Correlates and consequences of injury in a large, predatory stream salamander (Dicamptodon tenebrosus)

Abstract

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 inñuencing the rate of injury at both the individual and habitat levels. We also found that density of older steelhead ( 1 -I-steelhead) had a strong, but highly variable positive impact on frequency of injury. This study shows that both conspecific and heterospecific factors infiuence 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.

Intraspecific facial bite marks in tyrannosaurids provide insight into sexual maturity and evolution of bird-like intersexual display

“…Although many behavioral interactions require direct observational study, in instances in which agonistic behavior causes bodily injury, aggression levels can be inferred by examining the relative frequency of wounds or scars. This approach has been used within a broad phylogenetic context that includes teleost fish (Santos 1996), amphibians (Ovaska 1987; Staub 1993; Camp 1996; Munshaw et al 2014), squamates (Schoener and Schoener 1980; Shine 1990; Jennings and Thompson 1999; Baird et al 2012; Morrison et al 2013; Baxter-Gilbert and Whiting 2018), chelonians (Kiviat 1980; Keevil et al 2017), crocodylians (Staton and Dixon 1975; Gorzula 1978; Webb et al 1983), rodents (Rose 1979; Forman and Brain 2006), cetaceans (Gerson and Hickie 1985; Scott et al 2005; Orbach et al 2015), cervids (Geist 1986), carnivorans (Ramsay and Stirling 1986; Minta 1993; Macdonald et al 2004; Derocher et al 2010), and primates (Owens 1975; Crockett and Pope 1988; Drews 1996; Sauther et al 2002; Cristóbal-Azkarate et al 2004; Arlet et al 2009).…”

Interactive abiotic and biotic stressor impacts on a stream‐dwelling amphibian

“…In addition to comparing speeds under different treatments, we also compared speed to known average strike speeds of known predators of D. tenebrosus including steelhead trout (Parker, 1993 ; Webb & Zhang, 2011 ), the terrestrial garter snake ( Thamnophis sirtalis ) (Alfaro, 2002 ; Nussbaum & Clothier, 1973 ), aquatic garter snake ( Thamnophis rufipunctatus ) (Alfaro, 2002 ; Nussbaum & Clothier, 1973 ), and conspecifics (Kleinteich et al., 2014 ; Munshaw et al., 2014 ; Reilly & Lauder, 1992 ). In line with our previous finding that trout chemical cue increases movement speed in D. tenebrosus larvae, we also saw that more larvae would move fast enough to evade a trout strike when chemical cue is present compared to when it is absent (Figure 6 ).…”