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Budongo Forest Chimpanzees struggle with reduced sodium availability due to loss of plant species diversity in the forest. The Mohamed Bin Zayed Species project has been studying and helping protect the chimpanzee in Budongo forest since 1990.For more information about this project follow this link.
http://www.speciesconservation.org/projects/chimpanzee/1055



The following information was taken from two sources

http://www.speciesconservation.org/projects/chimpanzee/1055

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0006194

The present study has shown that the Budongo chimpanzees eat the decaying pith of Raphia farinifera, a swamp forest palm tree, to obtain sodium. This species has all but disappeared from the forest owing to its excessive use by tobacco farmers, who use it to tie their leaves during the drying and curing process (http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0006194). As a result the chimpanzees have now switched to eating the decaying wood of a swamp forest tree, Cleistopholis patens. We are documenting the availability of this tree. And we are engaged in discussions with local tobacco growers, their representatives, and the senior staff of BAT and other tobacco companies, to attempt to get them to work with farmers to use cotton string instead of raphia twine.




The mission of the Budongo Conservation Field Station (BCFS) is to conserve the population of chimpanzees in the Budongo Forest, Uganda. Our objectives are to keep daily records of the chimpanzees, facilitate research on them, provide conservation education for local people, remove snares from the forest, and increase our veterinary capacity in order to deal with chimpanzee morbidity and mortality. The BCFS was established in 1990. We cover the Budongo Forest Reserve in Masindi District, Western Uganda. Target species is the chimpanzee, Pan troglodytes schweinfurthii, and we additionally conserve three forest monkey species: the blue monkey (Cercopithecus mitis), the black and white colobus monkey (Colobus guereza), and the red-tailed monkey (Cercopithecus ascanius).


Vernon Reynolds1,3*, Andrew W. Lloyd2, Fred Babweteera3, Christopher J. English2

1 Emeritus Professor, School of Anthropology, University of Oxford, Oxford, United Kingdom, 2 Faculty of Science and Engineering, University of Brighton, Brighton, United Kingdom, 3 Budongo Conservation Field Station, Masindi, Uganda and Faculty of Forestry and Nature Conservation, Makerere University, Kampala, Central Region, Uganda

Abstract Top
For some years, chimpanzees have been observed eating the pith of decaying palm trees of Raphia farinifera in the Budongo Forest, Uganda. The reasons for doing this have until now been unknown. An analysis of the pith for mineral content showed high levels of sodium to be present in the samples. By contrast, lower levels were found in bark of other tree species, and also in leaf and fruit samples eaten by chimpanzees. The differences between the Raphia samples and the non-Raphia samples were highly significant (p<0.001). It is concluded that Raphia provides a rich and possibly essential source of sodium for the Budongo chimpanzees. Comparison of a chewed sample (wadge) of Raphia pith with a sample from the tree showed a clear reduction in sodium content in the chewed sample. Black and white colobus monkeys in Budongo Forest also feed on the pith of Raphia. At present, the survival of Raphia palms in Budongo Forest is threatened by the use of this tree by local tobacco farmers.

Citation: Reynolds V, Lloyd AW, Babweteera F, English CJ (2009) Decaying Raphia farinifera Palm Trees Provide a Source of Sodium for Wild Chimpanzees in the Budongo Forest, Uganda. PLoS ONE 4(7): e6194. doi:10.1371/journal.pone.0006194

Editor: Virginia J. Vitzthum, Indiana University, United States of America


Received: March 7, 2009; Accepted: June 12, 2009; Published: July 10, 2009

Copyright: © 2009 Reynolds et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: Grant from Primate Action Fund (Conservation International) totalling $4,750. No other funds were available for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

* E-mail: vreynolds@btopenworld.com

Introduction Top
The chimpanzees (Pan troglodytes schweinfurthii) of the Budongo Forest Reserve, Masindi District, Western Uganda, were initially studied by one of us (VR) in 1962 [1], and have been studied continuously since 1990 [2]. The Budongo Forest habitat consists of moist semi-deciduous tropical forest, and contains a number of forest types, notably Cynometra Forest, Mixed Forest, Colonising Forest, and Swamp Forest [3]. The study community of chimpanzees is named the Sonso community after the River Sonso which runs through its range. At various places along the river, Swamp Forest prevails. Swamp Forest contains several Raphia farinifera palm trees. After a single flowering and fruiting, the trees of this species lose their foliage and die. The dead bole remains standing and is 15–30 ft high. The bole rots down until it consists of a hard outer bark with a soft, moist, fibrous woody pith. Chimpanzees make a small hole in bark at the base of the dead tree with their teeth, widen it with their fingers and later their hands. Through the hole, they extract dead pith, chew it thoroughly, swallow the juice and some particles of woody matter, and finally spit out a fibrous wadge of chewed pith. There is frequently competition for Raphia pith. Eventually trees are abandoned, often with large holes and much inner pith removed (Fig. 1). Until now, the reason for consumption of the dead Raphia pith has not been known.

