Tobacco growers threaten chimpanzees
Published 2 October 2009
It is well documented how tobacco is harmful to humans but researchers have discovered that it also poses a threat to one of our closest relatives – the chimpanzee.
Tobacco growers in Uganda are decimating raphia palms in the Budongo Forest Reserve which is home to 650 chimpanzees. Growers use the raphias to produce string to tie up and hang bundles of tobacco leaves during the drying and curing process. What the growers didn't realise until recently was that the palms contain a vital store of sodium which chimps probably need to stay healthy.
Professor Andrew Lloyd, Dean of the Faculty of Science and Engineering, at the University of Brighton, said: "This may represent a new and major conservation problem as no other major source of sodium has so far been identified."
Over the past year, the university has been supporting Professor Vernon Reynolds, an emeritus professor from Oxford University, as part of the Budongo Conservation Field Station programme to help conserve the chimpanzees.
Raphia leaves are used for making the well-known string of that name 'raffia' and the stems of the leaves are used for basket making. What wasn't realised until recently was how much chimps rely on them to supplement their diet.
As recently reported by the Public Library of Science, Professors Reynolds and Lloyd and their team analysed the dead pith of the palms for mineral content and found it contained high levels of essential sodium.
For many years, members of the team working in the forest had observed chimps making holes in the bark of dead raphia palms, inserting a finger, a hand or even an entire arm into the cavities, and scraping out some of the dead pith inside.
The chimps were observed chewing the pith until they tired of it and spat it out. Professor Lloyd said: "Now we know what they are after – an essential mineral not present in the rest of their diet."
"This is the first time a rich source of sodium has been shown in the natural diet of wild chimps, though a similar discovery was made two years ago for gorillas, which eat dead wood for sodium."
Raphia palms, which are found in swamp forests, take many years to grow to maturity and then flower and fruit before the entire top of the tree falls down, leaving the trunk standing as a dead spike, often 20ft high.
It is these dead trees that the chimps exploit. The outer bark is very hard but using their teeth they make a hole in it, big enough to insert a finger to reach the damp, inner pith.
Gradually, they make the hole bigger, pulling out more pith until the opening is big enough for a small chimp to climb inside.
The scientists believe the sodium that chimps extract from the pith is probably essential. Without it, nerves and muscles would cease to function, the absorption of major nutrients would be disrupted and the body would not be able to maintain adequate water and mineral balance.
The race is therefore on to find an alternative string to save the chimps. Nylon twine, cotton and twine made from sisal have already been shown to the farmers, with mixed reactions. Professor Lloyd said: "The cost factor is not decisive – in due course we can try to convince the large tobacco companies working in Uganda, chiefly BAT and Continental, to switch to the more chimp-friendly materials."
Recently Professor Reynolds has been awarded a grant from the Mohamed Bin Zayed Species Conservation Fund which includes £4,500 to the University of Brighton to continue analytical support to the research programme. Core funding for the Budongo Conservation Field Station comes from the Royal Zoological Society of Scotland at Edinburgh Zoo.
As part of this programme, meetings are being arranged with tobacco farmers in the region to impress upon them the need for conservation. Professor Reynolds said: "We are informing them that they should not continue using raphia as they provide an essential part of the chimpanzees' diet, a fact farmers are not aware of."
Professors Reynolds and Lloyd said the need to protect and save the chimps' supply of sodium was urgent: "We need to find alternative kinds of string acceptable to the tobacco growers before the chimps begin to show signs of sodium deficiency."
Photo credit: Klaus Zuberbuhler.
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