Foraging: the search for food, which can include grazing, browsing, hunting, and scavenging.
provides energy
individuals must search for and capture food
know when to move on to another resource
Optimal Foraging Theory: a behavioral ecology modeling approach that predicts how an animal behaves when searching for food.
Optimal Diet Model: predicts that animals will select a diet that maximizes energy intake rate.
foragers maximize fitness by max. energy
food items are encountered one at a time
food items can be ranked by profitability
Handling Time: time to manipulate items before consumption.
Profitability: energy/ handling time.
Seagulls at the beach will take clams, fly with them, and then drop them to break them open.
Optimal Patch Use: predicts how long a forager should exploit a food patch.
foragers attempt to max. energy intake
all patches are identical
travel time is constant
Optimal Patch Time is Affected by Travel Time:
for shorter travel times, the optimal patch time is small.
for longer travel times, the optimal patch time is longer.
Animals can combine sample info. from a patch with prior knowledge about the distribution of patch types in the environment, using Bayesian statistics.
Antipredator Behavior: Behavior that reduces the likelihood of being preyed upon.
animals can do this alone or in a group, actively or passively
Active Social Defense Example:
meerkats come together (mobbing) to protect their colony against a snake. There is a guard to alert them of any dangers.
Passive Defense Example:
Harvest ants aggregating so they are less likely to be eaten by a dragonfly
Dilution Effect Hypothesis: proposes that associating in groups makes it less likely that any one individual will be preyed upon.
Selfish Herd Hypothesis: suggests that individuals in a group attempt to reduce predationrisk by putting other individuals between themselves and the predator.
"Using other animals as a shield between yourself and the predator"
Other Ways to Avoid Predation:
Blend In: camouflage yourself to the environment. Ex. moths
Stand Out: aposematic coloration to avoid being eaten. Ex. monarch butterflies.
Batesian Mimicry: palatable species mimics a dangerous species to deter predators. Ex. coral snakes
Stotting in Thomson's Gazelles
There are many hypotheses for stotting behavior. Stotting is when they jump and show their rear ends.
Alarm Signals
Social Cohesion
Confusion Effect
Attack Deterrence
The primary prediction of the selfish herd hypothesis is that individuals should do which of the following?
Attempt to move to the center of the group
Dispersal: a relatively short distance, one-way movement away from a site.
Competition Hypothesis: If two sites have the same density of individuals but differ in the quantity of food, we can expect higher levels of dispersal behavior in the site with less food.
Inbreeding Avoidance Hypothesis: one factor driving the evolution of dispersal is a minimization of inbreeding.
Breeding habitats differ in quality and therefore individuals differ in reproductive success.
individuals with low reproductive success may exhibit breeding dispersal
individuals with high reproductive success should exhibit site fidelity
Win Stay Lose Shift: many species exhibit site fidelity after reproductive success and exhibit breeding dispersal after a reproductive failure.
Migration: relatively long distance and a two-way movement.
Evolves when fitness benefit of migration > fitness cost of migration
In the Serengeti, mammals appear to track biomass and quality of grass during their migration.