Figure 1. Decaying Raphia farinifera tree with medium sized hole.

doi:10.1371/journal.pone.0006194.g001
.Results Top
Table 1 shows the results of the chemical analysis expressed as mg per kg of dried material for each sample. In this table, results for elements for which no more than trace amounts were obtained have been omitted. With one exception (samples 7 and 8) samples were independent of each other, coming from different trees or at different collection dates. In the case of samples 7 and 8, sample 8 was a wadge (a spit-out chewed sample) of sample 7 and was omitted from the analysis. For purposes of analysis, the samples were placed into two groups: Raphia pith (n = 10), and all other samples (n = 16). Statistical tests were done using SPSS version 7. Data were not normally distributed (Lilliefors test p<0.000). Mean mineral contents of the two groups were therefore compared using non-parametric Mann-Whitney U-tests. Results are shown in Table 2.

Table 1. Results (mg kg−1).

doi:10.1371/journal.pone.0006194.t001
.Table 2. Mann-Whitney U-test results: raphia samples (without wadge sample) vs all other samples.

doi:10.1371/journal.pone.0006194.t002
.As can be seen from Table 2, significant differences between group means (Raphia vs. all other samples) were found for four of the minerals tested, sodium, calcium, manganese and zinc. In the case of calcium (p = 0.004), higher values occurred in the ‘all other samples’ group and reflect the normal high level of calcium in leaves and fruits. In the case of sodium (p<0.000), manganese (p<0.006), and zinc (p = 0.007) higher values occurred in the Raphia group. Bark, leaves and fruits from other tree species did not contain the high levels of sodium found in the Raphia samples. These results are illustrated by box-plots (Fig. 2).

Figure 2. Box plots showing results for raphia samples (without wadge sample) vs all other samples: (a) sodium (b) manganese (c) zinc (d) calcium.

All values are mg.kg−1.

doi:10.1371/journal.pone.0006194.g002
.Discussion Top
Since study of the Sonso community of chimpanzees began in 1990, individuals and small parties of the animals have been seen occasionally eating the pith of dead Raphia trees, but until now the reason for doing so has not been known. The first report showing high levels of sodium in samples of dead wood eaten by apes was that of Rothman et al for mountain gorillas (Gorilla gorilla beringei) in Bwindi Impenetrable National Park, Uganda [4]. In that study it was estimated that the sodium obtained from dead wood constituted 95% of the sodium in the gorillas' diet. Using similar methods to those employed here, a mean dry sodium weight of 810.7 mg kg−1, with a range of 100–1920 mg kg−1 was measured.. This compares with the mean dry sodium weight for Raphia samples in the present study of 5432 mg kg−1, range 1431–14616 mg kg−1. Raphia palm trees in Budongo Forest therefore offer higher concentrations of sodium to the chimpanzees than dead wood does to the Bwindi gorillas.

Rothman et al found that sodium levels were significantly higher in dead wood than in other items in the diet [4], and this was also the case in the present study. As they point out, sodium is an essential item of diet for apes, lack of which has wide-reaching effects on health [5]. In the Budongo Forest too, there appears to be little sodium in the other plant parts eaten and tested here (bark, leaves and fruits), although sodium is present in small quantities. In particular, the greater part of the chimpanzees' daily diet (up to 95%) consists of leaves and fruits [6] which contain only small quantities of sodium. There is however one important dietary difference between chimpanzees and mountain gorillas. The Budongo chimpanzees eat meat sporadically, mainly in the form of colobus monkeys (Colobus guereza) which are hunted, and this provides an additional source of sodium. The interaction between Raphia eating and meat eating was not explored in this study.

