Does environmental enrichment really matter? A case study using the eastern fence lizard, Sceloporus undulatus

Environmental enrichment for reptiles in European zoos: Current status and perspectives

Zoos and aquaria are paying increasing attention to environmental enrichment, which has proven an effective tool for the improvement of animal welfare. However, several ongoing issues have hampered progress in environmental enrichment research. Foremost among these is the taxonomic bias, which hinders our understanding of the value of enrichment for neglected groups, such as reptiles. In this study, we evaluated the status of environmental enrichment for reptiles in European zoos using a survey approach. A total of 121 zoos (32% response rate) completed our main survey, focusing on the use of different enrichment types for reptiles. We found significant differences in the use and/or type of enrichment between reptile groups. Tortoises (family Testudinidae) and monitor lizards (genus Varanus) were the most enriched taxa while venomous snakes were the least. The enrichment types most used across taxa were structural/habitat design and dietary. A second, more detailed, questionnaire followed, where participants were questioned about specific enrichment techniques. A total of 42 enrichment methods were reported, with two being represented across all taxa: increasing structural/thermal complexity and enrichment objects. Finally, we present information from participating zoos on enrichment goals, assessment methods, sources of information for enrichment ideas, and whether enrichment for reptiles is considered essential and/or implemented routinely. Results suggest that, although usage is widespread across European zoos, our understanding of enrichment for reptiles needs to be re-evaluated, since many of the techniques reported tread a fine line between basic husbandry and actual enrichment.

The Effect of Enrichment on Leopard Geckos (Eublepharis macularius) Housed in Two Different Maintenance Systems (Rack System vs. Terrarium)

The aim of this study was to test the usefulness of environmental enrichment for Eublepharis macularius depending on the maintenance method (terrarium vs. rack system). The hypothesis was that reptiles kept in an extremely low-stimulus environment (rack system) would be more prone to interact with environmental enrichment items than those kept in a biotope terrarium. During the study, 21 female geckos were kept in two types of captive enclosures: 9 in terrariums, and 12 in rack system boxes in groups of 3 animals per enclosure. During the enrichment sessions, geckos were observed for 45 min while enrichment items (dry and wet hides, a new feeding method, a new object) were present in the enclosure. All geckos showed interest in enrichment items that enabled hiding and climbing. Animals kept in the rack system showed significantly lower latency in approaching enrichment items and a higher frequency of enrichment interactions than lizards in biotope terrariums. However, no significant differences were found in the total time spent interacting with enrichment items between geckos in the two settings.

Overlooked and Under-Studied: A Review of Evidence-Based Enrichment in Varanidae

Enrichment has become a key aspect of captive husbandry practices as a means of improving animal welfare by increasing environmental stimuli. However, the enrichment methods that are most effective varies both between and within species, and thus evaluation underpins successful enrichment programs. Enrichment methods are typically based upon previously reported successes and those primarily with mammals, with one of the main goals of enrichment research being to facilitate predictions about which methods may be most effective for a particular species. Yet, despite growing evidence that enrichment is beneficial for reptiles, there is limited research on enrichment for Varanidae, a group of lizards known as monitor lizards. As a result, it can be difficult for keepers to implement effective enrichment programs as time is a large limiting factor. In order for appropriate and novel enrichment methods to be created, it is necessary to understand a species’ natural ecology, abilities, and how they perceive the world around them. This is more difficult for non-mammalian species as the human-centered lens can be a hinderance, and thus reptile enrichment research is slow and lagging behind that of higher vertebrates. This review discusses the physiological, cognitive, and behavioral abilities of Varanidae to suggest enrichment methods that may be most effective.

Evaluating Environmental Enrichment Methods in Three Zoo-Housed Varanidae Lizard Species

Environmental enrichment has been shown to enhance the behavioural repertoire and reduce the occurrence of abnormal behaviours, particularly in zoo-housed mammals. However, evidence of its effectiveness in reptiles is lacking. Previously, it was believed that reptiles lacked the cognitive sophistication to benefit from enrichment provision, but studies have demonstrated instances of improved longevity, physical condition and problem-solving behaviour as a result of enhancing husbandry routines. In this study, we evaluate the effectiveness of food- and scent-based enrichment for three varanid species (Komodo dragon, emerald tree monitor lizard and crocodile monitor). Scent piles, scent trails and hanging feeders resulted in a significant increase in exploratory behaviour, with engagement diminishing ≤330 min post provision. The provision of food- versus scent-based enrichment did not result in differences in enrichment engagement across the three species, suggesting that scent is just as effective in increasing natural behaviours. Enhancing the environment in which zoo animals reside is important for their health and wellbeing and also provides visitors with the opportunity to observe naturalistic behaviours. For little known and understudied species such as varanids, evidence of successful (and even unsuccessful) husbandry and management practice is vital for advancing best practice in the zoo industry.

Technological Advances in Herpetoculture

Technology plays a vital role in herpetoculture because ectothermic animals rely on their environment to carry out basic physiologic functions. Controlling the environment appropriately ensures the health and welfare of captive reptiles and amphibians. This article summarizes some of the technological advances and products currently available, including lighting, climate control, and recordkeeping.

