Social and Solitary Foraging Strategies

Social and Solitary Foraging Strategies

This lesson is designed to look at the trade-offs of social and solitary foraging in various environments by exploring how the environment might influence an animal’s decision to forage individually or as part of a group. In this lesson, we also explore foraging theories such as optimal foraging (using a strategy that maximizes the rate of food acquisition) and risk sensitivity (minimizing the chance that an individual doesn’t acquire its needed food supply). Students begin by playing a foraging scavenger hunt game as individuals, and then repeating the game working together in small groups. Students are awarded “calories” for the items they collect and use those calories to explore the costs and benefits of social and solitary foraging. Through the activities in this lesson, students will gain a better understanding of the risks and choices wild animals face when foraging for food to survive.

Social and Solitary Foraging Strategies
Day ______
Learning Objective(s):
AZ ---Grade 7, Strand 4, Life Science, Concept
PO2: Explain how organisms obtain and use resources to develop and thrive in niches
PO3: Analyze the interactions of living organisms with their ecosystems
CORE IDEA —“How organisms obtain resources”
·  Social vs solitary foraging strategies: What are the costs and benefits of foraging as a social group versus a solitary individual?
·  How do environmental conditions affect an organism’s foraging strategy?
Materials:
o  Marbles-approximately 50
o  1 bag of bite sized candy bars
o  4 Plastic bins each containing
o  16 bags of topsoil (3 bags per bin plus 4 individual bags)
o  1 quarter
10 minutes / Engage
1.  A few volunteers are selected to come to the front of the room. One student is seated in a chair. The others are asked to lift the student off the ground. They can take suggestions from their classmates to solve the problem. The student lifting is instructed to avoid tipping the student seated in the chair over. The goal is to lift the student in the chair slightly off of the ground so that all legs of the chair are elevated a small amount and stop.
a.  Are they able to lift the student working individually?
b.  Is it easier to lift the student when working as a group?
2.  Students will be shown a video of social foraging in army ants (army ants hunting a solpugid) and a video of a salamander (play until 0:35 seconds) foraging solitarily. They’ll also see a short video of a coyote, which is known to switch foraging strategies.
3.  Students are asked to write down their observations from each video in their research notebooks.
a.  Students are then asked to compare and contrast the foraging styles.
i.  What did you notice about the strategies used by the ants, salamander, and coyote?
ii.  What are the benefits to each strategy? What are the costs?
10 minutes / Explore
1.  Students are instructed to hunt for “food items” (marbles, coolers filled with water, and sunflower seed bags) as individuals. The goal of the game is to collect enough calories to survive. In order to survive students must gather 20 calories (2 candy bars). They are instructed that they must lift the bags of seeds and coolers. They are asked to collect as many as they can in 2 minutes and bring them to their assigned “nest” (an spot in the room chosen by each student). Like food that they might eat, different types of food have more nutritional value than others. The nutritional value of each type of food item is explained to them prior to beginning the game. They aren’t allowed to communicate with each other in any way. At the end of this round, students will calculate the number of calories they collected while the food items are hidden for the second round. Candy bars will be distributed among the individuals. One candy bar per 10 calories will be awarded.
2.  Students are then divided into groups of 2-5 and asked to repeat the activity working as a group. Following the activity, they will be asked to calculate the calories they gained when foraging as a group member (total calories/number of group members). Five candy bars will be distributed among the groups. One candy bar per 10 calories will be distributed evenly among group members. If there is an odd number of candy bars, members will flip a coin to see who gets the extra candy bar.
3.  Students will also be asked to calculate their foraging rate (calories/time). They’ll also be asked to determine whether or not they survived the game.
10 minutes / Explain
1.  This section will be used to ask students questions and have them develop ideas about the interaction of the environment and foraging strategy. Concepts that will be introduced include: solitary foraging, social foraging, optimal foraging, cost/benefit analysis, and risk sensitivity.
2.  Students are asked to think about the type of environment that would result in each strategy being the most successful.
3.  They are introduced to the idea of resource limitations. Risk sensitivity will be discussed here.
4.  Students are introduced to the idea of costs and benefits of each foraging strategy.
a.  This will be linked to the foraging game the students played. Students are asked to think about the benefits of foraging on their own vs as groups. Did the costs outweigh the benefits?
b.  They are asked to think about whether solitary or social foraging would be more beneficial when resources are limited.
5.  Students will be asked to think about the two foraging strategies in terms of energy costs and gains and risk sensitivity.
a.  How much energy did you use during each strategy?
b.  How did food discovery rate vary?
c.  How much food did each of you end up with using the two different strategies?
d.  How did you organize while foraging socially?
e.  Based on the calculations in your table, which strategy was the optimal foraging strategy?
f.  Does social foraging reduce the risk of not surviving?
6.  Students will be introduced to the colonial orb-weaving spider Metepeira spinipes using photos and the description included below.
a.  Ask students to think about why they cooperate when prey is abundant and not when prey is scarce? Remind them to think of limited resources and cost-benefit analysis.
b.  Ask them to work in small groups to generate other situations that may result in social foraging being beneficial. Then discuss as a class. This will lead into the expand activity.
Expand
Part 1:
o  With the example of the spiders in mind, students will be asked to match cards of predators/foragers to situations when they would forage in groups and situations when they would forage as individuals. The back of each card includes a description of the environment or of the foraging strategy being used by the animal.
o  As students are matching the cards, ask them to make predictions about the foraging strategy animals will use in each situation and write them in their research notebooks. An example would be: Given an environment with low prey availability and knowing that Metepeira spinipes can switch between social and solitary foraging, the orb weaver would form individual web and undergo solitary foraging. Ask the students to write down why they made the prediction they did. They can work on this as groups, but their answer can differ from their group members’ if they don’t all agree.
o  After students have matched all of the cards, we will discuss their decisions as a group. They will be asked to explain why they think foraging strategies differ in each situation.
o  Use the spare set of cards to match them up as a class on the board. Try to have students work as groups to solve any discrepancies within the class. The students should explain their choices to each other and discuss the answers.
Part 2: if time permits
o  This portion of the expand provides the students with an opportunity to apply their understanding of risk sensitivity.
o  A thought question is written on the board.
o 
You’ve flown to Florida to appear on a game show. You’re given a choice between two envelopes. One is guaranteed to have $100.00 in it. The other could be empty or could have $200.00 in it. For which plane ticket home is it better to choose envelope A or B? Assume you have no money or form of payment with you.
A.  $50.00:
B.  $200.00:
C.  $100.00:
D.  $101.00:
o  Students are asked to record their answers and why they chose the answer in their notebooks.
o  Students will be asked to reason through their answers in a large group discussion.
o  The plane ticket cost is analogous to the number of candy bars needed to survive in the explore game. If students are struggling, giving them this prompt may help.
10 minutes / Evaluate
o  The students will be asked to list five benefits of foraging in a group and five costs of living in a group. Students will be asked to write these in their research notebook. We will regroup to discuss them.

