Measuring behaviour recording and sampling rules

Transcription

1 1 Adfærdsbiologi øvelse 1 uge 50 Measuring behaviour recording and sampling rules 1. Introduction The study of animal behaviour aims at investigating 4 aspects of what animals do: functions, mechanisms, development and evolution. Whatever the aspect, studying animal behaviour implies: 1. asking a question, initially broad and later more refined as the behaviour is studied in detail 2. making preliminary observations from which one or more hypotheses can be formulated 3. making predictions (forudsigelser) from the hypotheses 4. choosing the appropriate measures of behaviour (adfærdsmål) to answer the questions and test the predictions 5. choosing the appropriate recording methods (registreringsmetoder) (sampling and recording rules) and recording medium (registreringsudstyr) that fit the measures chosen and the question asked 6. collecting the data 7. analysing the data to confirm or deny if the results fit the predictions 8. presenting the results to the scientific community in the form of reports, articles and seminars 9. asking new questions that stem from the new knowledge The first three steps require some basic knowledge of the phenomena and a good dose of curiosity, creativity and imagination. The questions, hypotheses and predictions can be formulated using a combination of basic observations and published information. This practical will cover steps 4. and 5., with some theoretical background, and then you will try steps 4. to 7. by observing and recording the behaviour of a pair of kittiwakes (rider) Rissa tridactyla on the nest from a video clip. You will also try all nine steps above in the other practicals of the course. 2. Measures of behaviour 2.1. Description of behaviour Behaviour can be described either in terms of its structure, i.e. its appearance and physical form (e.g. run bill along wing feathers ) or in term of its consequences, i.e. the effect of the behaviour on the environment, other individuals or the subject itself (e.g. preen fjerpleje ). Description of structure is usually preferable because it can be more accurate and repeatable, and because it is neutral. However, it may generate unnecessary detail. Description by consequences is often less detailed and therefore more practical, but caution should be used to avoid excessive interpretations and neutral terms should be preferred. Behaviour can also be described in terms of the spatial relation of the subject to the environment or other individuals (e.g. approach the mate or leave the nest ). Behaviour is a continuous stream of actions, and in order for it to be quantified and described we need to divide it in categories, which should be appropriate for the question asked, precisely defined, independent of one another and homogeneous. For some questions it will be necessary to look at details, often referred to as behaviour elements (adfærdselementer), e.g. 1) neck stretched obliquely upwards and forward, 2) wings slightly elevated and 3) long call in the black-headed gull (hættemåge) Larus ridibundus. For other questions it will only be relevant to consider more complex behaviour patterns

2 Adfærdsbiologi øvelse 1 uge 50 2 (adfærdsmønstre) which are combinations of behaviour elements, for instance long-calling in the black-headed gull that consists of the above mentioned 3 elements. For still other questions it would be sufficient to look at behaviour sequences (adfærdssekvenser), for instance the meeting ceremony in the black-headed gull that consists of a fixed sequence of 3 behaviour patterns starting with long-calling Measures Whatever the level of description (element, pattern or sequence) behaviours can be quantified using four basic types of measure: 1. Latency (latenstid) = time from some specified event (e.g. start of recording) to the onset of the first occurrence of the behaviour. 2. Frequency (hyppighed/frekvens) = number of occurrences of the behaviour per unit time 3. Duration (varighed) = length of time for which the behaviour lasts (total, average etc.) 4. Intensity (intensitet) = defined according to behaviour (e.g. loudness of the long-call in the black-headed gull, partly or fully raised head feathers in a jay (skovskade) Garrulus glandarius, or low and high intensity of fighting according to absence or presence of physical contact, respectively). Behaviours can be defined according to types which lie at the extremes of a duration scale: events and states. Events (begivenheder): behaviours of instantaneous to short duration, which are best described by their frequency (e.g. vocalisations). States (tilstande): behaviours of relatively long duration, which can be best described by their total or average duration (e.g. body postures or position in the environment). These categories are not strict, and events can also be described by duration if we re looking at a small time scale (e.g. duration of different vocalisation types), while states can be measured by frequency when measured over a large time scale (e.g. number of reproductive events in a season or in a lifetime). Events are often repeated rapidly in bouts (serier) that can be measured both by their duration and frequency. 3. Recording methods The rules for recording behaviour refer to who to watch, when and how. Sampling rules (observationsregler) define essentially who we watch (one or many individuals, or a particular behaviour). Recording rules (registreringsregler) define how we record the behaviour with respect to time Sampling rules There are four sampling rules to define who to watch: Ad libitum, focal animal, scan and behaviour sampling. Ad libitum sampling (ad libitum observationer): the recorder notes down all that is visible and seems relevant, without constraints on which animal to watch. This rule is very useful for preliminary observations, but does not yield homogeneous measures of behaviours and tends to overestimate the most common or conspicuous behaviours.

