This study takes place in the context of emerging infectious diseases now recognized as a major threat to biodiversity. The impact of Ebola epidemics which induced up to 95% mortality in Western lowland gorilla populations (Gorilla gorilla gorilla) led to the classification of this taxon as "critically endangered". This study focuses on the recovery potential of gorilla populations after Ebola. On the basis of a unique set of data in preand post-epidemic periods, we evaluated the impact of the epidemic on the social structure and dynamics of a population. We then estimated its potential of recovery during the six years following the outbreak. Our results on demography and dynamics, coupled with statistical approaches and a modeling work at a demographic age and sex level, including immigration, showed 1) a deleterious impact on the breeding potential, because of the social organization of gorillas, 2) the advantages of the social flexibility and the social organization of gorillas in the recovery of the demographic structure of their population, 3) the role of immigration in the long-term recovery of population size. Our determination of the demographic features characterizing a population affected by Ebola allowed us to specify that a studied neighboring population was unaffected. These findings highlighted that Ebola impact had been heterogeneous at a regional level, which probably induced some population fragmentation. This new insight lets discuss the hypotheses on the emergence and spread of the virus and questions the impact of the fragmentation on population dynamics and recovery of affected local populations. Our results suggest a low resilience of populations of lowland gorillas against Ebola virus and the threat to population persistence. However, a better understanding of the ability of individuals to disperse at the regional level and the development of demographic models that take into account this dimension would allow to better clarify this resilience.
Recovery capabilities of a population of lowland gorillas Western Gorilla (Gorilla gorilla gorilla) following a demographic collapse caused by an Ebola epidemic