Most African elephant ivory is from a very few places
African elephant eating savanna grass in Tanzania. Photo by Rhett A. Butler.
A study published last week in Science showed that most of the ivory being trafficked today comes from two areas in Africa: savanna elephant ivory from southeast Tanzania in East Africa and forest elephant ivory from the meeting point of Gabon, the Republic of Congo, Cameroon, and Central African Republic.
The illegal killing of tens of thousands of elephants each year threatens both forest and savanna elephants with extinction.
While the poaching of elephants for their tusks happens all across their ranges in Africa and Asia, nearly 70% of seized ivory by weight during the past decade came from the elephants from these two areas.
By identifying these major poaching hotspots, lead author Dr. Sam Wasser and colleagues hope to guide law enforcement to the most targeted areas and thus help stop the poaching.
Central African and East African elephant poaching hotspots, estimated from DNA of large ivory seizures made between 1996-2014.
How did the researchers determine the ivory origin locations?
They extracted DNA from representative tusks of 28 large ivory seizures and compared their genetic makeup to that reference samples collected across Africa. These 1,350 Africa-wide reference samples were part of a geographically referenced database created from DNA extracted over
years from elephant dung, skin, and hair collected at 71 locations across 29 African countries.
To use DNA to determine origin, the researchers needed samples of viable DNA – that is, intact enough to allow analysis of the genetic composition (or genotype) – both for the reference database and the ivory samples from the seizures. Wasser and colleagues have been able to extract sufficient DNA from the small skin, hair, feces, and ivory samples, all collected using non-invasive techniques.
With viable DNA in hand, the researchers used statistics to infer, from the genetic data, the origin of each new sample, as elephants that live near and are related to one another will have more similar genotypes than those living far away. Populations that are isolated will start to show distinct genetic variation over time.
Specifically, they compared the DNA in the poached ivory samples of unknown origin to the samples in the reference database statistically, estimating the ivory’s geographic origin through the frequencies of the gene variants (alleles) at 16 specific locations (loci) on microsatellite DNA. Wasser estimates that ~25 reference samples, each from a separate family group, are needed to distinguish the allele frequencies from a given reserve or landscape.
A male elephant in Tanzania’s Serengeti ecosystem
What did they find?
The analyses could distinguish savanna elephants and forest elephants, as well as more isolated populations within each of these species/sub-species, based on the animals’ DNA.
The findings suggest that the majority of ivory confiscated from large shipments since 2006 come from two main reserve complexes in Africa: southeastern Tanzania, but including northern Mozambique and the intersection of Gabon, Cameroon, Republic of Congo, and Central African Republic. The savanna elephant poaching hotspot in Tanzania shifted northwest over the decade toward Tanzania’s second largest elephant population in the Ruaha/Rungwa ecosystem, while forest elephant poaching remain relatively consistent over that same period.
The DNA data also show that poached ivory is shipped out of Africa from countries other than where the elephants were killed.
Forest elephant ivory seized between 2006 and 2014 was assigned mainly to the TriDom region of NE Gabon, NW Republic of Congo, and SE Cameroon, plus Dzanga-Sanga Reserve in Central African Republic. The first map shows the reference sample locations (green crosses) and the box contains the area shown in all subsequent maps. The blue circles represent locations assigned to poached ivory samples. Country names are where the ivory was seized. Source: Wasser et al (2015) Science. DOI: 10.1126/science.aaa2457. Click to enlarge.
Savanna elephant ivory seized between 2006 and 2014 was assigned mainly to southeastern Tanzania. The first map shows the reference sample locations (orange crosses) and the box contains the area shown in all subsequent maps. The blue circles represent locations assigned to poached ivory samples. Country names are where the ivory was seized. Source: Wasser et al (2015) Science. DOI: 10.1126/science.aaa2457. Click to enlarge.
How can these results be used?
Such forensic data can help catch criminals in the act of trafficking wildlife or plant products illegally. More generally, they can improve enforcement of international law by recognizing countries with more severe trafficking problems.
Researchers can use the information to begin to infer the degree and time of isolation of populations and relative similarity among them. An earlier study of African elephant DNA showed that savanna elephants are significantly less genetically diverse than forest elephants, which suggests that perhaps forest elephant populations are more isolated from one another (a potential conservation problem), or perhaps they evolved from a more diverse source population and have remained isolated naturally.
Most urgently, wildlife and park agency directors can strategically focus ranger patrol effort and resources to areas with more intensive poaching problems. If new seizures continue to be provided for DNA analysis on a timely basis, these methods can track any shifts to other areas that might result from law enforcement pressure on the current hotspots.
Forest elephant in Gabon. Photo by Rhett A. Butler.
For example, the primary source for forest elephant ivory abruptly shifted around 2006 from eastern Democratic Republic of Congo to the current intersection of Gabon-Cameroon-Republic of Congo. Similarly, the main savanna elephant ivory source shifted from Zambia to SE Tanzania between 2006-2007 and since 2011 moved north toward central Tanzania, as supply (read: elephant populations) has dwindled: Niassa National Reserve in northern Mozambique has continued to lose thousands of elephants each year to poaching.
The findings should be an urgent call for enhanced patrolling and resources dedicated to the identified hotspots. The research team hopes their work will lead to tougher laws and more strategic and coordinated international enforcement in these targeted areas to halt the slaughter of elephants for ivory.
Acknowledgement: We thank Sam Wasser for his helpful review of and corrections to this post. Read more: A non-technical article by Dr. Sam Wasser in TheConversation.com.
CITATION: S. K. Wasser, L. Brown, C. Mailand, S. Mondol, W. Clark, C. Laurie, and B. S. Weir. Genetic assignment of large seizures of elephant ivory reveals Africa’s major poaching hotspots. Science, 18 June 2015 DOI: 10.1126/science.aaa2457