3 Adfærdsbiologi øvelse 1 uge 50 3 Focal animal sampling (fokaldyrs observationer): the recorder chooses one individual (or any other unit, e.g. a group of animals) and records all behaviours performed by the individual in a specified time window. This is probably the most common and most useful rule, but can be time consuming if many individuals need to be sampled. Scan sampling (skanning observationer) the recorder notes the behaviour of many individuals at once at regular time intervals. This rule normally limits the number of behavioural categories which can be used, since the time to note the behaviour of all individuals should be as short as possible. It also tends to overestimate conspicuous behaviours. Behaviour sampling (adfærdsobservationer) the observer notes all the occurrences of a specific behaviour, together with who is performing it. This method is used to quantify the occurrence of important rare behaviours Recording rules There are two ways to record behaviours with respect to time, continuous recording and time sampling (periodisk registrering), the latter divided in instantaneous and one-zero sampling. Unlike continuous recording, time sampling does not give exact frequencies and durations, only approximations of them. Time sampling is therefore only used when continuous recording is not possible, usually because too many behaviours occur too frequently. Continuous recording (kontinuerlig registrering) all occurrences of the behaviours are recorded, together with information about the time and duration of occurrence. This rule gives the most accurate estimate of frequencies, latencies and durations of behaviours and the records obtained contain the most information about the behaviour. Sequence recording (sekvensregistrering) is continuous recording without time information, i.e. this rule only gives frequencies and succession of behaviours. Instantaneous sampling (øjebliks registrering) the observation session is divided in short intervals (registrerings intervaller) by sample points (registrerings tidspnkter), and at each sample point the recorder notes if the behaviour is occurring. The measure obtained is the proportion of sample points in which the behaviour occurred. Instantaneous sampling, which is often used to quantify states, may give a good estimation of the total duration of a state if the intervals are short relative to the duration of the states. One-zero sampling (interval registrering) again the observation session is divided in short intervals, and at each sample point the recorder notes if the behaviour has occurred during the previous interval. The measure obtained is the proportion of sample intervals in which the behaviour occurred, which is not a true duration or a true frequency. Onezero sampling is mostly used to quantify events Recording media Behaviour may either be measured directly while it is performed, or later on (as in this practical) from audio and video recordings of the behaviour. The basic tools for recording behaviour, especially in the field, are pencil and paper. These are simple, cheap, flexible and reliable (no loss of data due to technical problems). The paper can be from simple white

