Adaptive significance of food income in European snakes: body size is related to prey energetics

Abstract

Feeding strategies and diet patterns have been extensively investigated in vertebrates and, more specifically, in snakes. Although it has been hypothesized that prey species may differ in terms of energy content, almost no theoretical or practical study has been carried out to determine actual nutritional values of the common prey types of wild snakes. Our model taxa were a selection of widely distributed and well known European snake species, which have all been studied in depth: approximately 76% of their diet is composed of mammals, reptiles, and insects. We therefore selected a single model species for each of these categories and proceeded with the analyses. Nutritional values were determined using a standard procedure: lizards and mice were richer in proteins than insects (crickets); insects and mice were richer in lipids than lizards, and mice and crickets have a higher energy content than lizards; lizards were rich in ashes. We then applied our experimental results to a selected sample of European terrestrial snakes (11 populations, ten species, seven genera, two families) characterized by different body size (50-160 cm total length) and reproductive strategies (oviparous versus viviparous), aiming to correlate these parameters with patterns of energy income. A direct relationship was found between body mass/body length ratio (BCI, body condition index) and meal energetics: the higher the BCI, the higher was the metabolic requirement, whereas BCI was independent of species or of reproductive system effect. Large-sized snakes thus need a highly diversified and more energy-rich diet than smaller snakes, supporting previous hypotheses. The simple applicability of this method could be of valuable support in further comparative research work, reducing experimental costs and stimulating further ecological, behavioural, and, possibly, phylogenetic comparisons.

Forest Fragments Surrounded by Sugar Cane Are More Inhospitable to Terrestrial Amphibian Abundance Than Fragments Surrounded by Pasture

“…Many of the species observed in the sampled fragments are generalists and theoretically less dependent on forest environments. It can be argued that the occurrence of many of these species is favored by deforestation and the formation of open areas resulting from land use activities [40]. This is undoubtedly the case for Physalaemus cuvieri [43,65,68,[71][72][73][74].…”

“…For biometric analysis, we measured data from snoutvent length (SVL), biomass, and mean biomass/SVL, from individuals of the most abundant species (Rhinella ornata), which we collected in January 2011. This analysis is a more subtle and refined scale for determining the matrix influence on the forest fragment biota [38][39][40]. After all, before declining and disappearing, a population under impact should show signs of withering, such as reduced average growth or weight loss.…”

Body size and body condition in the nose-horned viper (Vipera ammodytes): effects of sex and populations

“…The two other populations (Lazarev Canyon, Ibar River Gorge) are situated in markedly less disturbed rocky habitats where lizards are abundant. Smaller body size and lower mean body condition indicate that food availability and prey quality (lizards are less beneficial food items for vipers than micromammals; Zuffi et al 2010;Tomović et al 2022) might be lower compared to SV traditional agriculture landscape.…”

“…Indeed, trophic resources are limited, thus growth in stature trade-offs against body condition increases (Stearns 1992). Overall, complex interactions between environmental factors, sexual dimorphism, reproductive strategies and trophic ecology affect body size and body condition in snakes (Bonnet et al 2001Aubret et al 2002;King 2002;Beaupre 2008;Zuffi et al 2010).…”