Passage III

Prey can use visual cues and/or chemical cues to iden­tify predators. Students conducted 2 experiments to deter­mine if visual cues and/or chemical cues affected how guppies (a prey fish) responded to cichlids (a guppy predator).

Experiment 1

Four identical tanks (Tanks 1-4) were filled with water. A barrier was placed in each tank to divide each tank into 2 equal halves, the predator half and the prey half. The type of barrier was different for each tank (see Table 1). Three regions (Regions X-Z), each 10 cm wide, were des­ignated in the prey half of each tank (see diagram).

A guppy was added to the prey half of each tank, and a cichlid was added to the predator half of each tank. The guppy in each tank was observed every 15 sec for the next 5 min, and the region in which the guppy was located at the time of each observation was recorded. Then, the percent of observations recorded for each region was determined (see Figure 1).

Experiment 2

Tanks 1-4 were emptied. Then, Experiment 1 was repeated in every respect but the following: 4 guppies were added to the prey half of each tank, and the location of each of the guppies was recorded at the time of each obser­vation (see Figure 2).

Figures 1 and 2 adapted from Jason Jones et al., "Senses & Sensibility: Predator-Prey Experiments Reveal How Fish Perceive & Respond to Threats." @2008 by the American Biology Teacher.