Name:  Sample Student Lab Report                                    Date:  July 1998

TITLE: Food Preferences of the Common Pavement Ant (Tetramorium caespitum)
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INTRODUCTION: 
The common pavement ant (Tetramorium caespitum) is a common insect in the Northeastern United States.  They are found under sidewalks and in lawns everywhere.  Because ants are social creatures, they exhibit complex behaviors in which the entire ant colony, which can number in the thousands, acts as a "superorganism." (Holldobler and Wilson, 1990)  One of the most common behaviors that involves several ants of the same colony is foraging behavior.  In this case, a scout ant will search widely for a good food source and then leave a chemical pheromone trail back to the nest.  At the nest, that scout ant can notify the recruitment ant which will give a message, often through body language, to the rest of the ants.(Holldobler and Wilson, 1990)  This will cause a large number of ants to seek the food source by following the pheromone trail. With this information in mind, we studied the food preferences of the common pavement ant for food substances that were readily available to us.
 
PROBLEM STATEMENT:

Do ants prefer one food type to another?  What kinds of food do ants prefer?

HYPOTHESIS: 

If ants are given a choice of food sources, they will prefer the samples that have the most fat and protein.
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MATERIALS AND PROCEDURES: 

Materials:
    Stopwatch    food    ruler    string    data table

Procedures:
    1.  Located an ant dwelling that is at least 5 feet from any other ant dwelling.
    2.  Collected several types of  food (about a 1 in. x 1 in. square piece).
    3.  Created data table for the experiment.
    3.  Placed each food type 2 feet from ant hole in a circle or a semicircle around the ant hole.
    4.  At five minute increments counted the number of ants at each food source and recorded in the data table.
    5.  Continued this procedure for sixty minutes.
    6.  Created graphs of the data.
    7.  Made conclusions about the ant food preferences based on our data.
    8.  Analyzed lab techniques for further study and improvement.
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RESULTS: 
 
Table 1.  Response of ant colony to various foods TRIAL 1
PLACEMENT SITE                    1                            2                                3                            4                                5                                6                            7
TIME FROM FOOD PLACEMENT (MIN))
TATER TOT
WHITE BREAD
WHEAT CRACKER
CARROT
SLICED TURKEY AND HAM 
BROCCOLI
BANANA
5
4
0 
0 
0 
0
 0
 0
10
45+
0
0
0
0
 0
 0
15
90+
1
0
0
4
 0
 0
20
100+
35
2
0
5
 0
 0
25
100+
50
19
0
4
 0
 0
30
150+
75
60
0
4
 0
 0
35
150+
100+
100+
0
7
 0
 0
40
200+
100+
130+
1
13
 0
 0
45
150+
130
150
3
35+
 0
 0
50
150+
150
150
2
85+
 0
 0
55
150+
100+
100
0
100
 0
 0
60
150+
100+
100
0
100+
2
0

The ants seemed to avoid the carrot and the broccoli even though they did have time to explore the pieces.  The banana was not eaten despite having been "scouted out."

The fried tater tot appeared to have the most ant activity.  Most of the ants (about 200 ants) were eating the outside of the tater tot even though they had access to the center part. Ants were clustered around the bottom of the tater tot.  This was the first piece of food that the ants discovered.

The bread and the cracker appeared to be the second most visited pieces of food (maximum 150 ants). The ants spent a significant amount of time cutting off pieces of bread and bringing these pieces back to the nest.  They did the same with the cracker once they found the cracker.  There seemed to be a constant stream of ants carrying both foods back to the ant hole.

In Fig 1., the slopes of the lines for tater tot, cracker, bread, and turkey/ham were similar at the start of ant recruitment.

The increases in the numbers of ants roughly followed the order of the placement sites.  In other words, the food at placement site 1 had increased ant visitation first, then there was an increase in the visitation at site 2, and so on.
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Table 2.  Response of ant colony to various foods TRIAL 2
 PLACEMENT SITE                1                            2                                3                            4                            5                                6                            7
TIME FROM FOOD PLACEMENT (MIN)
TURKEY/HAM
BREAD
WHEAT CRACKER
TATER TOT
BANANA
CARROT
BROCCOLI
5
0
0
0
1
2
0
0
10
1
0
0
0
1
0
0
15
1
2
0
2
0
0
0
20
1
2
6
0
0
0
0
25
2
6
50+
2
0
0
6
30
2
8
50+
8
0
0
6
35
10
15
50+
8
0
0
6
NOTE: Ants from other nests found the food as well.  Because of this confusion, this trial was shortened by 25 minutes.

