Differences in cautiousness between mainland and island Podarcis siculus populations are paralleled by differences in brain noradrenaline/adrenaline concentrations.

•Mainland (ML) and an islet (ISL) Podarcis siculus  populations occupy different ecological niches.•ML lizards spend significantly more time hiding after a predator encounter in the field.•ML lizards explore less a novel space in an open field test.•ML lizards contain higher whole-brain noradrenaline (NA) and adrenaline (ADR) levels.•Differing environmental factors modulate cautiousness through activity of NA/ADR circuits.