The fascinating study by E.Mori, M.Menchetti & F.Dartora, highlights previously unknown aspects of carrion feeding by long-eared owls.
Owls, particularly those belonging to the order Strigiformes, are fascinating nocturnal raptors whose sensory adaptations are crucial for their survival and hunting success. Unlike many birds that rely heavily on sight, owls have evolved to depend primarily on their exceptional auditory systems. This shift in reliance from vision to hearing is largely due to their nocturnal habits, which make it difficult to rely on sight alone in the dark. Their large eyes, relative to their skull size, do aid in gathering light, but it is their acute hearing that plays the most significant role in their ability to hunt effectively at night.
The specialized auditory systems of owls are a product of evolution, fine-tuned to detect even the faintest sounds in their environment. This adaptation is critical for locating prey, which often includes small mammals such as rodents that are active during the night. The ability of owls to hear their prey moving on the ground, even under conditions where visibility is low, gives them a significant advantage. Additionally, the fringed edges of their flight feathers allow owls to fly almost silently, further enhancing their ability to approach prey undetected. This combination of silent flight and acute hearing makes owls formidable hunters in their nocturnal environments.
Given these adaptations, one might assume that owls primarily hunt live prey. However, the question of whether they consume carrion, or dead animals, has been a topic of interest among researchers. The diet of owls is typically studied through the analysis of pellets, which are regurgitated masses containing indigestible parts of their prey, such as bones and feathers. This method provides valuable insights into the types of prey that owls consume but does not always clarify whether the prey was captured alive or found as carrion. This ambiguity makes it challenging to assess the full extent of necrophagy, or carrion consumption, among owls.
Studies have documented carrion consumption in 8.43% of Strigiformes species, indicating that while it is not a common behavior, it does occur in some species. In Europe, necrophagy has been observed in a few owl species, including the eagle owl (Bubo bubo) and the barn owl (Tyto alba). These instances are relatively rare, and in some cases, they may be influenced by environmental factors such as the availability of live prey.
One species of particular interest is the long-eared owl (Asio otus), a medium-sized nocturnal raptor that is widely distributed across the Holarctic region. The diet of the long-eared owl primarily consists of small mammals, particularly voles and mice, which are considered its staple food sources. However, the diet of this species can vary seasonally, particularly in winter when snow cover makes it difficult to access ground-dwelling rodents. During these times, long-eared owls may supplement their diet with birds, which are more readily available.
The winter diet of the long-eared owl has been extensively studied across its range, providing a detailed understanding of its feeding habits during this challenging season. One aspect of its behavior that has been suggested, though not conclusively proven, is scavenging or the consumption of carrion. A notable instance of this was reported by Erfurt and Stubbe (1987), who found a small bone fragment, possibly from a roe deer, within a long-eared owl pellet. This finding suggested the possibility of carrion consumption, although definitive evidence has been lacking.
Pellet analysis is a widely used method for studying the diet of owls, and it also provides valuable data on the small mammal communities in a given area. This information is essential for both research and conservation efforts, as it helps scientists understand the dynamics of local ecosystems. However, because the long-eared owl is typically considered a feeding specialist with a preference for small mammals, its pellets are not always prioritized for these studies. Instead, pellets from generalist species like the barn owl are often preferred, which may contribute to gaps in our knowledge about the diet of the long-eared owl.
In a recent study, researchers conducted an analysis of long-eared owl pellets as part of a project to create a checklist of mammal communities in a Natura 2000 site in southern Tuscany. This study, carried out between December 2012 and April 2013, involved the collection and examination of 106 pellets from a single site within the village of Prata, located in the municipality of Massa Marittima. The study area, which is part of a rural hilly landscape at elevations between 475 and 903 meters above sea level, includes a variety of habitats, such as mixed deciduous woods, fallows, chestnut woods, cultivated areas, pinewoods, built-up areas, and scrubwoods.
The site is also part of the Natura 2000 network, a European network of protected areas aimed at preserving biodiversity. The presence of this network, along with the International Waterbird Census (IWC) area known as “Gabellino,” highlights the ecological importance of the region. Within the study area, four other species of Strigiformes have been recorded: the barn owl, the tawny owl (Strix aluco), the little owl (Athene noctua), and the scops owl (Otus scops). Interestingly, the long-eared owl is the least common of these species in the area, according to a two-year survey, with the tawny owl being the most frequently detected.
The pellets were collected from beneath a winter roost used by six long-eared owls, which was located on a stone pine tree beside the main street of the village. The pellets were gathered every three days, then dried, softened in hot water and ethanol, and carefully dissected to identify the prey species. Identification was done to the genus or species level using comparative references and a binocular microscope. In total, 112 prey items belonging to 9-10 species were identified from 106 pellets. These species included 5-6 rodent species, 3 species of shrews (Soricomorpha), and one carnivore species.
Despite the comprehensive analysis, the study did not find irrefutable evidence of carrion consumption by long-eared owls. While there was one historical instance where a bone fragment from a possible roe deer was found in a pellet, this study did not provide further evidence to support the hypothesis that long-eared owls regularly scavenge. This suggests that while scavenging may occur occasionally, it is not a common behavior for this species.
In conclusion, the study of long-eared owl pellets in southern Tuscany has provided valuable insights into the diet of this species during the winter months. While the primary focus was on understanding the species’ feeding habits and the local small mammal communities, the research also contributed to the ongoing investigation into the potential for carrion consumption in owls. Although definitive evidence of scavenging behavior in long-eared owls remains elusive, the study underscores the importance of continued research in this area. By expanding our understanding of owl diets and their ecological roles, we can better inform conservation efforts and contribute to the preservation of these remarkable nocturnal raptors.
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