The smell of desperadoes? Beavers distinguish between dominant and subordinate intruders
Olfactory signals can contain information, such as age and social status, and play a vital role in competitor assessment. In many territorial species, subordinates must leave their natal colony to obtain their own territory and mate. These individuals could be aggressive opponents in agonistic encounters, as they will have little to lose (the desperado effect). In this study, we tested the hypothesis that dominance and age are coded in the anal gland secretion (AGS) of the monogamous and highly territorial Eurasian beaver (Castor fiber), and if this information is used by conspecifics to evaluate the potential threat posed by an intruder. Territorial intrusions were simulated by presenting residents with a two-way choice test of AGS from an unknown male territory owner (i.e., dominant) and his son (i.e., subordinate; either 1 or ≥2 years old). Residents spent more time investigating AGS from subordinates than their fathers and responded more aggressively to subordinates than their fathers when subordinates were ≥2 years old. Chemical analyses gas chromatography and multivariate data analysis supported our behavioral findings and revealed differences between chemical profiles of territory owners and subordinates, as well as between the subordinates in different age classes. This study reveals that information about age and social status is coded in AGS of beavers and that this information is used to determine the level of an eventual future response to the signaler.
KeywordsAnal gland secretion Castor fiber Chemical communication Competitor assessment Desperado effect Dominant–subordinate discrimination
We would like to thank Howard Parker, Jon Swenson, and Dan Blumstein for useful comments on a previous version of the manuscript; Bjorn Steen for help with the GC-MS analysis; Frode Bergan for technical assistance; and Moritz Klein, Christian Robstad, and Patricia Graf for beaver trapping. Finally, we are sincerely grateful to Dr. Kathreen Ruckstuhl and two anonymous referees who provided critical comments on the drafts of our paper and improved its quality. This work was funded by Telemark University College.
All trapping and handling procedures were approved by the Norwegian Experimental Animal Board and the Norwegian Directorate for Nature Management and met the guidelines approved by the American Society of Mammalogists (Gannon and Sikes 2007).
Conflict of interest
The authors declare that they have no conflict of interest.
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