As in the present study, Rothman et al found significantly lower values for calcium and phosphorus in decaying wood than in the rest of the diet [4]. They also found lower values for manganese which was not the case in the present study, in which manganese was higher in the Raphia samples (p = 0.059). The reason for this may be the high levels of manganese in groundwater along the Albertine Rift [7]. Mahaney et al found high levels of manganese in clay eaten by chimpanzees living in the Mahale mountains, Tanzania, also along the Rift Valley [8]. Significantly lower values for other minerals, magnesium, potassium, zinc, and copper found by Rothman et al were not found in the present study [4].

Black and white colobus monkeys (Colobus guereza) are also known to consume Raphia pith in Budongo Forest (pers. comm., field assistants at BCFS) and during the present study hairs of this species were twice found at Raphia feeding sites. Oates found high levels of sodium, iron, manganese and zinc in swamp plants eaten by black and white colobus monkeys living in Kibale Forest, western Uganda, also along the Albertine Rift [9]. High mineral content was also found in some clays collected from stream-banks in the forest. Concentrations for swamp plants and clays were higher than in dry-land leaves, buds and fruits constituting the major part of the monkeys' diet.

An interesting feature of the samples collected concerns samples 7 and 8. These were the only two non-independent samples collected, coming from the same tree during the same observation period. Sample 7 consisted of Raphia pith collected with a knife from inside the tree. Sample 8 consisted of a discarded wadge of Raphia pith from the same tree, collected on the ground at the feeding site. Comparison of the sodium content of these two samples shows that the uneaten Raphia pith (sample 7) contained 7194 mg kg−1, whereas the chewed and spat-out wadge (sample 8) contained 1095 mg kg−1, evidence that the individual which chewed this sample did indeed ingest sodium.

In recent years Raphia farinifera, a tree we now know to provide the chimpanzees of Budongo Forest with essential sodium, has become scarcer. Besides natural predators such as baboons and pigs that eat its shoots, it provides humans with two products. The living trees are occasionally felled and the trunk opened to allow air into the pithy centre, which then ferments and produces an alcoholic palm wine beverage which is bottled and sold. This, however, is not thought to be the main cause of the decline in numbers of Raphia. The main danger to this species comes from local tobacco farmers, who kill the tree during its growth period, before flowering and fruiting, in order to strip its leaves for Raphia string (‘raffia’), which is then used to tie tobacco leaves during and after the the drying and curing process [10]. As a result, Raphia palms are becoming scarce in Budongo Forest. Tobacco farmers and British American Tobacco, a company which buys much of the crop, will be approached about this problem and it is hoped a solution may be found.

Materials and Methods Top
(a) Field collection
Between 16 Feb and 2 April 2008, samples of pith (including one wadge) from Raphia trees were collected, in each case when chimpanzees had been observed feeding on the trees just before collection. Samples weighed <50 g. Pith samples were obtained from the inside of trees with use of a knife. The wadge was collected from where it was dropped, beside the hole in the tree. Each sample was placed into a sample tube using gloves or tweezers, tubes were closed and marked with sample no., date, tree location, species of tree, name(s) of chimpanzees feeding on the tree, nature of the sample (bark, pith or wadge), initials of collector. Collectors were in all cases trained field assistants of BCFS or in one case VR. During the same time period, samples of rotten wood, bark, leaves and fruits seen being eaten by chimpanzees were collected in the same way, in adjacent forest, to be analysed for comparison with the Raphia samples.

All samples were taken within a period of 2 hours to the field base where they were removed from the bags with tweezers and dried separately in a warm dry space at room temperature. Samples were dry in 1–3 days and all dried satisfactorily. The dry samples were placed in polythene bags which were sealed, marked, and taken by air to the UK for analysis. In the UK prior to analysis they were kept in a dry room at room temperature. No samples were spoiled during the pre-analysis period.

(b) Laboratory analysis
The samples of material were dried to constant weight in an oven at 105°C. The samples were then ashed at 550°C in a pyrolysis oven. The total mass of the ashed material was determined before digesting a sample (circa 0.1 g) of each material in 3 mL of aqua regia in a water bath at 100°C for 2 hours. The digested samples were diluted to 10 mL using distilled water before serially diluting to obtain 1 in 10, 1 in 100 and 1 in 500 dilutions. The elemental content of each sample was then determined using a Perkin Elmer Optima 2100 DV Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) using 5 and 10 mg L−1 elemental standards.

