Parturition date for a given female is highly repeatable within five roe deer populations

Area of Science:

• Reproductive Biology
• Animal Behavior
• Ecology

Background:

• Mammalian births are often synchronized, but individual female repeatability of parturition date is poorly understood.
• Previous studies in birds show repeatable laying dates, but evidence in mammals is limited.
• Variability in repeatability across different mammal populations has not been assessed.

Purpose of the Study:

• To quantify the repeatability of parturition date in individual female roe deer.
• To assess between-population variability in this repeatability.
• To investigate lifetime changes in parturition timing relative to age.

Main Methods:

• Longitudinal study of parturition dates in five roe deer populations.
• Statistical analysis to determine repeatability of birth timing for individual females.
• Examination of age-related trends in parturition dates.

Main Results:

• Parturition date repeatability in roe deer varied significantly between populations (0.54–0.93).
• Individual females consistently gave birth earlier or later each year.
• All females exhibited a trend of giving birth progressively earlier with advancing age.

Conclusions:

• Roe deer display the highest parturition date repeatability reported for any mammal, indicating low phenotypic plasticity.
• Consistent timing suggests strong selective pressures or constraints on reproductive phenology.
• Early birth timing, potentially beneficial for offspring survival, was achieved by few females.