Primate Diets Flashcards
What is a quote by Fleagle (1999) on food as a selective pressure?
“Diet is the single most important parameter underlying behavioural and ecological differences”
What are primates mainly, in terms of diet?
Omnivorous, but each species has their own special diet
What is the problem with diet consisting of plants?
Toxins are produced by plants to deter herbivores
In what part of plants are toxins concentrated?
In adult leaves that tend to be tuff and leathery
What are the 2 theories on food as a selective pressure?
1) Satisfy nutritional requirements
2) Maximize nutritional gain
What is the theory on satisfying nutritional requirements?
Food is required for maintenance of body (physiology, immune functions, etc.)
What is the theory on maximizing nutritional gain?
Maximizing net energy gain results in maximization of fitness
What is maximizing nutritional gain predicted by?
Optimal foraging theory, which assumes animals are limited by food, therefore should have evolved adaptations to maximize their energy gain
What is optimal foraging theory?
Foraging behaviour is based on the intrinsic properties of potential foods
What are the intrinsic properties of potential foods?
1) Nutritional quality/content
2) How much time/energy it takes to find and harvest
What are the questions that optimal foraging theory asks?
1) What items should be included in the diet
2) What kinds of patches are good to occupy
3) How long one should spend in patches
According to optimal foraging theory, what must be maximized and minimized?
1) Maximize the amount/quality of food
2) Minimize time searching/processing/digesting, and minimize competition
What are the 4 factors that determine how much food is required?
1) Basal metabolic rate
2) Active metabolism
3) Growth rate
4) Reproductive effort
What is basal metabolic rate and patterns associated?
Energy spent in resting state, where higher body weight results in lower basal metabolic rate
What does the relationship between basal metabolic rate and body mass entail?
Primates can subsist on poorer quality nutrition as they become larger
What are the patterns seen with reproductive effort?
Lactating females spend 17-30% more energy
What are the adaptations associated with frugivory (3)?
1) Large, broad incisors (cutting)
2) Low-cusped, flat molars (grinding)
3) Large digestive system (though relatively unspecialized)
What are foliage?
Leaves/stems, rich in protein but often toxic and tough (fiber)
Which primates are folivores?
Specialized primates such as colobines (OWM), but most other (frugivorous) primates eat leaves as fallback foods
What are the adaptations associated with folivory?
1) Large body size (larger animals can afford poorer quality foods)
2) Small incisors
3) Sharp, shearing crests on molars (scissor-like to cut through vegetation)
4) Enlarged, well developed digestive systems
What are some examples of digestive systems of folivores?
1) Colobus monkey has extra chamber stomach
2) Lemurs have large cecum
3) Macaca have enlarged large intestine
What are the differences in fiber intake for primates compared to humans?
Primates eat a lot more fiber
1) in apes/monkeys = 30-35% fiber 2) humans = 5-10%
What are durophagous foods?
1) Hard (but not tough) foods such as seeds,
2) Protected by shells and/or toxins and
3) Rich in lipids/protein
What are adaptations associated with durophagous primates?
Thick-enameled molars that prevent cracking and allows for species to open nuts
What are some primates that are durophagous?
Mangabey and White-faced Saki (also have long canines)
What are the characteristics of insects?
1) Rich in lipids and proteins
2) Easy to digest
3) Hard to catch
Which primates eat insects?
Small primates such as tarsiers (most insectivorous, eats no plants) and aye-ayes
What are adaptations of insectivores (5)?
1) Large canines
2) Sharp cusps
3) Short, simple guts
4) Aye-ayes have big incisors (processing adaptation)
5) Tarsiers have pointy molars (slices animal)
What are the feeding differences between chimpanzees and gorillas?
Chimpanzees and gorillas both prefer fruits and have fibrous foods as fallback but:
1) Gorillas eat more fiber than chimpanzees
2) Gorillas have evolved adaptations associated with folivory (e.g., large stomachs, large mass, big chewing muscles)
What is Liem’s paradox and its characteristics?
Species often prefer not to eat the foods to which they are specifically adapted
1) Niche differentiation is not obvious when preferred foods is abundant
2) Niche differentiation is obvious when preferred food is scarce
What are the differences in behaviour when fruit is scarce between gorillas and chimpanzees?
Chimpanzees tend to continue seeking fruit while gorillas settle for foliage
How do we explain Liem’s paradox?
1) Preferred foods (such as fruit) tend to be easy to eat therefore does not require special adaptations
2) Adaptations tailored toward diet when food is scarce because Individual variation in feeding success matters most
What is the socio-ecological model?
Ecology shapes social system where
1) Food distribution and predation determines their foraging strategy
2) Foraging strategy shapes female distribution and sociality
3) Female ecological strategies shape male mating strategies (distribution and sociality)
4) Females develop counter-strategies
What is feeding competition?
Reduced feeding efficiency due to the presence of other individuals
What is the type of feeding competition determined by?
Nature of resources:
1) Abundance
2) Distribution
3) Quality of food
What is scramble competition?
When increasing the group size results in less food for every individual
What is contest competition?
Dominant individuals get access to food over subordinates
Does competition take place within-groups or between-groups?
Can be one or the other, or both
What does success depend on in scramble competition?
Since monopolizing resources and/or fighting each other for food is useless, being quick to collect the lots of pieces = success (maximize foraging efficiency)
What does success depend on in contest competition?
Since food can be monopolized, fighting ability, dominance, status = success (alliances are also helpful)
What are scramble competition food traits?
1) Item size is small
2) High density of item
3) Resources divided equally
4) Obtained by efficiency
5) Affects group size
What are contest competition food traits?
1) Item size is large
2) Item density is low
3) Resources divided unequally
4) Obtained by dominance
5) Affects status, allies
What is the ecological constraints model?
Increased group size results in increase in within-group feeding competition
What are the consequences of scramble competition and who suffers from this?
Scramble competition = depletion of resources quickly
1) A bigger group = more competitors
2) More competitors = more travelling required for adequate food supply
3) More travel = more energy expenditure
Frugivores suffer from this
What is the hypothesis for optimal group sizes?
Natural selection should balance the costs and benefits of group-living to result in optimal group sizes, therefore intermediate group sizes should be associated with better feeding success (higher RS, low stress, etc.)
Are optimal group sizes seen in all primates?
No. Only in some.
What are some of the data on optimal group sizes?
1) Blue monkeys: Individual survival did not vary by group size but conception rates peak in groups close to mean size
2) Geladas: lower deaths per female in midsize groups, increased offspring survival in midsized groups
