Aquatic Zoos - Captive Animals Protection Society

column shows the percentage of individual rays showing such behaviour in each particular public aquarium with respect to the total
of individuals rays showing the behaviour, the seventh column shows the number of visible rays for each public aquarium, the
eighth column shows the percentage of rays showing SBB with respect to the number of rays seen in each aquarium, and the
remaining columns the same than columns five to eight but for rays of the genus Raja. The last row shows the values for all public
aquaria put together.
Figure 16. Ray of the genus Raja performing ‘Surface Breaking Behaviour’ behaviour in a UK public aquarium.
Several reasons have been given to explain the existence of SBB: the animals ‘curiosity’ made them ‘look’
outside the water often, they are smelling the visitors that come along to see them, they are ‘asking’ for
a physical interaction with visitors because of their ‘sociability’, or they are expecting the next feeding
time with impatience. Most of these explanations are given by public aquarium keepers when visitors ask
but they are rarely based on any research made on the subject.
The exception is the study of Scott & Rollison (1999) observing 17 Raja rays of four different species in a
UK public aquaria testing the hypothesis that the fact the rays were fed by keepers from ‘the top’ of the
enclosure was the cause of the behaviour (figure 17). Indeed, they found that rays when fed exhibited
higher levels of SBB that those which did not, and therefore they concluded that SBB could be thought
as an appetitive behaviour appearing in a particular artificial environment with a particular feeding
procedure. However, when modifications on the feeding method were made by scattering the food
across the aquarium floor using a net (Scott & Rollison, 1999b), although the behaviour was reduced in
frequency it did not eliminate it.
It is true that increased performance of behaviour associated with feeding food is often an indication
that captive animals have a deficient diet in terms of quantity or quality (Broom & Jhonson, 1993;
Appleby & Lawrence, 1987), but as any shortcoming of a captive environment this could be the initial
trigger that developed the behaviour, which later on it becomes fixated as stereotypy almost becoming
independent of the initial cause. The reason that we encountered this behaviour mainly in rays and
sharks could be because the ventral position of the mouth, which makes the animal raise itself out of the
water to take the food when fed from above, but when the feeding stops the continuous array of visitors
approaching the tanks could make the animals believe that more food is coming, so the behaviour
continues. When these visitors interact with the rays and sharks by touching the water or the animals
themselves (very common practice in public aquaria holding these species, as will be seen below) they
keep reinforcing the behaviour which eventually becomes fixated.
39