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UTM 4: The Chimpanzee Diet

(week 8)

Dave Samson

on 28 September 2018

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Transcript of UTM 4: The Chimpanzee Diet

Sister Species: Lessons from the chimpanzee
The chimpanzee's place in nature
The Chimpanzee Diet Project
What is being treated?

Intestinal parasites are common
87% of chimp feces sampled by Goodall had roundworms
A number of other intestinal parasites are common, too
Cause lethargy and diarrhea
They can cause pain and discomfort
They undoubtedly interfere with digestion

They fine-tune their strategy by:
Anticipating which food items will be available
Passing over items low on their optimal diet list

Large, sugar-rich, low antifeedant fruits
Small, sugar-rich, low antifeedant fruits
Fatty insects
Starchy fruits with low antifeedants
Sugary fruits with acceptable levels of tannins and/or toxins

Large, sugar-rich, low antifeedant fruits
I.e., they love sugary fruits, but would pass by such fruits to hunt monkeys

They pass by less-preferred items when they expect to encounter preferred items
Items are rank-ordered from the most highly desired to least
E.g., If they know items #24 is out there, pass by #225

How do chimpanzees select food items?
Although list of food items is long, chimps eat selectively
Some items are eaten every time they encounter them
Other items only when near starvation

Chimps seek to minimize effort i.e. energy expenditure
Avoid injury
Minimize time spent foraging
Minimize antifeedants
Maximize calories
Threshold of minerals, vitamins
Medicinal Plants

Lesson: Medicine has a deep evolutionary history
Probably in common ancestor of apes/humans
Medicinal Plants

Leaf surface is rough, hairy, sandpaper-like
Physically scrape the parasites of the intestinal walls
Shock the parasites with antibiotics
Secondary compounds shown to kill bacteria, fungi
Intestinal parasites and maybe even malaria
Induce fluid production in great abundance to flush parasites

Medicinal plants are eaten slowly
They are not chewed
They emerge in the dung whole
They often eat little else in the course of the day

Medicinal Plants

Wrangham and Nishida (1983) discussed this odd behavior when eating a plant called Aspilia
Plants are rarely eaten
Only when individuals seem sick

Medicinal Plants

KDH Field notes:

Night: normal
7:30 CH sick
Walked slowly
Made another nest and took a nap

Why would chimpanzees eat things for reasons other than nutrition?
Why not eat everything you can eat?
If you fill your stomach with poor food, no room for
“good” food

Optimal Foraging Theory
Foraging Imperatives
Optimal diet list
Optimal diet list
Foraging imperatives
Sleep increases immunocompetence
Especially last few hours (extra sleep)
Well rested individuals less prone to come down with colds
Chimpanzee foraging
For chimps, cellulose is a poor nutrient, eaten purposefully only when starvation threatens

FIBER: indigestible cellulose

Chimps seek sugar, fats, threshold amounts of other nutrients

But the world is much more complicated than this…

Their low quality diet requires chimpanzees to have larger stomach (to hold the greater volume)
Larger intestines (to absorb more nutrients)

Most animals select ripe fruits; they disappear quickly
Fruits ripen at different times: a fruit laden tree has only some ripe fruits
Many sweet fruits must be avoided because of antifeedants

As fruit ripens enzymes neutralize alkaloids
Enzymes break down tannins
Break down complex carbohydrates into sugars

There are two principal types of such
chemical deterrents

Toxins: enter bloodstream by crossing tissue barriers; interfere with physiological processes, particularly neural activity
Mostly alkaloids
caffeine, cocaine,
nicotine, strychnine,
morphine, codeine,
LSD, solanine

There are two principal types of such
chemical deterrents

Tannins: bind with plant proteins in the gut to make them difficult to digest
Or bind with digestive enzymes
Taste dry
Some break down in heat (cooking)
High in unripe fruit

Strategy: produce extra digestive enzymes in saliva, in gastric juices

1976: suggested only purpose of most secondary compounds is as chemical deterrents
They are defensive
10,000 known, may be 400,000 total

Mammals require coevolved gut bacteria to break down cellulose
Break open cell walls
A steady stream of nutrients pushed downstream
‘Fermentation’ requires a large colon as fermenting chamber

Chimps seek sugar, fats, threshold amounts of other nutrients

At the same time, they try to avoid a class of compounds called antifeedants

Lesson: An ounce of strawberries has differing amounts of calories according to which animal eats it!
But what if an animal produces and
enzyme that counteracts this substance?

