Do spawning salmon indirectly influence ungulate space use in the Copper River Delta, Alaska by attracting bears?

Abstract

One of the key challenges in ecology is understanding the drivers of animal movements and distributions. Here, I used remote camera photography to examine whether the timing of spawning salmon altered ungulate space use due to the presence of bears. Using observational data collection methods, I quantified ungulate and bear presence at individual salmon spawning sites. I then analyzed relationships between bear and ungulate detection data to test for indirect effects between salmon and ungulates by applying linear regression models. A zero-inflated negative binomial model suggested that increases in bear detections are associated with decreases in ungulate detections. Results did reveal little overlap in the timing of ungulate and bear use of stream habitat during salmon spawning times, however, rigorous testing of my hypothesis may be limited by low rates of ungulate detection. Research dedicated to understanding the indirect effects of the timing of salmon spawning in the Copper River Delta can help evaluate the evidence for trophic interactions at various ecosystem levels. It may also offer insights into the potential magnitude the impact salmon has on the prey of large predators, other herbivore densities, plant communities, riparian area morphology, and essential ecosystem functions.