Otters Lutra lutra Switch to Costly Territorial Advertising when Occurrence Frequency Increases

Abstract

Otters (Lutra lutra) mark territories by depositing feces on prominent spots, like rocks or large tussocks of grass. However, sometimes they defecate on intentionally mounded heaps made of mud and/or plant material. We show that in sites occupied by otters the frequency of heap-making significantly increases with the frequency of otters occurrence and is independent of the availability of naturally occurring potential marking spots. Constructing a heap is presumably costly, and thus heap-making could be an honest signal of propensity for defending territory. We propose that it should positively correlate with the quality of the territory and its owner.