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Variation in herbivore space use : comparing two savanna ecosystems with different anthrax outbreak patterns in southern Africa
Huang, Yen-Hua; Owen‑Smith, Norman; Henley, Michelle D.; Kilian, J. Werner; Kamath, Pauline L.; Ochai, Sunday Ochonu; Van Heerden, Henriette; Mfune, John K.E.; Getz, Wayne M.; Turner, Wendy C.
BACKGROUND : The distribution of resources can affect animal range sizes, which in turn may alter infectious disease
dynamics in heterogenous environments. The risk of pathogen exposure or the spatial extent of outbreaks may vary
with host range size. This study examined the range sizes of herbivorous anthrax host species in two ecosystems and
relationships between spatial movement behavior and patterns of disease outbreaks for a multi-host environmentally
transmitted pathogen.
METHODS : We examined range sizes for seven host species and the spatial extent of anthrax outbreaks in Etosha
National Park, Namibia and Kruger National Park, South Africa, where the main host species and outbreak sizes differ.
We evaluated host range sizes using the local convex hull method at different temporal scales, within-individual
temporal range overlap, and relationships between ranging behavior and species contributions to anthrax cases
in each park. We estimated the spatial extent of annual anthrax mortalities and evaluated whether the extent was
correlated with case numbers of a given host species.
RESULTS : Range size differences among species were not linearly related to anthrax case numbers. In Kruger the
main host species had small range sizes and high range overlap, which may heighten exposure when outbreaks
occur within their ranges. However, different patterns were observed in Etosha, where the main host species had
large range sizes and relatively little overlap. The spatial extent of anthrax mortalities was similar between parks but
less variable in Etosha than Kruger. In Kruger outbreaks varied from small local clusters to large areas and the spatial
extent correlated with case numbers and species affected. Secondary host species contributed relatively few cases to
outbreaks; however, for these species with large range sizes, case numbers positively correlated with outbreak extent.
CONCLUSIONS : Our results provide new information on the spatiotemporal structuring of ranging movements of
anthrax host species in two ecosystems. The results linking anthrax dynamics to host space use are correlative, yet
suggest that, though partial and proximate, host range size and overlap may be contributing factors in outbreak
characteristics for environmentally transmitted pathogens.
Description:
DATA AVAILABILITY : Coordinates of anthrax mortalities and elephant movement data in this study
are not publicly available due to potential sensitivity. Movement data on
springbok and zebra (9 individuals) in Etosha are available from Movebank
(https://www.movebank.org/), and data on wildebeest, zebra and buffalo in
Kruger are available from AfriMove (https://afrimove.org/) Thinned movement
data (excluding elephant datasets) and analysis code are available from the
Dryad Digital Repository (https://doi.org/10.5061/dryad.rn8pk0pf4).