Temporal change in the diet of Tyto alba (barn owl) near a Natal long-fingered bat (Miniopterus natalensis) maternity roost in Limpopo province, South Africa

Abstract

Regurgitated pellets of Tyto alba (barn owls) are useful in determining small mammal communities. This study examines variation in the diet of T. alba in relation to an increase in abundance of a migratory bat, Miniopterus natalensis. An estimated 150 000–200 000 Min. natalensis migrate into the study cave (Madimatle Cave) during October–November to give birth. We hypothesised that this bat would predominate in the diet of T. alba when the abundance of this bat was highest. Relative abundance for Min. natalensis, and other bats, was obtained using a bat-detector station located 600 m from the cave entrance and 70 m from an owl roost. Tyto alba pellets were collected at the roost on five sample occasions over eight months between November 2016 and May 2017.Each pellet was dissected, and its contents were recorded. Sixty-four pellets were analysed, the contents of which were 43.5% arthropods and 56.5% mammals, with no birds or herpetofauna. Fourteen mammal species were recorded. Two shrew species (Suncus lixus and Suncus varilla) were recorded for the first time in the area. A significant positive relationship (P = 0.006)was found between the abundance of Min. natalensis in the cave system and the diet of T. alba over the period sampled. This suggests that when the large numbers of Min. natalensis females and young are present at Madimatle Cave T. alba diet selection was determined more by prey abundance than preference.