The elephants of Ruaha-Rungwa in southern Tanzania have been well surveyed in recent years, and the latest research confirms their significant decline due to poaching, despite the complexities of interpreting and presenting census results.
By Dr. Trevor Jones
Last week at the 10th TAWIRI (Tanzania Wildlife Research Institute) Scientific Conference in Arusha, the results of the 2015 TAWIRI-led re-census of the Ruaha-Rungwa elephant population, now East Africa’s largest since the tragic decimation of the Selous herds over the last decade, were announced by the Government. Tanzania’s Daily News immediately reported on a “comeback” for Ruaha’s elephants – a misleading headline, and complacent misrepresentation of the new findings. Once again, as scientists, we have failed to effectively communicate to the public what an aerial census has been able to tell us – and what it cannot tell us.
Ruaha-Rungwa is now the most frequently surveyed elephant population in Tanzania in recent years, with censuses conducted using the SRF (Systematic Reconnaissance Flight) sampling method in 2006, 2009, 2013, 2014, and again in 2015 (following controversy over the low 2014 result). We must bear in mind that although this is the most practical method of counting elephants over large areas (>40,000 km2 in the case of Ruaha-Rungwa), only about 6% of the actual area is surveyed. The population estimate and crucially, the estimated margin of error, are then calculated statistically from this sample count.
The official TAWIRI estimates that the five most recent censuses of the Ruaha-Rungwa ecosystem (all dry season counts, between September and November) have generated, are as follows. It is important to note that the area surveyed has increased, and that elephants were counted in 2015 that were outside of the previously defined census zone.
|Population Estimate||Standard Error||Population Estimate Range||Area Surveyed (km2)|
|35,461||± 3,653||31,808 – 39,114|
|34,664||± 4,178||30,486 – 38,842||43,641|
|20,090||± 3,282||16,808 – 23,372|
|8,272||± 1,652||6,620 – 9,924|
|2015||15,836||± 4,759||11,077 – 20,595|
And this is what these results look like over time, with a trendline added:
I would contend that at least three clear observations can be made from analysing this figure (and all other series of SRF census results over time). The first is that any single population estimate cannot be taken in isolation as the truth; there are too many real-world factors affecting accuracy and leading to variation between years (including distribution of elephant across the landscape, and degree of leaf cover in the woodlands affecting detectability of elephants and carcasses).
Second, the Standard Error bars are more informative than the actual population estimate, as they show the range of possible numbers of elephants at that time. The large Standard Error on the 2015 population estimate means that these results alone only tell us that the area censused had between 11,077 and 20,595 elephants.
Third, when we have enough counts to compare between years, the trend in the population – the most important finding from a conservation point of view – is clearly shown. This trend is downwards, at an extremely worrying rate.
Also at the Conference last week, I presented data showing changes in the population structure of Ruaha-Rungwa’s elephants which support this decline, and illustrate some of the effects of heavy poaching in the ecosystem, including the loss of nearly all older individuals (based on 535 elephants sampled, less than 1% of the population are over 40 years old).
The last few months have brought some encouraging news that this devastating elephant poaching crisis can be brought to an end. At the demand end of the trade, prices of ivory in China are falling, eroding the profit of poachers and traffickers, however the threats to elephants will persist until China and other countries actually close their ivory markets completely.
In Tanzania, recent arrests of ivory traders Yang Feng Lan (dubbed the “Queen of Ivory”) and Boniface Mariango (dubbed “Shetani”, or Devil in Swahili), and many elephant poachers, are to be applauded – but this is only a beginning to the solution, as President Magufuli recognised in his inaugural address to the Tanzanian Parliament on 20th November 2015: “…there has been poaching in which the responsible ministry must be involved, for it is not possible for ivory of such large amounts from our country to be seized in other countries without the knowledge of our local officials…”.
Crucially, while there is good work happening on the ground across Tanzania, there is no concrete evidence yet that levels of elephant poaching are slowing down. We can enjoy the positive likelihood that not as many elephants have been lost in Ruaha-Rungwa as was feared after the 2014 census, but we cannot afford to allow scientific findings to be misrepresented, nor to become complacent in any way. The struggle to save Tanzania’s elephants goes on.
Dr. Trevor Jones is Director of the Southern Tanzania Elephant Program (STEP). STEP has an active elephant monitoring and protection program in the Ruaha-Rungwa ecosystem, and was an invited participant in the 2015 census project. We worked closely with the TAWIRI team, carrying out parallel aerial surveys with the STEP microlight, and placing 90 camera-traps in remote areas to assess relative elephant abundance and behaviour patterns. All results will be included in the forthcoming TAWIRI final census report. However, the views expressed here are of the author only.