Cumulative costs of reproduction in a long-lived ungulate.

Cumulative costs of reproduction are predicted by life-history theories of aging, but empirical support for cumulative costs of reproduction in ungulates is limited. Examinations of the relationship between previous reproductive effort and future reproductive output are often limited to successive years. We analyzed pregnancy status, lactation duration, and age class of Elk (Cervus canadensis) in Utah, United States, from 2019 to 2022 to better understand the relationship between previous reproductive effort and future reproductive output, particularly in nonsuccessive years. Pregnancy status 1 year prior, pregnancy status 2 years prior, and age had no effect on the likelihood of pregnancy in Elk. However, lactation duration 1 year prior and lactation duration 2 years prior had a negative effect on the likelihood of pregnancy. The best-fitting model to explain the relationship between pregnancy status and previous lactation was the positive interaction between lactation duration 1 year prior and lactation duration 2 years prior. The results of our study suggest long-lasting (i.e., multiple-year), cumulative costs of reproduction can influence reproductive output in female Elk, but differences in individual quality may have an even greater influence. High-quality individuals may be able to override the costs of reproduction and minimize reproductive trade-offs.