Using a robotic fish to investigate individual differences in social responsiveness in the guppy

Abstract

Responding towards the actions of others is one of the most important behavioural traits whenever animals of the same species interact. Mutual influences among interacting individuals may modulate the social responsiveness seen and thus make it often difficult to study the level and individual variation in responsiveness. Here, open-loop biomimetic robots that provide standardized, non-interactive social cues can be a useful tool. These robots are not affected by the live animal's actions but are assumed to still represent valuable and biologically relevant social cues. As this assumption is crucial for the use of biomimetic robots in behavioural studies, we hypothesized (i) that meaningful social interactions can be assumed if live animals maintain individual differences in responsiveness when interacting with both a biomimetic robot and a live partner. Furthermore, to study the level of individual variation in social responsiveness, we hypothesized (ii) that individual differences should be maintained over the course of multiple tests with the robot. We investigated the response of live guppies (Poecilia reticulata) when allowed to interact either with a biomimetic open-loop-controlled fish robot-'Robofish'-or with a live companion. Furthermore, we investigated the responses of live guppies when tested three times with Robofish. We found that responses of live guppies towards Robofish were weaker compared with those of a live companion, most likely as a result of the non-interactive open-loop behaviour of Robofish. Guppies, however, were consistent in their individual responses between a live companion and Robofish, and similar individual differences in response towards Robofish were maintained over repeated testing even though habituation to the test environment was detectable. Biomimetic robots like Robofish are therefore a useful tool for the study of social responsiveness in guppies and possibly other small fish species.

Keywords: Poecilia reticulata; biomimetic robots; fish-inspired robots; robotic fish; social responsiveness.

Figure 1.

The Robofish system. (a) The robot unit is driving on a second level below the test arena. (b) Close-up of the robot unit. (c) A picture of a live guppy female served as template for the virtual three-dimensional mesh that was printed on a three-dimensional printer. (d) Guppy replica with a group of female guppies in the test arena.

Figure 2.

Example track of Robofish with live guppy in an 88 cm × 88 cm test arena. After the live fish left the start cylinder (upper left), Robofish moved in a natural stop-and-go pattern along a zigzagged path to the opposite corner. Upon arrival, Robofish moved to either the bottom left or the top right corner (here: top right) and described a circular path.

Figure 3.

Differences between Robofish pairs and live fish pairs (experiment 1, main text) in (a) IID, (b) TLXC as well as their relations in (c) live fish pairs and (d) Robofish pairs. Shown are means ± s.e.m. (a,b). Asterisks indicate significant differences in t-tests (see the main text).

Figure 4.

Results from repeated testing with Robofish. (a) IID and (b) TLXC. Note that IID and ΔTLXC for trial 1 were significantly different from those for trials 2 and 3 (post hoc least significant difference tests). (c) Relationship between IID and TLXC separate for Robofish and focal fish. Shown are pooled data from all three trials. (d) ΔTLXCs over the repeated testing. Each line represents a focal individual's ΔTLXC in each of the three consecutive trials. Shown are means ± s.e.m., (a,b). Asterisks indicate significant differences in t-tests (see the main text).