Are Termite Mounds Always Grazing Hotspots? Grazing Variability with Mound Size, Season and Geology in an African Savanna
2019
Foraging site selection by large
herbivoresis influenced by multiple factors varying across landscapes and spatial scales. Termite mounds harbour highly nutritious plants compared with the savanna matrix, making them preferred foraging patches in many savannas. However, it is unknown whether termite mounds equally influence
herbivore
grazingintensity across geological substrates and mound sizes. These knowledge gaps hamper our ability to draw general trans-ecosystem conclusions about the effect of termite mounds for savanna
herbivores. We measured
grazingintensity on mounds of three different size classes (small, medium and large) across two geologies with differing soil nutrition (granite and
basalt) in Gonarezhou National Park, Zimbabwe. We recorded measurements across three seasons (hot wet, cool dry and hot dry), and at multiple distances from mounds.
Grazingintensity on mounds was higher on nutrient-poor granite than nutrient-rich
basalt, and termite mounds of all sizes had a significant effect on
grazingon granite during the cool
dry season.
Grazingwas highest on large mounds on both geologies throughout the year. Large mounds also had the largest spatial influence on
grazingin the cool
dry season, up to 8 m beyond the mound edge on granite and 2 m on
basalt. When scaled up to the landscape level, mounds influenced about 15% of the granite landscape, but only about 0.5% of the
basaltlandscape. Our results show that the positive effects of mounds on
grazingintensity were pronounced on nutrient-poor soils but negligible on nutrient-rich soils, and that the magnitude of these effects varied across seasons and with mound size.
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