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

• Final Report Year: 2020

Final Report Abstract

The evolution of life histories in Galapagos sea lions happened under great environmental uncertainty. Working with Galapagos sea lions was and is still a challenge for me, but the project has been very successfully established by my predecessor Fritz Trillmich and the ongoing collaboration between us is very rewarding from my side. Despite two major problems in terms of permits and logistics during the last funding period, we have shown that there is great variation in the age at first reproduction (4-9 years), but that there are currently no significant factors explaining this variation. It appears on current evidence that once females start their reproductive careers, they do not seem to vary either inter-birth interval or pupping rate in response to whether they started early or late nor whether they were born in good or bad conditions. Females give birth to around 0.4 pups per year and there is no evidence of a decline in old ages, either due to low sample sizes or absence of effects. We have been able to produce survival rate estimates for the entire length of the life history for the first time and they are at the lower bound in comparison to other pinnipeds. Combining both vital rates in a matrix model yielded population projections that mostly predict very negative population growth rates over the next 50 years. First evidence from census data also seem to indicate that the population is in decline. Being able to closely observe the behaviour of sea lion pups and their mothers, we were able to establish protocols and tests to document animal personalities in these pups and mothers. Behaviour of pups is systematically affected by the presence of their mothers. We very recently showed that these personalities are related to space-use on the island.

Publications

• (2016) Complex interpretation of census data: insights from a study of an endangered pinniped. PLoS One 11: e0154588
  Trillmich, F., Meise, K., Kalberer, S., Mueller, B., Piedrahita, P., Pörschman, U., Wolf, J. B. W. & Krüger, O.
  
• (2018) Recent demographic histories and genetic diversity across pinnipeds are shaped by anthropogenic interactions and mediated by ecology and life-history. Nature Comms. 9: 4836
  Stoffel, M. A., Humble, E., Paijmans, A. J., Acevedo-Whitehouse, K., Chilvers, B. L., Dickerson, B., Galimberti F., Gemmell, N., Goldsworthy, S. D, Nichols, H. J., Krüger, O., Negro, S., Osborne, A., Pastor, T., Robertson, B. C., Sanvito, S., Schultz, J., Shafer, A. B. A., Wolf, J. B. W. & Hoffman, J. I.
  
• (2018) Reproductive performance of a tropical apex predator in an unpredictable habitat. Behav. Ecol. Sociobiol. 72: 108
  Kalberer, S., Meise, K., Trillmich, F. & Krüger, O.
  
• (2019) Evolution of age at primiparity in pinnipeds in the absence of the quality-quantity trade-off in reproduction. Ecol. Evol. 9: 5450-5456
  Kalberer, S., DeRango, E., Trillmich, F. & Krüger, O.
  
• (2019) Intraspecific variation in boldness and exploration shapes behavioral responses to stress in Galápagos sea lion pups. Behav. Ecol. Sociobiol. 73:166
  DeRango, E., Schwarz, J. F. L., Piedrahita, P., Paez-Rosas, D., Trillmich, F. & Krüger, O.
  
• (2019) Intrinsic and maternal traits influence personality during early life in Galápagos sea lion (Zalophus wollebaeki) pups. Anim. Behav. 154: 111-120
  DeRango, E., Kalberer, S., Schwarz, J., Paez-Rosas, D., Piedrahita, P., Trillmich, F. & Krüger, O.