Engineering Effects of Cape Ground Squirrels on Biodiversity in Semi-Arid Grasslands

Abstract

Burrowing mammals that have a disproportionate effect on their physical environment, creating habitat and providing resources for other organisms, are ecosystem engineers. Such modifications are particularly important in dry grassland environments where precipitation and soil nutrients are low, limiting plant growth. We examined the impact of Cape ground squirrels (Xerus inauris ) on plants and animals in a semi-arid grassland of South Africa. At each burrow and paired control site without burrows, we estimated plant cover, height, and richness using quadrats, and small mammal and invertebrate abundance and richness using mark-recapture and pit-fall traps, respectively. We determined nitrogen concentrations in grasses on and off burrows and measured carbon and nitrogen stable isotopes in plants and squirrel hair to determine squirrel diet. Burrows had greater plant cover and richness, particularly higher shrubby vegetation, but not greater plant height. Small mammal and invertebrate abundance and richness were greater on burrows, but plant nitrogen concentrations did not differ on and off burrows. Squirrel disturbances in semi-arid grassland improved conditions for disturbance-dependent shrubs, which provide cover for small mammals and invertebrates, and are valuable forage for antelope. By altering habitat for plants reliant on disturbance, Cape ground squirrels enhance the biodiversity of the region.

Keywords: Xerus inauris, semi-arid ecosystems, ecosystem engineer, semi-fossorial rodents, South Africa