Anuran consumption by burrowing owl (Athene cunicularia Strigiformes) in lower Chubut river valley, Patagonia, Argentina

Abstract

Burrowing Owl (Athene cunicularia Strigiformes) is widely distributed in American continent and mainly feeds on arthropods and small mammals, with anurans as an important prey seasonally. In Argentinean Patagonia, anurans presence was documented in one study that assessed the diet in Somuncurá plateau. Here we assessed the consumption of anurans by Burrowing Owls in the lower Chubut river valley (Chubut province, Argentina) and its relation with seasons. Two species of anurans are present: Rhinella arenarum (Bufonidae) and Pleurodema bufoninum (Leptodactylidae). Owl pellets were collected seasonally between 2018 and 2022 and dry-disintegrated in the laboratory. Minimum number of anuran individuals was calculated on the basis of ilea and the effect of years and seasons was evaluated with GLM. We analyzed 365 complete owl pellets and 64 prey remains. Anurans represented 44%F of consumed vertebrates and GLM analyses showed higher effect in spring and lower in summer. We identified the 24.2%F as R. arenarum and the 75.8%F undetermined species. We can infer that owls feed during day and night, given the activity pattern for anurans. Our results are similar for those found in spring in Argentina, but differ for other seasons, probably in relation to how anurans use the irrigation channels (spring-summer) and also activate when precipitation is more frequent (winter and spring). Considering that all prey remains and cranial bones belong to R. arenarum, and lacking direct evidence of P. bufoninum, we could suppose that unidentified ilea belong to the former. Nevertheless, this assumption cannot be confirmed until the presence or absent of P. bufoninum was recorded through sampling.