from a few hours to several months. During the study period, animals of both sexes crossed the river without difference. There were crossings in all seasons, in daytime and nighttime also. We could not find any difference between the seasons, but there were more crossings in the daytime when we excluded the data of an outlier animal. Water level or human disturbance (live brown hare capture) had no impact on crossings. We conclude that the Tisza River does not represent a real barrier to the movements of roe deer, and our assumption was not supported.