An Improvement in Enclosure Design Can Positively Impact Welfare, Reduce Aggressiveness and Stabilise Hierarchy in Captive Galapagos Giant Tortoises

Abstract

The interest in the welfare of zoo animals, from both the public and the scientific community, has long been biased towards mammals. However, growing evidence of the complex behavioural repertoires of less charismatic animals, such as reptiles, reveals the necessity to better comply with their welfare needs in captivity. Here, we present the effects of an enclosure change towards a more natural habitat in captive Galapagos tortoises (Chelonoidis spp.) held at ZSL London Zoo. Using behavioural observations, we found that the tortoises habituated to their new enclosure in six days. This represents the first quantification of habituation latency to a new enclosure in a reptile model to our knowledge—which is important information to adapt policies governing animal moves. The tortoises expressed time budgets more similar to those of wild individuals after their transition to the new enclosure. Interestingly, the hierarchy between the individuals was inverted and more stable after this change in environment. The tortoises interacted less often, which led to a decrease in the frequency of agonistic encounters. We also found that higher ambient sound volume was associated with increased likelihood of interactions turning into fights. Taken together, our results demonstrate the potential of appropriate enclosure design to improve reptile welfare.

Review of the Effects of Enclosure Complexity and Design on the Behaviour and Physiology of Zoo Animals

“…Initially, a zoo exhibit can be perceived to be complex by its inhabitants, but if that complexity is unvarying, then its positive impact on animal welfare will fade with time [ 32 ]. To combat this situation, zoos typically will add complexity to their exhibits in the form of environmental enrichment [ 33 ].…”

“…In this way, less sociable individuals would benefit from habitats offering such structures. Such barriers that allow the avoidance of social contact may reduce aggression and competition for resources [ 32 , 59 ]. Some biological states, such as pregnancy and lactation, can influence how females use their habitat.…”

“…The behavioural and physiological effects of a life in a complex captive environment are mostly positive, increasing the animals’ positive experiences and elevating their welfare [ 78 , 79 ]. Creating complex exhibits helps to increase the positive experiences of animals across the five domains of animal welfare [ 32 , 59 ], namely environmental, behavioural interactions, health, and nutritional domains, with a consequent positive outcome on the mental domain [ 60 , 61 ]. This is provided that exhibits enable individual choice and control over the environment.…”

“…DNA methylations can be used as biomarkers of past and present environmental stress, as well as biomarkers of physiological conditions [ 131 , 132 , 133 ]. Since an enclosure’s complexity can decrease captive stress [ 32 ], it can reduce the deleterious effects of DNA methylation [ 134 ], increasing the role of the captive population in conservation efforts [ 135 ]. This information shows how the integration of epigenetics (analysis of DNA methylation profiles) and animal husbandry with conservation biology can corroborate data on the physiological, biological, and ecological status of animals [ 131 , 136 ].…”

The Benefits of Increased Space and Habitat Complexity for the Welfare of Zoo-Housed King Penguins (Aptenodytes patagonicus)

“…It was also difficult to disentangle these factors during a POE conducted on Galapagos tortoises (Chelonoidis spp.) at the ZSL London Zoo [8]. As these examples illustrate, it can be difficult, if not impossible, to identify specific causal factors for changes in animal behavior in most POE studies, given the multitude of factors that are generally altered in habitat improvements and the entangled relationship between space and complexity.…”