Abstract

Large herbivores generally depend on and interact with a food resource that is heterogeneous at different spatial scales. Plants allocate resources to rapid growth or to defence mechanisms depending on the availability of resources relative to loss of resources from herbivory. Herbivores select food and feeding habitats in order to maximize intake rate of nutrients and digestible energy, while avoiding chemical and structural deterrents. To optimize foraging, herbivores select habitats and food items in a hierarchical way, and different attracting and deterring factors may govern selection at different scales. We studied the impact of twig biting by a guild of indigenous browsers in three vegetation types in a semi-arid savanna in Botswana. The heaviest browsing pressure was in the vegetation type richest in preferred plant species, although that type was also richest in defended species. There were large differences in relative utilization between plant species, and ranking of species was roughly similar in the different vegetation types. Browsing pressure varied between species from almost 0-30%. Overall, spinescent trees were less browsed than non-spinescent ones, and evergreen species were less browsed than deciduous ones. In two of the three vegetation types there was a negative correlation between browsing pressure on a species and its frequency. there was a high incidence of rebrowsing, and once a tree had been browsed, the probability that it would be browsed again increased. The results largely agree with predictions based on the resource availability hypothesis, the scarcity accessibility hypothesis and recent theories on the significance of plant defences and on plant's response to browsing and the subsequent response by herbivores on the plant's responses

Published in

Ecography
2000, Volume: 23, number: 5, pages: 632-640
Publisher: MUNKSGAARD INT PUBL LTD

SLU Authors

• Bergström, Roger

  • Department of Animal Ecology, Swedish University of Agricultural Sciences
    

• Danell, Kjell

  • Department of Animal Ecology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Environmental Sciences related to Agriculture and Land-use


Publication identifier

DOI: https://doi.org/10.1034/j.1600-0587.2000.230514.x

Permanent link to this page (URI)

https://res.slu.se/id/publ/6289