DOI: 10.5061/dryad.x95x69pvd
title: Data from: Deriving birth timing of roe deer fawns from body measurements to limit mowing mortality

description: 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.
description: <strong>Data collection</strong>
 We systematically searched for roe deer fawns every day during
 springs (April 25 to June 30), 2020, and 2023, with four teams.
 Specifically, we systematically scanned agricultural areas at regular
 spatial intervals using unmanned aerial vehicles (UAV) (DJI Matrice 200
 with a DJI Zenmuse XZ2 thermal camera, DJI Mavic 2 Enterprise Advanced
 with an M2EA 640p thermal camera, and Yuneec H520 with a Yuneec CGOET10
 thermal camera). In addition, chains of people were formed to search for
 fawns in forested areas. Furthermore, in the spring of 2021 and 2023, we
 searched for fawns of female roe deer equipped with radio-gps collars
 (LiteTrack 360; LOTEK WIRELESS INC, Newmarket, Canada). Radiocollared does
 were monitored, and if movement parameters or physical appearance
 indicated birth (Baur et al., 2024), fawns were identified using thermal
 drones or thermal binoculars (Pulsar Accolade 2 LRF XP50).
 Our search teams, of two people each, were trained in advance to
 take standardized measurements of physical growth parameters and estimate
 the ages of the detected roe deer fawns. To estimate age, we evaluated the
 condition of the umbilical cord according to Jullien et al. (1992).
 Specifically, we differentiated eight umbilical cord conditions to
 determine fawn age during the first eight days of life. For fawns
 determined to be older than eight days, we retrospectively predicted their
 age based on our predictive model. To build this predictive model, we
 measured different conditions and constitutional parameters, namely body
 mass (BM), crown-rump length (CRL), and hind foot length (HFL), for each
 fawn detected by our search team. From spring 2022 onwards, the total body
 length (TBL) and head length (HL) were also measured. We used a folding
 meter stick to measure the HFL and a flexible measuring tape to measure
 the TBL, HL, and CRL (accuracy of 5 mm). The HL was measured from the tip
 of the nose to the top of the head between the ears. This point (the top
 of the head between the ears) was also the starting point for the CRL
 measurement. To measure this length, the measuring tape was extended along
 the dorsal line up to the tail stump. The TBL was measured in the same
 manner. To determine this, a measuring tape was placed along the dorsal
 line from the tip of the nose to the tail stump. Fawn BM was determined
 using the Pesola Spring Scale (Macro 5 kg; Macro 10 kg).<strong>
 </strong>Finally, we recorded sex and the presence of
 siblings. 
description: # Deriving birth timing of roe deer fawns from body measurements to limit
 mowing mortality
 [https://doi.org/10.5061/dryad.x95x69pvd](https://doi.org/10.5061/dryad.x95x69pvd) ## Description of the data and file structure The data file included in the submission consists of Stehr_2024_Data_roe_deer_fawn.csv. The study focuses on developing a robust method for estimating the birth timing of roe deer fawns using body measurements, drawing on a comprehensive dataset of over 1.300 individuals. By achieving greater accuracy in age estimation and identifying a shift in parturition timing, likely linked to environmental adaptability, our findings have critical implications for mitigating mowing-related mortality—a topic of increasing public and scientific concern. The integration of these results into wildlife management strategies has the potential to reduce the risk to neonate roe deer during agricultural mowing, a recurring issue that receives significant media and policy attention. Furthermore, the findings contribute valuable insights to the broader understanding of ungulate biology under changing environmental conditions. Since we worked with live animals and handling them during the measurements required increased caution, it was not always possible to collect all data. Missing data, which could not be measured, were marked as N/A in the dataset. ## Code/software All statistical analyses were performed using IBM SPSS Statistics version 29.0.1.0.