Owl Pellets Research Articles

Long Eared Owls (Asio otus Linnaeus, 1758) as Field-Assistants in an Integrative Taxonomy Survey of a Peculiar Microtus savii (Rodentia, Cricetidae) Population

Voles from the Genus Microtus are rodents with a subterranean lifestyle. Central Italy is populated by two species of the Genus, the North-Western Microtus savii and the South-Eastern endemic Microtus brachycercus. Although morphometric features able to help distinguish M. savii from M. brachycercus are lacking, a peculiar morphology of the anterior end of the first lower molar is typical, but not exclusive, of M. brachycercus. Since some skulls with a compatible dental morphology were collected from Long-eared owl pellets in Umbria (Central Italy), a genetic assessment was deemed necessary to verify the possible presence of M. brachycercus outside of its known distribution range. Hemimandibles were isolated and used for both genetic and morphometric dental analyses. Despite the fact that this could suggest the presence of a M. brachycercus population, genetic analyses confirmed the species attribution to the M. savii complex, showing peculiar genetic polymorphisms that can either be due to the wide sampling area, represented by the owls’ hunting grounds, or to the recent evolutive history of the analysed population. This study, once again, underlines the importance of integrative taxonomy, suggesting the key role of predators as field-assistants to minimize the impact of sampling campaign on natural populations.

Large-scale grid-based detection in occupancy surveys of a threatened small mammal: A comparison of two non-invasive methods

Monitoring the status and trends of wildlife is key to understand how species respond to natural and human-derived threats, and to evaluate and improve conservation planning and management. Large-scale, grid-based assessment of species distribution, abundance, and population trends over time is an important component of biodiversity monitoring. However, such assessments still present important challenges related, for instance, to how the choice of the sampling method may affect species detectability and thus, overall data accuracy. Here, we address this issue, focusing on the Cabrera vole (Microtus cabrerae), a threatened small mammal, listed in the Habitats Directive (Annexes II and IV), hence requiring regular evaluation of its population status and trends. We used occupancy modelling to estimate method-specific detection probability of the species over large-scale, grid-based (10 × 10 km2) surveys relying on two non-invasive sampling techniques: sign surveys and owl pellet analysis. Results provided evidence for a greater cost-effectiveness of sign surveys compared to owl pellet analysis for detecting the species in occupancy surveys, suggesting that large-scale population monitoring of Cabrera voles (or other species also producing easily identifiable signs of their presence) may fairly rely on sign-surveys. Overall, our study supported the view that while owl pellet analysis provides a valuable option when the aim is to assess small mammal assemblages (i.e. multiple species) in a region, other complementary methods may be required to increase the detection probability of certain species that because of their secretive behaviour or rarity remain less predated by owls. We thus argue that the choice of the sampling method should be context-dependent and evaluated based on the study aims, the surveyed area (i.e. local factors), the target species (i.e. life history traits) and the available resources. Based on our results we recommend that researchers and managers explore survey-design trade-offs to ensure the proposed designs have sufficient power to detect real population trends.

A Kist o’ Whistles

A Kist o’ Whistles

Mammals in Tawny Owl (Strixaluco) pellets from Kharkiv Region, Ukraine.

The Tawny owl (Strixaluco) is a common owl species in Europe, demonstrating generalist diet strategy. Its main prey are small rodents and numerous studies show that the composition of its diet broadly reflects changes in prey species abundance in its habitats. Due to strictly sedentary habits of adult birds and their year-round territoriality, it is possible to locate habitats of their prey with a precision of several hundred metres. Analysis of owl pellets is a traditional method in faunistic studies to provide data on distribution of small mammals, especially cryptic species which are hard to be found using trapping. Here, we present a dataset on mammals found in Tawny owl pellets collected during up to 13-year studies in the Kharkiv Region, Ukraine in three territories. Data from two territories were collected in a systematic way and allowed us to make analysis of seasonal, year-to-year and habitat variability in the Tawny owl diet and local mammal species composition.

Deciphering Alterations of Rodent Bones through In Vitro Digestion: An Avenue to Understand Pre-Diagenetic Agents?

