Intraspecific variation in diet within and between trophic morphs in larval tiger salamanders (Ambystoma tigrinum nebulosum)

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Abstract
Larvae of A. t. nebulosum are dimorphic. The broad-headed morph is cannibalistic and has a wider head and enlarged vomerine teeth compared with typical larvae. Larvae were collected from 4 habitats in Arizona, USA, to quantify how diet varies within and between morphs relative to habitat, and how diet varies relative to age in typical morphs from 1 habitat. Broad-headed or cannibalistic morphs occurred in both sexes and most of their diet (.hivin.x = 84%) was other salamanders. A variety of invertebrates comprised the remainder of their diet. Typical morphs ate primarily macronivertebrates and plankton, and rarely (1 of 170 larvae analyzed) conspecifics. Young typical larvae consumed a narrow range of prey, mostly plankton, compared with older larvae, which consumed a diversity of macroinvertebrates in addition to plankton. Description of broad-headed larvae as cannibals is justified because most of their diet is other salamanders; typical morphs rarely eat salamanders. Both morphs also eat invertebrates. With regard to diet in larval A. tigrinum, cannibalistic vs. typical refers to a predilection and is not an absolute categorization.