Climate, female traits and population features as drivers of breeding timing in Mediterranean red deer populations

Abstract

Understanding the factors that lead to variation in the timing of breeding in widespread species such as red deer (Cervus elaphus) is crucial to predict possible responses of wild populations to different climate scenarios. Here, we sought to further understand the causes of inter-annual variation in the reproduction timing of female deer in Mediterranean environments. An integrative approach was used to identify the relative importance of individual, population and climate traits in the date of conception of free-ranging deer, based on a dataset of 829 hinds culled during 12 years. We found that a population trait, density, was the most important factor explaining the variation in conception dates, with greater densities causing later conception dates. Body mass was the second in importance, with heavier females conceiving earlier than lighter ones. Almost equally important was the spring real bioclimatic index, a measure of plant productivity, causing later conception dates in the least productive springs (drier and hotter). Another climatic component, the end of summer drought, showed that the sooner the autumn arrives (greater rainfalls and cooler temperatures) the earlier the conception dates. Interestingly, age class was found to be a minor factor in determining conception date. Only older females (≥10 years old) conceived significantly later, suggesting reproductive senescence. This study highlights not only the importance of population and individual traits but also the influence of climatic parameters on the deer reproductive cycle in Mediterranean environments, giving valuable insight into how reproductive phenology may respond to seasonality and global climate changes.

Habitat and Harvesting Practices Influence Horn Growth of Male Ibex

“…We combined average monthly temperature and precipitation with water runoff and soil water retention capacity to calculate the Real Bioclimatic Index (RBI). The RBI is considered a plant productivity indicator and a proxy of resources availability (Peláez et al 2017). We calculated the RBI for 2 periods of particular relevance for vegetation productivity and horn growth: the green‐up period (Apr–May) and the start of the senescence period (Aug–Sep) because horn growth patterns are age‐ and season‐dependent (e.g., spring‐summer conditions are those experienced by males during the growth stage).…”

“…The RBI positive values represent good conditions for vegetation growth (precipitation and warm temperatures), whereas negative values express limited primary production (no precipitation, drought). Further details on RBI calculation are specified by Martínez‐Jauregui et al (2009) and Peláez et al (2017).…”

Progesterone and Cortisol Levels in Blood and Hair of Wild Pregnant Red Deer (Cervus Elaphus) Hinds

“…The red deer (Cervus elaphus L., 1758) species, as the majority of the cervid taxa, shows a very deep relationship between its peculiar reproductive physiology and the their living environment [1]. It is widely diffused in almost all of continental Europe; in Italy it can be identified in a large Alpine area that extends from Cuneo to Udine, while in the Apennines the red deer occupies four distinct areas: the first corresponds to most of the mountain territory of the provinces of Pistoia, Prato, Florence, and Bologna, the second to the Tuscan-Romagna Apennines, the third is represented by the Abruzzo National Park together with the neighboring territories and the fourth by the mountain massif of the Maiella.…”

“…In order to guarantee a good survival rate and growth of the offspring, hinds need to give birth at an appropriate time [4]. In the Mediterranean area, calves are usually born in spring and lactation goes on during summer [1], in order to exploit the most favorable time of the year, implying an extremely high synchronization between male and female reproductive activity during the rutting period. Red deer hinds are seasonally polyestrous, with a mean length of the estrous cycle of 18 ± 7 days and a gestation of approximately 231 days [5].…”

Ambient temperature provides an adaptive explanation for seasonal reproduction in a tropical mammal

“…Importantly, the factors which drive natural selection for reproducing at certain times of year (ultimate causes) may differ from the cues which trigger reproduction (proximate causes, Tinbergen, 1963). In the red deer example above, food availability provides an adaptive explanation for reproductive timing, but photoperiod plays an important role in triggering reproductive activity (Webster & Barrell, 1985;Simpson, Suttie & Kay, 1984), alongside nutrition (Pelaez et al, 2017). In red deer, as in most other temperate-zone mammals (Bronson, 1985), photoperiod acts as a cue which allows animals to predict likely future food availability in seasonal environments.…”