Sex, size and eco-geographic factors affect the feeding ecology of the Iberian adder, Vipera seoanei

Abstract

Numerous dietary studies have shown that European vipers (genus Vipera) present low feeding frequency and a specialist diet, which is characterised by a marked ontogenetic shift. However, how eco-geographic factors shape species’ feeding ecology remains scarcely addressed. We investigated the feeding ecology of the Iberian adder, Vipera seoanei, examining 402 specimens distributed across its distributional range and addressing how biological, temporal and eco-geographic factors relate to the species feeding activity and dietary consumption. Our results indicated a low feeding frequency in the species, higher in juveniles than in adults. Adult females showed higher rates of prey consumption than adult males, which match to the distinct reproductive demands of both sexes, although no differences between reproductive and non-reproductive females were found. V. seoanei preyed on a varied taxa spectrum, but showed a rather specialist diet based on small mammals. Amphibians and reptiles were also an important part of its diet, particularly in the juveniles. Body size was found as the single biological trait related to the consumption of major prey groups, supporting the occurrence of an ontogenetic shift in the diet. Two habitat and two climatic factors correlated to the consumption of major prey groups, reflecting the ecological requirements of prey across the viper’s range. Overall, this study extends the existing knowledge on the feeding ecology of European vipers, signalling how energy intake and allometric constraints shape the feeding activity and dietary consumption of the species across the geography, leading to distinct feeding strategies in juveniles and adults.

First helminthological data on the Iberian adder, Vipera seoanei

“…For example, those snake species living in dry habitats and feeding on rodents are weakly infested by helminths (Kirillov and Kirillova 2021). Although the factors found here as predictors of helminth occurrence are not the same as those related to the consumption of major prey types in this viper species (Espasandín et al 2022), they align with the aforementioned pattern in V. seoanei. Helminths occur in vipers inhabiting lowlands, areas of high temperature and precipitation levels, and with abundance of pastures (Fig.…”

“…In reptiles, body length correlates to age due to an undetermined growth throughout their life (Candan 2021). Indeed, assuming 325 mm as SVL at sexual maturation (Lucchini et al 2020;Espasandín et al 2022) we indicate that helminths were mostly found in adults of V. seoanei. This agrees with results from other reptile species in which body length also has a signi cant effect on the occurrence of parasites.…”

“…1). Samples consisted of stomachs and intestines preserved in 70% ethanol, resulting from a previous dissection of specimens performed to study the species feeding activity (Espasandín et al 2022). The dataset included samples from: (i) ethanol-preserved specimens stored in three Spanish collections, Museo Nacional de Ciencias Naturales -CSIC, Madrid (n = 163), Sociedad de Ciencias Aranzadi, Donostia (n = 76), and Departamento de Biología, A Coruña University, A Coruña (n = 22); and (ii) ethanol-preserved roadkill specimens from the particular collection of F. Martínez-Freiría (n = 43), and J.C. Brito (n = 13) (CIBIO, Vairao, Portugal).…”

“…We consider two sets of predictors that could affect the occurrence of parasites in vipers. These two sets of predictors were previously considered in the study of the feeding activity of V. seoanei (Espasandín et al 2022 The rst set comprises three biological traits, intrinsic to each viper: SEX (categorical variable, two categories: female/male), SVL (Snout-Vent Length, continuous variable, measured in mm) and PREY (categorical variable with two categories: presence/absence of prey in the gut). The second set consist of nine continuous eco-geographic predictors that describe the environmental conditions of the geographic position where each viper was collected.…”

“…This pattern in the two studied Iberian vipers may be explained by their dietary habits which are characterized by long periods without eating and a rather specialised diet, based on small mammals in adult vipers, but also including amphibians and lizards immature ones. (Espasandín et al 2022 . Consequently, we expect that the occurrence of helminths in V. seoanei could correlate with humid environments as depicted by eco-geographic factors.…”