Extremely low primary production after a decade long drought contributed to the local extinction of a group-living rodent

Annemarie van der Marel , Madan K Oli, Azad Hossain, Praveena Krishnan, Tim Wilson, Loreto Correa, Luis A Ebensperger, Loren D Hayes

Some species exhibit physiological and behavioral plasticity to survive adverse periods, such as changing climates or reduced food availability. Yet, during extreme climatic events the mechanisms to respond to these adverse periods may not be sufficient, potentially driving local population extinctions. We studied the population dynamics of a common degu (Octodon degus) population in central Chile using a 12-year long dataset (2009-2020) and investigated what environmental factors affected recruitment, survival and population growth. Our study period also coincided with a decade-long megadrought, allowing us to examine how this extreme climatic event contributed to the observed local extinction of this population in 2020. We used Pradel’s capture–mark–recapture (CMR) modeling framework to assess what factors influence population parameters. We analyzed two seasons: the breeding season, which aligns with the austral winter and coincides with the mating, gestation and lactation period, and the nonbreeding season spanning austral spring, summer, and fall, which coincides with offspring care. We found that survival and recruitment varied by year, season, and sex. Female survival was higher during the breeding season than in the nonbreeding season whereas male survival was higher in the nonbreeding season. Recruitment primarily occurred during the breeding season and was higher for males. Population growth was positive from 2009 to 2019. When incorporating environmental covariates, season, and sex, we found that survival was primarily driven by gross primary production, and recruitment by seasonality and gross primary production. We suggest that a year with very low gross primary production, induced by a decade-long megadrought contributed to the local extinction of this population. Our results provide important insight into which populations may be vulnerable to population declines in face of a changing climate, or instead, will be resilient to forecasted climate change.