Pillbug lab--Animal behavior

1. Abstract

     Using pillbugs so as to observe animal behavior, a series of labs was conducted in a behavior chamber divided into two areas both covered with filter paper. My parter and I observed pillbug behavior for 7 minutes and 30 seconds for each lab, recording lab data (number of pill bugs in each area) every 30 seconds. The first lab showed that pillbugs strongly prefer a wet environment to a dry one, the second lab that pillbugs, albeit moderate, prefer an environment of high sugar content, and the third that pillbugs have fairly strong affinity to rocky terrains artificially created with beads.

 

2. Introduction

     Animal behavior is, to rephrase the definition written in the pre-lab handout distributed beforehand, an animal's response to external stimuli. The study of animal behavior consists of two different types of questions: proximate questions and ultimate questions. Proximate questions are focused on the ostensible mechanics of a particular behavior. An example of a proximate question regarding bird song would be ‘how often and long does the bird sing?’ or ‘what muscles enable the bird to sing?’ Ultimate questions, on the other hand, deal with more fundamental causes of a behavior mainly pertaining to the evolutionary reasons. One ultimate question regarding bird song is ‘how does the singing affect the bird’s chance of survival in the ecosystem?’ Fixed action pattern is an animal’s instinctive, genetically inherent behavioral response to what’s called a sign stimulus, an occurrence of a particular situation that stimulates an animal to show the response. Prominent examples of fixed action pattern include mate dancing of birds and aggression between male sticklebacks (Wikipedia, s.v. fixed action pattern). Imprinting refers to the process by which an animal acquires a certain reaction mechanism to a particular stimulus that soon becomes an instinct. For instance, a baby goose, between 13 to 16 hours after hatching (Wikipedia, s.v. imprinting), a period known as a ‘critical period’, would ‘imprint’ on its memory a particular subject (not necessarily an adult goose) as its lifelong guardian. Kinesis and taxis are two types of animal responses—kinesis is a random, undirected reaction to a stimulus, and taxis a specific one with well-guided directions. The pillbug experiment gives good sense of the two concepts. Taxis occurred when pillbug moved from one area to another in accordance with its preference of light, heat, moisture, sound or chemicals. Kinesis was exhibited when the pillbugs simply moved around the filter paper regardless of the stimulus. Classical conditioning is a type of learning in which the repeated memories of a certain stimulus trigger an involuntary reaction to another stimulus. After experiencing loud thunderstorms at least once in our lifetimes, we automatically close our ears when we see a lightening from the sky due to classical conditioning. Operant conditioning refers to a learning of a behavior aimed for practical benefit or reward. When a dog, knowing that he will be rewarded with a treat afterwards, obeys his master’s order to sit down, a perfect example of operant conditioning has been exhibited.


3. Hypotheses

         Independent variable: water (wetness of the filter paper), honey (sugar content of filter paper), beads (rockiness of the terrain)

         Dependent variable: Number of pillbugs in each chamber

A.   Moisture Lab

If a wet environment is created, the pillbugs would exhibit taxis by moving there instead of staying in a dry one.

B.    Honey Lab

If we drench one chamber with honey, the pillbugs would be attracted to it due to its general preference of sugar, also exhibiting taxis.

C.    Terrain Lab

       

If a rocky terrain is formed, the pillbugs, exhibiting kinesis until it reaches there, would eventually show the tendency to prefer a rockier environment.

 

4. Materials

- 10 pill bugs

- 3 behavior chambers

-approximately 10mL of water

-app. 10ml of honey

-around 50 beads

-Brushes

-6 pieces of filter paper

 

 

5. Procedure

 

A.   Place 10 pillbugs in a behavior chamber whose two rooms are covered with filter papers. One should always remain dry as a control.  

B.    Record the number of pillbugs every 30 seconds in each room, carefully observing their behaviors.

C.    After at least 7 minutes, put the pillbugs back into the beaker using brushes. Prepare for the next experiment, changing the independent variable.

 

6. Results

 

A. Moisture lab:

 

Time (minutes)	# in dry chamber	# in wet chamber
0	2	8
0.5	2	8
1	2	8
1.5	2	8
2	1	9
2.5	1	9
3	0	10
3.5	0	10
4	0	10
4.5	0	10
5	0	10
5.5	0	10
6	0	10
6.5	0	10
7	0	10

 

The initial hypothesis was true. Pillbugs definitely preferred a wet environment to a dry one.

 

B. Honey Lab

 

Time (minutes)	# in dry chamber	# in honey chamber
0	2	8
0.5	2	8
1	2	8
1.5	2	8
2	3	7
2.5	3	7
3	3	7
3.5	2	8
4	3	7
4.5	2	8
5	1	9
5.5	3	7
6	4	6
6.5	4	6
7	3	7

Belying our initial hypothesis that pillbugs would show strong affinity to honey, the pillbugs were rather evenly spread in both chambers, albeit exhibiting a moderate preference of honey.

C. Terrain Lab

Time (minutes)	# in dry chamber	# in bead chamber
0	0	10
0.5	1	9
1	3	7
1.5	5	5
2	6	4
2.5	5	5
3	7	3
3.5	6	4
4	7	3
4.5	9	1
5	10	0
5.5	9	1
6	10	0
6.5	8	2
7	9	1

 

The preference of an uneven terrain was very obvious at first, but the pillbugs soon started to freely move around, perfectly exhibiting kinesis. However, since their behavioral tendency to gather around the beads was very dramatic, I would still call the initial hypothesis valid.

7. Conclusion

Apart from superficial observations, the lab suggests a significant ultimate question regarding adaptive traits often maintained and evolved through natural selection. The behavioral tendencies pillbugs demonstrated were in many cases related to adaptive traits acquired so as to increase their chances of survival in nature. Pillbugs, over time, have evolved/adapted to live under dark, damp objects such as trees or organic garbage to avoid their predators. This accounts for their preference of wet filter paper. Sugar can possibly be a good source of nutrient for the pillbugs to generate ATP. Pursuit of sugar must have been beneficial to their survival. Likewise, pillbugs are fond of rocky terrains for they are capable of inhabiting under rocks, a desirable trait that prevents them from being noticed by predators.