How African Lions Respond to Human-Caused Mortality Risk In their Habitat
By Marisa Riordan
Did you know that humans are causing 78% of mortalities in a lion population in Zimbabwe? As the human population continues to grow, human-animal interactions are rapidly increasing. This can result in habitat loss and increases exposure of protected areas to people, which directly shape the distribution and threatens the conservation status of many living species. If we want to protect the African Lion from extinction, we need to develop and implement better conservation methods throughout Africa.
Why study mortality events in African Lions?
Different sources of wildlife mortalities arise at reserve edges where the most human-wildlife contact occurs. This includes legal and illegal hunting of animals, trophy hunting and human-wildlife conflict related deaths. Large carnivores have particularly large ranges of daily activity. So, they often roam outside of protected areas, making them more vulnerable to human-caused mortalities. Recent research has shown this is particularly detrimental to African Lion populations, greatly impacting their population density, population structure, increasing adult mortality and resulting in a loss of juveniles.
Designing an effective conservation strategy starts with understanding how African Lions are affected by human-caused mortalities. In a recently published paper, Andrew Loveridge and his colleagues tried to capture human-caused mortality risks by mapping them onto a landscape to try to understand how to better protect lions (Loveridge et al., 2016). They modeled the landscape of mortality risks based off of lion mortality data for 13 years in and around Hwang National Park in Zimbabwe. They also tracked lions using GPS radio collars so they could understand how lions used the landscape.
Researching mortality events in Lions in Zimbabwe
The study area in Hwang National Park consisted of different landscapes, including: protected land, communal lands used for agriculture, and trophy hunting areas. The scientists gathered a total of 206 human-caused mortality events during the 13-year study. They tracked the daily location of 84 GPS collared individuals to ultimately identify the cause of death for those individuals. Surprisingly, human-caused mortality affected female and male lions differently. Because of this, the scientists calculated cause-specific mortality rates for each gender, which were used to build a map of mortality risk for each cause of death. This map was used to determine the risk lions take depending on where they spent their time in relation to human activity.
With this data, scientists were able to ask if lions killed by humans used the landscape differently from lions that died of natural causes or survived to the end of the study. They also used this data to determine if lions could detect risk.
Using the data from the GPS-collared lions and the mortality map they created, scientists were able to see how lions spent their time in varying areas of risk. Scientists found that lions of both genders tended to avoid areas classified as medium, high, and very high risk. Scientists also discovered that mortality from human-causes increased as the time spent in risky areas increased.
Bottom line: How do Humans Affect Lions?
This study revealed that human-caused mortality in African lions is extremely high.
Over this 13-year study, humans caused 78% of lion deaths in Hwang National Park.
In particular, 88% of male lion deaths were a result of humans with the majority (65%) of deaths occurring through trophy hunting. In contrast, 67% of female lion deaths were a result of humans with the largest proportion (30%) of deaths occurring through snaring.
Trophy hunting creates mortality hot spots and represents an ecological trap for lions. This ecological trap arises because lions still use these lands as hunting areas with the same level of intensity as protected reserves. This habitat is pristine, with a low incidence of people, so there are no obvious signs lions should avoid this area. As a result, high intensity of use by lions is coupled with high rates of human-caused mortality.
Another ecological trap for lions is high quality communal areas with lots of prey; but, where snaring for meat is frequent. Since snaring is an illegal activity it often goes undetected, resulting in even higher instances of mortality for lions in areas they otherwise believe are safe.
In addition, this study reveals how detrimental edge effects can be. Lions closer to protected park boundaries have a higher rate of contact with people, which leads to increased incidence of human-caused mortality. Thus, the fully protected core of the park is reduced by 38%. This reduces the amount of safe habitat available to lions and simply does not provide enough space to protect them.
If these mortality hot spots surrounding the National Park are more sustainably managed, then it will conserve intact habitat essential for lions and can play an important role as a buffer around protected lands.
All of these results are vital to understanding and identifying areas where animals are most at risk so we can prioritize the allocation of conservation and management resources to these areas. This study reveals that humans have profound impacts on lion populations, specifically in smaller, less-protected areas. As human populations continue to increase in Sub-Saharan Africa, human-caused mortality of lions needs to be limited to protect the species and the health of the ecosystem. Additionally, the ecological traps and edge effects caused by trophy hunting and snaring need more attention by conservationists.
Predator species are continually proven to be essential for a healthy ecosystem, and the loss of these species results in negative effects throughout entire ecosystems. This study, as well as countless others, demonstrates that predator species, like the African lion, need to be protected by intensifying conservation efforts to limit human-caused mortalities. If further protection is not provided, then large predator species will quickly slip toward extinction creating irreversible effects throughout their ecosystems.
Loveridge, A. J., et al., (2017). The landscape of anthropogenic mortality: how African lions respond to spatial variation in risk. Journal of Applied Ecology, 54: 815–825.