Sun Ruijiao

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  • Article
    Causes and consequences of pair‐bond disruption in a sex‐skewed population of a long‐lived monogamous seabird
    (Ecological Society of America, 2022-04-01) Sun, Ruijiao ; Barbraud, Christophe ; Weimerskirch, Henri ; Delord, Karine ; Patrick, Samantha C. ; Caswell, Hal ; Jenouvrier, Stephanie
    Many animals form long-term monogamous pair bonds, and the disruption of a pair bond (through either divorce or widowhood) can have significant consequences for individual vital rates (survival, breeding, and breeding success probabilities) and life-history outcomes (lifetime reproductive success [LRS], life expectancy). Here, we investigated the causes and consequences of pair-bond disruption in wandering albatross (Diomedea exulans). State-of-the-art statistical and mathematical approaches were developed to estimate divorce and widowhood rates and their impacts on vital rates and life-history outcomes. In this population, females incur a higher mortality rate due to incidental fishery bycatch, so the population is male-skewed. Therefore, we first posited that males would show higher widowhood rates negatively correlated with fishing effort and females would have higher divorce rates because they have more mating opportunities. Furthermore, we expected that divorce could be an adaptive strategy, whereby individuals improved breeding success by breeding with a new partner of better quality. Finally, we posited that pair-bond disruptions could reduce survival and breeding probabilities owing to the cost of remating processes, with important consequences for life-history outcomes. As expected, we showed that males had higher widowhood rates than females and females had higher divorce rates in this male-skewed population. However, no correlation was found between fishing effort and male widowhood. Secondly, contrary to our expectation, we found that divorce was likely nonadaptive in this population. We propose that divorce in this population is caused by an intruder who outcompetes the original partner in line with the so-called forced divorce hypothesis. Furthermore, we found a 16.7% and 18.0% reduction in LRS only for divorced and widowed males, respectively, owing to missing breeding seasons after a pair-bond disruption. Finally, we found that divorced individuals were more likely to divorce again, but whether this is related to specific individual characteristics remains an important area of investigation.
  • Thesis
    Causes and consequences of pair-bond disruption in socially monogamous species
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2023-09) Sun, Ruijiao ; Jenouvrier, Stephanie
    Many animals, from crustaceans to humans, form socially monogamous pair-bonds which are maintained during one or more consecutive breeding seasons. However, the ecological consequences of the disruption of monogamous pair-bond have rarely been addressed because it is difficult to estimate the rates and demographic impacts of pairbond disruption (divorce or widowhood). This dissertation investigates the effect of global changes and individual heterogeneity on pair-bond disruption (divorce or widowhood) and their consequences for vital rates and life-history outcomes for socially monogamous species. In Chapter 2 and Chapter 4, analyses of long-term demographicdatasets reveal different patterns of pair-bond dynamics between the population of wandering albatross (Diomedea exulans) breeding in sub-Antarctica and the snow petrel (Pagodroma nivea) breeding in Antarctica. In wandering albatross, divorceis nonadaptive with no improvement in breeding success, while divorce triggered by breeding failure is adaptive in Snow Petrels, resulting in a higher subsequent breeding success. Widowhood rates are male-biased due to lower survival rates of females in wandering albatrosses. In both wandering albatross and snow petrel, remaining single after a pair-bond disruption results in a reduction in individual lifetime reproductive success due to missed breeding seasons. Chapter 3 presents a link between individual personality and divorce in wandering albatrosses demonstrating the important implications of behavior types for the dynamics of social relationships. Personality was measured on a shy-bold continuum, linked to individual risk-taking tendencies, with bolder individuals more likely to take risks and shyer individuals. In wandering albatrosses, shyer males exhibit higher divorce rates than bolder males but no such relationship was found in females. Chapter 4 shows that environmental fluctuations can affect the prevalence of pair-bond disruption in snow petrels, with higher rates of pair-bond disruption under unfavorable environmental conditions. Moreover, the findings suggest a potential increase in the prevalence of pair-bond disruption towards the end of the current century. As a whole, this thesis advances our understanding of the effects of pair-bond disruption on demography which should not be ignored when providing guidelines for the conservation and management of endangered species.