Primate Ecology PDF - Anthropology 201 Fall 2024

10. Primate Ecology Anthropology 201 Fall 2024  Primate Ecology Ecology = interactions between organisms and their environment – physical environment (habitat) – biological environment (other organisms) It’s a broad topic, but we will focus on how primates make a livi...

10. Primate Ecology Anthropology 201 Fall 2024  Primate Ecology Ecology = interactions between organisms and their environment – physical environment (habitat) – biological environment (other organisms) It’s a broad topic, but we will focus on how primates make a living in their environments and the effect of ecological variables on social systems 2  Objectives Understand and identify the different energy requirements of organisms – (BMR, AMR, Growth and Reproduction) Understand how different primates meet these needs Understand the relationship between diet, range and territoriality – And impact on sociality Identify predation avoidance mechanisms Reading: Chapter 5, p. 125-132 and p. 137-138 3 Making a living as a primate… Two main concerns: – 1) how/what to eat – 2) how to avoid being eaten These two concerns influence sociality 4 1. How and what to eat 5  Organisms need energy Food provides energy (calories) essential for growth, survival and reproduction Total energy required depends on FOUR components: – Basal metabolism – Active metabolism – Growth and growth rate – Reproductive effort 6  1. Basal Metabolism Basal metabolic rate (BMR) = rate at which an animal expends energy at rest, for basic body maintenance – e.g. maintaining body temp Larger animals have absolutely higher BMR, but relatively lower (fewer calories per unit body weight) (Dashed line is 1-to-1 line) 7  2. Active metabolic rate The energy required above and beyond baseline for daily activities – e.g. for locomotion, digestion Depends on size of animal, how far/fast it’s travelling – For a baboon-sized primate = ~2x BMR 8  3. Growth Rate Building new tissue requires energy beyond BMR and AMR – Juveniles/infants have higher energy requirements than predicted for their size 9  4. Reproductive Effort For females, additional cost of reproduction – Late pregnancy: +25% calories – Lactation: +50% calories 10  Nutritional Requirements Diet must satisfy energy requirements & specific nutrients they cannot synthesize themselves – Protein/amino acids for growth, reproduction, regulation of bodily functions We cannot make aa’s ourselves – Fats, oils, & carbohydrates provide energy – Trace vitamins & minerals also important for specific physiological functions (e.g., iron & copper for hemoglobin synthesis) 11  Nutritional Requirements Diet must also minimize dangerous toxins – Secondary compounds are plant defenses: Alkaloids – can disrupt normal cell processes Tannins – reduce digestibility of plants – Secondary compound concentration is highest in mature leaves, seeds; lower in fruits, flowers, new leaves Caffeine (an alkaloid) 12 Primate Foods Fruit (frugivory) Leaves (folivory) – Young (more easily digested proteins and sugars) – Mature (high cellulose content, requires specific adaptations) Insects (insectivory) – Social insects vs. solitary Also: – Grasses, tubers, corms (enlarged stems) – Gum – Vertebrates (birds, frogs, bats, monkeys) – Bark, fungus, soil (often for traces minerals) For all: Water (directly or through food items) 13 Primate Diets – generalizations Primate diets are diverse, but: 1) Most primates rely on one food type high in protein (P), one high in carbohydrates (CH) Many Strepsirrhines: insects (P) and gum/fruit (CH) Many Monkeys/Apes: insects/young leaves (P) and fruit (CH) 14 Primate Diets – generalizations 2) Primates rely more heavily on some types of foods than on others – e.g. chimps eat ripe fruit preferentially, aye- ayes eat grubs – Gives us the terms: folivores, frugivores, insectivores, etc… 15 We are what we eat Primate diets are reflected in tooth and gut morphology Useful for inferences in the fossil record See Box 5.1 in textbook 16 Primate Diets – generalizations 3) In general, insectivores < frugivores < folivores – BMR scales with body size – Smaller animals require small but high-quality foods that can be processed quickly (e.g. insects), – Larger animals are not constrained by the quality of their food (more by quantity), they can process it more slowly (longer guts, can process leaves) 17 Diet Composition and