Importance of the long-eared owl (Asio otus) for rodent control in southern Moldova

Abstract

Introduction. The long-eared owl (Asio otus L.) is a sedentary and common nocturnal prey bird. During the winter period, the density of the species increases due to the migrant individuals from the northern regions and they form colonies of several dozen individuals. It is well adapted to anthropic environment and its wintering colonies are frequently registered in localities. After the digestion, owls regurgitate indigestible prey remains as pellets. After digestion, owls. Studying these pellets provides important data on local small mammal fauna. Purpose of the study. This study aimed to determine the diet of the long-eared owl in southern Moldova and to assess the importance of Asio otus in regulating rodent species numbers. Material and methods. A wintering colony of approximately 15 individuals was recorded in Slobozia Mare, located in a patch of coniferous trees near the village museum. Approximately 200 pellets were collected during the cold period of 2022–2023. The pellets were measured and weighed. The bones were then cleaned and categorized. Mammal species were identified based on skull bones and teeth. Results. The trophic spectrum of Asio otus was studied during the winter period in Slobozia Mare, where 212 pellets were collected and 578 individuals were identified. Pellet length ranged from 16.2 mm to 54.3 mm, with a mean of 32.7 mm. The diet consisted primarily of small mammals (>90%), with passerine birds making up the remainder. Microtus sp. was the dominant prey, constituting 58% of the diet and appearing in 72% of the pellets. The second most abundant and frequent species were from the Mus sp., followed by Apodemus sylvaticus. Other rodent species had low abundance and frequency. Birds, represented by Passeriformes, constituted 6.5% of the diet with a low frequency. The total biomass of consumed prey was 8.12 kg, demonstrating the significance of this predator in regulating rodent populations during the winter. Conclusions. After analyzing 212 pellets, 578 individuals were identified. The number of individuals per pellet varied between 1 and 4, the average being 2.66 individuals. In winter period the trophic spectrum of long-eared owl consisted of 7 mammal species and birds. The filed vole dominated in the pellets, constituting about 60%, with a frequency of more than 70%. The second most abundant and frequent species were Mus sp., followed by Apodemus sylvaticus. Other rodent species had a low share and frequency. The high abundance and biomass of field voles prove the importance of Asio otus in pest control in open type ecosystems, including agricultural lands.