Abstract:

Aims: In light of the profound impact of urbanization on wildlife habitats, understanding the circadian activity patterns and ecological dynamics of urban terrestrial mammals is crucial for biodiversity conservation.

Methods: This study employed 60 camera traps from November 2019 to November 2021 across urban areas of Tianjin, China, to assess the circadian rhythms and temporal overlaps of key terrestrial mammal species, such as dogs (Canis lupus), cats (Felis catus), Siberian weasels (Mustela sibirica), Amur hedgehogs (Erinaceus europaeus), Tolai hares (Lepus tolai) and Asian badgers (Meles leucurus). Various circadian rhythm indices, including mean vector, concentration, circular variance, activity level, and attributes, were utilized alongside kernel density estimation to determine temporal overlaps. Additionally, the study employed a generalized additive model (GAM) to explore the influence of urbanization level on temporal overlap coefficients.

Results: With a sampling effort totaling 11,517 camera nights and 2,428 independent terrestrial mammal detections, the study revealed diverse activity patterns. Dogs were predominantly diurnal, while Siberian weasels, Amur hedgehogs, and Asian badgers exhibited nocturnal tendencies. Cats and Tolai hares displayed cathemeral behavior. Tolai hares exhibited the highest activity level (0.68, 95% CI: 0.56–0.73), whereas Asian badgers displayed the lowest (0.40, 95% CI: 0.29–0.44). Despite substantial (80%) temporal niche overlaps, according to the Mardia-Watson-Wheeler test results, significant differences were observed in diurnal activity patterns among species. For instance, cats and Siberian weasels demonstrated the highest temporal overlaps ($\overset{\scriptscriptstyle\frown}{\Delta }$= 0.88, 95% CI: 0.82–0.93), while dogs and Amur hedgehogs exhibited the lowest ($\overset{\scriptscriptstyle\frown}{\Delta }$= 0.35, 95% CI: 0.31–0.40). Moreover, the temporal niche overlap of cats-hedgehogs and hedgehogs-hares correlated positively with urbanization levels. In contrast, the overlap coefficient of dogs-hedgehogs showed a non-linear trend with the urbanization level.

Conclusion: This pioneering study offers a systematic analysis of circadian rhythms in terrestrial mammals in urban areas of Tianjin, China. Findings underscore the considerable heterogeneity in circadian behaviors across mammalian species and unveil a nuanced multi-response model depicting temporal overlaps in response to urbanization levels. These insights contribute to understanding wildlife coexistence mechanisms within urban landscapes, and offer valuable guidance for the conservation and management of urban wildlife in China.

Key words: urbanization, camera trapping method, terrestrial mammals, circadian rhythm, temporal correlations