Age-independent and age-dependent decreases in reproduction of females

• Published in: Ecology letters Vol. 14; no. 6; pp. 576 - 581
• Main Authors: Martin, Julien G. A., Festa-Bianchet, Marco
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.06.2011; Blackwell
• Subjects: Age; Age at death; Age Factors; Animal and plant ecology; Animal reproduction; Animal, plant and microbial ecology; Animals; Biological and medical sciences; Female; Fertility; Fundamental and applied biological sciences. Psychology; General aspects; Hypothesis testing; Longevity; Male; Reproduction; reproductive effort; senescence; Sexual Behavior, Animal; Sheep - physiology; terminal allocation; Reproductive effort; Reproduction; Senescence; Female; terminal allocation; Age; Age at death
• ISSN: 1461-023X; 1461-0248
• DOI: 10.1111/j.1461-0248.2011.01621.x

Ecology Letters (2011) 14: 576–581 The terminal allocation and senescence hypotheses make opposite predictions about how age‐specific reproductive effort should vary during old age. There is empirical support for both hypotheses, although reports on senescence are more numerous. Individual heterogeneity and selective mortality, however, decrease our ability to measure how reproductive effort varies during late life. The damage accumulation model proposes that terminal allocation and senescence could be partly age‐independent. Using a reverse‐age approach, we analysed an unusually complete record of annual reproductive success for 90 bighorn ewes that died between 7 and 18 years of age. We estimated age‐specific and age‐independent variation of reproductive effort in late‐life. Reproductive effort decreased in the two last reproductions, independently of age at death. Fecundity also decreased in the last 2 years of life, with a steeper decline for older individuals. Our study reveals that reproductive senescence includes both age‐dependent and age‐independent components.