Video-based quantification of escape behaviors in individual and groups
of fish exposed to a simulated visual predator
J.D. Salierno1 and A.S. Kane1,2
1Aquatic Pathobiology Laboratory,
Department of Veterinary Medicine, University of Maryland, College Park,
MD, USA
2Virgina-Maryland Regional College of Veterinary Medicine, College Park,
MD, USA
The ability of fish to actively avoid and evade predation is essential
to the success of the individual. In order to accomplish these feats,
fish must maintain a functional suite of behaviors to cope with predation
pressure. Further, these behaviors must be adaptive in order to accurately
respond to fluctuations in predation pressure. We examined predator response
behaviors of individual and groups of killifish, Fundulus heteroclitus,
to a simulated visual aerial predator, to investigate if response behaviors
remain similar after repeated simulated threats, and if responses
vary based on whether they are alone or in a group. The killifish is a
good model for the investigation of predator avoidance behaviors because
they live in shallow estuarine habitats and are vulnerable to aerial predation
threats. We used a computer-based video tracking system (Videoscript Professional©,
v. 3.1) to record 15 seconds of baseline movement before, and 15 seconds
of movement after, presentation of the visual fly-by stimulus.
The stimulus consisted of wood bird silhouettes that flew
over the exposure arenas. The visual fly-by stimulus elicited
a signi.cant response whereby 96% of the individual fish and 95% of the
groups of .sh exhibited a startle response followed by cessation of movement.
This cessation of movement lasted for 12.4 (±0.9) seconds for individual
fish and 8.2 (±0.3) seconds for groups of fish, which were significantly
different. Velocity and percent movement for groups of fish, before and
after the simulated predator presentation, were consistently higher than
what was observed for individuals. Groups of fish responded with significant
decreases in average velocity, shoal velocity, interactions, movement
and shoaling activity, along with significant increases in aggregation
(no movement component). Groups of fish displayed a higher degree of overall
movement and initiated swimming behaviors compared with individuals, thus
punctuating the ability for killifish to alter predator response behaviors
based on social dynamics. As a result, these eminently repeatable and
quantifiable responses could serve as endpoints for the investigation
of alterations in predator avoidance behaviors in association with stress
or toxicant exposure.
Paper presented
at Measuring Behavior 2005
, 5th International Conference on Methods and Techniques
in Behavioral Research, 30 August - 2 September 2005, Wageningen, The
Netherlands.
© 2005 Noldus
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