Trends in demography, genetics, and social structure of Przewalski's horses in the Hortobagy National Park, Hungary over the last 22 years

The world population of Przewalski's horses has recovered from very few survivors, and is still categorized as Endangered in the IUCN Red List of Threatened Species. For this reason, the maintenance of genetically valuable populations is highly important. The 3000 ha Pentezug Reserve in Hortobagy National Park, Hungary, was home to 270 Przewalski's horses at the end of 2018, approximately 30% of the total European population. In this study, we show the main changes in demographic, genetic, and social characteristics of the population since the establishment of the reserve in 1997. The first years clearly demonstrated that the steppe ecosystem and the wetlands in this area were ideal for the population. We observed that the growing number of individuals affected the total number of harems, but not the average size of the harems. Remarkably, a new phenomenon, herd formation, also appeared. The number of foals per year increased for 17 years (the zenith was in 2014, N = 60 per year) then started to decrease due to both non-human factors (e.g. delay in female fecundity and decreasing foaling rate) and human intervention (e.g. immunocontraception treatment). The total number of horses peaked in 2017 (N = 328) and in 2018 decreased (N = 276) due to decreasing foaling rate, exports, and a population crash. The inbreeding coefficient increased slightly after 2012, while gene diversity stabilized at a relatively high value. Today many individuals from this well-monitored population can be found in Russia and Mongolia. Collectively, understanding of the social structure and mechanisms of population self-control in Przewalski's horses is improved by our observations. From a population management point of view, our study highlights the importance of human interventions for birth-control and interactions between Przewalski's horse projects in different countries. (c) 2020 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

The population of Przewalski's horses in Hungary's Pentezug Reserve has experienced changes in demographic, genetic, and social characteristics since 1997, with the number of foals increasing for 17 years before decreasing in 2018 due to various factors. The inbreeding coefficient slightly increased after 2012, while gene diversity remained relatively high.