Recent taphonomic studies have shown that avian predators such as owls are responsible for most small-mammal fossil accumulations, and that predators cause bone loss and breakage as well as modification to the surface of bones that are preserved. However, the specific physiochemical alterations and the alterations of bone microstructures that predators induce remain poorly understood. In order to better separate and characterize the effects of bone digestion by owls, we performed an experimental study to simulate digestion by a predator. We put fresh rodent long bones into various solutions to simulate the digestive effects of predators. We first tested an acid solution, followed by other solutions containing key enzymes such as trypsin, lipase, and trypsin + lipase. Next, we compared the results of the simulated digestion experiments with partly digested long bones recovered from Tyto alba and Bubo bubo pellets. We observed that acid action alone did not reproduce the modifications observed on bones from owl pellets, while the enzymatic activity (notably trypsin and trypsin + lipase) produced modifications most similar to those observed on the bones from the owl pellets. These results open a promising field of future experimentation to better understand the early diagenetic modification induced in small mammal bones by digestion, which can improve our ability to recognize the role of nocturnal predators in fossil accumulations.

Monitoring of the mammal fauna by studying owl pellets: a case of small mammals in protected areas of Podillia

Using owl pellets analysis to monitor mammals in protected areas makes it possible to accumulate a unique material to study the distribution and relative abundance of both common and rare species. Due to the ease of collecting and accumulating of pellets, this method helps to quickly obtain a large amount of material to monitor the changes in natural areas and objects during certain time intervals without interfering with the course of natural processes. The proportions of small-mammal species in the diet of most owls are representative of the proportions of species in their groups. Therefore, the pellet method can be used to organise monitoring of mammal species of natural regions. We analysed nearly 2000 pellets of several species of owls collected in Podillia in the course of the study. Pellets are mostly collected within protected areas. Small mammals form the basis of the diet of the studied species of owls. The diet of the short-eared owl is the most diverse, and it includes 18 species of small mammals. The common vole occurs the most often. The diet of other owl species is also diverse, in particular of the little owl, tawny owl, and eagle owl. As in the case of the short-eared owl, the main prey of the barn owl and grey owl is a common species—the common vole. The diet of the eagle owl, unlike others, is dominated by larger small-mammal species—brown rat, white-breasted hedgehog, and European hamster. In addition to common species, the analysis of owl pellets allows us to identify not only the most common, but also rare species, such as the European hamster, bicoloured shrew, lesser white-toothed shrew, and various bats. Therefore, the pellet method of research is highly effective in analysing the composition of the fauna and the structure of communities, of both prey and predator species. Owl pellet analysis is a valuable asset during small-mammal monitoring studies, and is especially useful for sampling of indicator small-mammal species during environmental impact assessments in protected areas. The method has considerable advantages compared to standard survey methods of small mammals— it does not require the removal of animals from the natural environment, which makes it relevant for use in protected areas.

Distribution of Four Vole Species through the Barn Owl Tyto alba Diet Spectrum: Pattern Responses to Environmental Gradients in Intensive Agroecosystems of Central Greece.

Voles are the most common vertebrate pests in European agriculture. Identifying their distribution and abundance patterns provides valuable information for future management. Barn Owl diet analysis is one of the optimum methods used to record small mammal distribution patterns on large spatial scales. From 2003 to 2005, a total of 10,065 Barn Owl pellets were collected and analyzed from 31 breeding sites in the largest agroecosystem in Greece, the Thessaly plains. A total of 29,061 prey items were identified, offering deep insight into small mammal distribution, specifically voles. Four discrete vole species (Harting's vole Microtus hartingi, East European vole Microtus levis, Thomas's pine vole Microtus thomasi, and Grey dwarf hamster Cricetulus migratorius) comprised 40.5% (11,770 vole prey items) of the total Barn Owl prey intake. The presence and abundance of the voles varied according to underlying environmental gradients, with soil texture and type playing a major role. M. levis showed no significant attachments to gradients, other than a mild increase in Mollisol soils. It was syntopic in all sites with M. hartingi, which was the dominant and most abundant small mammal species, preferring non-arable cultivated land, natural grasslands, set-aside fields, and fallow land. M. thomasi was strictly present in western Thessaly and strongly associated with a sandy-clay soil texture and Alfisol soils. C. migratorius was the least represented vole (162 items), exclusively present in eastern Thessaly and demonstrating a stronger association with cereals, Mollisol soils, and an argillaceous-clay soil texture. This is the first study in Greece at such a large spatial scale, offering insights for pest rodents' distribution in intensive agroecosystems and their response to environmental gradients including soil parameters.