History of predator exposure affects cell-mediated immunity in female eastern fence lizards, Sceloporus undulatus (Squamata: Phrynosomatidae)

On exposure to stressors, energy is diverted from non-urgent functions towards those important for immediate survival. The degree and nature of reallocation may be affected by the evolutionary history of the animal. The eastern fence lizard (Sceloporus undulatus) coexists in parts of its range with invasive fire ants (Solenopsis invicta), which attack and wound lizards and elevate stress-relevant hormones (corticosterone), whereas other populations have never been exposed to fire ants. We examined how a history of fire ant invasion affected the immune response in female lizards after exposure to exogenous corticosterone (mimicking exposure to a stressor) during gestation (dosing regimens differed among corticosterone-exposed lizards owing to the constraints of the original studies, but we found no evidence that this affected the outcome of the present study). A history of exposure to predatory stressors (fire ants) and corticosterone treatment affected cell-mediated immunity. Lizards from fire ant-invaded sites had a reduced immune response compared with those from uninvaded sites. Corticosterone treatment had no effect on the immune response of lizards from invaded sites but reduced the immune response of lizards from uninvaded sites. This suggests that an evolutionary history of exposure to wounding alters the immune response to corticosterone. Future work on how the immune system responds to environmental threats will be informative for the prediction and management of these threats.

Potential role of lava lizards as pollinators across the Galápagos Islands

Lizards have been reported as important pollinators on several oceanic islands. Here we evaluate the potential role of Galápagos lava lizards (Microlophus spp.) as pollinators across their radiation. Over 3 years, we sampled pollen transport by 9 lava lizard species on the 10 islands where they are present, including 7 single-island endemics. Overall, only 25 of 296 individuals sampled (8.4%) transported pollen of 10 plant species, the most common being Prosopis juliflora, Exodeconus miersii, Sesuvium sp. and Cordia leucophlyctis. At least 8 of these plant species were native, and none were confirmed as introduced to the archipelago. Despite the low overall proportion of individuals carrying pollen, this was observed in 7 of the nine lizard species, and on 8 of the ten main islands (Española, Fernandina, Floreana, Isabela, Marchena, Pinta, Santa Cruz and Santiago), suggesting that this is a widespread interaction. The results reported here support the potential role of lava lizards as pollinators across their radiation, although they may represent a relatively modest contribution when compared with birds and insects. However, we cannot discard that lizards may be ecologically significant for particular plant species and ecosystems given the specific climatic condition and functional diversity of each island.

A Review of Welfare Assessment Methods in Reptiles, and Preliminary Application of the Welfare Quality® Protocol to the Pygmy Blue-Tongue Skink, Tiliqua adelaidensis, Using Animal-Based Measures

Reptiles are held at wildlife parks and zoos for display and conservation breeding programs and are increasingly being kept as pets. Reliable indicators of welfare for reptiles need to be identified. Current guidelines for the captive management of reptiles utilize resource-based, rather than animal-based indicators; the latter being a more direct reflection of affective state. In this paper we review the literature on welfare assessment methods in reptiles with a focus on animal-based measures. We conclude that, whilst a number of physiological and behavioral indicators of welfare have been applied in reptiles, there is need for further validation of these methods across the diversity of species within the Class. Methods of positive welfare state assessment are comparatively understudied and need elucidation. Finally, we examine some widely-used welfare assessment tools in mammals and explore the application of the Welfare Quality^® Protocol to the endangered pygmy blue-tongue skink, Tiliqua adelaidensis. We propose that this framework can form the basis for the development of taxon-specific tools with consideration of species-specific biology.

Evidence-Based Reptile Housing and Nutrition

The provision of a good light source is important for reptiles. For instance, ultraviolet light is used in social interactions and used for vitamin D synthesis. With respect to housing, most reptilians are best kept pairwise or individually. Environmental enrichment can be effective but depends on the form and the species to which it is applied. Temperature gradients around preferred body temperatures allow accurate thermoregulation, which is essential for reptiles. Natural distributions indicate suitable ambient temperatures, but microclimatic conditions are at least as important. Because the nutrient requirements of reptiles are largely unknown, facilitating self-selection from various dietary items is preferable.

Comparative ecophysiology of a critically endangered (CR) ectotherm: Implications for conservation management

Captive breeding is a vital conservation tool for many endangered species programs. It is often a last resort when wild animal population numbers drop to below critical minimums for natural reproduction. However, critical ecophysiological information of wild counterparts may not be well documented or understood, leading to years of minimal breeding successes. We collected endocrine and associated ecological data on a critically endangered ectotherm concurrently in the wild and in captivity over several years. We tracked plasma concentrations of steroid stress and reproductive hormones, body condition, activity, and environmental parameters in three populations (one wild and two geographically distinct captive) of ploughshare tortoise (Astrochelys yniphora). Hormone profiles along with environmental and behavioral data are presented and compared. We show that animals have particular seasonal environmental requirements that can affect annual reproduction, captivity affects reproductive state, and sociality may be required at certain times of the year for breeding to be successful. Our data suggest that changes in climatic conditions experienced by individuals, either due to decades-long shifts or hemispheric differences when translocated from their native range, can stifle breeding success for several years while the animals physiologically acclimatize. We also found that captivity affects stress (plasma corticosterone) and body condition of adults and juveniles differently and seasonally. Our results indicate that phenotypic plasticity in reproduction and behavior is related to environmental cues in long-lived ectotherms, and detailed ecophysiological data should be used when establishing and improving captive husbandry conditions for conservation breeding programs. Further, considering the recent revelation of this tortoises’ possible extirpation from the wild, these data are critically opportune and may be key to the survival of this species.