Further Information
Still images and video clips of Raphia eating are available from the first author and from C. Hobaiter, School of Psychology, St Andrews University, email: clh42@st-andrews.ac.uk

Acknowledgments Top
Grateful thanks are due to Kenneth Burton and Andrew Smith for initial advice, and to Roman Wittig, Zephyr Kiwede and Concy Olanya for help in the field situation. We were helped by the staff of the Budongo Conservation Field Station, in particular Geresomu Muhumuza, and all others who assisted in various ways in this study. We are grateful to the Primate Action Fund of Conservation International for funding for this project. We thank the National Forest Authority, the Uganda Wildlife Authority, the Uganda National Council for Science and Technology, and the President's Office. Finally we thank the Royal Zoological Society of Scotland for provision of core funding for BCFS, without which this project would not have been possible.

Author Contributions Top
Conceived and designed the experiments: VR. Performed the experiments: FB. Analyzed the data: AL CE. Contributed reagents/materials/analysis tools: AL. Wrote the paper: VR AL FB.

References Top
1.Reynolds V, Reynolds F (1965) Chimpanzees of the Budongo Forest. In: DeVore I, editor. Primate Behaviour: Field studies of monkeys and apes. New York: Holt Rinehart and Winston.
2.Reynolds V (2005) The Chimpanzees of the Budongo Forest. Oxford University Press.
3.Eggeling WJ (1947) Observations on the ecology of the Budongo Rain-forest, Uganda. J Ecol 34: 20–87. Find this article online
4.Rothman JM, Van Soest PJ, Pell AN (2006) Decaying wood is a Na source for mountain gorillas. Biol Lett 2: 321–324. Find this article online
5.Robbins CT (1993) Wildlife feeding and nutrition. San Diego, CA: Academic Press.
6.Newton-Fisher NE (1999) The diet of chimpanzees in the Budongo Forest Reserve, Uganda. Afr J Ecol 37: 344–354. Find this article online
7.British Geological Survey (2001) Groundwater quality: Uganda. NERC Information Sheet.
8.Mahaney WC, Hancock RGV, Aufreiter S, Huffman MA (1996) Geochemistry and clay mineralogy of termite mound soil and the role of geophagy in chimpanzees of the Mahale Mountains, Tanzania. Primates 37: 121–134. Find this article online
9.Oates JF (1978) Water-plant and soil consumption by Guereza monkeys (Colobus guereza): a relationship with minerals and toxins in the diet? Biotropica 10: 241–253. Find this article online
10.Kyeyune S (2003) Abundance and size distribution of Raphia farinifera in Budongo Forest Reserve, Western Uganda. BSc dissertation, Faculty of Forestry and Nature Conservation, Makerere University, Kampala, Uganda.

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Gorilla Doctors - Gorilla Doctors Blog - Kwitonda and Magumu 

http://www.nytimes.com/2010/06/22/science/22chimp.html. the following article came from this link in the new york times

Every day, John Mitani or a colleague is up at sunrise to check on the action among the chimpanzees at Ngogo, in Uganda’s Kibale National Park. Most days the male chimps behave a lot like frat boys, making a lot of noise or beating each other up. But once every 10 to 14 days, they do something more adult and cooperative: they wage war.

A band of males, up to 20 or so, will assemble in single file and move to the edge of their territory. They fall into unusual silence as they penetrate deep into the area controlled by the neighboring group. They tensely scan the treetops and startle at every noise. “It’s quite clear that they are looking for individuals of the other community,” Dr. Mitani says.

When the enemy is encountered, the patrol’s reaction depends on its assessment of the opposing force. If they seem to be outnumbered, members of the patrol will break file and bolt back to home territory. But if a single chimp has wandered into their path, they will attack. Enemy males will be held down, then bitten and battered to death. Females are usually let go, but their babies will be eaten.

These killings have a purpose, but one that did not emerge until after Ngogo chimps’ patrols had been tracked and cataloged for 10 years. The Ngogo group has about 150 chimps and is particularly large, about three times the usual size. And its size makes it unusually aggressive. Its males directed most of their patrols against a chimp group that lived in a region to the northeast of their territory. Last year, the Ngogo chimps stopped patrolling the region and annexed it outright, increasing their home territory by 22 percent, Dr. Mitani said in a report being published Tuesday in Current Biology with his colleagues David P. Watts of Yale University and Sylvia J. Amsler of the University of Arkansas at Little Rock. Dr. Mitani is at the University of Michigan.

