When placed together most decapod crustaceans (i.e. crayfish, lobsters) will fight readily. Interactions invariably increase in intensity until one of the combatants withdraws, and success is based largely on physical superiority. The typical scenario of an encounter begins with extensive threat displays upon first contact, continues with periods of ritualized aggression and restrained use of the claws, and terminates in a brief session of unrestrained combat. Predictions of game theory (i.e. assessment strategies) provide a useful framework for the understanding of fighting in lobsters. The presence of a highly structured behavioral system may reduce the potential for damage in fights among conspecifics, and may prove useful in attempts to study the neurobiological causes of complex behavioral patterns such as aggression.
In our lab we use the behavior as a bio-assay to determine the precise effects of everything from infused chemicals to previous losses. It is therefore essential that we use consistent and well-defined criteria when we do this. This page attempts to guide you through the terminology and the individual steps of the procedure.
The basic units of our efforts are dyadic interactions between two individuals. Behavioral measures quantified for each bout include duration, maximum intensity, the first instances at which different intensities occcurred during the fight, frequency of unrestrained use of the claws, and the identities of the initiating and retreating animals (Huber and Kravitz 1995; Huber and Delago 1998). Use the following Filemaker Pro 3 template to enter your data.
Keep all interactions of all of your experiments in a single file but make sure that data from eacvh interaction is characterized with regard to experiment number or the particular treatment.
Begin your observations by completing the fields in the green area. The content remains the same for all interactions of an experimental period.
Exp: number your experiments consecutively
Ind.A and Ind.B: enter IDs for each animal. Use the same IDs that match them up with your database of experimental animals. In fields such as "Start Who" and "End Who" just refer to these individuals as A or B. If treatment refers to only one individual, then enter it as A.
SexA and SexB: enter sex (male, female) for each animal
WgtA and WgtB: enter weights (in grams) for each animal
CLA and CLB: enter carapace length (in mm) for each animal
ClawA and ClawB: claw condition for each animal
CardDomA and CardDomB: if known and relevant - enter cardinal dominance ranks for each animal
OrdDomA and OrdDomB: if known and relevant - enter ordinal dominance ranks for each animal
SizeDif: enter the qualitative size difference between the opponents
ExpStart: enter the video time (from the tape) when the divider is removed
ExpType: chose the experiment type that fits best with your experiment, if none fits well, then let me know and I help you add another option to this menu
ComA and ComB: if relevant - enter comments for each individual animal
Comment: if relevant - enter comment for the experiment or the interaction
Now use the blue section to characterize the type of treatment the interacton came from. Most likely you will use the generic Treat
Treat: enter the type of treatment
Next enter numbers into the yellow section. These data all refer to one single interaction and are used to completely characterize it in behavioral terms
InitTime The beginning of an interaction is defined as the point in time when: (1) two opponents advance to within one body length AND (2) overtly react to each other's presence. It is NOT an interaction if one individual backs into or climbs over another without visibly acknowledging the other animal. Record the video time (from the tape)
InitWho: The more actively approaching animal is termed the initiator. Leave blank if both individuals initiate at the same time
InitInt: Record how intense the initiator starts the interaction as: (1) slow approach (< 1 bodlength/second), (2) rapid approach (> 1 bodylength/second), (3) lunge
Int2, Int3, Int4: Record the video time from the tape when the fight for the first time reaches intensity 2, 3 or 4 (for definitions of intensity levels see below), Leave fields blank for levels of intensity that did not occur.
MaxInt: Enter the maximum level of intensity that was reached during the interaction according to the following criteria: (0) no fighting: neither animal attacked its opponent or one animal consistently retreated from the advances of the other; we call it fighting if both animals contested the interaction, resulting in intensities > 0: (1) threat postures: both animals contested the interaction using threat displays or ritualized fighting without physical contact, (2) physical contact: both animals contested the interaction and at least one individual touches the opponent with antennae or open claws; (3) claw lock: both animals contested the interaction and at least one animal used its claws to grab the opponent; (4) strike and rip: both animals contested the encounter and at least one animal made unrestrained use of the claws in an attempt to rip or tear off appendages. Note that the main rational for this progression of intensities lies in the danger for injury, i.e. no physical contact < touch with antennae or open claws < claw lock < unrestrained use of claws
NInt4: Note how often intensity 4 was observed, leave blank, if interaction ended at a lower maximum intensity than 4
EndTime: The fight ended when an animal turned or walked away from its opponent, increasing the distance between them to more than one body length. There should be a break of at least 5 seconds until the beginning of the next interaction.
EndWho: The identity of the retreating animal was recorded as the loser. Leave blank if both individuals retreat at the same time
EndInt: Record with what intensity the loser retreats as: (1) slow retreat (< 1 bodlength/second), (2) rapid retreat (> 1 bodylength/second), (3) tailflip
Start: Number of seconds elapsed between the start of the experiment and the start of the interaction.
TSlice: group "start" into 15 minute intervals
Int2, Int3, Int4: seconds elapsed between start of the fight and first instances of intensities 2, 3, and 4
Duration: Number of seconds between start and end of the interaction
unlabelled field check for various errors: "cool" if record passed the test, "shit" if not
Weight: average of WeightA and WeightB
WDif: Weight difference between individuals A and B
CLDif: Carapace length difference between individuals A and B
Export the records as text file if you need to subject your data to statistical analysis. Import that data file then into your preferred statistical program. We have different types of java programs for more specialized analyses - see our Java Grinders site.
for comments please contact lobsterman