10.6084/m9.figshare.12017805.v2 Mari Aas Fjelldal Mari Aas Fjelldal Kate Layton-Matthews Kate Layton-Matthews Aline Magdalena Lee Aline Magdalena Lee Vidar Grøtan Vidar Grøtan Maarten J. J. E. Loonen Maarten J. J. E. Loonen Brage Bremset Hansen Brage Bremset Hansen Results from Viterbi algorithm in E-SURGE from High-Arctic family planning: earlier spring onset advances age at first reproduction in barnacle geese The Royal Society 2020 population ecology age at first reproduction arctic climate change multi-event state uncertainty 2020-04-08 12:32:38 Journal contribution https://rs.figshare.com/articles/journal_contribution/Results_from_Viterbi_algorithm_in_E-SURGE_from_High-Arctic_family_planning_earlier_spring_onset_advances_age_at_first_reproduction_in_barnacle_geese/12017805 Quantifying how key life-history traits respond to climatic change is fundamental in understanding and predicting long-term population prospects<i>.</i> Age at first reproduction (AFR), which affects fitness and population dynamics, may be influenced by environmental stochasticity but has rarely been directly linked to climate change<i>.</i> Here, we use a case study from the highly seasonal and stochastic environment in High-Arctic Svalbard, with strong temporal trends in breeding conditions, to test whether rapid climate warming may induce changes in AFR in barnacle geese, <i>Branta leucopsis</i>. Using long-term mark–recapture and reproductive data (1991–2017)<i>,</i> we developed a multi-event model to estimate individual AFR (i.e. when goslings are produced). The annual probability of reproducing for the first time was negatively affected by population density but only for 2 year old, the earliest age of maturity. Furthermore, advanced spring onset (SO) positively influenced the probability of reproducing and even more strongly the probability of reproducing for the first time. Thus, because climate warming has advanced SO by two weeks, this likely led to an earlier AFR by more than doubling the probability of reproducing at 2 years of age. This may, in turn, impact important life-history trade-offs and long-term population trajectories.