Linking the energetics of reproduction to population demography in a marine apex predator

• Applicant: Professor Dr. Oliver Krüger
• Subject Area: Sensory and Behavioural Biology ; Evolution, Anthropology
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 258933449

Changes in a population are due to changes in birth, death and/or immigration rates. A deeper understanding of the underlying mechanistic processes affecting these vital rates is essential for better estimation of population growth rates. This in turn, will allow the a priori assessment of the likely impact of environmental change on populations. We propose such a bottom-up approach to understand the linkage between environmental variation, the energetics of lactation and subsequent variation in juvenile survival and female fertility in a population of a marine apex predator, the Galapagos sea lion (Zalophus wollebaeki). Building on our long-term, individual-based study that has been running since 2003, we propose to measure the energetics of lactation by the doubly-labelled water method in combination with stable isotope analyses of yearlings. This will allow us to understand how variation in foraging behaviour of yearlings relates to variation in suckling behaviour. On the maternal side, we will be able to estimate the energetic cost of lactation and how this covaries with fertility schedules. This will provide us with an unusually detailed insight into how variation in vital rates arises from proximate processes. We will incorporate this variation in vital rates in age-structured matrix models where vital rate entries are functions of environmental variation. In a subsequent second model step, we will incorporate strong cohort effects and test the hypothesis that population stability is mainly due to some cohorts surviving and reproducing much better than average and that these average vital rate estimates do hence not capture the processes driving population growth. Our long-term sea lion study is hence in a unique position to combine proximate and ultimate factors because the population data and the large environmental perturbations allow us to gain a deep insight into the driving processes.

• DFG Programme: Research Grants
• International Connection: United Kingdom, USA
• Participating Persons: Professor Dr. Daniel Costa; Professor Dr. John Speakman; Professor Dr. Fritz Trillmich; Professorin Dr. Christiane Werner