What happens when the lights are left on? Transcriptomic and phenotypic habituation to light pollution

Artificial light at night (ALAN) is one of the most ubiquitous
human-induced environmental stressors. ALAN can induce immediate
behavioral and physiological changes in animals, sometimes leading to
severe health consequences. Nevertheless, many organisms persist in
light-polluted environments and may have mechanisms of habituating to
ALAN, reducing responses to repeated exposure over time. The capacity for
animals to habituate to ALAN has yet to be tested experimentally. We
conducted a 6-month repeated-measures experiment with zebra finches
(Taeniopygia guttata) to test whether birds can habituate to repeated ALAN
exposure. We measured individual changes in behavior, physiology
(oxidative stress and telomere attrition), and gene expression to test for
concordance among behavioral, physiological, and transcriptomic responses
to ALAN. We present evidence of tolerance to chronic ALAN exposure,
persistent behavioral responses lasting 8 weeks post-exposure, and
habituation to subsequent re-exposure. We found no changes in telomere
attrition and a decrease in oxidative stress associated with ALAN
exposure, indicating potential protective effects of long-term dim ALAN.
Changes in blood transcriptome within individuals revealed unique
responses to both previous ALAN exposure and subsequent re-exposure. These
results represent organismal resilience to chronic stressors and shed
light on the capacity of individuals to persist in an increasingly
light-polluted world.