Causes and consequences of pair-bond disruption in a sex-skewed population of a long-lived monogamous seabird

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Ruijiao Sun, Biology Department, Woods Hole Oceanographic Institution, Falmouth, MA, Ruijiao Sun, The Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, Henri Weimerskirch and Christophe Barbraud, Centre d'Etude Biologiques de Chizé, Villiers en Bois, France, Karine Delord, Centre d'Etudes Biologiques de Chizé, Villiers en Bois, France, Samantha C. Patrick, School of Environmental Sciences, University of Liverpool, Liverpool, United Kingdom, Hal Caswell, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, Netherlands, Stephanie Jenouvrier, Biology department, Woods Hole Oceanographic Institution, Woods Hole, MA

Background/Question/Methods
Many animals form long-term monogamous pair-bonds, and the disruption of a pair-bond (through either divorce or widowhood) can have important demographic consequences.
However, little is known about the causes and consequences of pair-bond disruption in long-lived monogamous species.
Here, we investigated causes and consequences of pair-bond disruption by distinguishing divorce from widowhood in a male-skewed population of wandering albatross (Diomedea exulans).
We developed a novel Multi-Event Capture Mark Recapture model (MECMR) to estimate divorce and widowhood rates.
Results/Conclusions
We found that females had a higher divorce rate and a lower probability to become widowed than males.
We hypothesized that higher widowhood rates in males can be caused by higher mortality rates of females due to incidental fishery bycatch.
However, we found no correlation between fishing effort and widowhood rates.
We also suggested that divorce may be an adaptive strategy, with females having more opportunities to mate with a new partner in this male-skewed population.
Interestingly, divorced individuals were more likely to divorce again.
However, lower previous and long-term breeding performance with a partner did not increase divorce rates. Furthermore, no immediate or long-term change of breeding success was found as a result of divorce, which suggests that divorce may be a non-adaptive process.
Conversely, breeding success was positively related to divorce in females suggesting different life-history strategies related to individual quality.
Finally, our modeling framework allowed us to characterize the consequences of pair-bond disruption on vital rates and life-history outcomes using Markov chain models.
We showed that pair-bond disruption had no direct impact on survival and reproduction.
However, we found a 16.7% and 18.0% reduction in Lifetime Reproductive Success (LRS) for divorced and widowed males, respectively, compared to individuals remaining in a pair-bond.
This was not due to a direct effect on reproductive success itself but was instead driven by a reduction in breeding frequency due to the long duration of remating processes.
We found that divorce is a repeatable trait, and further research is needed to understand why some individuals divorce more often, especially since pair-bond disruption imposes a significant cost on LRS because of fewer breeding opportunities.