The objective of the 10-year campaign was clearly to capture territory, the researchers concluded. The Ngogo males could control more fruit trees, their females would have more to eat and so would reproduce faster, and the group would grow larger, stronger and more likely to survive. The chimps’ waging of war is thus “adaptive,” Dr. Mitani and his colleagues concluded, meaning that natural selection has wired the behavior into the chimps’ neural circuitry because it promotes their survival.

Chimpanzee warfare is of particular interest because of the possibility that both humans and chimps inherited an instinct for aggressive territoriality from their joint ancestor who lived some five million years ago. Only two previous cases of chimp warfare have been recorded, neither as clear-cut as the Ngogo case.

In one, a chimp community first observed by Jane Goodall in Tanzania’s Gombe National Park split into two and one group then wiped out the other. But the chimps had been fed bananas, to enable them to be observed, and some primatologists blamed the war on this human intervention. In a second case, in the Mahale Mountains National Park of Tanzania, Toshisada Nishida of Kyoto University noticed that a chimp group had disappeared, presumably killed by its neighbors, but he was not able to witness the killings or find the bodies.

Dr. Mitani’s team has now put a full picture together by following chimps on their patrols, witnessing 18 fatal attacks over 10 years and establishing that the warfare led to annexation of a neighbor’s territory.

The benefits of chimp warfare are clear enough, at least from the perspective of human observers. Through decades of careful work, primatologists have documented the links in a long causal chain, proving for instance that females with access to more fruit trees will bear children faster.

But can the chimps themselves foresee the outcome of their behavior? Do they calculate that if they pick off their neighbors one by one, they will eventually be able to annex their territory, which will raise their females’ fertility and the power of their group? “I find that a difficult argument to sustain because the logical chain seems too deep,” says Richard Wrangham, a chimp expert at Harvard.

A simpler explanation is that the chimps are just innately aggressive toward their neighbors, and that natural selection has shaped them this way because of the survival advantage that will accrue to the winner.

Warfare among human groups that still live by hunting and gathering resembles chimp warfare in several ways. Foragers emphasize raids and ambushes in which few people are killed, yet casualties can mount up with incessant skirmishes. Dr. Wrangham argues that chimps and humans have both inherited a propensity for aggressive territoriality from a chimplike ancestor. Others argue the chimps’ peaceful cousin, the bonobo, is just as plausible a model for the joint ancestor.

Dr. Wrangham’s view is that since gorillas and chimps are so similar, their joint ancestor, which lived some seven million years ago, would have been chimplike and therefore so would the joint ancestor of chimps and humans when they parted ways two million years later. “So I think it’s very reasonable to think this behavior goes back a long way,” he said, referring to the propensity to wage war against one’s own species.

Dr. Mitani, however, is reluctant to infer any genetic link between human and chimp warfare, despite the similarity of purpose, cost and tactics. “It’s just not at all clear to me that these lethal raids are similar sorts of phenomena,” he said. More interesting than warfare, in his view, is the cooperative behavior that makes war possible.

Why do chimps incur the risk and time costs of patrolling into enemy territory when the advantage accrues most evidently to the group? Dr. Mitani invokes the idea of group-level selection — the idea that natural selection can work on groups and favor behaviors, like altruism and cooperation, that benefit the group at the expense of the individual. Selection usually depends only on whether an individual, not a group, leaves more surviving children.

Many biologists are skeptical of group-level selection, saying it could be effective only in cases where there is intense warfare between groups, a reduced rate of selection on individuals, and little interchange of genes between groups. Chimp warfare may be constant and ferocious, fulfilling the first condition, but young females emigrate to neighboring groups to avoid inbreeding. This constant flow of genes would severely weaken any group selective process, Dr. Wrangham said.

Samuel Bowles, an economist at the Santa Fe Institute who has worked out theoretical models of group selection, said the case for it “is pretty strong for humans” but remains an open question in chimpanzees.

Chimp watching is an arduous task since researchers must first get the chimpanzees used to their presence, but without inducements like bananas, which could interfere with their natural behavior. Chimpanzees are immensely powerful, and since they can tear each other apart, they could also make short work of any researcher who incurred their animosity.

“Luckily for us, they haven’t figured out that they are stronger than us,” Dr. Mitani said, explaining that there was no danger in tagging along behind a file of chimps on the warpath. “What’s curious is that after we do gain their trust, we sort of blend into the background and they pretty much ignore us.”