Questions in the study of foraging behavior How do animals select prey? 2.When should animals leave one feeding site and go on to another? 3. How should animals divide their time between food-gathering and other activities?

________ | | | LOAD TIME Travel Time Searching Time 10

________ | | | LOAD TIME Travel TimeSearching Time 10 X1X1 Y1Y1

________ | | | LOAD TIME Travel TimeSearching Time 10 X2X2 Y2Y2 Load/Time is maximized at X 2,Y 2

________ | | | LOAD TIME Travel TimeSearching Time 10 X1X1 X2X2 Short optimum Long optimum

________ | | | Load Round trip travel time

STEPS IN ANALYSIS 1.Determine relevant variables through observation 2. Establish (you think) how these variables interact 3. Make predictions 4. Test

Crows feeding on whelks  Select the largest whelks available  Fly roughly 5.5 m high to drop the whelk on the rocks below  If whelk doesn’t break open, select the same whelk to drop again

Patches Problem: When to leave a patch?

Constraints that affect “optimal” foraging behavior 1. Physiological constraints 2. Motivational constraints 3. Ecological constraints 4. Life history constraints

________ | | | Energy constraint Sodium constraint Rumen constraint Intake of aquatic plants (gm) Intake of terrestrial plants (gm)

Constraints that affect “optimal” foraging behavior 1. Physiological constraints 2. Motivational constraints 3. Ecological constraints 4. Life history constraints

Food Choice (reward x probability) reward probability 2 pellets x 1.0 average yield of 2 0 pellets x pellets x 0.5average yield of 2

Testing Conditions Starved for 1 hour Starved for 4 hours Food Choice (reward x probability) 2 pellets x 1.0 = avg. 2 (0 pellets x 0.5) + (4 pellets x 0.5) = avg. 2

Testing Conditions Starved for 1 hour Starved for 4 hours Food Choice (reward x probability) 2 pellets x 1.0 = avg. 2 (0 pellets x 0.5) + (4 pellets x 0.5) = avg. 2

Constraints that affect “optimal” foraging behavior 1. Physiological constraints 2. Motivational constraints 3. Ecological constraints 4. Life history constraints

Constraints that affect “optimal” foraging behavior 1. Physiological constraints 2. Motivational constraints 3. Ecological constraints 4. Life history constraints

Life History Evolution The study of how individuals allocate, throughout life, time and energy to various fundamental activities, such as growth and reproduction

Life Histories: An inherent trade-off Investment in any one activity limits an animal’s ability to invest in others. As applied to reproduction, a parent’s dilemma: investment in any one offspring limits an animal’s ability to invest in others.

Growth and Development Reproduce Early or Delay Clutch Size vs. Clutch Number Offspring Size and Offspring Number Offspring Size and Parental Care Components of Life Histories: Where the trade-offs occur

Life histories: the major questions Why do organisms age and die? How many offspring should an individual produce in a given time? How big should each offspring be?

Life history traits – characteristics of an individual that influence survival and reproduction Age at maturity years 3-6 years Salmon African elephant 2 months House Mouse

Life history traits – characteristics of an individual that influence survival and reproduction Salmon African elephant House Mouse 1 calf every 3-8 years 1,500 to 8,000 eggs once 5-8 young every month Number of offspring produced

Life history traits – characteristics of an individual that influence survival and reproduction Salmon African elephant House Mouse Number of reproductive events ~ ~6-12

Life history traits – characteristics of an individual that influence survival and reproduction Salmon African elephant House Mouse Lifespan years3-6 years ~2 years

K-strategists: long lived produce few offspring parental care Reproductive strategies Population is controlled by density-dependent limiting factors - e.g. food example: food

Gypsy moth caterpillars r-strategists: small short life no parental care many offspring Reproductive strategies Population is controlled by density- independent limiting factors: weather, pond drying

2.1m 12-Arm Radial Maze

________ | | | % Corr. Delay (hours)

Food-storing Birds Clark’s nutcracker: 33,000 seeds, 7,500 sites Pinon jays: 22,000 seeds, clumped Scrub jays: 6,000 seeds

% correct, 1 st 4 choices Block (avg of 5 trials) Nutcracker Pinyon jay Scrub jay Mexican jay Cache retrieval in corvids Kamil et al. 1994

________ % correct Nutcrackers Pinyon jays Scrub jays Mexican jays | | | | | | | | | | | | | Retention interval (min)

Meadow Vole: Polygynous Prairie Vole: Monogamous Female ranges Male range

Olson et al ? ?

Strict behaviorism: Any stimulus can, through conditioning, be associated with any response or reinforcer Learning is a general process phenomenon: All associations are learned equally easily All responses are reinforced equally easily

Biological constraints on learning Saccharine taste + lights + noise BECAME SICK SHOCKED (Garcia & Koelling 1966)

Biological constraints on learning Saccharine taste + lights + noise Avoided saccharine, But no fear of light or noise Fear reaction to light and noise, but no aversion to saccharine BECAME SICK SHOCKED (Garcia & Koelling 1966)

Summary: Economic decisions Increasing evidence that animals make “calculations” when foraging -- make adaptive “choices” among alternative foods -- estimate past rates of return and compare them with current rates

Summary: Memory 1.Natural selection has shaped the minds and behaviors of animals so that they optimize (as near as possible) the exploitation of their environment -- species differences in memory -- memory of a very specific sort -- species differences in the brain structures that support memory -- sex differences, too -- differences in the kind of associations that are formed