Enrichment devices for green turtles (Chelonia mydas) reared in captivity programs

Environmental enrichment supports the well-being and welfare of captive animals. In the current study, the most suitable form of enrichment device for captive green turtles (Chelonia mydas) was investigated, to support head-start programs rearing turtles for release into their natural habitat. Fifteen-day-old turtles (113-114 g initial weight, n = 75) were randomly distributed into 15 experimental plastic tanks, comprising 5 treatments across three pools of each condition. The turtles in the experimental groups were exposed to four forms of enrichment devices (RS, ring shape; HSQS, hollow square shape; SS, sphere shape; CS, cylinder shape), and their outcomes related to growth, feed utilization, behavior, reduction of injury from conspecifics, and several health parameters were compared to those of a control group. At the end of the 10-week trial, the growth and feed utilization parameters did not differ across the five groups (p > .05). Of the turtles in the experimental treatments, those in the RS treatment spent more time interacting with the enrichment device, followed by the HSQS group. The percentage of wounds suffered through biting was significantly reduced in the groups exposed to enrichment devices, notably in the turtles exposed to the SS device, followed by the RS device. Significant differences between experimental groups in the specific activities of the major intestinal protein-digesting enzymes (trypsin and chymotrypsin) were observed. There were no effects noted in the hematological parameters and the main carapace elemental profile as compared to the control treatment. These findings suggest that the RS device is most appropriate in enriching the environment of juvenile green turtles in captivity programs, as well as in zoos or aquaria.