Ethology. 2018;1–9. wileyonlinelibrary.com/journal/eth | 1 © 2018 Blackwell Verlag GmbH 1 | INTRODUCTION Scent-marking is a widespread form of communication in mammals (Johnson, 1973). Different types of information can be transmit- ted via scent-marking, for example, concerning the sex, age, so- cial and reproductive status, and body condition of an individual (Buesching, Waterhouse, & Macdonald, 2002; Scordato & Drea, 2007; Tinnesand, Jojola, Zedrosser, & Rosell, 2013). Therefore, scent communication can serve multiple purposes. It can function to mark territorial boundaries (Brashares & Arcese, 1999), thereby signaling territory ownership (Roberts & Dunbar, 2000) in order to avoid physical conflicts. It can also be used to attract mates and sim- ply to advertise an individuals’ presence and status to family group members, neighbors, and intruders (Wolff, Mech, & Thomas, 2002). Further, scent-marking might serve different functions for different individuals (Lewis, 2006). Generally, helper systems occur where nonbreeding group members assist breeders in protecting and feeding the offspring (Hamilton, 1964; Lukas & Clutton-Brock, 2012; Zahed, Kurian, & Snowdon, 2010). In mammals, helpers are found in several mo- nogamous species (Lukas & Clutton-Brock, 2012), for example, in mongooses (Clutton-Brock et al., 2001), canids (Moehlman & Hofer, 1997), and primates (Zahed et al., 2010). In animals living in social family groups, subordinates might scent-mark to help their parents with the territory defense (Clutton-Brock, 2002). By helping with territorial defense/maintenance (Clutton-Brock, 2002; Heap, Byrne, & Stuart-Fox, 2012; Pasquaretta et al., 2015) and the provisioning of offspring (Cockburn, 1998; Hatchwell & Komdeur, 2000; Preston, Briskie, & Hatchwell, 2016), subordinates can increase their inclusive fitness via kin selection by increasing the breeders’ fitness. While remaining in the natal family group and delaying dispersal, subordi- nates can also obtain direct benefits due to increased experience in Received: 27 January 2018 | Revised: 17 April 2018 | Accepted: 16 May 2018 DOI: 10.1111/eth.12762 RESEARCH PAPER Scent-marking behavior by subordinate Eurasian beavers Katrin Hohwieler 1 | Frank Rosell 2 | Martin Mayer 2,3 1 Department of Integrative Biology, Institute of Wildlife Biology and Game Management, University of Natural Resources and Life Sciences, Vienna, Austria 2 Department of Natural Sciences and Environmental Health, University of Southeast Norway, Bø i Telemark, Norway 3 Department of Bioscience, Aarhus University, Kalø, Denmark Correspondence Martin Mayer, Department of Bioscience, Aarhus University, Grenåvej 14, 8410 Rønde, Denmark. Email: m.mayer89@web.de Funding information University of Southeast Norway; Norwegian Environmental Agency; County Authorities of Telemark and Vestfold; Oslo municipality (Urban Environment Agency) Abstract Chemical communication by scent-marking is widespread among mammals and can serve different purposes, such as territory demarcation, mate attraction and self- advertisement. In this study, we examined scent-marking behavior by subordinate Eurasian beavers (Castor fiber) in a population in southeast Norway. We conducted scent experiments in 18 family groups, simulating a territory intruder using experi- mental scent mounds (ESM). In total, we recorded 196 territorial reactions (destroy- ing and/or overmarking of scent mounds). Subordinates contributed 14% of all territorial reactions and first overmarked 12% of the ESM, and the number of subor- dinates in the family group did not increase the total number of territorial reactions. This suggests that the contribution by subordinates plays a minor role in territorial defense. The number of territorial reactions by subordinates was positively related to the age of their parents, suggesting that subordinates might take over territorial du- ties with increasing parental senescence, likely because they have increased chances of inheriting the territory. Increased experience in territorial activities possibly helps subordinates to successfully gain and defend a territory of their own. KEYWORDS Castor fiber , chemical communication, helpers, intruder experiment, territory defense Editor: L. Fusani