Translocating ratsnakes: does enrichment offset negative effects of time in captivity?

Context Wildlife translocation is a conservation tool with mixed success. Evidence suggests that longer time in captivity may negatively affect an animal’s post-release behaviour and survival. However, environmental enrichment may reduce the deleterious effects of captivity for animals that are going to be released into the wild. Aims The aim of the present study was to compare first-year post-release survival and behaviour of translocated ratsnakes (Pantherophis obsoletus) held captive for varying durations (1–7 years) either with or without enrichment, with that of resident and wild-to-wild (W–W)-translocated ratsnakes. Key results Being in captivity before release negatively affected survival; 11 of 19 (57.9%) captive snakes died or were removed from the study within 12 months, compared with 3 of 11 (27.3%) resident snakes and none of five (0%) W–W snakes. Furthermore, survival probability declined the longer a snake had been in captivity. Six of the seven snakes (86%) that we released that had been in captivity for four or more years before release died during this study, regardless of whether they were enriched or not. Although W–W-translocated ratsnakes moved more often and further than did snakes in other groups, this difference was apparent only in the first month post-release. We found no evidence that abnormal movement patterns or winter behaviour was the cause of reduced survival for captive snakes. Instead, our data suggested that spending time in captivity reduced concealment behaviour of snakes, which likely increased the vulnerability of snakes to predators. Captivity also compromised the foraging ability of some of the snakes. Although there were no overall differences in percentage weight change among the four groups, two snakes (one enriched, one unenriched) were removed from the study because of extreme weight loss (>30%). Conclusions Our results suggested that environmental enrichment did not offset the negative effects of captivity on ratsnakes and that the likely mechanism responsible for low survival was vulnerability to predators. Implications Whether extended periods in captivity render other species unsuitable for translocation, how long it takes for captivity to have deleterious effects, and whether environmental enrichment is also ineffective at offsetting captivity effects in other species remain to be determined.

The influence of complex and threatening environments in early life on brain size and behaviour

The ways in which challenging environments during development shape the brain and behaviour are increasingly being addressed. To date, studies typically consider only single variables, but the real world is more complex. Many factors simultaneously affect the brain and behaviour, and whether these work independently or interact remains untested. To address this, zebrafish (Danio rerio) were reared in a two-by-two design in housing that varied in structural complexity and/or exposure to a stressor. Fish experiencing both complexity (enrichment objects changed over time) and mild stress (daily net chasing) exhibited enhanced learning and were less anxious when tested as juveniles (between 77 and 90 days). Adults tested (aged 1 year) were also less anxious even though fish were kept in standard housing after three months of age (i.e. no chasing or enrichment). Volumetric measures of the brain using magnetic resonance imaging (MRI) showed that complexity alone generated fish with a larger brain, but this increase in size was not seen in fish that experienced both complexity and chasing, or chasing alone. The results highlight the importance of looking at multiple variables simultaneously, and reveal differential effects of complexity and stressful experiences during development of the brain and behaviour.

The Use of Refuges by Communally Housed Cats

Simple Summary

Captive domestic cats frequently suffer from the lack of physical space and opportunities to perform species-typical behaviors, such as climbing or hiding. Environmental enrichment is a technique that helps transform the space available to animals into a more appropriate habitat. In this study, we tested horizontal and vertical refuge boxes as environmental enrichment for cats living communally in a cat rescue shelter. The provision of boxes in the environment increases the use of available space by the cats. We suggest this improves the cats’ welfare while in communally-housed rescue shelters.

Abstract

The increase of domestic animals kept in shelters highlights the need to ensure animal welfare. Environmental enrichment can improve animal welfare in many ways, such as encouraging captive animals to use all the space available to them. The effects of physical environmental enrichment on the spatial distribution and behavioral repertoire of 35 neutered domestic cats housed communally were analyzed. The provision of boxes in the environment increases the use of available space by the cats. We suggest this improves the cats’ welfare while in communally-housed rescue shelters. The frequencies of active and especially inactive behaviors also increased in the enriched condition. In a test with vertical environmental enrichment, the animals showed an increased length of stay in refuges located at a height of 0.5 m compared to those on the ground (0.0 m). However, the entry frequency was higher in refuges at 0.0 m. Both horizontal and vertical environmental enrichment increased the use of available space, demonstrating that box refuges as enrichment are effective in providing a refuge when at a height, or a place to explore at ground level. We suggest it enhances the welfare of cats in communally housed shelters. This information adds to the body of evidence relating to cat enrichment and can be useful in designing cat housing in veterinary clinics, research laboratories, shelters and domestic homes.