Population and habitat connectivity of Grevy's zebra Equus grevyi, a threatened large herbivore in degraded rangelands

Smith, Chelsea V., Gilbert, Tania C., Woodfine, Tim, Kraaijeveld, Alex, Chege, Geoffrey, Kimiti, David, Low-Mackey, Belinda, Mutinda, Mathew, Ngene, Shadrack, Rubenstein, Dan, Wandera, Anthony and Riordan, Philip (2022) Population and habitat connectivity of Grevy's zebra Equus grevyi, a threatened large herbivore in degraded rangelands. Biological Conservation, 274, [109711]. (doi:10.1016/j.biocon.2022.109711).

Abstract

Land degradation, competition with livestock, infrastructure development, and climate change have reduced habitat availability and reduced population connectivity for many wildlife species. Large herbivores are particularly vulnerable, and approximately 90 % of global large herbivore diversity is in Africa. The endangered Grevy's zebra illustrates the decline and fragmentation of large mammalian herbivore populations, with extensive population loss across their range in northern Kenya and Ethiopia. A better understanding of the factors influencing population connectivity and movement patterns of Grevy's zebra, highlighted in national strategies, offers valuable insights for other threatened species.

Using location and movement data for Grevy's zebra from GPS collars deployed between 2010 and 2017, seasonally-explicit landscape resistance was modelled as a function of water availability, vegetation, cattle density, topography and proximity to roads and settlements. Maximum entropy models identified habitat suitability during wet and dry seasons respectively. Population connectivity analyses using least-cost paths and circuit theory determined landscape resistance to movement and highlighted linkage pathways. Movement was modelled over a range of distances, using GPS data.

Grevy's zebra reliance on water was confirmed, with an apparent trade-off between habitat suitability and proximity to people. Connectivity models highlighted potentially isolated populations, with reduced seasonal connectivity being most apparent between north to south distribution areas. These results can inform sustainable land management planning in northern Kenya and offer support for Grevy's zebra conservation actions. These results also provide insights that can be applied to other large herbivores occurring in this region and in arid or degraded environments elsewhere.

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Contributors

Author: Alex Kraaijeveld

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