Abstract
Altered disturbance regimes, increasing atmospheric CO2, and other processes have increased woody cover and homogenized vegetation in savannas across the planet. African savannas with extensive versus minimal woody cover often have vastly different animal communities. However, we lack a clear mechanistic understanding of why animal communities are changing with vegetation structure. Our goal for this study was to understand how vegetation structure in an African savanna shaped the perceived predation risk of small mammals, hence affecting their activity. Using a reciprocal measure of standard giving-up-densities, amount of food eaten, we found sharp declines in rodents’ perceived predation risk and increased rodent activity underneath shrub cover. This response was consistent across species; however, species showed subtle differences in their responses to grassy vegetation. Our findings suggest that areas of minimal or extensive shrub cover (shrub encroachment) may be homogenizing rodents’ perceptions of predation risk and thus shaping their use of space.
Highlights
Altered disturbance regimes, increasing atmospheric CO2, and other processes have increased woody cover and homogenized vegetation in savannas across the planet
We developed a suite of 15 a priori grassy areas models with single variables and additive models using the variables Max Ht, Binary Ht, Shrub Size, horizontal visual obstruction (HVO), and Ground Cov
We evaluated the suites of six shrub proximity models and 15 grassy areas models for the activity levels (Minute-Visit) of each species individually
Summary
Altered disturbance regimes, increasing atmospheric CO2, and other processes have increased woody cover and homogenized vegetation in savannas across the planet. Our goal for this study was to understand how vegetation structure in an African savanna shaped the perceived predation risk of small mammals, affecting their activity. Using a reciprocal measure of standard giving-up-densities, amount of food eaten, we found sharp declines in rodents’ perceived predation risk and increased rodent activity underneath shrub cover. This response was consistent across species; species showed subtle differences in their responses to grassy vegetation. With anthropogenic forces altering the ratio of grass and woody components in savannas, perceptions of fear may facilitate shifts in small mammal communities. One way to initiate an understanding of the factors that influence small mammals’ perceptions of fear is to investigate their behavior on the fine scales at which they conduct most of their daily activities such as foraging for food[45]
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