Effects of individual, population and environmental factors on parameters of reproductive success of female roe deer (Capreolus capreolus L.)

Flajšman, Katarina (author), Pokorny, Boštjan (mentor), Jerina, Klemen (comentor)

We studied the effects of various individual (age and body mass) and environmental factors (several factors, determining the habitat quality), and population density on selected parameters of reproductive potential of European roe deer (Capreolus capreolus L.) females. By determining the presence and counting number of corpora lutea in ovaries we determined fertility, potential litter size and potential reproductive output of roe deer females. We analysed 1894 samples (1312 of them were suitable for further statistical analyses) of female roe deer reproductive organs collected in the period 2013–2015 in 85 hunting grounds, covering whole gradient of roe deer abundance in Slovenia. The research was upgraded by the study on effects of body mass, population density and mean July temperature on reproductive success of does at the continental scale. For this, we performed the meta-analysis of data (population means), collected from 29 studies on 61 roe deer populations from 15 different European countries. Furthermore, we also determined the sex ratio of offspring, firstly based on 39 samples of uterus with developed foetuses, and secondly based on the data on 180 does culled together with their fawns in the period 2013–2015. Our results revealed a high reproductive potential of roe deer females in Slovenia: 97.6 % of females (both yearlings and adults) were fertile, potential litter size (when considering only fertile individuals) was 1.85, and potential reproductive output (when considering also non-ovulating females) was 1.80. Body mass was the most important influential factor that had positive effect on reproductive performance. The (positive) effect of body mass was age-related and its effect was more pronounced in yearlings than in adults. We detected a direct effect (after excluding the effects of age and body mass) of the mean annual temperature: with higher temperatures the reproductive ability increased. Population density did not have any influence on reproductive potential of roe deer females in Slovenia; however, the negative effect was confirmed at the European level where the gradient of population density is much larger. We observed pronounced inter-annual differences in reproductive parameters of yearlings, and also the differences among different regions of Slovenia (both in yearlings and adults). Sex ratio of foetuses was 1:0.9 in favour of males and sex ratio of fawns 1:1.1 in favour of females, but we did not find any clear influence of maternal body mass on the sex ratio of their offspring.

• Language: English
• Keywords: roe deer, Capreolus capreolus, reproduction, reproductive potential, litter size, fertility
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: BF - Biotechnical Faculty
• Year: 2017
• PID: 20.500.12556/RUL-99463
• COBISS.SI-ID: 4984486
• Publication date in RUL: 24.01.2018

Secondary language

• Language: Slovenian
• Title: Vpliv individualnih, populacijskih in okoljskih dejavnikov na izbrane parametre razmnoževalnega uspeha samic evropske srne (Capreolus capreolus L.)

Abstract

Ugotavljali smo vpliv individualnih (starost in telesna masa) in okoljskih dejavnikov (več dejavnikov, ki opredeljujejo kakovost habitata) ter populacijske gostote na izbrane parametre razmnoževalnega uspeha samic evropske srne – srnjadi (Capreolus capreolus L.). Plodnost in potencialno velikost legla smo določali s štetjem rumenih telesc v jajčnikih. Analizirali smo 1894 vzorcev rodil srn (1312 jih je bilo ustreznih za nadaljnje analize), odvzetih v obdobju 2013–2015 v 85-ih loviščih vzdolž celotnega gradienta prisotnosti srnjadi v Sloveniji. Vpliv povprečne telesne mase samic v populaciji, populacijske gostote srnjadi in julijske temperature na razmnoževalno sposobnost srn smo ugotavljali tudi na nivoju celotne Evrope, in sicer z meta-analizo podatkov, zbranih iz 29 raziskav oz. 61 populacij srnjadi iz skupno 15 evropskih držav. Ugotavljali smo tudi vplive na spolno razmerje mladičev, in sicer na podlagi 39 vzorcev z že razvitimi zarodki ter s pomočjo podatkovnih baz, iz katerih smo pridobili podatke o 180-ih srnah, uplenjenih skupaj z dvema mladičema v obdobju 2013–2015. Srne v Sloveniji imajo v splošnem velik razmnoževalni potencial: 97,6 % vseh analiziranih samic (mladic in odraslih srn) je bilo plodnih (so imele ovulacijo v letu, ko so bile odstreljene), povprečna potencialna velikost legla (upoštevaje samo plodne osebke) je bila 1,85, povprečna potencialna razmnoževalna sposobnost (upoštevaje tudi neplodne osebke) pa 1,80. Na razmnoževalno sposobnost srn je imela največji (pozitiven) vpliv telesna masa srn; vpliv je tudi starostno pogojen in je večji pri mladih kot starejših srnah. Med okoljskimi dejavniki je imela največji neposredni vpliv (po izločitvi vpliva starosti srn in vpliva telesnih mas) povprečna letna temperatura: z naraščanjem le-te se razmnoževalna sposobnost srn povečuje. Vpliva populacijske gostote srnjadi na nivoju Slovenije nismo zaznali, bil pa je potrjen na nivoju Evrope, kjer je gradient populacijskih gostot precej večji kot v Sloveniji. Ugotovili smo tudi izrazite medletne razlike v razmnoževalnih parametrih mladic in razlike v potencialni velikosti legla mladic ter odraslih srn med posameznimi regijami, ki so posledica različnih klimatskih in habitatnih dejavnikov. Ugotovljeno spolno razmerje zarodkov je bilo 1:0,9 v prid samčkov, spolno razmerje mladičev pa 1:1,10 v prid samičk, izrazitega vpliva telesnih mas mater na spolno razmerje pa nismo ugotovili.

• Keywords: evropska srna, Capreolus capreolus, razmnoževanje, razmnoževalni potencial, velikost legla, plodnost