Observational Techniques
Behavioral ecologists need to be able to quantify animal behavior in order to answer questions pertaining tohow behavior contributes to survival, reproduction, and population growth of a species. Today, you will practice three different procedures used to quantify animal behavior. Think about their advantages and disadvantages and situations where each technique might be the most useful.
Female guppy Male guppy Male guppy
Procedure
1) Work in groups of two or three for this exercise. You will be watching some guppies (Poecilia reticulata) in a small tank at your table. Watch the guppies for a few minutes to see what they are doing today. The male guppies are the small ones with the fancy tails; the larger, less fancy fish are females. Please look carefully at the fish so that you can tell them apart and note which fish you are watching. You will probably want to use behavior categories like swim, chase, bite, court, follow, or feed.
2) Practice using the three sampling methods for 30 minutes (total).
Then,
3) One person should observe the fish using Focal Animal Sampling (see below), while the second person should observe the samefish using Instantaneous Sampling. This will mean that you are both watching the same fish at exactly the same time, one recording its behavior with one approach, while the other uses a different method to record exactly the same behaviors at the same time. Follow this protocol for 20 minutes.
4) Now one person switches and uses the 1/0 Sampling, while the other still samples using the Focal Animal procedure. Sample using this approach for a second 20-minute period.
The overall objective of this lab is to contrast the activity budget of the guppies using the three different methods. You have two contrasts to make, the first is Focal Animal versus Instantaneous, and the second is Focal Animal versus 1/0 Sampling. Which method would be best for a long-term study of guppy behavior?Discuss the advantages and disadvantages of each method and how they differ in what they record.For an actual long-term study, the type of statistics that could be used to analyze the data would also have to be considered.
SAMPLING PROTOCOLS
Focal Animal Sampling (or Continuous Sampling)
Record the time whenever your focal guppy switches behaviors. Given the transition times, you can calculate the exact amount of time (duration) the target animal devoted to each behavior during the sample. You can also easily calculate the frequency with which each behavior occurred.
Example:
00:00 - (Start) swim
01.38 - chase
01.45 - swim
03.17 - court
03.39 - chase
03.41–swim
04.10 - chase
etc.
During this interval you can calculate that the animal swam three times (frequency) for a total duration of (00.00 to 1.38) 98 sec + (01.45 to 03.17) 92 sec + (03.41 to 04.10) 29 sec = 219 seconds.
Advantages:
This method is very detailed and almost no information is lost.
Disadvantages:
Substantial effort is required to collect this kind of data over a long period of time. Imagine if you collected this data over 1 year, for maybe 2000 hours. Sometimes researchers use tape recorders to get all the information, but then the narrative must be transcribed and the data picked out of the narration. Event recorders, which are basically notebook computers, make the entering of data much easier, but these are expensive, and may not be reliable in some rough field conditions.
Instantaneous Sampling
First, choose a sampling interval - say every 30 seconds. Once the sample starts, every 30 seconds, on the mark, record the behavior of the target guppy.
Example:
00:00 - (Start) swim
00.30 - swim
01.00 - swim
01.30 - swim
02.00 - chase
02.30 - bite
03.00 - swim
03.30 –swim
Advantages:
This is a more manageable approach that provides an easily analyzed data record that reflects the amount of time spent in each behavior. Think about what you would use as an independent sampling unit.
Disadvantages:
The activity budget derived from this data is based only on about 1/30 of the time spent observing the target animal - lots of data are lost. Given large enough data sets, an accurate picture of some behaviors (namely those that have long durations) may be obtained, but with smaller samples there are often biases in the data. For example, say we are sampling on the minute and we know, somehow, that guppies bite once every minute and that the average bite lasts about 2 seconds. We then expect to find about 2/60 (=1/30) of the activity budget composed of biting: In other words in a 30-minute sample we expect 1 of the minute observations to be bite. But that expectation ignores random variation. It is easy to imagine that during a 30 minute sample none of the bites happened to fall on the minute mark.
Behaviors of short duration relative to the chosen interval (for example aggression) tend to be inaccurately sampled unless the total number of intervals is very large.
1/0 Sampling (Hansen Frequencies)
A time interval is chosen – commonly 1 minute. Then, if a given behavior occurs during a minute, that minute gets a score of 1 (or a +) for that behavior; if it does not occur the minute gets a score of 0 or - (it should not be left blank, that implies missing data).
Example:
TimeSwimChaseFeedCourt
00.00 + + - -
01.00 + + - -
02.00 + + - +
03.00 + + - -
Advantages
The main advantage of this method is that it is simple, provided that the set of behaviors that you are checking off are suitable (think carefully about the categories before starting and make your check sheet before you begin). Unlike the instantaneous sampling, it does not miss very short behaviors.
Disadvantages
Frequency and duration of the behaviors can not be determined. In the above example "swim" occurred during all observation segments (minutes): Does that mean that the focal fish spent 100% of its time traveling? Did it travel exactly 4 times?
This lab was adapted from one used by Drs. Colin and Lauren Chapman at the University of Florida. The guppy photos were used with permission from Angel’s Plus.
Practice Session Data:
Continuous Sampling
Instantaneous Sampling
1/0 Sampling
Session 1 Data:
Type of Sampling:
Session 2 Data:
Type of Sampling:
Discuss the advantages and disadvantages of each method and how they differ in what they record.Include examples from your actual data to illustrate your points.
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