Wednesday, April 2, 2014
Can sharks be taught?
Sharks have traditionally been considered to be mindless killing machines, designed exclusively for hunting, but current scientific research is showing that these perfectly adapted cartilaginous fish are indeed intelligent and are capable of exhibiting problem-solving skills. The complex social behaviors of many shark species equally points to their intelligence and research is indicating that sharks are quite capable of learning.
Oceans Research’s Maze project aims to assess the relative learning capabilities of benthic sharks using an open plan choice-based maze.
Three species, namely, the pajama (Poroderma africanum), puff adder (Haploblepharus edwardsii) and the leopard cat shark (Poroderma pantherinum), are used for this experiment to ascertain whether differences in learning behavior exist between species.
Initially, a fiberglass coated, wooden maize was constructed in which sub-adult and adult cat sharks could be tested. More recently, a smaller glass maize was constructed, in which juvenile cat sharks representing the three species already mentioned, were tested. These juveniles were selected for the maize experiment from the age of six months and were initially trained or conditioned prior to their use in the maize, to accept appropriately sized pieces food from a plastic tong or “grabber”.
Most recently, a structure approximately two thirds the size of the original wooden maize was constructed within the original maize, to accommodate the growing juvenile sharks.
The maize project aims to show whether benthic sharks of three species can be taught to identify a visually distinct color, if offered a reward for making the correct choice.
This project is divided into distinct phases, namely a control, training, two testing (the first of which incorporates a reward and a second, during which rewards are not presented) and an extinction phase.
The colors “black” and “white”, being those offering the most contrast, were chosen and two doorways, one painted black and the other painted white, were positioned halfway down the length of the maize. For this experiment, the color white was decided upon to be color of choice.
During the control phase, the sharks are allowed to randomly choose through which doorway they will pass and each shark “ran” six trials per session during this phase.
The original food reward has currently fallen away and has been replaced by a “shelter” reward. Sharks under captive conditions arguably expend far less energy when compared to their wild counterparts and require (and through observations frequently accept) less food quantity wise, than would be expected and for this reason, the food reward has been replaced with a more appropriate reward, namely an appropriate shelter, which in this case, is a section of hollow plastic pipe.
Eight trials per session are run during each of the two training phases. During these “training” phases the sharks receive their reward if they chose the correct doorway. As mentioned above, as the protocol was refined, the food reward has been replaced by a “shelter” reward, which the sharks readily accept.
During an “extinction” phase, the reward is removed in order to gauge the length of time each individual shark will continue to “remember” which color it needs to choose, even though it does not receive a reward for doing so.
One shark at a time “runs” the maize. This individual is placed into the first compartment, which represents the starting block and is allowed five minutes to swim out of this area and through the rest of the maize, once a “guillotine” type door is lifted. If the shark has not moved after the five minute period, it is gently “prodded” on the caudal area with a clean, plastic stick, but this is the only time during the experiment that physically contact is made with the shark.
Once the shark leaves the “starting block” compartment, it is faced with the choice of the black or white colored doors.
After making its choice of doorway, the shark swims into the end compartment, where it receives the reward, should it have made the correct color choice.
The extinction phase, during which a reward is not given, offers the opportunity to gauge the length of time the sharks remember which color was the correct one, despite not receiving a reward for doing so.
As of March 2014, insufficient data for a publication or to evaluate the success of this project has been gathered and the maize experiment continues.
Shark Lab Aquarium Manager