Observing Behavior

A primer to interactions that may be seen in Biosphere2 Coral Reef Biome fishes

 

Finding a comprehensive behavioral ethogram that encompasses a spectrum of coral reef fish is a big feat.  One of the most complete ethograms published is Arthur A. Myrberg's Ethology of the Bicolor Damselfish, Eupomacentrus partitus (Pisces: Pomacentridae): A Comparative Analysis of Laboratory and Field Behavior (1972). Focusing on the Bicolor Damselfish, the aims of the study included: 1) observation of activities of a small, unrestricted colony in a natural habitat; 2) quantitative analyses of the behavior of territorial males to estimate the predictability of behavior; 3) identification of the elements of behavior that were unique to that environment. Because of the holistic approach of Myrberg's ethogram, it has been synthesized and served as a guideline to construct our generalized   ethogram, and it is a great reference for those interested in an introduction to the behavior of nearshore fishes.

Behavior can be split into three basic units. These include MOTOR PATTERNS (locomotory movements and posture), COLOR PATTERNS and SOUNDS. For our particular study, the focus is on motor patterns; the behavior of fishes that stems from the initiation of motor (movement) systems. These patterns are considered instantaneous events since they last for only a few seconds. The goal is to record all patterns and analyze them statistically to reach an understanding of the intricate mechanisms controlling fish behavior, and gain knowledge of the importance of fish herbivory on algae and corals within the biome. It is important to note that elementary action patterns are relatively stereotyped: descriptions in Myrberg’s ethogram are based largely on convenience and not upon Fixed Action Patterns (Lorenz 1956) criteria. One needs to be patient and cognizant of as much as possible. Behavior can be slight and rapid. During a1/2 hr observation period, as many as 600 distinct patterns can be recorded. But in our study we are principally interested with the importance of species and functional diversity in maintaining particular motor patterns such as grazing or nipping of corals and algae, and so the exclusion of more subtle patterns is acceptable.

 

 

OBSERVABLE BEHAVIOURS

 

I. Territoriality

            Males can be extremely active in their social interactions compared to females.  They may continue to defend a small specific area throughout a year.  Females can be largely passive in their social interactions. Rapid movement during defense may be extremely difficult to follow.

 

II. Social Hierarchy

            Both males and females are known to demonstrate social hierarchies.  Hierarchy tends to be most evident outside territorial boundaries.  In laboratory settings, Braddock (1945) observed a distinct, straight-line, size-dependent, nip-dominant social hierarchy. 

 

III. Feeding

            In natural conditions, feeding may be in the water column during dawn or dusk.  Fish may feed directly on or near the substrate.  In addition, individuals may move higher in the water column, maximum distances being largely dependent upon fish size. However, if there is a lack of current and pelagic food, nipping of algae from substrate appeared to substitute for water-column feeding.

 

IV. Reproduction

            Reproductive activities may be present during all seasons. Reproductive phases can be associated with increasing territorial chasing.  Other reproductive activated include nest preparation (cropping algae and other matter from a site). Males, females, or both can perform nest preparation, depending on species. Various courtship and spawning behavioral patterns may be observable. In labs, spawning occurs on smooth walls or plastic filter tubes, but never in nooks and crannies of rocks. There are three general phases;

 

            Initiation of courtship:

Carryout a brief bout of Close-Swimming or Skimming (anywhere from 15s to 1min)

            Oviposition and fertilization following courtship (anywhere from 2-15min)

 

Complete spawning may not be observable, though in Myrberg’s study after sunrise initiation of courtship was observed. Full reproductive cycles (from courtship to recruitment) have not been observed in B2 fishes, but many species have made it to the egg production phase. Males may tend to eggs, visiting usually once or twice per minute by a guardian male during the period of incubation. Visits are usually 10-12s. Males fan, nip or simply “inspect” the eggs. During periods of incubation, there may be increased viciousness in defense of territory. On two separate occasions, damselfish nests have been built and maintained within view of our underwater cameras.

