Surface thermal landscapes of subterranean social organization: Burrow-entrance architecture and thermal patterning in Harting’s vole (Microtus hartingi) across Mediterranean island habitats

Harting’s vole (Microtus hartingi) is a socially organized burrowing rodent with a fragmented Balkan–Anatolian distribution and exceptional biogeographical interest in the Mediterranean basin. Lesvos, Greece, is the only Mediterranean island known to host a population of a social vole and one of only three islands inhabited by Microtus species. Across the island, M. hartingi occupies olive groves, maquis formations, and open forest areas, where communal burrow systems form colony structures expressed through multiple entrances and spatially arranged openings. Here, we examined whether surface thermal landscapes above active burrow systems encode a detectable spatial signal of subterranean social organization after accounting for habitat background. Infrared thermal imagery was acquired from active colonies and paired nearby non-colony reference substrates across the three habitat types. Burrow entrances were mapped in GIS, allowing each colony to be characterized by entrance number, entrance density, spatial configuration, and colony extent. Thermal information was quantified at two scales: entrance-level thermal anomalies relative to adjacent substrate and colony-level thermal patterning relative to paired references. Paired mixed-effects models tested colony-reference and habitat effects, regression models evaluated whether entrance architecture explained colony-level thermal heterogeneity, and NMDS summarized multivariate separation among colony and reference profiles. Active colonies produced distinct surface thermal landscapes structured around their entrance networks. Colonies with denser spatial configuration showed stronger reference-normalized thermal heterogeneity, indicating that surface thermal patterning partly reflects the organization of the underlying communal burrow system. Habitat context further modulated this relationship, with open forest areas showing the clearest colony-reference separation, while olive groves and maquis displayed more buffered thermal expression. Through the integration of entrance architecture and colony-level thermal patterning, subterranean social organization becomes visible as a surface microclimatic landscape, revealing a hidden functional dimension of burrowing-mammal ecology in Mediterranean island ecosystems.