Data from: Large scale variation in birth timing and synchrony of a large herbivore along the latitudinal and altitudinal gradients

1. Hopkins’ Bioclimatic Law predicts geographic patterns in phenological
timing by establishing a correspondence between latitudinal and
altitudinal gradients. First proposed for key phenological events of
plants, such as leaf sprouting or flowering dates, this law has rarely
been used to assess the geographical equivalence of key life history
traits of mammals. 2. We hypothesize that (H1) parturition dates of
European roe deer (Capreolus capreolus) are delayed and more synchronized
at higher latitudes and altitudes, (H2) parturition timing varies along
latitudinal and altitudinal gradients in a way that matches the Hopkins’
Bioclimatic Law, and (H3) females adjust parturition timing to match the
period of high energy demand with peak resource availability. 3. We used
parturition dates of 7,444 European roe deer from Switzerland to assess
altitudinal variation in birth timing and synchrony from 288 to 2,366 m
a.s.l. We then performed a literature survey to compare altitudinal
results with those from different populations along the species’
latitudinal range of distribution. Finally, we performed spatial analysis
combining our highly resolved altitudinal data on parturition dates with
plant phenology data. 4. As expected, parturition dates were delayed with
increasing latitude and altitude. This delay matched the Bioclimatic Law,
as the effect of 1º increase in latitude was similar to 120 m increase in
altitude. However, while parturitions were more synchronized with
increasing altitude, we did not detect any trend along the latitudinal
gradient. Finally, plant phenology explained altitudinal variation in
parturition timing better than a linear effect of altitude. 5. Our
findings clearly demonstrate the ability of a large herbivore to match
parturition timing with phenological conditions across the altitudinal
gradient, even at the smallest spatial scales.