 
In Trial 2, the wheat cracker was by far the most visited piece of food (over 50 ants max) despite the fact that it was not the first piece of food examined by the colony in this trial.  By the end of the 35 minutes, the bread had the second highest number of ants present (15 ants max), followed by the meat (10 ants max) and the tater tot (8 ants max).
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Table 3.  Response of ant colony  to various foods  TRIAL 3
 PLACEMENT SITE                1                            2                                3                            4                            5                                6                            7
TIME FROM FOOD PLACEMENT
TURKEY/HAM
BREAD
WHEAT CRACKER
TATER TOT
BANANA
CARROT
BROCCOLI
5
0
0
0
0
0
3
0
10
0
0
2
0
9
5
2
15
0
0
3
0
35
8
4
20
5
2
4
0
100
8
6
25
50+
0
20
0
150+
5
5
30
60+
2
20+
0
150+
4
6
35
75
2
8
0
150+
2
6
40
100+
1
35
0
200+
4
8
 
This was a repeat of the previous trial to see if the ant food preferences in half an hour were consistent.  The banana had the highest number of visitors (over 200 ants max), followed by the turkey/ham (over 100 ants max).   The wheat cracker was the next most visited (over 35 ants max).  The broccoli, carrot, bread, and tater tot had between 0 and 8 ants visiting at the end of the experimental period. The amount of visitation to the bread was unusually low (only 1 ant after 40 minutes) as compared to the results of TRIALS 1 and 2 (over 100 after 40 minutes and 15 after 35 minutes, respectively).

DISCUSSION/CONCLUSIONS: 
 
Discussion from TRIAL 1: Since the tater tot was visited first, this may have led to more ants clustering around the tater tot.
The bread and cracker may have had more activity because they were easily chopped into smaller pieces.  The carrot and the broccoli may have been avoided because of the difficulty in removing pieces of the food easily. They also contained less sugar and starch than the tater tot, bread, and cracker.  Once the ants found the meat sample, several ants were recruited.  If the first trial was continued for more than one hour, then the number of ants on the meat may have been greater.  In addition, the slope of pavement may have led the ants to the tater tot first.  The other food samples were discovered when the scout ants radiated out from the tater tot.

Discussion from TRIAL 2:  All of the foods had been sitting in a refrigerator for two days before the experiment was repeated.  This may have allowed some of the foods to dry out or ripen so that they were not in the same state as they were during the previous trial.  In addition, the foods were placed around a different colony and the foods were placed in a circle, rather than a semicircle as they were in the previous experiment.

Discussion from TRIAL 3:  The most surprising result was that the banana had visitation by 200 ants by the end of the trial.  Other surprising results from this trial were that the broccoli and the carrot had more visitation than all the previous trials.  After other ants had visited the broccoli and carrot, they seemed to leave saliva or some other secretion that caused the broccoli to be slimy.  The ants then chopped off parts of the broccoli, much as they had chopped off the pieces of bread, and carried the parts back to their nest. Another factor that may have affected our results was that the banana had started to rot over the course of the experimental period.

General Discussion:  There were several variables besides food type in the sample.  These include surface area, freshness, temperature of food sample, and weather conditions when the trials were performed.  The surface area of the food sample would allow for more or fewer ants on each piece of food.  The freshness of the food sample may have affected the ant response to the food.  The second and third trials were performed on the same day, right after one another, whereas the first trial was performed two days earlier.  The weather conditions for the first trial were hot and humid, with temperatures about 32 degrees Celsius.  For the remaining  two trials, the weather was less humid, with a temperature about 29 degrees Celsius.  The temperatures at which the ants foraged fall within the common range for pavement ants (Holldobler and Wilson, 1990).

Conclusion:  The food type that the ants seemed to prefer most was the wheat cracker, which was one of the top three samples preferred by the ants in all three trials.  Thus, our results did not support our original hypothesis.  The experiment did, however, lead us to several further questions for study.  These include:
            Does the shape of the cracker/food sample affect food preference?
            Do the pavement ants prefer the salt, the starch, or the sugar of the cracker (or some mix of the three)?
            What kinds of crackers do pavement ants prefer?
            Which of the top food choices of each trial (tater tots, wheat crackers, bananas) is preferable to ants?
            Does the degree of ripeness of a piece of fruit make a difference as to ant food preference?
            Do ants prefer foods of a particular pH?

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