 

V. Interspecific Interactions

            Interspecific aggression may be directed to substrate-feeding species in which nests are located, or in which algal gardens are maintained (see Kaufman,1977, for example). In fact, whenever a need to defend territory is perceived, an aggressive response may be initiated. On wild reefs fish predation is common, but there are few prey-predator interactions in the B2 fish community. Similarly, mutualistic relationships are limited in the B2 system because most of the necessary species (cleaner fishes, for example) are missing from the B2 system. Experimental fish introductions are being planned to investigate the importance of these relationships in the B2 oceanarium.        

 

THE ETHOGRAM

 

Locomotion/Posture

• FORWARD SWIMMING  (may not be apparent in certain species)

Largely done by the caudal fin with the pectoral fish being used for changing directions. 

• BACKWARD SWIMMING Accomplished by pectoral fins and posterior portion of dorsal fin is used as a rudder.
• HOVERING when a fin remained motionless in the water column. This pattern may be uncommon in active species, but can be observed while feeding.
• FIN SPREAD Evident during agonistic encounters or in braking movements, followed by a rapid maneuver. Body is usually horizontal
• HEAD STAND  Evident during interspecific interactions. Body is inclined, head is pointed downward, and all fins maximally spread. Angle of inclination varied, from a small angle to over 60’ from the horizontal.  Explosive swimming often precedes a Head Stand.  Head Stands are rarely seen interspecifically.
• WANDERING  Slow or moderate swimming by a fish that is neither interacting directly with other fish nor showing a recognizable motor pattern. 

Maintenance

Patterns that appear to aid fish by removing matter from the body, or provide a type of muscular activity. Maintenance patterns occur independently of a direct social context, feeding or nesting, but do not form from a common set of causal factors. 

• CHAFE  Behavior that occurred against some hard object. Just prior to reaching an object, the fish accelerated slightly, then, rubbed part of its body against the object with fins fully expanded.  Chafed may occur in multiples, and species may prefer smoother objects to a rough/scoured area.
• FIN-FLICK Often associated with chafing. While swimming, a fish occasionally folded and then expanded rapidly one or more of its fins.
• YAWN  Involves a rapid opening of the mouth, and rapid extension and lowering of median and pelvic fins.
• TAIL-DOWN  When a fish swimming very close to  the substrate suddenly stops, and then drops its caudal fin to the substrate.
• TAIL-DIG  Rapid beating of the caudal fin at the substrate, with sand being swept to the side or into the water column. 
• BODY-SHAKE  Lateral shaking of the entire body, two or three times in rapid succession. 

Feeding

• JERK-SWIM (gulping/suction feeding) Sometimes difficult to discern. Consists of rapid movement that covered a few centimeters in any direction, ending with Fin-Spreading and snapping of the mouth. Jerk-Swim may be more easily observable in larger individuals. 
• NIP  (bite) Rapid dart at an object with an open mouth. Fins neither expanded nor folded.  At the moment of contact, the mouth rapidly closed. Nipping can be directed to benthic algae, and numerous other objects. Following nipping, if food was unpalatable, it would be ejected.

Courtship/Spawning

For courtship and other reproductive activated, certain patterns of behavior are only carried out by territorial males.

• TILT  Lateral tilting of the body, 20’ to 40’, followed by a return to normal vertical position.  Only performed by males
• DIP  A vertical, or near-vertical dive from a position 1-2 m above the substrate.  Upon completion, the fish may swim rapidly up the water column. This pattern may be enhanced by the caudal fin suddenly flicking upward as the dive begins. 

Both patterns can be observed together, in a series of Tilt-Dip actions. 

• NUDGE  Directed to a female by a male who just completed a dip.  Male slightly tilted, head-down swims in an exaggerated fashion towards the female.  Unique head-down posture and exaggerated swimming towards a female can be defined as a Nudge.
• LEAD  Rapid movement by a male to its nest area, showing exaggerated tail movements.
• QUIVER  Performed solely by males, depends on female behavior. Male stood on its head and quivered its head. 
• CLOSE-SWIM  Near a nest site, when a female enters. Male moves rapidly towards female. Both fish expand their fins.  Coloration changes may also be exhibited.
• SKIM  Male moving its venter above the substrate.  Body vibrates slightly, and head is held a bit higher than the rest of the body.  Females exhibit same pattern, though her venter rests directly against substrate.
• SPAWNING  Skimming, with release of eggs and milt. Can be a long or short occurrence. Short breaks occur during spawning. Spawning terminated by female who left nest not to return.
• FLUTTER  Consisted of male tilting the body laterally, usually 20’ to 40’, expanding all fins and swimming rapidly towards the female.  Often, Flutter was followed by a short series of forwards and backward movements.  