EXPLORE:

Foraging Game

*This game should be played outside.

àSolitary foraging:

·  The goal of the game is to collect enough calories to survive. 40 calories (2 candy bars are needed to survive).

·  Marbles will be hidden throughout the foraging area.

·  Four bags of topsoil will be hidden throughout the foraging area.

·  Bins containing three bags of topsoil each will be placed throughout the foraging area.

·  Students choose a home to bring gathered food to. Students may not steal each other’s food.

·  Students will be instructed to walk around the foraging area and collect as many food items as they can and take them to their home. They’ll be asked to lift the coolers and sacks of seeds rather than dragging them.

·  The nutritional value of each food item will be provided to the students before they begin foraging. It would be helpful to write this on the board for them.

o  1 Marble = 2 calories

o  1 bag of topsoil = 25 calories

o  1 bin with three bags of topsoil = 50 calories

·  Students will be asked to avoid communicating with others because they are foraging on their own as the salamander did.

·  After 2 minutes students will be stopped and asked to count and record the number of each type of food item they collected.

·  Students will be asked to calculate the number of calories they collected while the food items are hidden for the second round.

·  Candy bars will be distributed among the students. 20 calories = 1 candy bar

àSocial foraging:

·  Food items will be hidden in new locations. The goal of the game will remain the same.

·  Students will be divided into groups of 2-5 and will choose a group home.

·  Students will be instructed to walk and collect food items while working with their group.

·  They will be asked to communicate with their group but not with any other individuals or groups.

·  After 2 minutes students will be stopped and asked to count the number of marbles their group gathered.

·  They’ll also be asked to calculate the number of calories the group collected and the number each of them would receive from the group’s food.

·  Groups will receive one candy bar per 20 calories, and candy bars will be distributed evenly. If there are an odd number of candy bars for the group, they will need to flip a coin to see who gets the extra candy bar.

·  Students will also calculate foraging rate (number of calories/time) and determine whether or not they survived.

Record the results for the foraging game.

Strategy / # marbles x 5 calories / # feed sacks x 20 calories / # coolers x 50 calories / Total Points / Total calories/time foraging (2 minutes)
Solitary
Group: Group success
Group: Individual Success

DATA TABLE:

EXPLAIN:

Terms:

1.  Social foraging—animals find or capture food items/prey with other individuals of the same species in the vicinity or by cooperating with other individuals of the same species. The food may be shared among individuals or information about food locations may be shared.

2.  Solitary foraging— animals find or capture food items/prey without the presence of individuals of the same species nearby and without the assistance of other individuals. The food isn’t shared among individuals and there is no transfer of food location knowledge among individuals.

3.  Optimal foraging theory— This theory describes the process of foraging so that the net energy (calories or nutrition points in the foraging game) gained from food is maximized per unit of time spent foraging for the food. Depending on food density and availability, individuals may change their foraging strategy to reach the maximum energy gain per unit time.

4.  Cost-benefit analysis— The process of comparing the costs and benefits in terms of energy gained from food using various foraging strategies. For example, foraging socially may be costly because an individual must share food with the group, but the group may be able to gather larger food items resulting in the energy gained from the larger food item outweighing the cost of sharing food.

5.  Risk sensitivity—minimizing the chance of not getting enough energy (food) to survive during an allotted period of time (e.g. overnight). An example of risk sensitivity would be minimizing the chance of not getting enough food to survive a school day without being hungry. Animals take more risks as they get closer to running out of time and haven’t met the food acquisition goal.