Landscape and Season Influence Bat Activity and Richness in a Mediterranean Metropolitan Area

Abstract

Urbanisation alters landscapes and filters biodiversity, yet its effects in Mediterranean cities remain poorly understood despite their unique ecological and climatic context. As adaptable insectivores and key providers of ecosystem services, bats are an important component of urban biodiversity. We investigated how landscape composition, artificial illumination, and seasonality shape bat activity and species richness in Naples (Southern Italy), a densely inhabited Mediterranean metropolis. We hypothesized that: (1) artificial illumination would favor light-tolerant species; (2) urban areas would enhance bat activity through roosting and foraging opportunities; and (3) urban warming would reduce seasonal declines in activity. Passive ultrasonic recorders were deployed in summer and winter across 12 1 × 1 km cells spanning a gradient of green space size and fragmentation. We recorded seven species and one Myotis group, with communities dominated by synurbic taxa (Pipistrellus kuhlii, Hypsugo savii, Pipistrellus pipistrellus). Artificial illumination did not influence activity, and no species responded positively to light. Urban land cover and Mediterranean shrublands reduced both total activity and species richness, and the hypothesis that urbanization would enhance foraging opportunities for tolerant species was rejected. In contrast, urban natural parks increased bat activity and richness, favoring H. savii and Tadarida teniotis, while P. pipistrellus preferred open rural areas but avoided intensively managed agricultural land.Pipistrellus Seasonality emerged as the most consistent driver: bat activity and richness declined markedly in winter for all species, including presumed urban exploiters such as P. kuhlii and H. savii. Even the mild Mediterranean climate and urban heat island effects did not eliminate strong seasonal patterns. Mediterranean cities act as environmental filters, supporting only a few tolerant species. Urban natural parks provide critical refugia and should be prioritized alongside habitat heterogeneity, reduced pesticide use, and light pollution mitigation. Despite urban warming, pronounced winter declines persist, highlighting the need for continued monitoring to detect climate-driven phenological shifts.

Keywords: Naples; bat; city; green areas; park; seasonality; urbanization.

FIGURE 1

The location of the twelve 1 × 1 km cells where bat richness and activity were sampled in Naples' metropolitan area (Italy).

FIGURE 2

Predicted number of total bat passes and species richness (mean ± SE) in the metropolitan area of Naples, Italy, based on generalized linear mixed models (GLMMs). Total bat activity by (a) Season, (b) extent of Urban natural park areas, (c) extent of Urban areas, and (d) extent of Mediterranean shrubland areas. Species richness by (e) Season, (f) extent of Urban natural park areas, (g) extent of Urban areas, and (h) extent of Mediterranean shrubland areas.

FIGURE 3

Predicted number of bat passes (mean ± SE) in the metropolitan area of Naples, Italy, based on generalized linear mixed models (GLMMs). Hypsugo savii passes by (a) Season, and (b) extent of Urban natural park areas. Pipistrellus kuhlii passes by (c) Season. Pipistrellus pipistrellus passes by (d) Season, (e) extent of open rural areas, and (f) extent of Agricultural areas. Tadarida teniotis passes by (g) Season, (h) extent of Urban natural park areas, and (i) extent of Mediterranean shrublands.