Primate Feeding Ecology Flashcards
Foraging Strategy
The types of food resources used and how primates search for them - Primates must find a MIX of food; sources of protein, carbohydrates, vitamins and minerals
Nutritional Requirements
At its simplest all mammals must have:
- source of energy (carbohydrates, fats or even protein)
- ability to maintain, repair, and build tissue (protein)
- regulate body processes (vitamins and minerals)
How Primates meet their Carbohydrate needs:
- FRUIT: especially ripe fruit, lots of sugar not alot of fiber-high quality rich in carbs (energy) low in fiber (easy to digest)- not mechanically challenging-usually
- TREESAP/GUM: (marmosets) rich in carbs BUT require adaptations to digest efficiently - long ceacum
- INSECTS: “perfect food” (protein, fat, carbs) BUT hard to catch
- SEEDS: good fat source BUT mechanically challenging
How Primates meet their Protein needs:
- VERTEBRATES (animals)
- INVERTEBRATES (insects)
- costly to find animals/insects and non-social insects dont provide large amt of food
- LEAVES & FLOWERS
- leaves are considered “lower-quality” harder to digest- high fiber; flowers are seasonal
How Primates meet their Vitamin and Mineral needs
- VITAMINS: (Vit C = Fruit) Haplorrhine primates cannot make on their own -> Scurvy
- MINERALS: -Geophagia (eat soil/termite mounds/clay), de-toxify leaf toxins, add minerals, help eliminate internal parasites (endoparasites)
Constraints on Feeding Ecology
Getting the right mix of food greatly complicates foraging strategy:
Chemical defenses of potential food items
- Limited availability; only stay ripe for so long
- Distribution of foods: leaves-nearly uniform, insects-random, fruit-clumped
- Fiber content
- Incomplete Nutrition
- Feeding Competition
Theory of Primate Diets:
Important factors affecting dietary choices (?)
- Body size
- Habitat (biome)
- Morphology (what teeth look like, presence of sacculated stomach)
- Sociality
Effects of size
A primate’s body size puts considerable restrictions on its feeding options, ecological options, eg locomotion and diet:
- Most differences in primate behavior and ecology are correlated w/absolute body size
- How big you are will predict if primate primarily arboreal or terrestrial: small body size=arboreal (unless have lots of adaptations-> orangutan); large body size=terrestrial
- Most primates are arboreal -> impacts foot morphology
- Most terrestrial primates are fairly lrg; 20+kg (44+lbs)
- Body size also affects where primates look for food and how they move w/in a particular habitat: sm=tend to leap; lrgr=tend to use suspensory behaviors and bridging
Basal Metabolic Rate (BMR)
the amt of energy consumed by a resting organism simply to maintain its basic functions
Kleiber’s Rule
Basal metabolism does not scale directly w/ body size - it scales to the power of 0.75
This means the BMR relative to body size actually *decreases as we go from smaller to larger animals
BMR for small vs larger animals:
- Relative to body wt, sm animals require more energy than lrgr animals
- This has a major effect on foraging strategies of lrg vs sm primates:
- Lrg animals need more food overall, but have lower energy requirements per unit body wt than sm animals
- Sm animals need less food overall, but have higher energy requirements per unit body wt than lrgr animals
- lr & sm animals have diff “foraging strategies”
Smaller primates (<500grams) : Galago
Require: less amt of food overall than lrgr primates, but food need to be “high quality” eg: energy rich and easy to digest
-insects are ideal; can provide all nutrients - carbs, protein, vitamins, ect..
Medium primates (500grams-1kg): Squirrel Monkey
- Makes it hard to get all energy requirements just from insects
- Must also add more abundant energy sources-gums, flowers, fruits
Larger primates (>1kg): Two strategies: Colobinae & Gorillas, Chimpanzees
Require:
- More food overall than small primates
- Protein source can be “lower quality” eg less energy-rich and more fibrous
* morphological adaptations such as sacculated stomachs (colobinae) or more volume in lrg intestine to digest leaves in their diet (gorilla) - OR high quality using behavioral strategies
* mixed foods: leaves, animals, fruits AND behavioral adaptations - tool use (chimpanzee- may maintain a relatively lrgr more expansive brain)
What we know in a general sense based on body size:
- Sm primates tend to be insectivores
- Med primates tend to be omnivores (eat mix fruit, leaves, insects) or frugivores
- Lrg primates are either folivores OR have traits (morphological &/or behavioral) allowing them to maintain a higher quality diet including fruits
Dietary Adaptations in Primates:
Ceacum:
Adaptation for eating high-fiberous foods, a “pouch” btwn the sm & lrg intestine
- Related to high fiber (leaves, gum) it contains bacteria & enzymes
- Ferments cellulose allowing the animal’s lrg intestine to digest the nutrients from cellulose
Dietary Adaptations in Primates:
Morphological - Emphasis on leaves
Digestive specializations:
- “scissor-like” molar crests
- teeth spikey - shearing crests (shred leaves apart)
- complex stomach (sacculated stomach)
- lrg ceacum
- greater volume of lrg intestine (colon)
Dietary Adaptations in Primates:
Morphological - Emphasis on gum
- Procumbent incisors or “tooth-comb”
- “claw-like” nails for clinging
- enlarged ceacum to process gum
Dietary Adaptations in Primates:
Morphological - Emphasis on fruit
- Broad incisors
- Low rounded molar cusps
- simple stomach
- sm ceacum
- greatest volume in sm intestine
Dietary Adaptations in Primates:
Morphological - Emphasis on insects
- sharp cusps on teeth
- simple stomach & intestines
- enlarged ceacum- minerals in chitin outershell of insects
How can we know what kind of diet humans are adapted for ?
As one of the largest primates, human diet can be deducted from our dental and gut morphology
Human dentition
Humans have “fruit-eaters” dentition:
-broad incisors w/ low rounded molar cusps
Human digestion relative to other ape species:
- slightly smaller simple stomachs
- “fast” food passage (26hrs vs 37hrs in chimps)
- more vol. in sm intestines/low vol. lrg intestines (colon)
- most other closely related apes have emphasis on lrg only humans emphasis sm intestines
Why do other apes emphasize the lrg intestine (colon)?
allows processing of higher fiber diet when higher quality foods are scarce
Are there any other primates with similar digestion to humans?
The Capuchin monkey (cebus) has the most similar proportions emphasizing the sm intestine
-they have a high quality diet of rich fruits, oil rich seeds, insects, and vertebrate pray
Why is capuchin (cebus) like humans?
they have lrg brains relative to body size
Hypothesis of Evolution of Human Diet
Aevillo & Wheeler: Tradeoff in brain & gut (intestines)
- brain & guts are BOTH big users of metabolic energy
- therefore you would reduce the gut to allow more energy to the brain
Extensive Tissue Hypothesis
Larger brain provided more complex foraging behavior, and a higher quality diet which reduced fiber allowing for rapid assimilation where more vol in the sm intestines, and less vol in lrg intestines increased energy available for the brain
How to maintain a high quality diet and yet continue to increase in body size over time?
data suggests that in order to maintain an increasingly lrg (& expensive) brain, our species depended more & more on novel ways to exploit a wide variety of high quality food resources
Dental Health
- tooth wear
- dental abscesses
Abscess
accumulation of pus in tissue as a result of infection
-often from breaks in tooth
Species patterns in dental health/injuries
Cavities:
Orangutans: 11%
Chimps: 14%
Gorillas: 3%
-correlations to diet: gorillas eat more leaves while chimps and orangutans eat more sugary/sticky fruit
