By Mike Chase and Scott Schlossberg – Elephants Without Borders (EWB)
Summary
1. In 2019, Botswana ended a five-year moratorium on the hunting of African savanna elephants (Loxodonta africana). Here, we provide expert, outside review of the hunting programme and its scientific basis. Notably, we used simulation models to determine how hunting quotas and environmental changes may affect elephant populations and expected trophy sizes.
2. Elephant populations in Botswana currently total ~140,000. The northern Botswana population, which includes 94% of the country’s elephants, has been stable since 2010. The current annual hunting quota of 410 elephants is 0.3% of the national population.
3. In Botswana, hunters prefer to kill larger, older bulls with big tusks. Our models show that any amount of hunting significantly reduces the number of mature bulls in the population, and the level of reduction increases with quota size. Hunting 0.3% of the population annually reduces the number of the oldest bulls, ≥50 years old, by 50% compared to no hunting. Mature bulls play important roles in elephant populations, so their numbers should be considered when setting quotas.
4. Botswana’s elephants now face increasing mortality due to drought, disease, poaching, and human-elephant conflict. Because bull numbers are already limited, any increase in mortality rates due to these causes will further reduce bull populations. Such reductions will also cause hunters to take younger, smaller bulls. To date, the Botswana Department of Wildlife and National Parks (DWNP) has not incorporated drought, poaching, or other sources of elephant mortality into planning for hunting.
5. Our models show that current quotas of 0.3% result in a relatively small pool of mature bulls and a population that is sensitive to increases in mortality from drought or poaching. In our models, setting the annual hunting quota to a 0.1% or 0.2% rate (140-280 elephants in Botswana today) consistently produces a much more resilient population with larger numbers of mature bulls. As a result, hunting at 0.1% or 0.2% lessens the effects of drought, poaching, or any other factors that increase elephant mortality.
6. DWNP has repeatedly stated that hunting 1% of the elephant population annually is sustainable. This is false and easily demonstrated with our simulation models. Hunting 1% of the population eliminates older bulls in a short time.
7. Current quotas for elephants in Botswana assume a single, well-mixed elephant population. In reality, hunting and nonhunting areas are distinct, and hunting can only be sustained with regular, net movements of elephants from non-hunting to hunting blocks. Anything that prevents such movements will affect hunting. DWNP has stated that their hunting quotas will be based on elephant numbers in hunting blocks. Current quotas, however, are around 0.9% of the population in hunting blocks, an unsustainable level if one looks only at the population in those blocks.
8. Much of DWNP’s justification for elephant hunting rests on a model developed by Craig et al. (2011). That model, however, has two flaws that make it invalid: invented survival values and a lack of density dependence. Consequently, the model is not fit to be the basis for elephant management. Despite this, the Craig model remains a central reference in DWNP’s justifications for elephant hunting in Botswana.
9. DWNP claims that harvested tusk sizes were stable from 19962013, which implies that elephant hunting is sustainable. But during that time, actual harvests averaged just 0.16% of the population per year. Current quotas are 0.3% of the population. Outcomes from hunting at those lower rates tell us nothing about future impacts of hunting at higher rates Elephants Without Borders Scientific Review of Botswana’s Elephant Hunting Programme.
10. Because elephants reproduce slowly, risks of overhunting are significant. Our model shows that a 10-year poaching outbreak (500 killed per year) will reduce trophy sizes for 50 years after the outbreak ends. Additionally, DWNP’s method of monitoring hunting by examining trophy (tusk) sizes is unlikely to detect depletion of bull numbers in time to prevent overhunting.
11. To ensure that elephant hunting is sustainable, we recommend increased monitoring for poaching as well as monitoring bull age structure in hunting blocks. We also recommend that regular, high-intensity surveys of northern Botswana continue every 4 years. Such surveys should be expanded to other parts of the country with hunting.
12. Based on our model results, we recommend limiting hunting to a maximum quota of 0.2% of the total population per year, ~280 elephants. With quotas at 0.3%, the lack of resilience to poaching, drought, or other changes in mortality risks depletion of bulls and reduced trophy sizes on hunts. Limiting hunting to 0.2% annually would increase the resilience of the population to environmental changes. Future levels of poaching, drought, and disease are unknown, so the precaution of making the hunting quota 0.2% will help to make the hunting programme “future proof.”
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