Small mammal community demography and reproductive seasonality under protection, pastoralism and agriculture in the Serengeti Ecosystem, Tanzania

Abstract

This work examined population demography and reproductive seasonality among small mammals under protection, pastoralism and agriculture in the Serengeti Ecosystem in 2017 and 2018. Small mammals were trapped to quantify variation in the proportions of actively breeding individuals, juvenile recruitment and adult sex ratio across land use types and seasons. Breeding peaked in the wet season, reflecting a corresponding underlying peak in resource availability and quality. The mean community proportion of reproductively active individuals was greater for females (60%) than males (40%) and under pastoralism than protection or agriculture. Juvenile recruitment was the highest in the pastoral land in the dry season. Adult sex ratio was biased towards males across all land use types and seasons but towards females in the pastoral than the agricultural land. This concurs with the Trivers-Willard hypothesis that nutritionally stressed females should produce more female offspring. Two generalist and pest species (Mastomys natalensis and Arvicanthis niloticus) dominated the pastoral areas indicating human disturbance. Anthropogenic activities degrade habitats, altering population demographics and promoting habitat generalists and pest species. Protection promotes habitat intactness and reduces opportunistic pests typically abundant in disturbed landscapes. Consequently, enhancing conservation around protected areas can improve diversity and control the abundance of opportunistic pest species.   Key words: Small mammals, seasonal breeding, juvenile recruitment, adult sex ratio, Serengeti ecosystem, pastoralism, agriculture, protection, rainfall, land use.