DOI: 10.5061/dryad.4qrfj6qmt
title: Drivers of individual differences in the sleep behaviour of fallow deer neonates

description: Inter-individual differences are necessary for selection to act, while
 plasticity (intra-individual variation) may buffer against selection.
 Sleep is a critical self-maintenance behaviour but, unlike most
 behaviours, the causes and consequences of its inter- and intra-individual
 variation in wild animals is poorly understood, particularly in neonates
 where sleep plays a key role in development. We have shown previously that
 free-ranging neonate fallow deer (Dama dama) differ in sleep during the
 first few weeks of life. Here, we test whether individual variability in
 sleep is organised systematically across the population, and whether these
 individual differences are associated with chronic stress measured using
 hair cortisol, or the timing of birth. Four dimensions of sleep behaviour
 (total sleep time, sleep fragmentation, sleep quality, and sleep
 distribution over 24-hours) were quantified using state-of-the-art
 triaxial accelerometers. We then used a multivariate mixed-effects model
 in a Bayesian framework to evaluate covariation between multiple
 dimensions of sleep behaviour, and quantify the relative importance of
 chronic stress and the timing of birth, while accounting for the
 confounding effects of environmental conditions and age. We found that the
 timing of birth and chronic stress were not associated with changes in
 sleep between individuals. While both total sleep time and the number of
 bouts per day declined with age, their rate of development covaried, but
 no other sleep dimensions covaried. Our results represent an in-depth
 analysis of natural variation in sleep, and show that individual
 differences in 4 aspects of sleep architecture in free-living fallow deer
 fawns are strong but independent of one another, and unrelated to chronic
 stress or the timing of birth. We suggest that covariation between sleep
 dimensions might emerge later in life and effects of cortisol and birth
 timing might be very short and transient.
description: # Drivers of individual differences in the sleep behaviour of fallow deer
 neonates
 [https://doi.org/10.5061/dryad.4qrfj6qmt](https://doi.org/10.5061/dryad.4qrfj6qmt) ## Description of the data and file structure ### Files and variables #### File: manuscript\_data.csv ##### Description: ##### Variables * tst_mins: total minutes slept for that date and individual * age_days_scaled: age in days (centered and scaled) for that date and individual * temp_c_scaled: mean temperature in degrees C (centered and scaled) for that date * birthdate_jd_scaled: birth date in julian days for that individual * cort_pgmg_scaled: hair cortisol measure in pg/mg for that individual * animal_id: unique animal ID * year: data collection year * ds_pct: distribution of sleep, the % of total sleep occurring between sunrise and sunset for that date and individual * bouts: total number of sleep bouts for that date and individual * longest: duration of longest sleep bout in minutes for that date and individual * humidity_pct_scaled: mean humidity as % (centered and scaled) for that date and individual * precip_mm_scaled: total precipitation in mm (centered and scaled) for that date and individual