Hunger sweetens the beans: evidence of opportunistic feeding behaviour of the little owl (Athene noctua, Scopoli 1769) from Peloponnese, Greece

Abstract The little owl (Athene noctua) is a common raptor in Mediterranean habitats. To acquire more information on its diet, this study identified cranial and post-cranial skeletal material from 70 owl pellets collected during the 2016 and 2017 breeding seasons. The material was used to quantify the little owl’s relative prey abundance using MNI (minimum number of individuals), a taphonomical unit. This study is the first to examine the diet of the little owl in the Peloponnese (southern Greece). After examining 3,691 isolated skeletal and exoskeletal remains from the processed pellets, a total of 78 and 108 prey items were recorded for the two consecutive years. This study, in congruence with previous research, showed that in both years the little owl favoured primarily small mammals and arthropods, with a clear predominance of Thomas’s pine vole (Microtus thomasi) and arthropods from the class Diplopoda. Finally, a redundancy discriminant analysis (RDA) was applied to our two-year results, along with those from similar studies in the Mediterranean region, to examine the relationship between habitat types and prey taxa, which supported the little owl’s opportunistic feeding behaviour, depending on variation of ecological factors.

Small mammal community in a Mediterranean target area of Sicily by the data from the long-eared owl pellets

Small mammal community in a Mediterranean target area of Sicily by the data from the long-eared owl pellets

Analysis of Toxic Heavy Metals in the Pellets of Owls: A Novel Approach for the Evaluation of Environmental Pollutants.

Massive quantities of unadvisable synthetic pesticides are used in modern agricultural industries in order to increase productivity to convene food demands. Wild birds are an excellent bio-indicator of environmental contaminations as pesticides and heavy metals are intentionally highly hazardous pollutants. Considerably, raptorial birds (owls) attract consumers in the food chain and food web because they have wider forager and foraging grounds. In the current investigation, owl pellets were used as a viable tool and novel approach to detecting environmental contaminants. In total, 30 pellets comprising five species were collected from selected farmlands, and 11 metals (Cr, Mn, Co, Mo, Se, V, Cu, Ni, Pb, Zn, and Fe) were analyzed using inductively coupled plasma mass spectrometry (ICP-MS). Undeniably, the Brown Fish Owl showed more metal accumulation than the Barn Owl, Spotted Owl, Indian Eagle Owl, and Mottled Wood Owl. Among the species, the levels of metals such as Manganese (Mn), Molybdenum (Mo), Vanadium (V), Copper (Cu) and Zinc (Zn) varied significantly (p < 0.05). Nonetheless, the research revealed that the agroecosystem was contaminated with heavy metals. The present outcome highlights that the management of the environment, especially the agroecosystem, must be examined with a careful assessment of contaminants, and it is a vital resource for human and other related wildlife faunal communities.

Small Mammal Diversity Changes in a Baltic Country, 1975-2021: A Review.

The structure and diversity of small mammal (SM) communities over the long term may show the influences of climate change, landscape changes and local disturbances. We review published data regarding SM trapping and owl pellet analysis from Lithuania (the most southerly of the three Baltic States, Northern Europe), covering the period 1975-2021. Over decades, we analysed trends in the diversity of SM communities and the proportions of species and proportions of trophic groups. The large increase in granivores, from 6.9% in 1975-1980 to 45.4% in 2011-2020 and 54.7% in 2021, coincided with a decrease in omnivores and insectivores. The proportion of herbivores increased less notably. At the species level, significant decreases in the proportions of M. arvalis, C. glareolus and S. araneus were accompanied by notable increases in the proportions of A. flavicollis and A. agrarius, the latter from 1.0% in 1975-1980 to 25.3% in 2021. Concluding, two periods were identified, specifically before the 1990s and subsequently. In the second period, in the aftermath of land-use changes within the country in 1990, diversity increased, and dominance decreased, a situation that has not subsequently changed. Not excluding the concomitant effects of climate change, we relate these patterns to the alterations in habitat and anthropogenic impact.

