Spatial variation in anthropogenic mortality induces a source–sink system in a hunted mesopredator
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Lethal carnivore management is a prevailing strategy to reduce livestock predation. Intensity of lethal management varies according to land-use, where carnivores are more intensively hunted on farms relative to reserves. Variations in hunting intensity may result in the formation of a source–sink system where carnivores disperse from high-density to low-density areas. Few studies quantify dispersal between supposed sources and sinks—a fundamental requirement for source–sink systems. We used the black-backed jackal (Canis mesomelas) as a model to determine if heterogeneous anthropogenic mortality induces a source–sink system. We analysed 12 microsatellite loci from 554 individuals from lightly hunted and previously unhunted reserves, as well as heavily hunted livestock- and game farms. Bayesian genotype assignment showed that jackal populations displayed a hierarchical population structure. We identified two genetically distinct populations at the regional level and nine distinct subpopulations at the local level, with each cluster corresponding to distinct land-use types separated by various dispersal barriers. Migration, estimated using Bayesian multilocus genotyping, between reserves and farms was asymmetric and heterogeneous anthropogenic mortality induced source–sink dynamics via compensatory immigration. Additionally some heavily hunted populations also acted as source populations, exporting individuals to other heavily hunted populations. This indicates that heterogeneous anthropogenic mortality results in the formation of a complex series of interconnected sources and sinks. Thus, lethal management of mesopredators may not be an effective long-term strategy in reducing livestock predation, as dispersal and, more importantly, compensatory immigration may continue to affect population reduction efforts as long as dispersal from other areas persists.
KeywordsMicrosatellite Canis mesomelas Genetic population structure Metapopulation Dispersal
This project was funded by the International Foundation for Science, the National Wool Growers Association, Red Meat Research and Development South Africa, the Koos and Rona Rupert Education Trust, the Nelson Mandela University (NMU), and the National Research Foundation (NRF) Knowledge, Interchange and Collaboration (KIC). Field transport was provided by the Mazda Wildlife Fund and Bidvest rent-a-car. LM was supported by the German Academic Exchange Service (DAAD) and the NRF joint scholarship programme, NMU postgraduate scholarship, and the Dormehl-Cunningham Scholarship. We would like to thank the following organisations and people that were instrumental in sample collection: South African National Parks, Mohair South Africa, all the farm and reserve managers involved in the project, and all the problem animal control specialists.
Author contribution statement
LM and GIHK conceptualised and designed the research. LM collected the data. HZ conducted the laboratory analyses. LM and AZ analysed the data. All authors contributed substantially to the preparation of the manuscript.
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