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

First successful head-start program of leatherback sea turtles (Dermochelys coriacea) in Thailand and proposed dietary strategy

Leatherback sea turtle (Dermochelys coriacea) hatchlings have previously been kept alive for over a year in captive conditions but these were the few survivors of initially larger groups. In this report, newly hatched leatherback sea turtles were randomly harvested from two nests in Thailand and successfully reared before release back to the wild. In captivity, the survival of the turtles decreased sharply during the first 4 or 5 months, and then steadied until the end of the 12-month trial. The survival of yearlings from one nest was 13.3% and from the other nest 46.7%. Their growth was exponential, reaching 1.36-3.35 kg (n = 9) at the end of program. The causes of death of the reared turtles were accidents (25.0-38.5%) and infections from water and live food (61.5-75.0%). The dietary requirements of the turtles were investigated by determining the digestibility of protein and carbohydrate in vitro, using enzymes from the digestive tracts of hatchlings that had died in an accident (70.1-92.9 g body weight). The results indicated that the most suitable source of protein was wheat gluten, followed by soybean meal, nonruminant meat and bone meal, fish meal, nonruminant meat meal, pork meal, and skimmed milk, while suitable carbohydrate sources were mashed cassava, corn, wheat flour, and alpha starch, followed by cereal meal and rice flour. Findings from the current report provide a practical protocol for head-starting leatherback sea turtles, and indicate the possible basis of an effective artificial diet for this species.

Sensory Stimulation as a Means of Sustained Enhancement of Well-Being in Leopard Geckos, Eublepharis macularius (Eublepharidae, Squamata)

Although the private keeping of reptiles has boomed in most western countries since the millennium, studies dealing with the recognition and promotion of welfare in these reptiles seem to represent a blind spot of scientific attention. The vast majority of studies from the field of animal welfare science still concern mammals and birds. The leopard gecko is probably the most common lizard that is kept in domestic terrariums worldwide. Due to its characteristic as an ecological generalist, it is easy to keep and breed, and it is considered a good "starter reptile" for beginners as it "condones" husbandry mistakes, even for extended periods. However, being a mass species is not a second-class classification. They, too, have an equal claim to good well-being as all animals in human care. The aim of the study was to test the hypothesis of whether an increase in stimulus density leads to an increase in activity and behavioural diversity and, thus, an increase in welfare. For this purpose, 18 leopard geckos were fed insects that were ≤1 cm in size, and both the quantity and quality of behaviour was documented and analysed in the pre-intervention, intervention and post-intervention stages. In addition, it was of interest whether behavioural indicators could be identified that indicate a state of positive well-being. The results showed that this type of enrichment led to a quantitative doubling of the activity levels from the baseline (total of 12,519 behavioural elements) to the intervention (total of 25,366 behavioural elements). And even 11 months after the introduction of small insect feeding (post-intervention total of 23,267 behavioural elements), the activity level was still significantly increased. The behavioural diversity, as the absolute number of behavioural categories across all 18 leopard geckos, also increased, although less than the behavioural intensity, between the baseline (5507 behavioural categories) and intervention (6451 behavioural categories) and between the baseline and post-intervention (6079 behavioural categories). The results clearly show that feeding small insects to leopard geckos is a very efficient tool to increase the welfare of leopard geckos. Attractively, this feeding regime can be implemented by any leopard gecko keeper without significant additional cost or time, and therefore, these methods have a potentially high impact.

Dietary protein requirement for captive juvenile green turtles (Chelonia mydas)

Head-starting programs are extremely important for restoring the population of sea turtles in wild whereas husbandry conditions and feeding regimens of captive turtles are still limited. In the current study, the optimal dietary protein requirement for green turtle (Chelonia mydas) was investigated to support rearing in head-starting programs. Twenty-five-day-old turtles (44.5-46.2 g body weight, n = 45) were randomly distributed into 15 experimental plastic tanks, comprising three treatment replications of 3 turtles each. They were fed fishmeal-based feeds containing different levels of protein (30%, 35%, 40%, 45%, and 50%) for 8 weeks. At the end of feeding trial, growth performance (specific growth rate = 1.86% body weight/day) and feed utilization (protein efficiency ratio = 3.30 g gain/g protein) were highest in turtles fed with 40% protein in feed (p < .05). These nutritional responses were significantly supported by specific activities of fecal digestive enzymes, especially trypsin, chymotrypsin, amylase, and the amylase/trypsin ratio. Also, this dietary level improved the deposition of calcium and phosphorus in carapace, supporting a hard carapace and strong healthy bones. There were no negative effects in general health status of reared turtles, as indicated by hematological parameters. Based on a broken-line analysis between dietary protein levels and specific growth rate, the optimal protein level for green turtles was estimated as 40.6%. Findings from the current study support the use of artificial diets of specific protein levels to rear captive green turtle before release to natural habitats.

