Fixed photoperiod and extreme temperatures decouple activity from movement in wide-ranging species

Daniel Gambra, Marta Peláez, Ramón Perea, Enrique Navarro, Birger Hornfeldt, Navinder J Singh

Aim: Animals facing environmental change must balance when they are active with how far they move. Yet activity and movement are often treated as interchangeable behavioural responses, even though animals may remain active without travelling far or may concentrate long-distance movement into short favourable windows.

Location: Scandinavia and Iberia, spanning approximately 35 degrees of latitude and contrasting sub-Arctic, boreal, temperate and Mediterranean light-temperature regimes.

Taxon: Golden Eagle (Aquila chrysaetos), used as a wide-ranging model species for testing how fixed photoperiodic constraints and variable thermal conditions shape realised movement.

Methods: We analysed multi-annual GPS data from 76 adult and immature Golden Eagles tracked between 2010 and 2025. We quantified the proportion of daylight spent active, total active hours and maximum daily straight-line displacement, and tested how these responses varied with photoperiod, temperature, latitude and age class using generalized additive mixed models with repeated observations accounted for by individual identity and year.

Results: Activity and movement were related but fundamentally non-equivalent responses to environmental constraints. Photoperiod and temperature shaped how active time was translated into movement, with activity peaking under intermediate day lengths and latitude-dependent temperatures, whereas displacement peaked under distinct seasonal and thermal contexts. This partial decoupling indicates that animals can respond to environmental variation either by adjusting time spent active or by modulating movement intensity within active periods. Additionally, similar displacement peaks emerged from different movement strategies, including migration in Scandinavia and nomadism in Iberia.

Main conclusions: Environmental constraints reshape not only how much time animals spend active, but how effectively that active time is converted into movement. Climate warming may alter movement opportunities while leaving photoperiodic constraints unchanged, creating mismatches between behavioural schedules, energetic demands, and resource availability across wide-ranging species.