Migratory grazers must move between ranges each year, and make daily movements to locate food, but landscape fragmentation and other obstacles to movement are increasing. At the same time, climate change is making droughts more frequent and extreme, requiring animals to move farther to locate sufficient food. How wildlife populations are affected by this combination of effects is of interest. Researchers from the U.S. and Kenya will address this topic in three conservation areas in Kenya. To track movements of wildebeest across the landscape, the researchers will place 45 collars, which contain global positioning devices, on the animals. Future landscape fragmentation in the areas will be modeled. A model will also be constructed to allow researchers to simulate movements of individual wildebeest within each population. Landscape fragmentation and frequency of droughts will be varied in simulations to quantify potential effects of land-use intensification and climate change on migratory wildebeest populations.
Wildebeest migration fascinates the public, but remarkably little is known about individual movements, and how fragmentation and climate change interact to alter movements. The results will shed light on effects on other mobile grazers as well, including livestock, and address the sustainability of current practices in landscapes shared by wildlife and humans. This research will facilitate the development of novel modeling approaches. Other broader impacts include training of three graduate students, which will include international experience, and incorporation of research results into university courses. In addition, information will be shared with land managers and citizens from Kenya and the U.S.
Migratory grazers like wildebeest move across landscapes each year to find the resources they need, and make daily movements to find food and water. In Kenya and many other areas, habitats used by animals are being broken-up and fragmented by fencing, houses, and agricultural plots. Climate change is also shortening the number of years between droughts in semi-arid areas like much of Kenya. How wildlife populations are affected by these changes is of conservation interest. We focused on wildebeest in three areas in western Kenya, a placed called Kitengela south of Nairobi National Park, the Amboseli area, and the Maasai Mara area (Figure 1). We had three main goals, 1) to track a number of wildebeest to learn how they selected the areas they used, 2) to try to project how the landscapes in the areas might look in the coming decades given their current rates of change, and 3) to simulate in a computer model wildebeest movements, to see how they respond to increased fragmentation of the lands they use and more frequent droughts. We also looked at how fragmentation and disturbance by people are affecting stress levels in wildebeest, how conservancies influence wildlife conservation, and human-wildlife conflicts in the area. Thirty-six collars that contained global position system (GPS) and cell-phone technologies were placed on animals, and they sent daily messages to project scientists giving the location of animals each hour. More than 300,000 locations were recorded, including some from two animals that moved hundreds of kilometers into Tanzania (Figure 2). As part of our tracking and outreach efforts, dozens of Kenyan students got to join in collaring efforts, and were taught in classrooms about our project (Figure 3). Fencing and housing development is expanding rapidly in the Kitengela area of Kenya. We used computer models to extend the current rate and pattern of growth out to 2035 (Figure 4). Other investigations looked at how the landscape might appear if more careful planning was used to guide development, and if a road was constructed south of Nairobi National Park, as has been proposed. In a computer simulation that included modeling the movements of individual wildebeest, we were able to change the spatial data in the model that animals responded to, mainly the amount of fences (Figure 5) and how much grass was produced each year, associated with how frequent droughts were. Analyses are still underway, but so far, we see about a 20% decline in the number of wildebeest that the landscape can support when it is fragmented at leaves we expect to see in about 2020 (Figure 6). More frequent droughts that reduce grass growth caused the number of wildebeest to decline, but the total number that could be supported on the landscape after a 10 year simulation was similar to the number supported under observed changes in the grass that was available. Our project provided the main support for four Ph.D. students to complete their degrees, plus support for several other graduate students, including students from under-represented groups. Undergraduate students in Colorado, Maine, and Kenya gained research experience under the Gnu Landscapes project. We also brought two school teachers from Colorado to Kenya to experience the region and learn research methods. Several peer-reviewed publications have been produced and an important database on animal movements will be available for anyone to use.