Consider a food item that contains about 20 calories: 1 oz. strawberries

Nutrient Total
Calories 19.56
Protein (g) 0.17
Fat (g) 0.17
Carbs (g) 4.93
vitA (IU) 25.52
vitC (mg) 10.49
satF (g) 0.05
Chol (mg) 0.00

In the chimpanzee world, fats and sugars are rare
Many fruits are almost tasteless
Wild figs, e.g., have very little taste
Unripe fruits have fewer sugars in them, more ‘bad things’

Tomatoes contain the alkaloid ‘a-tomatine when unripe

As fruit ripens enzymes neutralize alkaloids

Many toxins taste bitter
i.e., our physiology helps
us detect and reject poison

Defensive strategies
Detect, avoid them
Large liver
enzymes to detoxify

Secondary compounds are those
NOT be necessary for life
Plants contain many molecules, most of which are Primary Compounds

Primary compounds are necessary for life
Remove them, plants grow poorly, die

What if we add a substance to it that bonds with sugars and ties up half a calorie for every calorie in the fruit?

Now how many calories are in the fruit?

10 calories

Monkey bodies were also monkey-like

The controlled use of energy
The GREATEST human innovation!?

What was the impact?
Paleoanthro meets primatology

Charles Darwin considered fire to be among the single most important discovery made by early peoples: “the art of fire,” was “probably the greatest [discovery] ever made by man” and “dates from before the dawn of history (Darwin 1874: 50).”

“Of all human inventions the discovery of the method of kindling fire has probably been the most momentous and far-reaching ( Frazer 1930:1).”

Evidence for fire in the archaeological record
The morphological evidence
Richard Wrangham

proposed “the radical hypothesis that cooking was adopted around the origin of
Homo erectus
and was responsible for many of the features that characterize human evolutionary changes from australopithecines.”

The Cooking Hypothesis?
Reduction in teeth and jaw size, transition from large to a small gut, yet increase in energy expenditure (Wrangham et al. 1999)
“Raw foodist” diet suffer reduced reproduction function and are characterized by low levels of energy (Wrangham and Conklin-Brittain 2003)
Chimpanzees prefer cooked food items

Swartkrans, South Africa
1.6 mya
Burnt bones
Dmanisi, Georgia
Indirect, 1.8 mya
Temperate climate
But how many calories does it cost to
produce this enzyme?

Costs of consuming cellulose
Must carry the extra weight
Requires energy to chew
Volume that limits intake of better things
Dietary physiology
Ruminant (cellulose specialist): mammal that chews the cud regurgitated from its rumen
alkaloid lvl
Taxonomy: ideally, reflects how recently two species shared a common ancestor
Biological species - defined as a group of actually or potentially interbreeding natural populations, reproductively isolated from other such groups
The Sunday walk

Bought his book, used it to become backyard naturalists
Sunday—can’t work, what can you do?
After church, go for a walk in nature
I.D. a species or two
Many parish clerics in Europe amateur naturalists (Mayr)

Linnaeus believed there were 10,000 species
He knew 6,000
Modern science has classified more than 1.5 million species of plants, fungi, insects, and animals

1. Kingdom – Animalia [vs Plantae, Monera (Bacteria, Archaea),
Protista (e.g., Algae), Fungi (e.g. Molds, Yeasts, Mushrooms)]

Sunday Nature Walk
For the rich: Sunday carriage ride in nature
Evolved into the Sunday drive using a car to traverse the country

Scientists welcomed this regularization:

At last there was a system or structure to insert new species
A method to determine whether the spp. was new
An authority to dispense wisdom from on high
Educated lay-persons were eager to engage: it was pious

Primates: extraordinarily diverse ~340 species
Weight: 1 oz. (pygmy mouse lemur) to over 400 lbs (6400 oz.)

