Ontogenetic Variation in Head Morphology and Diet in Two Snakes (Viperidae) from Northeastern Argentina

Abstract Snakes are highly diverse in head morphology and in the types of prey they eat. Species of the Viperidae family have a high degree of morphological specialization; however, some species specialize in feeding on a single or a few prey species whereas closely related organisms take a diverse array of prey taxa. We compared head morphology and diet throughout ontogeny in two species of the family Viperidae. Rhinocerophis alternatus (Yarara grande) had a highly specialized diet, feeding exclusively on mammals throughout its life. Bothropoides diporus (Yarara chica) fed on small prey such as amphibians and reptiles and on large prey such as mammals. Mature specimens differed significantly in snout–vent length (SVL) between species whereas juvenile specimens did not. A statistical comparison of head morphology showed differences between species in both juvenile and mature specimens. Linear regression analysis showed that head variability throughout ontogeny was greater in R. alternatus than in B. dipor...