Data from: Deriving birth timing of roe deer fawns from body measurements to limit mowing mortality

Every spring, hiding roe deer fawns (Capreolus capreolus L.) in meadows
are injured or killed by mowing activities. To assess the temporal overlap
between mowing activities and the fawning period, and thus help reduce the
risk of mowing death, we have determined the average parturition date in
three regions of Bavaria, southern Germany. Data on physical body
parameters were collected from 1387 fawns over four consecutive springs
(2020-2024). Across all of the years studied, data collection started at
the end of April, independent of spring mowing activities. We searched for
fawns mainly using unmanned aerial vehicles (UAV) and recorded the status
of the umbilical cord, body mass, hind foot length, total body length,
head length, crown-rump length, and presence of siblings of each detected
fawn. A total of 118 of the 1387 fawns were found and measured multiple
times. To estimate age, we fitted a generalized linear mixed model (GLMM)
as a function of multiple physical parameters and subsequently determined
the age and birth date of all fawns based on this predictive model. Body
mass, head length, crown-rump length, and the presence of siblings were
the most important predictors of fawn age (R2 = 0,74). The estimated ages
were used to calculate the mean parturition dates for the region. The
results show that the first fawns were born as early as April. Across
years the mean parturition date was the 135 day of the year (DOY). Our
results confirmed that fawn birth dates and the hiding phase highly
overlapped with spring mowing events. However, based on the derived
knowledge of the exact birth times, our study can contribute to reducing
mowing-related mortalityrates. Our predictive model may also provide
researchers in other regions with an approach to accurately determine the
ages of roe deer fawns.