The effects of food level and conspecific density on biting and cannibalism in larval long-toed salamanders, Ambystoma macrodactylum

Abstract

Previous studies have examined abiotic and biotic factors that facilitate agonistic behavior. For larval amphibians, food availability and conspecific density have been suggested as important factors influencing intraspecific aggression and cannibalism. In this study, we examined the separate and combined effects of food availability and density on the agonistic behavior and life history of larval long-toed salamanders, Ambystoma macrodactylum. We designed a 2×2 factorial experiment in which larvae were raised with either a high or low density of conspecifics and fed either a high or low level of food. For each treatment, we quantified the amount of group size variation, biting, and cannibalism occurring. Additionally, we examined survival to, time to and size at metamorphosis for all larvae. Results indicated that differences in both density and food level influenced all three life history traits measured. Moreover, differences in food level at which larvae were reared resulted in higher within-group size variation and heightened intraspecific biting while both density and food level contributed to increased cannibalism. We suggest that increased hunger levels and an uneven size structure promoted biting among larvae in the low food treatments. Moreover, these factors combined with a higher encounter rate with conspecifics in the high density treatments may have prompted larger individuals to seek an alternative food source in the form of smaller conspecifics.

Consumptive and nonconsumptive effects of cannibalism in fluctuating age‐structured populations

“…Comparative data suggest that species with age-structured populations typically have higher thresholds (e.g., 55% to .140% for piscivorous fishes; Popova 1967, Claesson et al 2004, Persson et al 2006) than those in which size structure occurs mainly within generations (e.g., 20-30% for dragonflies, Wissinger 1992; 40% for caddisflies, Greig and Wissinger 2010; ,40% for terrestrial invertebrates, Polis 1981). Although cannibalism within cohorts of ambystomatid salamanders is commonplace and facilitated by the development of size structure, size thresholds have not been reported (e.g., Polis and Myers 1985, Petranka 1989, Van Buskirk and Smith 1991, Crump 1992, Maret and Collins 1997, Hoffman and Pfennig 1999, Ziemba and Collins 1999, Wildy et al 2001. In our study, we found that cannibalism between different year classes of tiger salamanders only occurred between individuals that differed by .50% in body size (Fig.…”

Stress hormones and the fitness consequences associated with the transition to a novel diet in larval amphibians

“…Food restriction generates substantial morphological and developmental plasticity among anuran (Wilbur and Collins, 1973;Werner and Anholt, 1996;Kupferberg, 1997) and urodele (Wildy et al, 2001;Rohr et al, 2004) larvae. Generally, studies have shown that food restriction causes reduced body sizes at metamorphosis, but the effects on development time vary depending on when the restriction is experienced.…”

Long-term survival of adult Arctic grayling (Thymallus arcticus) in the Kuparuk River, Alaska

“…Overlaying the effects of a changing environment is the influence of the population on its own survival rates. Densityrelated reduction in survival rates has been attributed to increased competition (De Leo and Gatto 1996), displacement into marginal habitats (Frederiksen and Bregnballe 2000), and increased agonistic interactions (Wildy et al 2001). Population survival rates may also be affected as the population structure changes owing to shifting sex ratios or the ad-vent of strong age-classes owing to sex-or age-specific mortality rates.…”