Primate Diets and Socioecology

What is the most important parameter of underlying behavioural and ecological differences among living primates?

Diet

What is a primates diet requirements?

• Carbohydrates

• Amino acids (proteins)

• Fats and oils

• Vitamins, minerals

• Water

What should primates avoid in their diet?

Toxins such as:

• Adults leaves

• Caffeine

• Tannins

• Alkaloids

Plant evolution strategies

Developing toxins to prevent primates from eating them

Theories on food as a selective pressure

1. Satisfying nutritional requirements

2. Maximize nutrition gain

Satisfying nutritional requirement

Getting enough nutrients to get by

Wanting to maintain condition, immune system etc.

Maximize nutritional gain

Minimize cost and maximize reward for foraging strategies

Move as little as possible to get as many calories as possible

Maximize net energy and fitness

Micronutrients

Dietary imbalance

Ex. Scurvy

Optimal foraging

Foraging behaviours based on intrinsic properties of potential foods

Ex. Nutritional quality, time/energy to find and harvest

Maximization of optimal foraging

• Amount of food

• Quality of food

Minimization of optimal foraging

• Travel/search time

• Processing

• Digestion

• Competition

Captivity primates food supply

Have more food and are able to produce more babies

Will have similar illness as humans (ex. Scurvy)

Ex. Provision baboons will grow faster and reach sexual maturity earlier

Wild primates food supply

Their food is limited

Have to strategize how to maximize return and minimize cost which if favoured by selection

Basal metabolic rate

The body’s resting rate of energy output

Active metabolism

Amount of energy expressed in calories that is needed for physical activity

Growth rate

Energy needed to be able to reach maturity/adult

Reproductive efforts

Energy needed to reproduce

17%-30% extra cost for lactating females

4 factors to determine how much food is required in a primates diet

• basal metabolic

• Active metabolism

• Growth rate

• Reproductive effort

What is the relationship between body mass and quality of diet?

The higher the body mass, the lower need for quality food

Can survive on a poor quality diet

Ex. Gorillas (eating leaves and vegetation)

Smaller/tiny animals cannot have low quality diets

Ex. Bushbabies and tarsiers (insects)

Wild Bananas

Low pulp to seed ratio

Pulp is dry, fibrous or strong tasting

Usually avoided

Human Bananas

All pulp and sugar

Highly digestible

Infinite pulp to seed ratio

Perfect!

Digestive adaption to frugivory

Large, broad incisors

Low cusped, relatively flat molars

Large (unspecialized) digestive system

Frugivory

Fruit eating

Leaves

Foliage (leaves and stems)

Main fallback food for frugivorous primates

Rich in protein, but also contains toxins

Digestive adaptions for Folivores

Large body size

Small incisors

Sharp shearing crests on molars (to cut the leaves)

Large, well developed digestive systems

Folivores

Leaf eating

Colobus

Have another stomach to ferment the leaves to help digestion

Geladas

Adapted incisor teeth to make digestion the leaves easier

Colobines

Preferred food are leaves

Gorillas

Get a lot of their protein from leaves

Fibre

Protect foliage by reducing digestibility, difficult to chew

Humans leave much less fibre than apes and monkeys

Ex. Hunter gathers (5-10% fibre diet) vs chimpanzees (30-35% fibre diet)

Seeds

Rich in lipids and proteins

Protected by hard shells, toxins or both

Require thick molars to eat to protect cracks from forming in your teeth

Specialization needed to crack nuts

Insects

Rich in lipids and proteins

Easy to digest

Hard to catch

Digestive adaptation for insects

Large canines

Sharp cusps

Tarsier

The most insectivorous of primates

No plant food diet

Have high cusped (pointy) molars for slicing prey

Aye aye

Huge incisors for gnawing wood (to get to larvae under the bark)

Chimpanzee diet

Kibale forest, Uganda

Preferred food: Ripe fruits are eaten in proportion to availability

Fallback food: Foliage

Eastern chimpanzees and Gorillas

Preferred: Fruits

Fallback: Fibrous food

Live sympatrically

Eat similar amounts of food

Liem’s Paradox

Species often prefer not to eat the food to which they are specifically adapted to

Ex. Gorillas have big guts and chewing muscles better for eating leaves, but prefer fruit

Sympatric

Living in the same place

Ex. Chimpanzees and gorillas

Niche differentiation is ______ when food is abundant

Not obvious

Ex. When food supply in scares, chimpanzees seek fruit while gorillas seek leaves

Feeding adaptation

Tends to be developed for eat fallback food

Solution to Liem’s Paradox

Look at the time of the year when food is most limited to view individual variation and RS

Female foraging strategies

To maximize their reproductive success

How does female foraging strategies work with males maximizing reproductive success?

Socio Ecological Model

Competition

Reduce feeding efficiency due to the pressure of other individuals

Scramble competition

Occurs when increasing group size results in less food for every individual

Ex. Piñata, there are a lot of small pieces that are not worth individually fighting for. Success is by collected a lot of pieces (maximize foraging efficiency)

Contest competition

Dominants get access to food over subordinates

Ex. Items are quite large and individuals will form teams to monopolize the resources. Success depends on fighting ability, dominance and status

Ecological Constrains Model

Optimization group size hypothesis

Is group size optimal?

Group size in Geladas