Is behavioural enrichment always a success? Comparing food presentation strategies in an insectivorous lizard (Plica plica)

• Behavioural enrichment device using crickets was provided to Plica plica.
• Device resulted in decreased amount of activity compared to scatter feed.
• Difference in feeding duration between the enrichment and scatter feed was not significant.
• The complex enclosure design and live food use are suggested as the reason behind this.
• Hence enclosure design can negatively affect the success of enrichment devices.

Staggering food availability through a delivery device is a common way of providing behavioural enrichment as it is usually thought to increase the amount of natural behaviour due to the unpredictability of the food source. Tree-runner lizards (Plica plica) are a Neotropical, scansorial, insectivorous species. We provided these lizards with an enrichment device that slowly released insect prey and tested its effect on the activity and frequency of a number of behaviours in comparison with a scatter control (where prey items were broadcast in the enclosure; standard food presentation for captive insectivorous lizards) and a non-feeding control. Both types of food increased activity and counts of several behaviours in comparison with the non-feeding control. However, we found the provision of the behavioural enrichment device led to a significantly lower frequency of almost all analysed behaviours in comparison with scatter control trials, mainly in behaviours associated with activity (unsuccessful strikes (= unsuccessful capture of prey) (p = 0.004), locomotion (p = 0.004), alertness (p = 0.004) and the number of times a boundary in the enclosure was crossed ie. activity (p = < 0.001)). The frequencies significantly increased in the enrichment trials (relative to the scatter control) were the number of successful strikes (=successful capture of prey; p = <0.001) and targeting prey (p = <0.001). There was no significant difference in latency to first strike (p = 0.24), duration of hunting activity (p = 0.83) or enclosure use (p = >0.05) between scatter and enriched trials. The relative success of the scatter feed in promoting activity and increasing hunting difficulty was likely partly due to the enclosure design, where the complex physical environment contributed to the difficultly in catching the prey. However, when the feeding duration and enclosure use was analysed there was no significant difference between the scatter control and enrichment trails. The results from this study highlight the importance of evaluating enrichment strategies, and the role of complex enclosure design in creating effective enrichment for insectivores, which can contribute to their welfare in captivity.