COMMUNICATION IN RIVER OTTERS: CREATION OF VARIABLE RESOURCE SHEDS FOR TERRESTRIAL COMMUNITIES

Movements and behavior of animals can result in transfer of nutrients between discrete spatial patches, leading to spatial and temporal variability in resource sheds, modification of nutrient cycling, changes in productivity and in community structure and function, and increases in landscape heterogeneity. In this study, we explored the function of scent-marking at latrines by coastal river otters (Lontra canadensis), through investigating spatial distributions of otters with respect to gender, sociality, and the distribution of their food resources. We then calculated the amounts of nitrogen (N) and phosphorus (P) transported to latrine sites based on otter foraging behavior and the function of scent-marking at latrines. Locations of 55 radio-tagged otters in Prince William Sound, Alaska, USA, were obtained through aerial telemetry over a period of four years. Data on fish densities and marine habitat features were concurrently obtained from scuba transects and aerial surveys. A plastic social organization in river otters resulted in different foraging strategies and scent-marking behaviors. Social otters were more closely associated with schooling fishes and used latrines for intra-group communication, whereas nonsocial otters, which concentrated on intertidal and subtidal fishes, probably signaled mutual avoidance. In contrast, females appeared to use latrines for the defense of territories. Social otters used fewer sites with greater intensity, whereas nonsocial otters used more sites with lower intensity. These different functions of scent-marking and associated behaviors of otters resulted in high variability in nutrient inputs to different latrine sites. Although some sites may receive 2.7 g N·m⁻²·yr⁻¹ and 0.4 g P·m⁻²·yr⁻¹, others may be fertilized with up to 47.6 g N·m⁻²·yr⁻¹ and 6.7 g P·m⁻²·yr⁻¹. This spatial variability and the temporal changes in resource sheds is likely to result in the creation of heterogeneous landscape at the land margin.