Transitions across agriculture-savannah edges: Why did the rodent cross the edge?

Abstract

Human-induced landscape alteration by agriculture is ubiquitous and impacts ecological processes and ecosystem services. The link between altered and native vegetation (hereafter edges) can create anthropogenic barriers for wildlife movement. Movement response to edges is dependent on landscape and functional group characteristics that shape spatial behavior in individuals; and affect population dynamics, dispersal, diversity, gene flow, and nutrient distribution. Few studies exist on small-mammal functional group movement response to edges, despite its integral role in behavioral and ecological processes. I analyzed the effect of altered land use on movement response in African savannah generalist Mastomys natalensis and specialist Lemniscomys rosalia. Each species was live-trapped for 2 months at 8 sites, across 2 boundary classes—homestead agriculture vs. savannah and commercial agricultural vs. savannah. Twelve individuals of each species were tracked and translocated at each transect with alternating treatments. Movement characteristics by M. natalensis showed a preference for altered land-use areas, possibly due to resource utilization. Conversely, L. rosalia showed a definitive trend (80%) to avoid edge crossing, regardless of abutting vegetative community, possibly due to their inability to cross and utilize altered landscapes. These results support the a priori hypothesis that altered land-use areas greatly impact specialists moving across the edge but only minimally affect generalist movements. Altered landscapes can affect small mammal movements and have cascading effects that alter vegetative and faunal communities.