Understanding demographic and genetic change in a recovering population through simulation modelling

The 27+ year study of the spotted hyena (Crocuta crocuta) in the Ngorongoro Crater, Tanzania, provides us with a unique opportunity to study the causes and consequences of demographic changes, genetics changes, and their interplay in a wild recovering population of a group-living mammal. To achieve this goal, we tailored an individual based simulation model (aka SHIM) to study a wide range of questions, covering both basic research as well as questions that have practical implications for conservation.

Project details
Duration: since 2020
Third-party funded: yes
Involved Department(s): Dept Evolutionary Ecology, Dept Evolutionary Genetics
Leibniz-IZW Project Leader(s):
Oliver Höner (Dept Evolutionary Ecology)
Leibniz-IZW Project Team:
(all: Dept Evolutionary Genetics)
Consortium Partner(s): -
Current Funding Organisation: DFG position awarded to Liam Bailey
Research Foci: -

Project details

Simulation modelling of wild animal populations is a useful tool to study how changes in individuals impact a population as a whole. Based on data from a 27+ year study of the spotted hyena (Crocuta crocuta) in the Ngorongoro Crater, Tanzania we have built an individual (agent) based model that incorporates social, demographic, and genetic information to create a robust simulation of this large,  group-living carnivore. We are using our demo-genetic model – called SHIM – to study and disentangle  the impacts of environmental, genetic, and demographic changes, as well as the role of conservation management strategies, upon various characteristics of the population. This work helps us better understand a keystone species in many African ecosystems and, more broadly, provides insights into the factors and mechanisms determining the recovery of wildlife populations.

Current research questions

Why did the spotted hyena population recover?
The Ngorongoro spotted hyena population has more than doubled in size since the beginning of its survey in April 1996. Using a combination of statistical analyses and simulation work, we study how different factors such as epidemics, competition, or conservation actions shape past and future number of individuals in this population. We also investigate how the recovery of the environment connects to that of the population. In this context, we also develop methods to assess changes in carrying capacity over time.

What is the impact of inbreeding depression in the population?
As wild populations become smaller or more disconnected due to human actions, inbreeding is likely to become more problematic. Thanks to its very close monitoring, who breeds with whom is well documented in the Ngorongoro spotted hyena population and both inbreeding levels and vital rates (survival, reproduction) are robustly inferred. We combine statistical analyses and simulation modelling to measure how inbreeding depression impacts the population as a whole. We do so by emulating the population as it is, but also as it could be under different counterfactual scenarios (e.g. under different mate choice scenarios or different conservation management strategies).