>>Peter said (about the teeth microwear studies):
>>>In your references are they specific about what fruits are the
>>mainstay of the chimp diet?

>Sorry, I was not clear. I meant what specific fruits do the chimps eat
>in the jungles today and in what proportions? If you do not know maybe
>you have an idea of where I could find this kind of info?

Peter, the info you are wanting is difficult to decipher because the field
researchers--at least in the few studies I have xeroxes of here at home--do
not have the same objectives when classifying fruit as we as who are into
vegetarian or "fruitarian" diet do. Mainly the researchers look at the
total number of fruit species eaten per month or per year, or whatever, but
they don't tend to publish very many specific charts of *which* species
make up what proportions of the total.

The biggest reason is that it is very difficult to calculate precise
*volume* proportions. What the researchers report is what they *can*
observe, which is feeding time spent on which foods, or numbers of
different kinds of fruit remains found in their stool samples. Trying to
project absolute volume proportions from this kind of data is difficult,
though from time to time, you'll hear the researchers give rough estimates.
(I.e., 2/3 fruit for chimps, 4-6% animal foods, etc.)

Goodall, however, has a chart for several different species of fruit eaten
in The Chimpanzees of Gombe by percentage of feeding time (pp. 234-235).
But you would have to get a botanical guide to African fruits to decipher
what the hell kind of fruits these are (only botanical names are given),
plus a ruler to measure percentages on the graphs, and a calculator to
figure proportions. And even then, you may not come up with usable figures
since only *some* fruits are listed. The charts here seem more oriented to
showing which how fruits are eaten over the year, which times of year
consumption crests during seasonal peaks, and which ones are more regularly
available throughout the year.

One book I haven't looked at in awhile which might have some interesting
data is Omnivorous Primates, written in the early 80s with Teleki as one of
the authors or editors. Another very good book is Chimpanzee Material
Culture, by W.C. McGrew, but it is more a look at characteristics of
chimpanzee life with an eye to how much they are influenced strictly by
physical evolution, and how much by cultural evolution. (There are some
differences between chimp communities in tool use, etc.) Generally, if you
just go to the nearest university library and go to where the QL737 call
numbers are in the stacks (assuming they are using the Library of Congress
classification scheme), you will find most of the books they have on apes.

The recent chimp studies I have seen have the objective of looking at how
the chimps adjust their diet depending on seasonal availability of the
major items in their diet. For instance, when the number of fruit species
of ripe fruit is at a low during the season, they will compensate by making
up the difference by eating more leaves, or pith, etc. My impression from
the studies is that, yes, chimps do eat quite a lot of high-sugar fruits,
but there is tremendous variability from season to season in numbers of
fruits, and even between chimp communities (due to locale, etc.).

>From what I can tell, the researchers have discovered that chimps seem to
try to maintain the level of 2 things (among others) in their diet at
fairly constant levels even when the availability of normally-favored items
fluctuate:

(1) the energy quotient of the food (i.e., calories, or whatnot), and
(2) the protein content of the food.

Fruits tend to predominate in sugar (energy), while leaves are higher in
protein but low in sugar. When fruit diversity is low during the dry
season, the diversity of the fruit species eaten obviously plummets, but
during this time the chimps will go to fallback fruits they may not
normally eat so much of, but are ones which may fruit through the dry
season.

Also pith consumption goes up during fruit scarcity as a substitute energy
source, but it is not necessarily because of the sugar concentration in
piths, which in most piths species is not that much higher than in leaves,
but rather because pith contains high concentrations of fermentable fiber.
(Flora/fauna in the chimpanzee gut can breakdown this fiber for energy,
apparently.)

Usually when fruit consumption goes down, pith and leaf consumption goes
up. Insect consumption tends to be fairly regular throughout the year,
although according to one researcher it does go a bit higher when more
leaves were eaten during the dry season when fruit availability is less
diverse. Goodall notes, though, that there are peak termite "seasons" as
well during the time the "reproductives" leave the main nest to form new
colonies. (In The Chimpanzees of Gombe, p. 248, Goodall also notes that the
lipid (fat) content of the insects may be one reason why they are regularly
eaten in addition to the animal protein content.) A factor in leaf
selection is that chimps generally will tend to avoid foods with high
tannin or phenolic content, no doubt due to the taste (these are digestion
inhibitors put out by the plants themselves), both of which tend to be
higher in mature leaves, so the chimps seem to favor young leaves if
available.

--Ward Nicholson <[log in to unmask]> Wichita, KS