Factors affecting the population size and distribution of the grevy's zebra (equus grevyii) in Northern Laikipia district

Abstract

This study aimed at comparing the ecology of the Grevy's zebra in private and communal ranches in terms of human-livestock interactions, habitat quality, population size and. structure and spatial temporal distribution. The study was carried out in a privately managed Mpala Ranch and communally managed Koija ranch in the Northern Laikipia District. Data collection involved physical observations and road counts for fauna data while vegetation data was collected using step point method and spatial point mapping with habitat assessment being done using a rangefinder technique. Descriptive and inferential statistics were used in the analysis. Comparatively, Mpala Ranch had more forage quantity in both dry and wet season than Koija Ranch (Dry; U=6.5, d.f=23, p= 0.001 and Wet; U=7; df=23 p=O.001). At the same time the ranch had more grass species diversity relative to Koija Ranch which on contrary had more herb species diversity (H' index Mpala; 2.7 and Koija; 1.7). The latter is an indication of overgrazing and reduced rangeland quality in the community ranch. In terms of Grevy's zebra population numbers, there was no significant difference between Mpala and Koija ranches in the wet season (t=0.57, d.f=7, p>0.05). However, in the dry season when forage was limited, no Grevy's zebra species were recorded in Koija Ranch contrary to the situation in ~p'~la Ranch which registered an increase in their population; mainly due to -1Ttfjuxes from the surrounding ranches. The study noted that there was no significant difference between the habitat openness of Mpala and Koija (t=2.02, d.f=23, p>0.05), nevertheless, the Grevy's zebra were found to prefer the more open areas (u=ii, d.f=5 1'=0.001) especially In Mpala Ranch perhaps 85 a precaution against predators. The study also found out that the Ewaso Ng'iro River is an important source of water for Grevy's zebra in both seasons, and particularly so in the community ranch. The dams were distributed close to the Bernas and as such people and their livestock monopolized the dams during the day. The study concludes that the private ranch has much better quality habitat in terms of forage cover and quality of the grass and herb species and attracts Grevy's zebra in the dry and wet seasons. Although, predation is a real threat in the private ranch, the Grevy's zebra seem to exercise caution by preferring the more open areas where they can detect predators from far. The community ranch is degraded with less forage cover and inhabited by unpalatable species and is used as only wet season dispersal areas by the Grevy's zebra. Range rehabilitation, livestock number regulation, proper grazing system, and provision of water are important factors in the conservation of the Grevy's zebra especially in the community ranch.