Impacts of Spatial-temporal Resource Variability on Grevy’s Zebra (Equus Grevyi Oustalet, 1882) Populations in Samburu- Laikipia Landscape, Kenya

Abstract

Grevy’s zebra is a large highly endangered African mammal in the world, occurring in the arid and semi-arid regions of northern Kenya. Since the mid-1970s, its range has shrunk immensely while its population has greatly declined from approximately 15,000 to under 2,500 by the early 2000’s. This represents a 75% population decline globally making it one of the most critically endangered mammals in the world and has been placed on CITES Appendix I since 1979. The Samburu-Laikipia landscape, is home to the largest Grevy’s zebra population where habitats resource abundance and quality vary on spatial-temporal basis. The survival and conservation of this species in this expansive landscape highly depends on its ability to select beneficial resources and habitats that are now highly impacted by human activities and climate change. The main aim of the study was to determine how spatial-temporal variations in food resources and water in combination with anthropogenic activities influenced Grevy’s zebra distribution, densities, movements and habitat selection within landscape. Grevy’s zebra densities were determined using distance sampling on pre-determined census routes in selected study sites on monthly rotation cycle. Selected random grids were used to conduct vegetation transects to understand food resource availability and distribution. The study area was classified into different land use types to understand the impacts of human activities on the species and their food resources. While habitat characteristics that included vegetation composition and structure, livestock densities, human habitation, distance to water and other environmental factors were determined for places where individuals of the species were located or/not to determine habitat selection. Rainfall data was obtained from various stations or rain gauges erected in study sites in the area to understand how rainfall patterns influenced spatial-temporal changes in resources and Grevy’s abundance. High densities and larger clusters sizes of Grevy’s zebra were observed on community lands during wet seasons when livestock grazing was heavy, stimulating grass growth and producing short, high

quality swards. During dry periods, the species spread out into protected areas, commercial ranches and community conservancies where lower levels of year-round grazing established grass banks of tall, low-quality vegetation swards. This indicates that pastoralist herd activity, in conjunction with seasonal rainfall patterns, shape Grevy’s zebra abundances and movements at a landscape level while influencing their local population densities in different areas. In dry season only territorial males, lactating females and their foals were found together and their clusters tended to be small. Bachelor males, non-lactating females and juveniles generally spread themselves evenly over the landscape, perhaps as a way of reducing competition during times of food scarcity. Conservation strategies for successfully increasing survival of all Grevy’s zebra will therefore require a mixture of rapidly growing grass swards and grass bank reserves maintained at a regional scale in order to enable seasonal movements across regions encompassing both dry and wet grazing areas driven by alternating rainfall patterns and livestock grazing pressures..........................................................................