1. Humans, as super predators, can have strong effects on wildlife behaviour, including profound modifications of diel activity patterns. Subsequent to the return of large carnivores to human-modified ecosystems, many prey species have adjusted their spatial behaviour to the contrasting landscapes of fear generated by both their natural predators and anthropogenic pressures. The effects of predation risk on temporal shifts in diel activity of prey, however, remain largely unexplored in human-dominated landscapes.
2. We investigated the influence of the density of lynx (Lynx lynx), a nocturnal predator, on the diel activity patterns of their main prey, the roe deer (Capreolus capreolus), across a gradient of human disturbance and hunting at the European scale.
3. Based on 11 million activity records from 431 individually GPS-monitored roe deer in 12 populations within the EURODEER network (http://eurodeer.org), we investigated how lynx predation risk in combination with both lethal and non-lethal human activities affected deer diurnality. 
4. We demonstrated marked plasticity in roe deer diel activity patterns in response to spatio-temporal variations in risk, mostly due to human activities. In particular, roe deer decreased their level of diurnality by a factor of 1.37 when the background level of general human disturbance was high. Hunting exacerbated this effect, as during the hunting season deer switched most of their activity to nighttime and, to a lesser extent, to dawn, although this pattern varied noticeably in relation to lynx density. Indeed, in the presence of lynx, their main natural predator, roe deer were relatively more diurnal. Overall, our results revealed a strong influence of human activities and the presence of lynx on diel shifts in roe deer activity.
5. In the context of the recovery of large carnivores across Europe, we provide important insights about the effects of predators on the behavioural responses of their prey in human-dominated ecosystems. Modifications in the temporal partitioning of ungulate activity as a response to human activities may facilitate human-wildlife coexistence, but likely also have knock-on effects for predator-prey interactions, with cascading effects on ecosystem functioning.

deer_id
Roe deer identity – individual-specific unique identifier for each monitored roe deer

year
Monitoring year [2003-2015]

julian_date
Number of days since January 1^st of a given year

area_subarea
Study area identity

subarea_name
Name of the subarea – when several subareas in a given study site

study_name
Name of the study site

hfi
Human Footprint Index – mean index of the overall level of human activities (based on Venter et al. 2016) within each individual’s seasonal home-ranges [4 - 34]

predator_presence
Predation risk - indexed by the presence of lynx and its relative density for each study site

no_lynx = absence of lynx

lynx_low = low density of lynx (sites with transient lynx and densities of ~ 1 lynx/100km²)

lynx_high = high density of lynx (sites with densities of ~ 2 lynx/100km²)

sex
m = males

f = females

diurnality_index
Index of diurnality (continuous) – relative level of activity during daylight compared to nighttime for each individual on each given day (see more details on the calculation in the manuscript)

crepuscularity_index
Index of crepuscularity – relative level of activity during daylight compared to nighttime for each individual on each given day (see more details on the calculation in the manuscript)

day_period
Period of the day related to the crepuscularity index (sunset or sunrise)