Timing and synchrony of birth in Eurasian lynx across Europe

Abstract

The ecology and evolution of reproductive timing and synchrony have been a topic of great interest in evolutionary ecology for decades. Originally motivated by questions related to behavioral and reproductive adaptation to environmental conditions, the topic has acquired new relevance in the face of climate change. However, there has been relatively little research on reproductive phenology in mammalian carnivores. The Eurasian lynx (Lynx lynx) occurs across the Eurasian continent, covering three of the four main climate regions of the world. Thus, their distribution includes a large variation in climatic conditions, making it an ideal species to explore reproductive phenology. Here, we used data on multiple reproductive events from 169 lynx females across Europe. Mean birth date was May 28 (April 23 to July 1), but was ~10 days later in northern Europe than in central and southern Europe. Birth dates were relatively synchronized across Europe, but more so in the north than in the south. Timing of birth was delayed by colder May temperatures. Severe and cold weather may affect neonatal survival via hypothermia and avoiding inclement weather early in the season may select against early births, especially at northern latitudes. Overall, only about half of the kittens born survived until onset of winter but whether kittens were born relatively late or early did not affect kitten survival. Lynx are strict seasonal breeders but still show a degree of flexibility to adapt the timing of birth to surrounding environmental conditions. We argue that lynx give birth later when exposed to colder spring temperatures and have more synchronized births when the window of favorable conditions for raising kittens is shorter. This suggests that lynx are well adapted to different environmental conditions, from dry and warm climates to alpine, boreal, and arctic climates. This variation in reproductive timing will be favorable in times of climate change, as organisms with high plasticity are more likely to adjust to new environmental conditions.

Keywords: Lynx lynx; carnivore; demography; reproductive phenology.

FIGURE 1

Lynx kitten in Slovenia on July 4th. Photo: Miha Krofel

FIGURE 2

Documented lynx reproduction events (N = 313) across Europe 1988–2021. Reproductive events were classified into three geographical regions based on latitude; >65°N (blue diamonds), 65–55°N (orange triangles), and <55°N (gray dots).

FIGURE 3

Distribution and density of reproductive events based on birth date represented as ordinal days separated between three different geographical regions; >65°N (blue), 55–65°N (orange), and <55°N (gray) and the vertical striped lines mean birth date for each region. The four birth dates later than ordinal day 190 were considered as outliers and are not included in the mean values, but are included here for illustration.

FIGURE 4

Eurasian lynx birth dates in relation to mean May temperature at 309 birth locations from 167 female lynx. Dots represent raw data (overlapping points give darker color), and the line shows the estimated birth date with 95% confidence intervals from a linear model including female lynx ID as a random intercept.

FIGURE A1

Distribution of reproductive events based on latitude at birth site. Based on this, events were classified into three regions; >65°N, 55–65°N, and <55°N. Data <45°N was too scarce to be separated out.

FIGURE A2

Timing and synchrony in birth dates of lynx in three geographical regions, separated by latitude, across Europe.

FIGURE A3

Variation in birth date for individual lynx females among years (i.e., number of days between the earliest and the latest birth date observed for the same female). Counts of observations (y‐axis) are stacked and colors represent the geographical region of the female.

FIGURE A4

Predicted probabilities (with 95% CI) of survival for lynx kittens depending on (a) timing of birth, (b) litter size, and (c) geographical region. Birth dates (ordinal dates 1–365) were standardized on regions before entering the model and the lowest and highest values represent relatively early and late birth dates in each region. Dots in a) represent raw data. Note that the 95% CI in (a) and (c) are to large to draw any meaningful conclusions.

FIGURE A5

Relationship between mean temperature in May and elevation at birth site locations for Eurasian lynx in three different geographical regions based on latitude; >65°N (blue), 55–65°N (orange), and < 55°N (gray).