Body Size Food availability varies in space and time Can be patchy in space and/or time Can be unpredictable Tropical forests may appear lush and fertile, but: - contain many species, only some of which have edible foods - are highly seasonal 19  Temporal Availability Seasonality – In tropics, depends on day length, rainfall During scarcity, may switch to lower quality diet (unripe fruit, mature leaves) and/or reduce energy expenditures (e.g., torpor in dwarf lemurs) Keystone Resources – Fall-back foods during scarce seasons – e.g., Ficus (figs) 20  Spatial distribution Food varies in density: – Most abundant food are leaves/foliage, – Fruits and flowers (also seasonal), – Lowest density = small prey (insects, vertebrates, etc) Primates need to travel to find their food The distance traveled will depend on the density of the food they’re after 21  Ranges Range = the geographical area in which a group (not a species) can be found – Home range: total area used by a group – Day range: area used by an individual on a daily basis Who has the larger home/day range, a folivore or a frugivore? 22  Food distribution influences range size Woolly monkey (Lagothrix) Howler Monkey (Alouatta) Frugivore Folivore Day range:~3km Day range:~100m Home range: >800 Ha Home range: 4-20 Ha 23  Territoriality varies amongst Food Distribution species Some exclusive (e.g. gibbons) – Territory = home range Some home ranges overlap (e.g. capuchin monkeys) Food distribution influences territoriality Resource distribution – Even = not defensible – Clumped, patchy = defensible Capuchin Territories, Barro Colorado Island in Panama  Territoriality Why are some primates territorial? Can have both costs and benefits in terms of an individual’s ability to survive and reproduce (fitness) – Costs: constant vigilance, advertising presence, engage in defense – Benefits: prevent outsiders from exploiting limited resources 25  Territoriality When do benefits outweigh costs? – Depends on the kinds of resources and their impact on fitness: For females = access to food for them and their dependents For males = access to females (mates) Territoriality serves two functions: – Resource defense (food, nesting sites…) – Mate defense 26  How/what to eat - Summary Energy requirements Resource Distribution Diet Range (size) Territoriality 27 2. How to avoid being eaten Predation significant source of mortality among primates Direct evidence hard to obtain 28  Evidence from predators Factors that increase predation risk: – Being terrestrial – Smaller group size 29  How to avoid predators? Alarm calls – e.g. vervets Swarm Associate with other primate species – Share different areas of the canopy LIVE/FORAGE IN GROUPS! 30  Sociality and Predation Groups provide safety from predators The three D’s: – Detection (more eyes on the lookout) – Deterrence (swarming/mobbing) – Dilution (“better him than me”) 2 animals = 50% chance of being “chosen” 10 animals = 10% 31  Primate Ecology and Sociality What to eat: How not to be eaten: Resource The three D’s distribution/density – Detection Ranges – Deterrence – Dilution Territoriality Groups are better at defending and controlling Groups improve resources/territories predator avoidance 32  Sociality has costs/benefits Benefits: – Resource control IntERgroup competition – Predator avoidance – Access to mates Costs: – Feeding/mate competition IntRAgroup competition – Disease risk – Cuckoldry, incest, infanticide, etc 33 Trade-offs between predation & food Small groups & solitary animals – Predation risk high, intragroup food competition low Large groups – Predation risk lower, intragroup food competition higher – may lead to fission Balance of these factors may produce optimal group size for a species or population 34  Polyspecific Associations Different species may travel & forage together for extended periods of time Permits greater predator Red Colobus protection without increased competition for food and/or mates Foraging benefits: mutual defense, finding food resources, scrounging Diana Monkeys 35  Summary What primates eat, and how they avoid being eaten, can influence range size, territoriality and group size There are trade-offs (costs/benefits) for territoriality and group size – Competition for defensible resources WITHIN and BETWEEN groups Likely a combination of feeding competition and predation drove the evolution of sociality in primates 36