Chronic traffic noise increases food intake and alters gene expression associated with metabolism and disease in bats

Anthropogenic noise exposure has deleterious effects on the foraging ecology of many animals. However, the effects of chronic anthropogenic noise on food intake and health condition in wildlife remain largely unknown. We tested whether traffic noise exposure over multiple days would change food intake and would have effects on the health of Asian particoloured bats. We broadcast traffic noise to the bats of two noise-exposure groups (group A, five bats; group C, six bats) and broadcast silence files to the bats of two control groups (group B, five bats; group D, six bats) for 12 days. We measured the changes in food intake, body weight and concentration of faecal triiodothyronine (T3) and thyroxine (T4) in groups A and B. We compared the transcriptional profiles in brain, kidney and liver tissues between bats in groups C and D. The bats exposed to traffic noise had a significantly higher daily food intake and a significantly greater body weight than bats in control group during the period of playback. Faecal T3 and T4 were higher in the noise-exposure group after playback had been on for more than 1 day. We found a total of 169 differentially expressed genes (DEGs) between noise-exposure and control groups. Some DEGs related to stress response were upregulated in the bats exposed to noise. The 169 DEGs were mainly enriched in Gene Ontology (GO) terms associated with metabolism, fundamental cellular processes, stress response and immune response. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways affected by noise exposure were linked with metabolism, disease, apoptosis, autophagy, phagosome and ribosome. Synthesis and applications. Our results suggest that bats exposed to chronic traffic noise while roosting may need more energetic intake and have a greater motivation to forage than others not exposed to noise, probably as a result of a stress response. Furthermore, chronic traffic noise may increase the risk of metabolic dysregulation, immune disorders and other diseases. Management measures for reducing noise disturbance, for example, implementing sound barriers, are essential.