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Abstract:
Herbivores do not forage uniformly across landscapes, but select for patches of higher nutrition and lower predation risk.
Macrotermes mounds contain higher concentrations of soil nutrients and support grasses of higher nutritional value than
the surrounding savanna matrix, attracting mammalian grazers that preferentially forage on termite mound vegetation.
However, little is known about the spatial extent of such termite infl uence on grazing patterns and how it might diff er
in time and space. We measured grazing intensity in three African savanna types diff ering in rainfall and foliar nutrients
and predicted that the functional importance of mounds for grazing herbivores would increase as the diff erence in foliar
nutrient levels between mound and savanna matrix grasses increases and the mounds become more attractive. We expected
this to occur in nutrient-poor areas and during the dry season when savanna matrix grass nutrient levels are lower. Tuft use
and grass N and P content were measured along transects away from termite mounds, enabling calculation of the spatial
extent of termite infl uence on mammalian grazing. Using termite mound densities estimated from airborne light detection
and ranging (LiDAR), we further upscaled fi eld-based results to determine the percentage of the landscape infl uenced by
termite activity. Grasses in close proximity to termite mounds were preferentially grazed at all sites and in both seasons,
but the strength of mound infl uence varied between savanna types and seasons. In the wet season, mounds had a relatively
larger eff ect on grazers at the landscape scale in the nutrient-poor, wetter savanna, whereas in the dry season the pattern
was reversed with more of the landscape infl uenced at the nutrient-rich, driest site. Our results reveal that termite mounds
enhance the value of savanna landscapes for herbivores, but that their functional importance varies across savanna types
and seasons.
