By Dr. Matt Becker, CEO Zambian Carnivore Programme (ZCP)
LUANGWA VALLEY ECOSYSTEM, ZAMBIA
African lions and other large carnivores are in decline across their range, and wire snares from bushmeat poaching pose one of the greatest threats–both from depleting the lion prey targeted by snares, and from deaths and severe injuries when cats are caught in snares as unintended
targets, also known as by-catch. In many lion populations snaring by-catch impacts can be severe.
While addressing the bushmeat crisis requires an array of long-term strategies ranging from increasing community benefits from wildlife to changing legislation and increasing protection, in the immediate term there is still a need to mitigate the impacts of snares catching and killing lions. Removing snares from injured lions provides clear benefits to the individual animal, but given the effort and resources required, does it provide any benefits to the population at large? A recent study in Zambia provides evidence that it does both.
The study, entitled “Effects of de-snaring on the demography and population dynamics of African lions” was published in the peer-reviewed scientific journal Biological Conservation as part of an invited special issue on the global impacts of snaring. The work was conducted by conservationists in the Zambian Carnivore Programme (ZCP), Zambia Department of National Parks and Wildlife (DNPW), and Conservation South Luangwa (CSL) in the Luangwa Valley. The Luangwa is the country’s premiere wildlife area and one of ten remaining lion strongholds on the continent, but like most populations is threatened by wire snare poaching. Long-term intensive lion conservation work on these populations has included darting and treating snared lions, and while these animals often were important breeders with dependent cubs (Fig. 1), the impact on the population at large had not been quantified.
Utilizing lion demography data and data on snared lions collected from 2008-2015, researchers sought to evaluate the impact of snared lion rescues on the survival, reproduction and growth rates of the population. Over the five-year period, information was collected on 386 intensively monitored individual cats. Prior work had evaluated the dynamics and trajectories of the population, and the mean population growth rate during this period was found to be positive, illustrating that the total number of individuals in the
population was likely to increase over time. These data were then used as a marker for comparison as the researchers then systematically removed direct and indirect benefits of snare removal from the model and evaluated the resulting population trends.
Given many of the snared lions in the population had dependent cubs or produced litters for many years following their de-snaring, analyses first evaluated the impact if all snared lions had not been rescued and succumbed to their injuries, and dependent cubs had died or not been produced. The resulting mean population growth rates shifted to a negative trend, suggesting that the total number of animals in the population would have declined if no action was taken to remove snares. Lastly, given the highly social nature of lions and the fact that pride males protect their cubs from being killed by incoming males (known as infanticide), the cumulative impact of losing snared lions, dependent cubs, and loss of protection from infanticide was then evaluated. As expected, with this loss of protection the mean projected population illustrated a severe decrease compared to the observed population trends with de-snaring efforts.
“While we knew that removing a snare from a lion had a positive impact on the individual animal, it was important to see if this work benefitted the population as a whole,” said ZCP’s Dr. Kambwiri Banda, the lead author on the study. “It was great to see that de-snaring can have strong benefits to the lion populations. Not only do our results suggest a positive impact on population growth from de-snaring but also suggests that de-snaring pride males helps keep them in the pride longer and thereby significantly improving cub and subadult recruitment.”
While de-snaring requires intensive effort and resources, the findings from this study indicate that this work can provide a key conservation action to appreciably reduce the effect of snaring on lion population dynamics. In Zambia these efforts have collaboratively expanded across the country’s large carnivore strongholds, with work ongoing between government and conservation partners.
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