Penny and penny laid up will be many: large Yellow anacondas do not disregard small prey

Abstract

The study of diet may help to predict the consequences of ontogeny and sexual size dimorphism in resource use. Although diet changes are expected in dimorphic species, ontogeny can be a factor in determining the degree of diet variation within a species. We studied large sexually dimorphic predator, the Yellow anaconda Eunectes notaeus, to learn how influences of sex and size on diet might lead to intersexual niche divergence, therefore avoiding intraspecific competition. We tested the consequences of sexual size dimorphism via two foraging metrics: prey size and feeding frequency. To test the consequences of ontogeny on trophic niche metrics, we related changes in feeding frequency and maximum prey size to increase in anaconda body size. Finally, we tested whether diet composition changed between sexes to the point where it could lead to reduced competition. While females (the larger sex) did eat larger prey compared to males, this effect disappeared when we removed the effect of body size. Females ate more frequently than males, even with body size effect was removed. Predator‐prey size ratios were positively affected by maximum prey size, and as expected from foraging theory, did not increase minimum prey size. Feeding frequency did not display any ontogenetic effects. While diet composition varied between sexes, overlap is high. This indicates that variations in resource use as a product of sex‐based differences in size are negligible in Yellow anacondas. Although females feed more frequently, this may be an effect of the greater energetic costs of reproduction. Ontogeny has a positive effect on maximum prey size, though this is a general trend, and has already been demonstrated for several other species. Finally, understanding of sex‐based changes in resource use will be improved if it can be determined whether such phenomena are consequences rather than causes for sexual size dimorphism.

Does urbanization influence the diet of a large snake?

“…As has been reported across many snake diet studies (e.g., Shine 1989 ; King 2002 ; Bryant et al 2012 ; Miranda et al 2017 ), body size (log-SVL) was a strong predictor of dugite diet. Larger snakes more frequently contained meals, and those meals were of a greater mass.…”

“…As it is not possible to distinguish between differences in population demographics or collection bias, we were unable to determine if there were any real differences in body size between locations. Because body size is known to influence diet in snakes (e.g., Shine 1989 ; King 2002 ; Bryant et al 2012 ; Miranda et al 2017 ), body size was, therefore, accounted for by including log-SVL as a covariate in all analyses. There were also sex differences in body size (of 453 specimens with complete data: female = 119, male = 105, undetermined sex = 229) ( Table 1 ), with females being smaller than males (M b : F 1,492 = 106.5; P < 0.001; SVL: F 1,492 = 107.4; P < 0.001).…”

Review of prey taken by anacondas (Squamata, Boidae: Eunectes)

“…Anacondas are specialized for aquatic hunting, where they sit and wait for prey to approach (Pizzatto et al 2009). Although this strategy cannot explain the high incidence of egg predation seen in E. notaeus, it does suggest that sit-andwait foraging is a principal component of a broader foraging repertoire (Miranda et al 2017). Anacondas lack venom to subdue prey, relying instead on their mass to constrict and drown prey (Strimple 1993).…”

Assessing the sustainability of yellow anaconda (Eunectes notaeus) harvest in northeastern Argentina

“…Yellow anacondas are generalist predators that both ambush and actively hunt for prey 42,43 . They feed on invertebrates, shes, reptiles, mammals, birds, eggs, and eventually carrion 30,[42][43][44][45] .…”

“…Yellow anacondas are generalist predators that both ambush and actively hunt for prey 42,43 . They feed on invertebrates, shes, reptiles, mammals, birds, eggs, and eventually carrion 30,[42][43][44][45] . Currently, the species is being assessed by the International Union for Conservation of Nature (IUCN) and-as all members of the Boidae family-it is listed in the Appendix II of the Convention on International Trade in Endangered…”