Microplastic contamination in terrestrial ecosystems: A study using barn owl (Tyto alba) pellets

Microplastics (MPs) are recognised as an emerging environmental problem that needs to be carefully monitored. So far, MPs have been widely recorded in marine and freshwater ecosystems. Still, few studies have focused on MP occurrence in terrestrial ecosystems, although soils are suspected to be one of the main MP reservoirs. To test a non-invasive method for assessing MP contamination in terrestrial ecosystems, we analysed the pellets of a top terrestrial predator, the barn owl (Tyto alba). Sixty pellets were collected from three agricultural areas (20 pellets each) and analysed to assess both barn owl diet and MP content. Thirty-four MPs were confirmed by micro-Fourier Transform Infrared Spectroscopy (μ-FTIR) analysis in 33% of the pellets (min-max 1–5 MPs per pellet). Most of the detected items were microfibres (88.2%). Polyethylene terephthalate, polyacrylonitrile and polyamide were the most abundant polymers. One of the three sites was significantly less contaminated. In the two sites with the highest MP occurrences, barn owl diet was characterised by predation on synanthropic rodents, particularly brown rats (Rattus norvegicus), which may indicate habitat degradation and increased exposure to MPs. Analyses also suggest that Savi's pine vole (Microtus savii) is the prey least at risk of MP contamination, probably due to its strictly herbivorous diet. We argue that the analysis of barn owl pellets may represent a cost-effective method for monitoring MP contamination in terrestrial ecosystems.

New Data on Distribution of Suncus etruscus Savi, 1822 (Mammalia: Soricidae) in Eastern Anatolia

A new record of Suncus etruscus from Eastern Anatolia was presented in this study. The record is based on jawbones and skull obtained from owl pellets. This cryptic species, which is very difficult to catch and observe alive, can be found in pellets. Therefore, findings based on pellets make it easier to obtain data on the distribution area of the species.

Non-volant mammals of the ‘Lago di Tarsia’ Regional Nature Reserve and Special Conservation Area (IT93100055; Cosenza, Southern Italy)

In this study we improved the knowledge about terrestrial mammals (excluding Chiroptera) of the 'Lago di Tarsia' Regional Nature Reserve (Special Conservation Area; Cosenza; Southern Italy), collecting a large amount both of direct and indirect original data (including road-killing remains and items obtained by small mammal traps, owl pellets, and phototraps), and bibliographic ones. We obtained 424 records belonging to 22 taxa classified at species level and one requiring a further taxonomic diagnosis (Microtus savii vel brachycerchus). Hystrix cristata Linnaeus, 1758, Vulpes vulpes (Linnaeus, 1758) and Martes sp. were the taxa with the highest number of records (> 10%). Sciurus meridionalis (Lucifero, 1907), Martes foina (Erxleben, 1777), Glis glis (Linnaeus, 1758), Apodemus cfr. flavicollis (Melchior, 1834), Lepus europaeus Pallas, 1778, Talpa romana (Thomas, 1902), Rattus cfr. rattus (Linnaeus, 1758), Arvicola amphibius (Linnaeus, 1758) were the taxa with the lowest number (<1%). Almost half of the records have been obtained by indirect traces (hairs, excrements, fingerprints, burrows, etc.). Records from owl pellets represented an important percentage. Although the study area is restricted in size, the high environmental heterogeneity make possible the co-occurrence of a high number of species, including specialized taxa (e.g., forest mammals, mustelids and Soricomorpha). Some species, occurring in the neighbouring, although not recorded in our study (e.g. Sorex spp., Neomys sp., Elyomis quercinus Linnaeus, 1766), could be confirmed improving the research effort. Further studies are necessary in this regard, also focusing on the role of this reserve as dispersal corridor for rare carnivores, occurring in the massifs and rivers neighbouring to the Reserve (e.g. Lutra lutra Linnaeus, 1758 and Canis lupus Linnaeus, 1758).

