Comparison of fang replacement rate in Viperidae snakes

Only a few studies have estimated fang replacement rate (FRR) in free-ranging snakes. We compared FRR between Crotalinae and Viperinae, two major clades of Viperidae. Crotalinae species differ by having pit organs which allow efficient strike at the prey, while, based on an earlier study, Viperinae species have relatively longer fangs. We hypothesized that FRR is related to the risk of fang damage and predicted that: (1) FRR is related positively to fang length; and (2) the FRR of Viperinae is faster than that of Crotalinae. To test these predictions, we determined the FRR, fang length, body size and hunting strategy of 21 Viperidae species, 7 Viperinae and 14 Crotalinae, controlling for allometric and phylogenetic effects. The average FRR of Viperinae was 2.6 times faster than that of Crotalinae, supporting our second prediction. However, in contradiction to our first prediction, FRR within subfamilies was related negatively to fang length. The phylogenetic analysis indicated that FRR and fang length covaried throughout the lineage, and that the relationship between FRR and fang length persisted beyond phylogenetic relatedness, implying that fang replacement of the two subfamilies followed different evolutionary pathways.