Fires are common in many ecosystems world-wide, and are frequently used as a management tool. Using South African carnivores as their focal community, Laura C. Gigliotti and colleagues explore the relative changes in carnivore intensity of use in post-fire landscapes associated with hypothesized changes in prey availability and top-down suppression.
Prescribed burning is a common form of habitat management and assessing wildlife responses to burning is crucial. In southern Africa, we know that a lot of herbivore species increase use of recently burned areas to take advantage of the flush of new vegetation. However, we have limited information on how carnivore species in this system are affected by prescribed burning — and more importantly, how prescribed burning might affect interactions among the carnivore community.
For example, we might expect that prescribed burning would create a localized increase of herbivore prey, which in turn would lead carnivores of all sizes to also increase use of the burned areas. Alternatively, we might expect that only the top-ranking apex carnivore in the system (the lion) would increase use of burned areas to take advantage of prey resources, leading to decreased usage of burned areas by subordinate carnivores because of the need to avoid the lions.
In our study, we took advantage of planned prescribed burning at a reserve in South Africa to try to better understand community-level responses to prescribed burning. Over the course of two years, we set camera traps at 104 sites, which were split between burned sites and un-burned control sites. We monitored all sites for approximately 1 month prior to the prescribed burning, as well as approximately 2 months after the burns occurred.
We also monitored a subset of sites 1-year post-burning to assess long-term effects. We detected a total of 48 species and used Bayesian community N-mixture models to analyze changes in intensity of use for both individual species and groups of species (herbivores, large carnivores, small carnivores) with regards to prescribed burning.
As expected, we found that many herbivore species exhibited higher intensity of use in recently burned areas. Out of the large carnivores, only the apex predator –the lion — exhibited increased use of recently burned areas, whereas all other large carnivore species showed neutral responses to burning. The majority of small carnivore species also exhibited neutral or weak positive responses to the burning. The increased use of burned areas was short-lived and all species that initially showed a positive response, did not exhibit the same increased use of the previously burned areas a year later.
Our results highlight the importance of understanding community-wide responses to management actions such as prescribed burning. Although no species were negatively affected by the prescribed burning (at least regarding their use of burned areas), we found high variability in how individual species responded to the burning.
For carnivores, although lions were able to increase their use of recently burned areas and likely take advantage of the associated prey in those areas, we suggest that burning might create a “suppression of opportunity” for subordinate predators, whereby they are unable to take advantage of potentially profitable burned areas because of the need to avoid the lions that are also in those areas. Therefore, when managers use prescribed burning as a form of habitat management, or to provide forage opportunities for herbivores, they need to be aware that the burning might result in complex community-wide responses.
Whilst our study focused on prescribed burning, the idea of understanding community or guild-wide responses to management can be applied to many other management scenarios. For example, supplemental feeding, artificial water points, or other types of habitat management such as timber harvesting could create situations where localized resource availability might differentially benefit individual species, ort alter interactions amongst species. Therefore, taking a community-wide approach to post-management monitoring could help advance our understanding of the complexities involved with managing wildlife communities.
Read the full article Community-level responses of African carnivores to prescribed burning in Journal of Applied Ecology.