In early 2021 our team joined forces with data visualization expert Cédric Scherer vom the Leibniz-IZW to create a map from our recent PNAS study. The intent was to illustrate the key findings of the paper and to submit the map to the MoveMapCompetition from the Special Interest Group “Movement Ecology” of the British Ecological Society. We are very happy for the support of all the voters who made us win the ‘pretty map’ category and runner-up for the RMaps category. In a blog post for the BES’ Journal of Animal Ecology website we wrote about the creation of the map and the research behind it!
We are grateful that the blog post, which was originally published on April 14, 2021, here was allowed for re-publishing on our website. The MoveMapCompetition can be reviewed in its enterity here.
MOVING FORWARD WITH CHEETAH RESEARCH AND CONSERVATION
The cheetah is the rarest big cat species in Africa and its numbers have substantially decreased over the last decades to now less than 7,000 adult individuals. In central Namibia, one of the most important strongholds of the species, the cheetahs live on privately owned farmland, not inside protected areas. This has caused conflict with cattle farmers on whose calves the cheetahs occasionally prey. In the past, they have been removed repeatedly by farmers. Solutions needed to be found to help both the cheetahs and the farmers’ businesses to thrive. Luckily, there is a solution emerging directly from the spatial ecology of the cats and this map from the Cheetah Research Project (CRP) of the Leibniz Institute for Zoo and Wildlife Research shows us how co-existence is possible!
The CRP started a research programme on the spatial ecology of cheetahs in 2002 and established a trusting collaboration with many farmers in Namibia. Supported by the farmers we caught more than 300 cheetahs and equipped many of them with high resolution GPS collars to thoroughly analyse their spatial behaviour. We are using GPS collars from www.e-obs.de which are remarkably energy efficient.
The collars are set to record GPS positions in a 15 min interval, which will be paused if no movement is detected for more than 30 minutes to save battery. In the case of cheetahs, we are saving approximately 50 percent of the fixes as cats spend a lot of time resting and sleeping. These gaps are filled afterwards with the last position taken when the animal had been already resting. This gives us an average lifetime of more than two years or about 35000 fixes per D-cell battery. The main investment for getting the long lifespan out of the battery is the energy efficient data download; data are not send via GSM or Iridium-network but downloaded via a UHF-radio-signal. For a successful data download we need to get into a range of few hundred meters of each collared individual. This is challenging, working with a wide-ranging species, but we are fortunate to have a small aeroplane at our disposal to do it and pilots willing to fly every three weeks for two long days. Additionally, data is downloaded by a handful of strategically positioned download stations near marking locations that help save flight time. Over the years we were able to build up a database of several million locations, which is, needless to say, an amazing dataset to work with.
With the help of this enormous dataset, we identified two distinct spatial tactics of male cheetahs. Approximately one third of all males own small territories which they scent-mark at 20 to 40 prominent landmarks such as trees, rocks or termite mounts in the core area.
Other males, called floaters, do not own a territory but roam over vast areas. The territories are not contiguous, but spread evenly across the landscape with a lot of open space between them. Floaters visit the core areas of the territories frequently to gather information on the current territory holders and to consider their chances of queueing for territory ownership or winning a fight for the territory. At the same time, the females regularly visit these areas in search of mating partners.
As a consequence, the core areas of the territories function as communication hubs for the local cheetah population and are effectively hotspots of cheetah activity. These communication hubs are typically 25 square kilometres in size, situated 20 to 25 kilometres apart and thus make up only 10 percent of the total area. They represent areas with a high local predation risk for livestock, whereas the remaining lands between communication hubs make up 90 percent of the total area and entail only a low predation risk. Although the communication hubs cover only a small part of the study area, mapping of all hotspots revealed that about 30 percent of the cattle farmers are affected to varying degrees by cheetah activity.
Based on these findings we designed an experiment together with the farmers. Where the farmers unwittingly kept breeding herds with young calves within the communication hubs, the scientists suggested to move them to areas with much less cheetah activity. These experiments were highly successful and reduced the livestock losses of farmers by more than 80 percent. The cheetahs did not follow the breeding herds, but maintained their spatial system of communication hubs and instead preyed on wildlife occurring naturally on the farms in the hotspot locations. This implies that there are no problem cheetahs, but problem areas with high predation risk.
The map illustrates the movement behaviour of three floaters that regularly visit core areas of male cheetah territories in central Namibia. All of them frequently move into one of these core areas, the communication hub called “P Hub” during the period from 16 to 31 December 2020. Three additional territories show similar concentrations of cheetah activity and visually support the findings that we derived from the movement data of several hundred cheetahs over a long period of time.
The data preparation and map design was completely done in R with the help of the {ggplot2}, {sf} and {stars} libraries. We created a hillshade map, derived from terrain tiles provided by AWS, and combined it with estimates of tree canopy cover (Hansen et al. 2013) to highlight the homogeneous character of the region. To make it possible to follow individual animals we decided to reduce the number to three floating individuals that regularly visited the same areas and to put an emphasis on a 2-week period. Additionally, we highlighted the general pattern of restricted movement behavior inside these communication hubs by mapping all other movement tracks of these three cheetahs in pale colors. Finally, illustrations, annotations and text boxes allow the reader to quickly explore how the movement ecology of the cheetahs has potential for solving the cheetah-farmer conflict.
We are very thankful to the BES Movement Ecology SIG for organizing this competition as it was a very nice opportunity to showcase our work. It really help to stimulate scientific exchange during these rather isolated Covid-times. We are very happy for the support of all the voters who made us win the ‘pretty map’ category and runner-up for the RMaps category.
How the cheetahs move, where they roam and in which spatial arrangements they interact and communicate – these fundamental ecologic findings have proven not only to advance our understanding of cheetahs, but also to warrant their future in central Namibia.
A special thanks to Cédric Scherer for joining forces with us and creating this wonderful map!
Dr Cédric Scherer is a computational ecologist at the Leibniz Institute for Zoo and Wildlife Research in Berlin, Germany. After his PhD with a focus on the interplay of movement ecology, landscape structure and disease persistence, he started working as a part-time freelance data visualization designer and workshop instructor. For all of his scientific, client and personal projects he uses R and ggplot2.