A review of welfare indicators for sea turtles undergoing rehabilitation, with emphasis on environmental enrichment

For animals undergoing rehabilitation it is vital to monitor welfare in a way that is feasible, practical, and limits stress to the animal. The industry gold standard is to assess welfare under the Five Domains model, including nutrition, environment, physical health, and behaviour as the first four physical domains and mental domain as the fifth. Feasibility and effectiveness of these domains for assessing welfare of sea turtles undergoing rehabilitation were reviewed and it was determined that the mental state can be best assessed through behavioural changes. A scoping review of the literature was conducted using Scopus and Web of Science to investigate use of environmental enrichment devices (EEDs) as a measure of welfare in sea turtles. Behavioural assessments using EEDs were found to be well-documented; however, most EED studies pertained largely to livestock or zoo animals. Furthermore, studies rarely concentrated on reptiles, and specifically sea turtles. Results also showed that certain welfare assessment methods may be less appropriate for short-term captivity experienced during rehabilitation. Additionally, the hospital environment limits the ability to address some of the domains (ie biosecurity, feasibility, safety of turtle, etc, might be compromised). This review shows that only three of the nine environmental enrichment strategies described in the literature suit the specific requirements of sea turtles in rehabilitation: feeding, tactile, and structural. It is documented that turtles display behaviours that would benefit from EEDs and, therefore, more specific studies are needed to ensure the best welfare outcomes for sea turtles undergoing rehabilitation.

Social Behavior Deficiencies in Captive American Alligators (Alligator mississippiensis)

Understanding how the behavior of captive American alligator (Alligator mississippiensis) congregations compares to wild congregations is essential to assessing the welfare of alligators in captivity. Wild alligator congregations perform complex social behaviors, but it is unknown if such behaviors occur in captive congregations as frequently. We observed the behaviors of a captive and wild congregation of American alligators in Florida, USA in January 2021. Social behaviors were, on average, 827% more frequent in the wild congregation than the captive, and the wild congregation had a richer repertoire of social behaviors, with growling and HOTA (head oblique tail arched) behaviors being particularly common. High walking, a nonsocial behavior, dominated the behavioral repertoire of the captive congregation (94% of behaviors, excluding feeding) and may be a stereotypy that can be used as an indicator of welfare. Both congregations experienced human disturbance and displayed flushing as a species-specific defense reaction. Captive environments differ from the wild with respect to size, structure, stocking density, resource availability, and human presence. These differences translate into behavioral differences between wild and captive congregations. We identified important behavioral differences between wild and captive alligator congregations that can serve as a platform for more detailed investigations of alligator welfare in captivity.

Rehabilitation of Marine Turtles and Welfare Improvement by Application of Environmental Enrichment Strategies

Simple Summary

Sea turtles are vital members of the marine ecosystem since they contribute to keeping balance in such environments. Unfortunately, they are endangered species whose absence may be detrimental. Conservation efforts aim to preserve sea turtles both at the population and individual levels. Rescue and rehabilitation aim to reduce individual morbidity and mortality as a result of injuries mainly caused by interactions with humans, in order to preserve their genetic diversity and help maintain and/or increase their population size. Environmental enrichment (EE) is a set of methodologies aimed to improve animal welfare during captivity/rehabilitation. This review presents successful cases of sea turtle environmental enrichment and its applications to improve their welfare in captivity and to increase their fitness prior to release into the wild. EE is a valuable tool that enhances welfare during the captivity and/or rehabilitation of sea turtles and improves their chances of survival and reintegration back into wild populations upon release. EE may be adopted in rescue and rehabilitation facilities around the world to improve individual survival and help boost conservation efforts.

Abstract

Sea turtles perform various ecological services in several marine environments and are considered architects of the marine landscape. At present, they are endangered species due to anthropogenic threats, pollution and degradation of marine habitats. These impacts make it urgent to increase protection and conservation efforts. Protective actions include the rescue and rehabilitation of injured individuals as a result of their interactions with humans and other threats. Environmental enrichment (EE) is a series of techniques and methods aimed to improve the welfare of animals in captivity and/or under rehabilitation. It uses external stimuli to enhance their psychological and physiological wellbeing to promote natural abilities and behaviors. These may increase the survival chances of rehabilitated animals upon release in the wild. This review presents data of studies where EE has been applied during the rehabilitation processes of different species of sea turtles, and its effect on welfare improvement during captivity/rehabilitation and on survival after release into nature. Technologies such as satellite tags are an important means to determine rehabilitation success and survival of injured individuals from endangered species after release into the wild, as they allow tracking and monitoring of such individuals, and determine their location in areas used by their natural populations for feeding or breeding.