Short-term effects of tagging on activity and movement patterns of Eurasian beavers (Castor fiber)

P M Graf,J Hochreiter,K Hackländer,R P Wilson,F Rosell

doi:10.1007/s10344-016-1051-8

Abstract

Bio-logging is becoming increasingly popular amongst wildlife researchers, providing a remote way of monitoring free-ranging animals in their natural habitats. However, capturing and tagging can be stressful and may alter animal behaviour. In this study, we investigated whether tagging altered activity and movement patterns of Eurasian beavers (Castor fiber) during the first week after release, predicting that beavers would be less active, travel shorter distances and stay closer to the lodge in the first nights after the tagging event. We captured 29 dominant free-ranging beavers (12 females, 17 males) in Telemark county, Norway, and tagged them with GPS units (n = 23; 12 males, 11 females) and tri-axial acceleration data loggers (n = 14; 9 males, 5 females). Accelerometer data was used to investigate activity levels (using mean overall dynamic body acceleration ODBA and principal activity periods), while GPS data was used to determine movement patterns (using distance moved and lodge displacement rate). Tagging effects were apparent only in activity levels of beavers, where we found lower mean ODBA values after release although the small effect size (Cohen’s d = 0.17) indicates only a minimal difference in activity. Neither principal activity periods nor distances moved or lodge displacement rate changed within the first week after release, which indicates that beavers were active and post-release space use within the territory was not affected by the tagging event in this respect.

Highlights

The tagging of wild animals with miniaturized electronic devices has proved pivotal to many wildlife studies and has become a commonplace within the field of animal ecology (Cagnacci et al 2010; Rutz and Hays 2009)
As the period of time between subsequent captures was at least 2 years (2, 3 and 5 years) and a different tag type (GPS vs. accelerometer) was deployed on the second capture, we included both datasets in our analysis
The accelerometer dataset consisted of 14 beavers (5 females, 9 males) and GPS dataset of 23 beavers (11 females, 12 males); five individuals were represented in both datasets as they were tagged with a combination of GPS unit and accelerometer (Table 1)

Summary

Introduction

The tagging of wild animals with miniaturized electronic devices has proved pivotal to many wildlife studies and has become a commonplace within the field of animal ecology (Cagnacci et al 2010; Rutz and Hays 2009). Cooke et al 2011; Kays et al 2015) These tags can be equipped with a suite of sensors related to animal state, such as heart beat frequency and/or body temperature (Butler et al 2004; Evans et al 2016; Friebe et al 2014), but may document movement patterns (Rhodes et al 2005; Zimmermann et al 2007), general activity, behaviour and proxies for energy expenditure (Shepard et al 2008; Wilson et al 2006). Tagging effects may accumulate over time and can have detrimental influence on life history parameters such as reproductive success or survival rate (Barron et al 2010; Blanchet et al 2014; Casas et al 2015), or may only be shorttermed and diminish over time (Dennis and Shah 2012; Morellet et al 2009)

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Conclusion