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Lucky To Be Alive, Luckier to Breed: Lifetime Reproduction in Weddell Seals
Alexis A Diaz1, Jay J Rotella2, Kaitlin R Macdonald2
1Department of Biology, Stanford University, Stanford, California, USA.
Ecology Letters
|July 2, 2026
Summary
Lifetime reproductive success (LRS) in Weddell seals is highly variable and largely determined by chance. Environmental conditions significantly impact survival and breeding, highlighting the role of luck in lifetime outcomes.
Area of Science:
- Ecology
- Population Biology
- Animal Behavior
Background:
- Lifetime reproductive success (LRS) is crucial for understanding population dynamics.
- Quantifying LRS distributions in natural populations is challenging.
- Variation in LRS can arise from environmental factors and individual traits.
Purpose of the Study:
- To compute and compare lifetime reproductive success (LRS) distributions using theoretical and empirical approaches in Weddell seals.
- To investigate the influence of environmental conditions and individual heterogeneity on LRS distributions.
- To assess the role of chance in determining lifetime outcomes.
Main Methods:
- Long-term study of Weddell seals.
- Comparison of LRS and age-at-death distributions across different environmental conditions.
- Analysis of populations with varying individual heterogeneity (reproductive strategies).
- Comparison of theoretical LRS distribution with empirical LRS distribution.
Main Results:
- Iceberg conditions increased the probability of zero LRS.
- Individual heterogeneity had minimal impact on LRS distributions.
- Age-at-death distributions were skewed, with early mortality affected by environmental conditions.
- Theoretical LRS distribution closely matched the empirical distribution.
- High inequality in LRS was observed, with only 74% of surviving females breeding.
Conclusions:
- Lifetime reproductive success in Weddell seals is significantly influenced by environmental variability and chance.
- Environmental conditions, particularly iceberg presence, play a critical role in survival and reproductive output.
- A substantial portion of variation in lifetime outcomes appears to be governed by stochastic events.
Keywords:
Weddell sealsindividual heterogeneityintegral projection modelslifetime distributionslifetime reproductive successmatrix populations modelsreproductive inequalityMore Related Videos
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