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PSYCH 2TT3 (28)


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Brett Beston

March 18 , 2013 Psych 2TT3: Animal Behaviour Foraging What should we Eat? - exercise: suppose you are on a very limited budget. What factor should guide your weekly grocery shopping? - Please write down at least 3 factors  Taste  price  hunger  location  nutrition  caloric value/energy  amount of preparation  health/allergies  quality - the 3 most important factors for humans:  nutrional content  energy content  cost The Role of Taste - we sense several tastes and textures through the mouth and numerous others through the nose. Sensed in the mouth: sweet, bitter, salty, sour, umami, fat, and hot (spicy) - taste is an evolved adaptation that guides animal food choice. The following basic tastes indicate:  sweet: simple carbohydrates  bitter: simply poisonous or spoiled food  salty: salt is an essential nutrient (rare for much of our evolutionary history)  sour: possibly spoiled food - umami: the taste of free glutamate, a common amino acid indicating the presence of protein  glutamate rich foods: meat, fish, milk, some vegetables (e.g. tomatoes), some mushrooms and algae - glutamate rich foods serve as natural taste enhancers (cheese, tomato sauce) - monosodium glutamate (MSG) is an artificial taste enhancer - MSG can bring side effects such as headaches - Fat – high energy content (more than twice (~9kcal) than carbohydrates and protein (~4 kcal)): nothing higher in energy content than fat itself - Hot (spicy) not a real taste: responding to presence of a pain response Is Spice Consumption Adaptive? - paper published that tried to get down to the function of spice - interested in understanding the evolution of our perception of spice - over the course of thousands of generations, why would natural selection have favoured liking spices and seeking out to add spices - did a survey, look at certain extremes - looking through recipes to find functional role of spices - myths: increasing body temperature (no relationship), spices grown in different countries (very little correlation between the two), temperature and spices, no nutritional value, taste or quality, helping food in warmer climates Antibacterial Effects of Spices “Why some like it Hot” - benefit associated with using spices due to its antibacterial effects - if you have a cultured dish with bacteria, they can grow in size, putting spices on the dishes, the growth of the bacteria is inhibited over a 24 hour period - some spices have a complete inhibition of bacterial growth: garlic, onion, allspice and oregano - prevent growth of bacteria Prediction - traditional recipes in warmer climates would contain more spices - warmer climate increases the growth rate of bacteria - 42 spices in 6707 recipes from 36 countries - as it gets warmer there is a dramatic increase in the use of spices Conclusion - variation in spice use between cultures may be partially an adaptive behaviour Pica Video Clip - if forages close to shelter because of predators (eagles) - it spends much of its time feeding and storing food for the winter - the food is low in calories and contain poisonous plant compounds - pica: disorder of eating non nutritional items - poison acts as a natural preservative - takes care to collect a variety of plants some with more poison then others - poisons breakdown overtime so they no longer have an effect in the long term Modern Humans’ Dilemma - the majority of people in western society face the novel problem of higher energy intake than energy expenditure Why? - animals are adapter to maximize consumption of food rich in energy and specific nutrients, which are typically in short supply (fat, protein, carbohydrates, salt) - animals are also adapted to minimize energy expenditure and exposure to danger (predators, injuries, dehydration, hypothermia, etc.) - many of the nutrients that were in short supply over evolutionary time are now very common and very cheap - the majority of people in western society can live nowadays with minimal energy expenditure - kraft dinner: 1000 calories per box 1.29$ at grocery store - if we think of the average caloric intake (~2000 calories) under 3$ but does not have all the essential nutrients - the heart attack grill - supersize me, ~5000 calories a day and reduce the energy output, little exercise - BMI standard in assessing the relative health of a population Obesity Rates (BMI>30) among Canadians over Age 18 - no distinction between children and adults - percent of a population that has been identified as obese class 1 - in almost every category, the percentage of the obese population has grown Obesity and Heart Disease among Canadians over Age 18 - likelihood of heart disease is more prevalent in obese class I and obese class II - certain strategies are adaptive within a certain environment - we have something that is now becoming maladaptive Causes of Premature Death in Canada, 2000 - increase in premature death related to diet and exercise: high blood pressure, high cholesterol, excess weight, diet insufficient in fruit and vegetable, physical inactivity - over 90,000 people - inadequate diet or exercise caused 63% of premature death in Canada, 2000 - premature death caused by inadequate diet or exercise 91,000 - premature in 2000 144,000 - lack of diet and exercise is more problematic then smoking Solution - humans must learn to eat less and exercise more, which is against two of animal’s most basic evolved adaptations Fruit and Vegetable Consumption and obesity Physically Active Canadians are less likely to be Obese Application of Animal Behaviour Research - an evolutionary analysis of animal feeding behaviour helps us understand a major modern human dilemma associated with disease and premature death Example: Optimal Fat Reserves - animals must maintain short-term and long-term fuel reserves - fat reserves have benefits and costs  benefits: insurance, insulation  costs: weigth: increased energy expenditure, reduced mobility, increased predation risk - animal show adaptive fat storage:  winter in higher latitudes: longer nights, lower temperature, higher variance & uncertainty Prediction 1: Animals in Higher Latitudes would Store more Fat in the Winter than either Fall or Spring - from November to march - the white throated sparrow stores more fat during the cooler months - availability of food is driving these changes Prediction 2: Animals Experiencing more Interruptions would Store more Fat - difference in the fat storage depending on feeding reliability - those in low predictability store more fat - better with smaller regular intervals What Should an Animal Eat - in making a foraging decision, look across environment for the different prey choices - focus on:  encounter rate (# of items encountered per unit time)  energy content (calories)  handling time (time from capture to complete ingestion) - basic mechanisms: maximum intake, minimize expendure Encounter Rate - for a bee, different flowers represent different sources of food - encounter some flowers more than others Energy Content and Handling Time - how much calories are in the food and how long will it take to obtain this energy What Should an Animal Eat? - regardless of how often an animal comes across a food type - their choices should always be guided by profitability - amount of calories divided by handling time determines profitability The Optimal Diet Model - a simple mathematical model that allows us to predict what prey types a forager should eat based on the energy content, encounter rate and handling time of each type Key Predictions of the Optimal Diet Model - if the encounter rate with the most profitable prey (prey 1) is above the threshold level, only this prey should be eaten - the encounter rate with prey 2 should not affect the decision whether to feed on prey 2 Key Predictions of the optimal diet model - what determines the foraging strategies of the great tit - created conveyor belt and varied the availability of food - meal worms that are cut in distinctive sizes - large items and small items - amount of work is approximately the same - differs in the amount of calories Protocol and Predictions when Varying Density and Encounter Rate - if density is higher they should start to be more selective - varying the proportion of large prey items vs. small prey items - low density the animal eats everything - in a high densit
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