Intraguild Predation on Congeners Affects Size, Aggression, and Survival among Ambystoma Salamander Larvae

I designed laboratory and mesocosm experiments to test the hypotheses that consumption of a congener as supplemental food can increase the size variance, size, aggression rates, and mortality of intraguild predator populations. Experimental populations of Marbled Salamander (Ambystoma opacum ), Jefferson Salamander (Ambystoma jeffersonianum ) and Tiger Salamander (Ambystoma tigrinum ) larvae that were initially fed a smaller congener Spotted Salamander (Ambystoma maculatum ) as a food supplement developed larger SVL and size variation after seven days than control larvae that were not fed a congener. Experimental treatment populations had greater initial size variation because some larvae ate a congener and others did not. Treatment larvae had increased SVL, aggression rates and mortality after 60 days compared to control populations. These results suggest that intraguild predation on a congener can affect fitness and population dynamics of predator populations. I hypothesize that intraguild predation on congeners results in size variation and then increased aggression and mortality caused by cannibalism.