Captive Experiments

In order to test or explore different research questions and hypotheses, scientists will often conduct controlled behavioral experiments on their subjects. This usually takes place in a laboratory. During such trials, environment and/or social conditions can be altered enabling researchers to determine their influence on the expression of behavior. For large marine predators like sharks, conducting controlled captive experiments is particularly challenging for obvious reasons.
 
At the Sharklab
Photo Credit: Matthew D Potenski
 
In Bimini to overcome the above difficulties we house juvenile sharks (i.e. nurse and lemon) in outdoor holding pens (~10m, diameter) built just offshore in shallow, sand-bottom flats. Pens are constructed of plastic mesh which exposes the sharks to ambient environmental conditions (tidal/lunar cycles, changes in salinity, temperature, light) that promotes natural behavior. They can be built in a range of shapes and sizes, with sliding doors and feeding targets to facilitate various behavioural studies. 
Here experimental sharks are given the choice between two stimuli (i.e. shark vs. no shark), presented behind a barrier and generally at either end of a test pen. The association preference of the test shark is scored by, for example, recording the time it spends within a certain distance of each stimulus. This method gives clear, easily recorded results and enables investigation of cues mediating this choice, e.g. visual or olfactory, by changing the type of barrier used. In Bimini we used this technique to investigate juvenile lemon shark social preferences (Past Research - Social Behaviour). 
The most commonly used alternative captive method to investigate social behaviour, is termed `nearest neighbour', which presents the test shark with a situation more accurately reflecting that found in nature. A group of sharks are released into a pen and the location of a focal test shark relative to others is recorded at discrete time intervals. Sharks are fitted with external markers (color code tags) to facilitate identification (Research Techniques - Identification Tags). These groups can vary in size and composition i.e. species, sex and location of capture to investigate social organisation and behaviour. In Bimini we are using this method to score juvenile lemon sharks for their ‘sociality’ i.e. are sharks consistent in their social behavior with conspecifics (Current Research - Personality). 

Sharks are usually one the most exciting attractions at aquariums around the globe. Such exhibits often have multiple sharks of various species living in close quarters with other large marine animals. In order to control feeding behaviors and reduce competitive and agonistic interactions aquarists often train sharks to feed from specific targets, such as PVC pipes or plastic sheets usually differing in color and or shape. Sharks learn to associate their particular target with food and so feed in a safer more structured manner. Here in Bimini we have adapted these types of practices to our semi-captive setup and use them as tools to investigate learning capacity and social learning capabilities of juvenile lemon sharks (Past Research - Learning).

At the sharklab we are always striving to use and trial the most cutting edge technology to ensure we are conducting research of the highest quality and exploring novel scientific questions. When such technologies become available it is important to test them in a safe, standardized environment where calibration of outputs and impacts on the behavior of focal sharks can be explored. In recent years we have tested the efficacy of proximity receivers (Research Techniques - Biotelemetry) to identify shark social behaviors and more recently calibrated the use of accelerometry loggers to investigate activity and feeding behaviors. Such testing is particularly complimentary to our field studies and is integral to the advancement and development of such technologies.
 
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