Male Reproductive Senescence in Mammals Is Pervasive and Aligned With the Slow-Fast Continuum

Area of Science:

• Evolutionary biology
• Reproductive biology
• Gerontology

Background:

• Reproductive senescence is well-documented in female mammals but poorly understood in males.
• Challenges in paternity assignment have historically limited studies on male reproductive senescence.

Purpose of the Study:

• To investigate the occurrence and drivers of male reproductive senescence across diverse species.
• To identify ecological and evolutionary factors influencing the onset and rate of male senescence.

Main Methods:

• Compiled age-specific reproductive data (mating and success) from a standardized literature search.
• Included data from 57 species across 73 populations.
• Analyzed senescence occurrence and intensity relative to life history traits and sexual selection.

Main Results:

• Evidence of male reproductive senescence found in 59.6% of species studied.
• Senescence detection improved with larger sample sizes and longer relative age ranges.
• Senescence onset and rate correlated with the slow-fast life history continuum; fast-living species showed earlier, stronger senescence.
• Senescence rate increased with sexual size dimorphism, indicating steeper decline in species with high sexual selection.

Conclusions:

• Male reproductive senescence is a widespread phenomenon influenced by life history strategies.
• Species with faster life histories and higher sexual selection experience more pronounced male reproductive senescence.
• Understanding male senescence is crucial for a complete picture of reproductive aging in animals.