Using eDNA to confirm the identity of raptors that cast pellets

Raptor pellets are regularly encountered in the field in a variety of habitats. Where multiple species of similar-sized raptors are sympatric, there can be uncertainty about which species produced a pellet based on visual assessments alone. We developed a DNA barcoding protocol that used environmental DNA (eDNA) to identify birds of prey that had produced pellets. Two different PCR primer pairs were required to successfully ascribe a pellet to the source bird species. Troubleshooting different suspension temperatures and applying multiple primer sets to the same eDNA sample provided sequences that successfully identified Red-tailed Hawk (Buteo jamaicensis) and Great Horned Owl (Bubo virginianus) pellets. Because eDNA degrades, this protocol will only work on pellets that have been in the environment for a limited time, probably <6 months.

Sample point variation in gastrointestinal bacteria of migrating Northern Saw-whet Owls (Aegolius acadicus) of eastern North America

We characterize bacteria of the gastrointestinal tract of 28 Northern Saw-whet Owls (Aegolius acadicus) netted on the Mohonk Preserve near New Paltz, New York, during autumn of 2017. We used selective culture media to determine the presence and assess the point infection level of Escherichia coli, Pseudomonas aeruginosa, Salmonella spp., and Staphylococcus aureus in the buccal, cloaca, feces, and pellets of Northern Saw-whet Owls. We tested for associations between bacteria type, sample point location, and infection levels and then assessed the influence of bacterial infection on the health of owls using multivariate analysis of mass/wing chord body condition index estimates and heterophil to lymphocyte ratios. All Northern Saw-whet Owls tested positive for at least one type of bacteria. We found an inverse relationship between the number of bacteria types detected per individual and the percentage of Northern Saw-whet Owls affected, with 46.43%, 32.14%, and 3.57% of individuals showing presence of 2, 3, and 4 types of bacteria, respectively. Multivariate analysis revealed a significantly heightened presence of S. aureus in the buccal cavity, and Spearman's rho analysis revealed positive correlations between site colonization levels and bacterial species levels. We found no significant relationship between bacterial load and mass/wing chord body condition indexes or heterophil to lymphocyte ratios. We did, however, find a positive relationship between heterophil to lymphocyte ratios and Leucocytozoon infections. Providing baseline information of common microflora can help future research recognize potentially harmful gastrointestinal pathogens. Therein, as the first study to characterize bacteria of the Northern Saw-whet Owl, this research adds to the information portfolio of the species and may benefit future research efforts.

PROPOZYCJA MONITORINGU RZĘSORKA RZECZKA (NEOMYS FODIENS, PENNANT, 1771) W POLSCE

The paper presents a proposal of methods for monitoring the Eurasian water shrew Neomys fodiens, belonging to the family Soricidae. This species has a wide range in Poland, although it has never been the subject of a nationwide survey. Water shrew has a sporadic and localised occurrence and little is known about its habitat requirements and population dynamics. Although there is no documented proof of population decline, there is concern that the species may be vulnerable to declines in abundance and occurrence as a result of habitat loss and pollution as it is closely associated with aquatic environment. The proposed method of population status assessment is based on estimating the number of specimen observed at selected monitoring sites by the capture-mark-recapture (CMR) method and an additional method of analysing owl pellets to establish the presence and abundance of the species in the area. Moreover, indicators assessing the condition of the habitat, such as presence of preferred water bodies, share of shoreline vegetation, slope of the shore and availability of shelters have been proposed. Regular monitoring can contribute to the recognition of potential changes in water shrew’s population dynamics.

