2.2.2. Novel Object Test

Each gecko was tested individually in their enclosures with 6 different objects selected according to their characteristics (size, texture, color, reflection and scent). Two little plastic insect figures (one a dragonfly and the other a butterfly, 7 cm long and wings 8 cm wide), two soft bigger figures with different colors (a yellow Pacman toy with a diameter of 6.5 cm and a red heart toy, with 7.5 cm), a mirror (11 cm long and 7.5 cm wide) and a scented wooden block (5 cm long, 3 cm wide). The scented block was created with feces of two snakes (Boa constrictor and Corallus hortulanus), which can be perceived as potential predators. One teaspoon of both feces was mixed with 5 mL of distilled water and placed in the block, which was air-dried for one hour before use. To control for changes in concentration over time and depositions of the geckos, one scent block was used per animal and then discarded. Each gecko was presented with the novel object in its enclosure, and after 10 min the experimental stimulus was removed. The duration of the test and the objects were selected following previous articles on geckos and other reptiles that use similar items as enrichment or to evaluate personality, e.g., [15,17,25,33,35]. All the objects except for the scented blocks (Figure S1: Photo of novel objects (Butterfly, dragonfly, heart, Pacman and mirror) were disinfected with distilled water and chlorhexidine before being tested with another individual to remove any chemical cue or to be equally unscented. The order of individuals in each test was assigned randomly, but at least 8 days passed before the presentation of a different object to the same gecko. All geckos received the same order of presentation of the object, and they were presented always in the same location in their terrariums. To avoid disturbance of the animals while placing the object and to be able to record their behavior, the position was near the glass at the right or the left of the enclosure (Figures S2−S4).

All the tests were video-recorded, to be coded later using continuous focal sampling on the free behavioral coding software BORIS (Behavioral Observation Research Interactive Software, version 7.13.6 for Windows) [47]. During coding, observers recorded the onset and offset of 8 state behaviors (Table 2 and Videos S1–S8) based on previous ethograms of geckos [33]. For these behavioral categories, we analyzed the latency of approximation (time needed to be in proximity), latency of manipulation and duration, and frequency of all the behaviors. Reliability data were gathered by a second coder for 10% of the tests. The Spearman’s correlation coefficient between the measures obtained by the original and the second coder was 0.997, demonstrating consistency between observers.

Behavioral categories used for analyses.