The Chimpanzee’s Place in Nature

The Chimpanzee’s Place in Nature
Primate phylogeny
Kingdom – Animalia
2. Phylum – Chordata
3. Class – Mammalia
4. Order – Primates
Suborder – Haplorhini
Superfamily –Hominoidea
5. Family – Hominidae
6. Genus – Homo
7. species – sapiens

Wet nose, long snout
More reliant on sense of smell than other primates

The Chimpanzee’s Place in Nature

2. Phylum – Chordata (other phyla include Mollusca, Arthropoda)
3. Class – Mammalia (vs Pisces, Amphibia, Reptilia, Aves)
There are 5,400+ species of mammals

4. Order – 12 Orders among mammals – Primates
(vs. Carnivora, Perissodactyla, Artiodactyla, Proboscoidea, Rodentia,
Cetacea, Chiroptera, Insectivora, Sirenia, Edentata, Lagomorpha)

Suborder – Strepsirhini, Haplorhini

Superfamily – 6 (Lemuroidea, Lorisoidea, Tarsiioidea,
Ceboidea, Cercopithecoidea, Hominoidea)
5. Family – Hominidae for us

Linnaean Taxonomic System
6. Genus – (54 genera in Primates)

7. species – (~340)

Tapetum lucidum
- layer in the retina of the eye for reflecting light. Even diurnal and crepuscular (active at dawn and twilight) lemurs of Madagascar have retained the tapetum

Week 4 Quiz (cell phones off)
1. Chimpanzees eat meat, leaves, insects, fruits, roots, flowers, and bark; that being said, they are “specialists” in one of the above. In which of these dietary categories is the chimpanzee a specialist? What proportion of their diet is dedicated to this special category?

2. Chimpanzees rely on hunted animal prey for essential micronutrients, and they favor meat over every other form of food. Yet it has been observed that chimpanzees rarely hunt when fruit is scarce. Why is this?

3. According to Wobber et al. (2008) chimpanzees prefer cooked over raw foods. What are the implications for this in evolutionary terms?

Choose 1 of the 3 questions:
Note: Please write down name and student ID
Home range routes
Pacmanzee (TM)
Differential caloric payoff
Reproductive fitness
Home ranges
Optimized patterns
Escape routes
Medicinal Plants
Secondary compounds
Or, why does shit smell like shit?
Reverse the logic of the question?

Why do you crave some things, whereas you are repelled by others?
Differential caloric payoff
Reproductive fitness
Home ranges
Optimized patterns
Escape routes
Greatest RF
Thought experiment
We call the ranked list of food items, from most preferred to least preferred, the chimpanzee optimal diet list
% feeding on ripe fruit

% trees with ripe fruit
Meat contains important, essential nutrients
Meat contains a whole host of micronutrients that are virtually nonexistent in plant foods
Vitamin B12, creatine, carnosine, cholecalciferol, docosahexaenoic acid and heme-iron
Meat also contains critical nutrients that, while not totally absent in foods other than animal protein, are difficult to obtain from plants:
Vitamin A, vitamin K, calcium, sodium, and potassium
Every critical amino acid "the building blocks of proteins"
When fruit is scarce, chimpanzees rarely hunt, and the more fruit there is the more hunting chimpanzees do
The larger the number of hunters, the greater the likelihood of success
Food = bigger Groups are needed for hunting
Food = more females in estrous
East African: lone trees mean cornering in isolated trees
West African: continous trees; hunting parites are larger, more coordination and more sharing which is relative to the amount of effort put into the hunt; predict likely escape routes
Solo hunting
Lone chimp = lone prey
brutally simple hunting strategy
Swings victim forcefully on tree trunk or fatal bite
If first attempt fails, often move on -- chases are expensive
"Inhumane" predator- prey relationship as chimps often "eat the prey to death"
While hunting rates vary, both by site and over time chimpanzees hunt about once a week and are successful about half to three quarters of the time, which means they eat meat about two or three times a month
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