Understanding the Impact of Trampling on Rodent Bones

Experiments based on the premise of uniformitarism are an effective tool to establish patterns of taphonomic processes acting either before, or after, burial. One process that has been extensively investigated experimentally is the impact of trampling to large mammal bones. Since trampling marks caused by sedimentary friction strongly mimic cut marks made by humans using stone tools during butchery, distinguishing the origin of such modifications is especially relevant to the study of human evolution. In contrast, damage resulting from trampling on small mammal fossil bones has received less attention, despite the fact that it may solve interesting problems relating to site formation processes. While it has been observed that the impact of compression depends on the type of substrate and dryness of the skeletal elements, the fragility of small mammal bones may imply that they will break as a response to compression. Here, we have undertaken a controlled experiment using material resistance compression equipment to simulate a preliminary experiment, previously devised by one of us, on human trampling of owl pellets. Our results demonstrate that different patterns of breakage can be distinguished under wet and dry conditions in mandibles, skulls and long bones that deform or break in a consistent way. Further, small compact bones almost always remain intact, resisting breakage under compression. The pattern obtained here was applied to a Pleistocene small mammal fossil assemblage from Wonderwerk Cave (South Africa). This collection showed unusually extensive breakage and skeletal element representation that could not be entirely explained by excavation procedures or digestion by the predator. We propose that trampling was a significant factor in small mammal bone destruction at Wonderwerk Cave, partly the product of trampling caused by the raptor that introduced the microfauna into the cave, as well as by hominins and other terrestrial animals that entered the cave and trampled pellets covering the cave floor.

Prey Delivery Inside an Artificial Nest Box and Burrows Used by Nesting Burrowing Owls in el Paso, Texas

ABSTRACT Determining the diet of species that nest underground, such as the Burrowing Owl (Athene cunicularia), is challenging. Prey information for Burrowing Owls is often limited to prey remains at nest sites and in owl pellets, images collected from above-ground trail cameras, or direct observations of prey acquisition and delivery. To document prey use and nesting behaviors, we equipped an artificial nest box and burrows at Rio Bosque Wetlands Park in El Paso, Texas, with a digital video recorder and three underground infrared cameras. Herein we document the types and frequencies of prey items delivered inside the nest box during the 2019 nesting season, as reflected in videos and images collected continuously from 1 April to 5 July. We reviewed 23,039 video files and documented 580 prey deliveries. We identified 463 (80%) of the delivered prey items to class and 237 items (41%) to family. Invertebrates made up 75% and vertebrates 25% of the identifiable prey items by frequency. Most (55%) of the invertebrates were insects, especially in the orders Orthoptera and Blattodea; scorpions (Scorpiones) were the second most common group (2% of all items). Vertebrate prey were delivered less often and mostly consisted of rodents (14% of all prey items), especially heteromyids, followed by squamate reptiles (6%). Results from this project will aid in conservation and management of this species.

Post-mortem enamel surface texture alteration during taphonomic processes-do experimental approaches reflect natural phenomena?

Experimental approaches are often used to better understand the mechanisms behind and consequences of post-mortem alteration on proxies for diet reconstruction. Dental microwear texture analysis (DMTA) is such a dietary proxy, using dental wear features in extant and extinct taxa to reconstruct feeding behaviour and mechanical food properties. In fossil specimens especially, DMTA can be biased by post-mortem alteration caused by mechanical or chemical alteration of the enamel surface. Here we performed three different dental surface alteration experiments to assess the effect of common taphonomic processes by simplifying them: (1) tumbling in sediment suspension to simulate fluvial transport, (2) sandblasting to simulate mechanical erosion due to aeolian sediment transport, (3) acid etching to simulate chemical dissolution by stomach acid. For tumbling (1) we found alteration to be mainly dependent on sediment grain size fraction and that on specimens tumbled with sand fractions mainly post-mortem scratches formed on the dental surface, while specimens tumbled with a fine-gravel fraction showed post-mortem formed dales. Sandblasting (2) with loess caused only negligible alteration, however blasting with fine sand quartz particles resulted in significant destruction of enamel surfaces and formation of large post-mortem dales. Acid etching (3) using diluted hydrochloric acid solutions in concentrations similar to that of predator stomachs led to a complete etching of the whole dental surface, which did not resemble those of teeth recovered from owl pellets. The experiments resulted in post-mortem alteration comparable, but not identical to naturally occurring post-mortem alteration features. Nevertheless, this study serves as a first assessment and step towards further, more refined taphonomic experiments evaluating post-mortem alteration of dental microwear texture (DMT).