Individual behaviour mediates effects of warming on movement across a fragmented landscape

Abstract

Summary Global warming and habitat fragmentation impose dramatic and potentially interactive impacts on ecosystems. Warming induces shifts in species' distributions as they track temperature changes, but this can be hindered in fragmented landscapes. Corridors connecting habitat patches might ameliorate the combined effects of fragmentation and global warming. Using novel automated tracking methods, the movement of woodlice (Oniscus asellus) ranging in body size from 15·3 to 108·6 mg was quantified across a temperature range from 15 to 25 °C as they moved around an experimental fragmented landscape. We used confirmatory path analysis to test causal effects of temperature and body size on individual movement and corridor crossing rates between two habitat patches. Results showed that woodlice behaved differently in corridors than patches by moving, on average, faster and more often. This is congruent with natural systems where corridors generally provide lower quality habitat than patches. Although metabolic theory suggests positive scaling of movement with body temperature (up to a peak) and body size, we found that corridor crossing rate was (i) not directly affected by body size and (ii) negatively influenced by temperature, possibly due to its indirect effects via humidity. Our path model revealed that metabolic scaling could only explain temperature effects on maximum body velocity, but decision‐based behaviour explained most variation in corridor crossing rates. This led to direct and indirect effects of temperature and size on individual movement between habitat patches. Our findings suggest that increasing mean global temperatures, coupled with increasing habitat fragmentation, could have synergistic negative impacts on populations through a combination of physiological and behavioural factors that mediate individual responses to temperature and fragmentation.