4 Adfærdsbiologi øvelse 1 uge 50 4 notepaper to a complex and organised check sheet (observationsskema) where information is coded by means of letters and symbols. Though still being one of the most used, check sheets are time consuming since data has to first be collected and then quantified and stored in a way that it can be analysed (generally in a computer). There are more technologically advanced methods, which go from dictated verbal description, through automatic event recorders to computer software and hardware. Dictated verbal descriptions can be even more time consuming than check sheets, but have the advantage of not requiring the recorder to look away from the subjects observed. Automatic recorders tend to be simple but rather rigid machines, which record for example levers being pressed or motion in an enclosure. The computer nowadays offers the most flexible and efficient methods of recording, storing and analysing behaviour data. In most cases a computer is used as a sophisticated even/state recorder, operated by the observer, where data is entered through coded key presses, and then is output directly in a form ready for analysis. It also allows a more accurate measurement of time. Some simple and flexible event recording software has been adapted to handheld computers for use in field studies (but also for laboratory studies). You will be using this medium for this and other practicals in this course. The software is called FIT-System and runs on a Palm handheld computer. It essentially records the position (x-y coordinates) and time of tapping on the screen with the stylus. The user can then assign a definition to each portion of the screen, corresponding to the behaviour categories observed. During this and other practicals you will try the handheld computer recording medium in association with most of the behaviour measures, types and recording rules described here, by applying them to a video clip of nesting birds. 4. Collecting data 4.1. Kittiwakes Kittiwakes are colonial seabirds, relatives of gulls (måge), that nest in large colonies on steep cliffs at northern latitudes (e.g. Bulbjerg, Northern Jutland). Males and females are similar and share the care for the young at the nest, which contains on average 2 eggs/young. Adults provide food (mainly fish) and surveillance for the young for 5 to 7 weeks, males and females taking turns at the nest. They are very vocal and produce a number of different calls during both courtship and parental care. Courtship also takes place on cliffs Video You will watch and take measurements from a digitised video recording of a pair of kittiwakes on their nest within a colony. The video file is called kittiwakes.mpg and will be available on the desktop of the computers you will use, in the folder called Practical 1 Kittiwakes. The video will also be shown to all by the lecturer before you are divided in groups and assigned to the computers. The video lasts 3 min in which the birds will be performing a number of different behaviours, more or less conspicuous. You will have to watch the video, which can be eventually rewound if necessary, and collect data on the behaviours using the Palm handhelds (see instructions). All groups will have the same video to watch Behaviours When you first watch the video, it appears that the birds are not doing anything interesting. If you reviewed it a number of times you would start noticing some regular patterns and some potentially relevant details of the animals actions. You can try to identify some potentially interesting and quantifiable behaviour patterns yourselves. Each individual

5 Adfærdsbiologi øvelse 1 uge 50 5 performs certain movements, is present or absent at a certain point in time and interacts with the other individual. The behaviours you will have to measure, at least in the beginning, are: 1. leave nest/return to nest 2. bill open/bill closed 3. touch other bird with bill These behaviours can be quantified using the measures described above (latency, frequency and duration) and can be assigned to one of two categories, event or state. For example, behaviour 1 results in a state defined as bird present/absent and can be measured in terms of duration (e.g. total time present at the nest). You will assign the other behaviours to the appropriate categories and apply the appropriate measure. You will then use a sampling rule and a recording rule to collect the behaviours. You will use focal animal sampling by observing only the behaviour of one of the two birds for the whole length of the video (you choose which bird). You will also use continuous recording ( alloccurrences ) for all the behaviours, since the handheld is especially powerful for the application of such recording rule Data collection Once you have opened the video, follow these steps to start collecting the data: 1. Turn on the handheld computer assigned to your group by pressing on the green button on the bottom left corner. 2. Tap on the house icon on the screen to see all the software available on the handheld. Tap then on the icon called FIT. 3. The screen will show three buttons: Record, Send and Delete. Tap on the Record button. 4. Assign a file name by tapping on the ABC icon at the bottom left of the screen and then on the letters that appear on the screen. Use your initials as file name. 5. Turn off the handheld WITHOUT tapping on the OK button At this point you are ready to begin recording the behaviour of the birds. To do this you will need the screen cover sheet (provided) where the behaviours are specified. The screen cover of the handheld computers you are given will show 12 rectangles (buttons), 7 of which are already assigned to specific behaviours: START/STOP you will tap on the START button as soon as you start the video and on the STOP button at the end of the observation/video ARRIVE you will tap on this button when the focal bird arrives at the nest DEPART you will tap on this button when the focal bird leaves the nest OPEN you tap on this button when the focal bird opens its bill CLOSE TOUCH you tap on this button when it closes it again you will tap on this button when the bill of the focal bird touches the other individual. Put the screen cover sheet on the screen and turn the handheld on again. You are now ready to start recording the behaviours. Tap on OK on the screen. The program has now already started recording time. Start the video and tap on the START button as quickly as possible. Continue the recording until the end of the video. One member of the group can use the handheld and the others watch and announce the behaviours. If you still have time after having completed all the operations, you can use the remaining 5 buttons to define and measure other behaviours you believe to be interesting or relevant to a particular question.

