Conspecific aggression is an important factor structuring population dynamics through intra- and interspecific interactions, but is rarely studied in un-manipulated populations. In this study, we evaluated rates of injury as a proxy for conspecific aggression using a depletion survey of predatory coastal giant salamanders (Dicamptodon tenebrosus) in a tributary of the South Fork Eel River, California. We tested a range of hypotheses including a suite of environmental and biotic factors for the rate of injury in a population by using an AIC model-selection approach that examined the weight of evidence for individual models. We examined both the probability of a given individual being injured, and the proportion of individuals within a given study pool being injured. We found strong support for models including salamander size, density of young-of-the-year steelhead, and density of the largest size-class of salamander as factors positively influencing the rate of injury at both the individual and habitat levels. We also found that density of older steelhead (1+ steelhead) had a strong, but highly variable positive impact on frequency of injury. This study shows that both conspecific and heterospecific factors influence intraspecific aggression for the dominant salamander throughout coastal Pacific Northwest streams. Our methodology demonstrates a non-manipulative approach to identifying correlates of natural injury in a cryptic species of amphibian. More work is needed to determine how these factors directly and indirectly influence the spatial distribution, individual fitness, and dynamics of salamander populations within streams.
Comparative food habits of four species of stream-dwelling vertebrates (Dicamptodon ensatis, D. copei, Cottus tenuis, Salmo gairdneri).
Poor nutritional conditions during the early larval stage reduce risk-taking activities of fire salamander larvae (Salamandra salamandra).
ShapovalovL.TaftA.C. (1954): Fish Bulletin No. 98. The life histories of the steelhead rainbow trout (Salmo gairdneri gairdneri) and silver salmon (Oncorhynchus kisutch) with special reference to Waddell Creek California and recommendations regarding their management. Fish Bulletin. Retrieved from http://escholarship.org/uc/item/2v45f61k
Effects of prey abundance on density and territorial behavior of young rainbow trout (Salmo gairdneri) in Laboratory Stream Channels.
Journal of the Fisheries Research Board of Canada31:
A comparison of the effectiveness of recommended doses of MS-222 (tricaine methanesulfonate) and Orajel® (benzocaine) for amphibian anesthesia.
A brief guide to model selection, multimodel inference and model averaging in behavioural ecology using Akaike’s information criterion.
Behav. Ecol. Sociobiol.65:
The effects of food level and conspecific density on biting and cannibalism in larval long-toed salamanders, Ambystoma macrodactylum.