State-space models reveal a continuing elephant poaching problem in most of Africa

Scientific Reports volume 10, Article number: 10166 (2020) Cite this article

Abstract

The most comprehensive data on poaching of African elephants comes from the Monitoring the Illegal Killing of Elephants (MIKE) program, which reports numbers of illegally killed carcasses encountered by rangers. Recent studies utilizing MIKE data have reported that poaching of African elephants peaked in 2011 and has been decreasing through 2018. Closer examination of these studies, however, raises questions about the conclusion that poaching is decreasing throughout the continent. To provide more accurate information on trends in elephant poaching, we analyzed MIKE data using state-space models. State-space models account for missing data and the error inherent when sampling carcasses. Using the state-space model, for 2011–2018, we found no significant temporal trends in rates of illegal killing for Southern, Central and Western Africa. Only in Eastern Africa have poaching rates decreased substantially since 2011. For Africa as a whole, poaching did decline for 2011–2018, but the decline was entirely due to Eastern African sites. Our results suggest that poaching for ivory has not diminished across most of Africa since 2011. Continued vigilance and anti-poaching efforts will be necessary to combat poaching and to conserve African elephants.

Introduction

Beginning around 2007, a wave of poaching for ivory affected populations of savannah elephants (Loxodonta africana) and forest elephants (L. cyclotis) across Africa1. The total population of savannah elephants decreased by 30% between 2007 and 20152, and an estimated 100,000 elephants of both species were poached between 2010 and 20123. In some countries, elephant populations declined by over 50% in under 10 years2. With elephant populations and ranges already greatly reduced from pre-colonial levels, such losses put many populations at risk of extirpation4,5.

Recent reports, however, indicate that elephant poaching may be abating6,7. Since 2016, some African parks have reported reductions or even a halt in elephant poaching8,9. Likewise, global ivory prices appear to have peaked and may have begun to fall, perhaps as a result of bans on ivory sales10. Accurately determining whether or not poaching is diminishing is critical for evaluating the success of ivory trade bans and other anti-poaching measures. Controversially, several African countries have proposed selling stockpiles of ivory11. Such sales may not be justifiable if elephant poaching is continuing at the high levels of the early 2010s.

Elephant population surveys tend to be infrequent, so our main source of information on poaching rates is the Monitoring the Illegal Killing of Elephants (MIKE) program, administered by the Convention on the International Trade in Endangered Species of Wild Fauna and Flora (CITES). Accordingly, rangers at sites across African gather data on the cause of death for elephant carcasses encountered during patrols12. The proportion of carcasses killed illegally, as opposed to deaths due to natural causes, legal hunting, or killing of problem animals by wildlife authorities, is known as “PIKE” and is considered an index of poaching rates3. PIKE data are typically aggregated to estimate regional or continental poaching rates. For all of Africa, estimates using the MIKE program’s methodology show a 31% reduction in PIKE between 2011 and 2018 (see Results). The program recently reported that PIKE has exhibited a “steady downward trend” since 20116.

CITES estimates PIKE values for Africa as a whole via general linear models, treating region and year as fixed effects so that

More: https://www.nature.com/articles/s41598-020-66906-w#Sec3

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