6 Adfærdsbiologi øvelse 1 uge 50 6 Once you have collected the data on the handheld, you will transfer it to the computer and use the FIT Manager application to assign each group of points to the appropriate behaviour and to export the data to the Excel format Data extraction Once you have sampled the behaviour from the video you will first transfer the handheld data to a single folder on the computer: 1. Connect the handheld to the computer with the cable provided. 2. Tap on the house icon, tap on HotSync and wait until the files are copied to the computer. 3. Open the FIT-Manager software (icon on desktop). 4. Open your data file, which is found in the Palm Backup folder on the desktop. 5. Open the template file, which is found in the Practical 1 Kittiwakes folder on the desktop. Eventually adjust the position of the rectangles so that all data points are included. 6. Export the data to an Excel file, saving it with the same name as the original file in the folder called Kittiwake Data Folder Data analysis The file containing your data is now in Excel format and can be analysed to extract information on frequencies and durations of behaviours. To do this you will use the Analyse FIT application, that scans the data file for the behaviours, which can then be assigned to the appropriate category (event or state) and for which different measures can be chosen and calculated. Proceed as follows: 1. Start the Analyse-FIT software (icon on desktop). 2. Under the /File/ menu, select /Open folder/ and find the Kittiwake Data Folder, click OPEN and the click OK in the next window. You should see a list of behaviours on the left hand side of the program window. 3. Now you have to tell the program where to start and where to stop looking at the data in each file. In the Start tab at the right hand side of the window select Zero, in the Stop tab select Named behaviour and then pick STOP from the list of available behaviours. 4. Click on the Add State button and select from the list: arrive, depart in this order. Check the Total duration box and click OK. This tells the program to calculate the duration of the bird present/absent states. 5. Do the same for the other behaviours. According to whether they are states or events, use the Add State and Add Event buttons. 6. Click on Analyse Data. 7. Click on Show Output to view the results of the analysis. The first column contains the file name, the others the behaviour data. 8. Click on Save Output and save the file in the Practical 1 Kittiwakes folder using you first names as file name. You can open the new data file with Excel and take a look at the values you have extracted. If you were now to repeat this procedure for a number of different kittiwake pairs (e.g. 20 pairs in a colony), you would be able to perform some statistical analyses, for example on the relationship between different behaviours. If you had, for example, some pairs from a colony in Denmark and some from one in Scotland, you could compare the behaviours between the two populations.

7 Adfærdsbiologi øvelse 1 uge Discussion Once you have completed the measurement and analysis operations, you will be asked to think about and discuss with the other groups and with the lecturer or the assistants the issues that may have arisen during the practical, among which we suggest: 1. This practical can be considered as an exercise in preliminary observations of behaviour. What questions on kittiwake behaviour did the observations suggest to you, if you wanted to continue with a more detailed study? 2. What context (kontekst) do the measured behaviours represent (e.g. aggression, courtship, alarm)? 3. How strict are the definitions of event and state for the present behaviours? 4. What other behaviours could be measured, and are they events or states? 5. Have you observed sequences of behaviour patterns/elements that are repeated in the same, or almost the same, order every time they are performed? 6. Which other sampling and recording rules could have given interesting results if applied to this case? 7. Could you have obtained the same results using other recording media? 6. Literature Martin, P. & Bateson P Measuring behaviour. An introductory guide. 2. ed.. Cambridge University Press.