Barn Owl Pellets Reveal Hidden Stronghold of One of the World’s Smallest Mammals in Georgia

Deep in the agricultural lowlands of eastern Georgia, an unlikely detective has been quietly compiling evidence about one of the world’s rarest and tiniest mammals. That detective is the barn owl (Tyto alba), a synanthropic predator that roosts in abandoned buildings and old churches, and whose regurgitated pellets preserve the skeletal remains of everything it has eaten. By dissecting thousands of these pellets, researchers have now confirmed that the pygmy white-toothed shrew (Suncus etruscus), an animal weighing barely three grams, is far more widespread in Georgia than decades of conventional surveys had suggested. The findings, published in the journal Caucasiana, transform our understanding of a species that has long been considered nearly absent from the South Caucasus country.

The pygmy white-toothed shrew, also known as the Etruscan shrew, holds a remarkable place in mammalian biology. At up to three grams in body mass, it ranks as the world’s second smallest mammal by weight, a distinction that makes it extraordinarily difficult to study in the field. Its global distribution stretches from Portugal and Morocco across to Vietnam and the island of Kalimantan, yet within the Western Palearctic it has largely been confined to the Mediterranean region. Scientists have increasingly suspected that the fragmented appearance of its range reflects limited research effort rather than genuine rarity, a hypothesis that the new Georgian data now strongly supports.

Within the South Caucasus, documentation of Suncus etruscus has been remarkably thin. In Russia, the species was recorded only once, in 1985, from North Ossetia and Ingushetia. Known localities in Türkiye lie far from Georgia’s borders, and while multiple historical records exist for Azerbaijan, the closest confirmed observations are restricted to the Shaki-Zagatala region. Records from Armenia near Lake Sevan remain disputed among specialists. Despite more than two centuries of mammalogical research in Georgia itself, references to the species from Tbilisi and Dusheti lacked preserved specimens, and verified material amounted to just three individuals held in Ilia State University collections, plus two recent visual observations uploaded to the iNaturalist platform, one of which was confirmed through genetic analysis.

The breakthrough came through an approach that exploits the barn owl’s own hunting behaviour. Between 2023 and 2025, researchers collected pellets from sites across Georgia, focusing on agricultural landscapes where the owls, which established themselves in the country in the early 2000s and are now common in lowland areas, typically roost. In total, 6,627 prey items were extracted and identified from the pellets. Among them, 41 individuals of Suncus etruscus were identified, recovered from 12 different locations spread across the Kakheti and Kvemo Kartli regions of eastern Georgia. Every single confirmed specimen came from these two regions, painting a picture of a species that is locally established rather than sporadically present.

The laboratory protocol behind the discovery was meticulous. To ensure safe handling, all pellets were first sterilised in an oven at 160 degrees Celsius for 40 minutes, following established procedures. After sterilisation, the pellets were softened in warm water, and skeletal remains including bones, skulls, and teeth were carefully extracted using forceps and dissection tools. Identification of the shrew relied on cranial characteristics assessed against established diagnostic keys, and whenever possible, skull measurements were taken with a caliper to the nearest tenth of a millimetre. Because digestion and regurgitation render the skulls fragile, most specimens were incomplete, but a subset yielded measurable features such as condylobasal length, braincase breadth, rostral breadth, and coronoid height, all of which fell within the known morphological ranges reported for the species.

Statistically, the pygmy white-toothed shrew accounted for 0.62 percent of all prey items in the barn owl’s diet across Georgia, a figure that rose slightly to 0.73 percent when considering only Kvemo Kartli and Kakheti. While this may seem a minor component of the owl’s menu, the fact that remains appeared at 12 separate sites, with some locations yielding up to 10 individuals across multiple collection dates, indicates a persistent and breeding population rather than chance occurrences. When combined with previously published records and citizen science observations, the total number of known localities for the species in Georgia now stands at 19, a dramatic expansion of its documented footprint.

A crucial element of the study’s reliability lies in the barn owl’s foraging ecology. As a largely sedentary species, the barn owl typically hunts within a limited radius around its nesting and roosting sites. Research from Israel has shown that the average foraging distance rarely exceeds two kilometres, with only minor variation between the sexes. This tight hunting range means that prey items found in pellets, including the tiny shrews, were almost certainly captured in the immediate surroundings of the pellet collection sites. The spatial accuracy of the resulting distribution map is therefore robust at this scale of analysis, allowing researchers to pinpoint where the species actually lives rather than merely inferring its presence from broad regional data.

The findings also carry an important methodological lesson. Conventional live trapping, the standard tool for surveying small mammals, is often ineffective for species as minute as the Etruscan shrew, which can slip through standard traps or escape detection entirely. Owl pellet analysis sidesteps this problem by leveraging a predator that has already done the sampling. The authors suggest that the species may have been previously overlooked in Georgia precisely because of these methodological limitations in traditional trapping surveys, a conclusion with implications far beyond the Caucasus for anyone studying cryptic small mammals.

Nevertheless, the researchers urge caution in interpreting the geographic pattern. Their sampling was restricted to habitats favoured by barn owls, primarily open agricultural landscapes with grassy meadows. Areas where barn owls are absent, such as dry steppe, semi-deserts, or dense forests, were not surveyed, and these environments could well harbour additional populations. Detecting the shrew in such habitats would require analysing pellets from other raptor species, including the little owl (Athene noctua), the eagle owl (Bubo bubo), or the tawny owl (Strix aluco), each of which occupies a different ecological niche. A confirmed occurrence near Kajiri Lake in a hot, arid steppe habitat further suggests that the species may inhabit environments beyond those frequented by barn owls.

Climate emerges as a compelling explanatory thread in the new data. The distribution of confirmed records aligns closely with the observation, drawn from recent Bulgarian research, that the species’ range is limited by the plus 12 degree Celsius annual isotherm. All of the Georgian records fall within the 12 to 14 degree Celsius temperature zone, consistent with this thermal boundary. Intriguingly, a historical record from Dusheti does not fit the pattern, as it lies in a cooler zone with average annual temperatures of 8 to 10 degrees Celsius. Equally puzzling is the complete absence of the species in pellets from western Georgia, despite targeted sampling. Although mean annual temperatures in the western lowlands exceed 12 degrees Celsius, the region’s humid subtropical maritime climate may not match the ecological preferences of this heat-associated shrew. Resolving these puzzles will require further targeted studies, but the message of the current work is clear: one of the planet’s smallest mammals has been hiding in plain sight, and the owls that hunt above Georgian farmland have finally revealed it.

Subject of Research: Distribution of the pygmy white-toothed shrew in Georgia revealed through barn owl pellet analysis

Article Title: Barn Owl ( Tyto alba ) Pellet Analysis Reveals Wider Distribution of the Pygmy White-toothed Shrew ( Suncus etruscus ) in Georgia

Article References: Kitel, D., & Bukhnikashvili, A. (2025). Barn Owl (Tyto alba) Pellet Analysis Reveals Wider Distribution of the Pygmy White-toothed Shrew (Suncus etruscus) in Georgia. Caucasiana, 4, 97-104. https://doi.org/10.3897/caucasiana.4.e162106

Image Credits: AI Generated

DOI: 10.3897/caucasiana.4.e162106

Keywords: Suncus etruscus, barn owl, Tyto alba, pellet analysis, Georgia, Kakheti, Kvemo Kartli, small mammals, biogeography, Caucasus, raptor pellets, species distribution