Nest Behaviors

Two motor patterns closely associated with tending eggs:

• FAN EGGS  A very brief behavior- male uses its pectoral fin nearest the egg mass and beats rapidly while other pectoral fin moves slowly. Upon completion, male may either Nip eggs or swim away. 
• NIP  (described earlier)

Agonism

Patterns included may be representative of territorial defense, establishment and maintenance of social hierarchy and/or competition for food, mates or additional space.

• FRONTAL-THRUST  Pattern that often initiates action. A rapid movement towards another individual – median fins expanded, pelvic fins tight against body. The fish body is often inclined, its head up, and mouth slightly open.
• FRONTAL-DISPLAY  Same as Frontal-Thrust, but no movement was involved. Fish are facing each other.
• LATERAL DISPLAY  Same as Frontal-Thrust and Frontal-Display, but fish are alongside (not facing) each other.
• HEAD-UP  Two fish at a territorial border, facing one another in a Frontal-Display.  One paddles its pectoral so that the anterior portion of its body moves upward, tail lowers slightly.  Followed immediately by:
• HEAD-DOWN  Opposite movement of Head-Up.  Anterior portion below, tail raised slightly.
• DUEL-UP  Usually followed by Head-Up or Head-Down.  Like Parallel-Swim, but fish swim vertically upward.
• DUEL-DOWN  Similar to Duel-Up but direction is vertically downward.
• PARALLEL-SWIM  Fish swim side-by-side in a horizontal plane.  Slight tail-wagging may be evident.
• CIRCLE  Often follows Parallel-Swim or mutual Frontal-Thrust. Fish move about in a small, imaginary circle, head-to-tail. Fins are fully expanded, mouths open, but not agape.
• CHASE / FLEEING  When one fish swims rapidly towards another fish (Chase), and other fish tries to remove itself  from advancing fish (Flee) 
• HALF-CIRCLE   Pattern shown by fleeing fish, suddenly turns to half-circle and brings fish head on to its adversary.
• VEER-OFF  Sudden tilting of the body and folding of the fins, usually accompanied by a rapid turn.
• CLOSE-DOWN  Shown most often by female near substrate when approached by a male.  Female tilted body slightly so one side was directed to line of approach of the other fish. Appeared to inhibit male from contact.
• TAIL-BACK  Approach adversary with tail first. All fins are expanded, and caudal fin beats rapidly. Often performed in a jerky reaction. 
• FIN-SPREAD  Described earlier, also an agonistic response.
• HEAD-STAND  Described earlier, also an agonistic response.

RECORDING BEHAVIORS

Observed behaviors are recorded using pull-down menus. The source, nature, and target of each behavior is selected, this information is submitted to a server, and the details are saved along with a time stamp that describes the precise time that the behavior was submitted. Collaborating researchers estimate the total time spent observing the B2 cameras, and the probability of observing behaviors is estamated as the number of times a behavior is observed divided by the total time spent observing. A practice form has been developed for gaining experience in the ethology process. Scientists and educators interested in working on the B2 ethology project should contact the Kaufman laboratory. All others are welcome to visit the Live Web-Cams of the Biosphere2 Oceanarium.

LITERATURE CITED

Kaufman, L.S. (1977) Threespot damselfish: effects of benthic biota of Caribbean coral reefs. Proceedings, Third International Coral Reef Symposium, University of Miami: 559-564.

Myrberg, A. (1972) Ethology of the Bicolor Damselfish, Eupocantrus partitus (Pisces: Pomacentridae): A comparative analysis of laboratory and field behavior. Animal Behavior Monographs 5(3): 199-283.