2.6. Data analysis

The detection system has a large number of measurable parameters, such as distance moved, turning angle, angular speed, fractal dimension, and more (see https://www.noldus.com/ethovision‐xt/benefits). In terms of locomotory parameters, we mainly focused on mean speed (calculated as the mean distance travelled per time unit), acceleration (calculated as the rate of speed change per time unit), and step length (calculated as the mean distance travelled between two consecutive locations, (x_{t ‐1} , y_{t ‐1}) and (x_t, y_t), per time interval). The presence of the patch walls is expected to influence the individuals’ locomotory parameters (Cloyed & Dell, 2019; Uiterwaal et al., 2019). Thus, tracking information on individuals’ locomotory behavior from the outer 1 cm of the patch was excluded, leaving an arena 11 cm in diameter.

In terms of space use behavior, the present case study made use of four descriptors:

The number of visits to each patch; a visit being defined as each time the animal entered a patch and remained in the patch for at least 30 s.

The giving‐up time (GUT), defined as the duration of a single visit (Krebs et al., 1974), computed here as the average time spent in a resource patch during each visit.

The total time spent by individuals in any patch in absolute terms (min) and as a fraction (%) of the experimental time.

The individual cumulative space used, defined as the total area of the resource patches used by individuals during the experimental time (ca. 360 min), and it was computed simply as the number of visits to a resource patch × the resource patch area (0.01 m²).

In order to identify differences between the number of patches visited by fed and unfed individuals, we performed a nonparametric Kruskal–Wallis test. Since total time spent and average giving‐up time were not normally distributed, the impact of body weight and resource density on these two variables was tested with a Sheirer Ray Hare test. An ANCOVA was used to test the response of cumulative space used, total time spent in resource patches and average giving‐up time to body weight as an explanatory variable. The percentage of experimental period that animal spent in any patch was modeled by generalized (logistic) linear regression. The analyses were performed in the R free software environment (R Core Team 2019) using the reshape (Wickham, 2007), lme4 (Bates et al., 2015), sjPlot (Lüdecke, 2018), and traj (McLean & Skowron Volponi, 2018) packages.

As part of the preliminary experimental setup, we tested conditions that could potentially affect the space use behavior of the model organism, namely:

The internal ventilation system regulating room temperature.

The near infrared backlight source (NIR).

Foragers’ satiety levels.

The tests indicated that the ventilation system should be set at the lowest possible speed, as it could cause waves on the water surface and create noise in the detection of the animals. Another factor we tested was the effect of the near infrared backlight source (NIR) on forager behavior. We observed that the use of NIR had no influence on the number of patches visited or other primary locomotory behaviors (such as speed, acceleration, and step length). In addition, we tested the potential influence of the foragers’ satiety on space use behavior by comparing two groups of animals consisting of (a) unfed animals starved for 24 hr before the measurements and (b) fed animals taken directly from the aquaria. The exploratory behavior of unfed individuals was found to be less chaotic and more uniform, with low variation at the individual level over time (see “Fig. S1” in supporting information for more details). Therefore, we used unfed animals for the experiment (see the following chapter for detailed analysis).