This article is part 3 of an EcoPress series focused on the theme of science and sustainability research at the Natural Resource Ecology Laboratory and the Department of Ecosystem Science & Sustainability. Part 1 can be found here, part 2 here.
By Jared Stabach
For many, thoughts of Africa likely conjure up images of vast unexplored places with grassland savannahs teeming with mega-herbivores and speckled with dangerous predators. While these areas do surely still exist, my experience from conducting research in parts of Africa is that these areas are disappearing at an alarming rate, along with the wildlife that inhabits them. But, protected areas such as Queen Elizabeth National Park in Uganda or the Maasai Mara National Reserve in Kenya are amazing places and give a person a small sense of what Livingstone or Stanley must have once experienced.
Protected areas are widely regarded as being important reservoirs for preserving biodiversity. However, they are often far too small to sustain the long-term viability of many large-bodied, mobile species. Blanc et al. (2003), for example, estimate that 84% of African elephant (Loxodonta africana) habitat lie outside of protected area boundaries. Protected areas are also thought to concentrate human activities (Wittemyer et al., 2008), since they often provide the resources necessary for communities to survive. From a scientific perspective, this means that in order for conservation to be successful, we need an improved understanding of how wildlife interact with the marginal habitat that exists outside of protected area boundaries and a better ability to engage local communities in active conservation.
For my part, I have been fortunate to be involved in a NSF funded project (DEB Grant 0919383) over the last four years. Together with my advisor, Dr. Randall Boone, and our collaborators, the University of Maine and the African Conservation Centre, we’ve been investigating the effects of habitat fragmentation and climate change on the movements of white-bearded wildebeest (Connochaetes taurinus) throughout three study areas in Kenya. These study areas, known as the dispersal areas in and around Amboseli National Park, Maasai Mara National Reserve, and Nairobi National Park, have experienced widespread and precipitous declines in wildebeest (and other wildlife) over the past 40-50 years. Wildebeest are the dominant herbivore, often referred to as a keystone species, throughout these systems (Sinclair and Byrom, 2006). The loss or serious decline of this one species can, therefore, have serious implications for the ecosystems as a whole.
Starting in 2010, we collaborated with the Kenya Wildlife Service and placed Lotek WildCellTM GPS transmitters on 36 wildebeest throughout these three study areas. The resulting dataset represents the most detailed movement dataset on wildebeest to date, with over 300,000 records already received. The movements of individual wildebeest are publicly available and can be viewed via our project website. Movement, of course, is a vital aspect of animal ecology, enhancing an individual’s ability to obtain resources, avoid predation, or disperse from an area when conditions deteriorate.
Preliminary results of the animal movement data highlight that wildebeest throughout the Nairobi National Park study area move the least. Unknown, however, is whether or not this reduced movement is having an adverse effect on animals throughout this study area. That is, do wildebeest become stressed when there are restrictions on their movement due to habitat fragmentation? To answer this research question, I added a field component to our study and collected fecal samples from a random sample of each study area population. I extracted the quantity of corticosterone (i.e., stress hormones) within each sample using a radioimmunoassay (RIA) laboratory technique. This type of analysis is becoming increasingly common to assess the average amount of circulating corticosterone in free-ranging wildlife populations, partly because fecal samples are far easier to collect than a blood sample.
Our results over a 3-month study period (January-April 2013) highlight that wildebeest managed fecal corticosterone levels similarly throughout each of our study areas, and stress levels declined with the onset of the wet season as vegetation quality improved. We discovered a strong positive effect related to the interaction between locally measured biomass and quantified levels of habitat disturbance, meaning that when biomass is of poor quality, levels of habitat disturbance adversely affect corticosterone stress levels in wildebeest. A longer study period is certainly necessary, especially one conducted over multiple seasons, but these results provide support for the hypothesis that habitat disturbance effects movement and are reflected in assays measuring average levels of circulating corticosterone.
The University of Maine has also provided landscape surfaces predicting land-cover changes over the next 25 years, based on past levels of development. We are incorporating these data and using the animal movement data to simulate movements of wildebeest across these landscapes. Aimed at policymakers making land-use decisions throughout the area, we hope to provide information that will be influential towards the long-term sustainability of wildebeest populations, and these landscapes in general.
Blanc, J., Thouless, C., Hart, J., Dublin, H., Douglas-Hamilton, I., Craig, C., Barnes RFW, 2003. African elephant status report 202: an update from the African elephant database.
Sinclair, A., Byrom, A., 2006. Understanding ecosystem dynamics for conservation of biota. J. Anim. Ecol. 75, 64–79.
Wittemyer, G., Elsen, P., Bean, W., 2008. Accelerated human population growth at protected area edges. Science (80-. ). 321, 123–6.