# Interaction Between Age and Individual Heterogeneity Shapes Breeding Probability in a Long‐Lived Marine Ectotherm

## TL;DR

A 52-year study on green turtles shows that individual quality and age strongly influence breeding patterns, with high-quality turtles breeding more consistently and maintaining reproductive value into old age.

## Contribution

The study reveals lifelong individual differences shape life histories in long-lived marine vertebrates, a factor previously overlooked due to monitoring challenges.

## Key findings

- High-quality turtles are more likely to breed consistently over consecutive years.
- Older turtles show a stronger link between individual quality and breeding status.
- Females maintain high residual reproductive value into old age despite physical aging.

## Abstract

In iteroparous species, reproductive skipping is generally considered an adaptive strategy. Non‐breeding individuals should have a greater annual survival probability and retain greater future reproductive potential. Yet, the role of age on changes in breeding probability remains untested in many long‐lived testudines. To bridge this knowledge gap, we leveraged a 52‐year dataset on captive green turtles, an ancient lineage of marine ectotherms. Sea turtles serve as an interesting model system because they exhibit a reproductive strategy characterized by delayed maturity followed by intense reproductive bursts. Using a multi‐event capture‐mark‐recapture framework, our results reveal that individual quality and age were the primary drivers of reproductive patterns. High‐quality turtles were more likely to remain breeders in consecutive years, and low‐quality turtles were more likely to remain non‐breeders, an effect that became more dramatic at older ages. Furthermore, there was an antagonistic relationship between age and breeding experience on the waiting time between breeding seasons. At the population level, we found evidence of actuarial [survival] senescence but negligible reproductive senescence, with females maintaining a high residual reproductive value into old age. Collectively, our findings demonstrate the role of lifelong individual differences in shaping life histories, a fact that has been historically overlooked in long‐lived marine vertebrates like sea turtles, largely due to the immense logistical challenge of monitoring individuals over timespans that may equal a single academic career.

Using a 52‐year dataset on captive green turtles, our study reveals that individual quality and age are the primary drivers of reproductive patterns. We found that high‐quality turtles bred more consistently throughout their lives and that females maintained a high reproductive value into old age despite evidence of physical aging. These findings demonstrate the critical and historically overlooked role of lifelong individual differences in shaping the life histories of long‐lived marine vertebrates.