Environmental enrichment can be defined as "The provision of stimuli which promote the expression of species-appropriate behavioural and mental activities in an understimulating environment". In an ideal world, all animals in captivity would be provided with environments that were maximally favourable to their (behavioural) welfare. Designs for truly naturalistic-appearing environments combined with responsive environmental designs should ultimately gain more respect and support for animals in captivity. Considering that the captive environment in zoos and aquariums will always have limitations, environmental enrichment is a necessity to accomplish its species welfare. Institutions that keep captive animals do not have unlimited resources, therefore prioritizing is often needed and decisions must be made concerning which species or individuals should be the initial or primary focus of more extensive enrichment effort. For enrichment efforts to be useful, effective and efficient, we need to have a theoretical framework based on our understanding of each species natural history and current husbandry to improve animals' well-being and stimulate their natural behaviours.
A conceptual framework to determine the enrichment need and priority
When you start enriching animal lives or developing an environmental enrichment program, it is essential to determine which animals have the most benefit from your enrichment efforts. For some animals, it is an obvious choice to enrich them daily. When you have a species or an individual that established atypical or stereotyped behaviour, enrichment is a beneficial tool to decrease such unwanted behaviours. There are many reasons why modern, professionally managed zoological institutions should be encouraged to plan and implement environmental enrichment programs. One way to determine the enrichment need and priority is to categorize by species with the same characteristics and behavioural needs. This is done by the example below.
This table is a conceptual framework and not the one-way solution to determine each priority. The categorization is based on the species behavioural time budget of appetitive and social behaviours, as well as their sensitivity for developing atypical and stereotyped behaviours. Carnivores have a high behavioural need for hunting, which take much effort and time before it can consume their food. Additionally, levels of intelligence are considered in this framework too. Primates and especially apes have a high behavioural need for cognitive challenges and require a high level of variation in their environment. Primates are notorious to be quickly bored and can develop abnormal behaviour faster compared to other types of species. In this framework reptiles and amphibians are classified as a lower priority to be enriched. Their husbandry and behavioural needs are more easily met and have less need for changing environments. Moreover, most of these animals can respond anxiously to large changes in their environments and sometimes result to refuse to eat for several days. This particular framework is easy and quick to use when you start developing enrichment, however, that the species are categorized by main characteristics instead of being assessed individually can be seen as a major drawback. At least within the animal diversity housed in captivity today, there is no such thing as 'one size fits all'. Another more extensive conceptual framework is based on five domains: Physical environment, social environment, species' characteristics, animal's behaviours, and legal and professional guidelines.
Within this framework, every species enrichment need is more extensively evaluated and has more focus on the complete behavioural needs of each species. Social stability, exhibit design and cognitive stimulation are contributing factors in a better prioritizing that enrichment should have a more extensive focus for this particular species. This approach is, therewith, more adapted to the earlier given definition, that enriching animals is especially required in understimulating environments. To make the application of this conceptual framework more efficient and easier to use a scoring system can be very practical and powerful. Yet, be aware that such a score is rather a well-thought guideline, not a binding rule.
A conceptual framework outlining your enrichment
When the animals' enrichment needs are classified and appointed, it is essential to outline enrichment aims. It is desirable to start outline three main subjects: Frequency, variety and variation. You can link the classification in the previous section within this context so it's in line with the behavioural needs.
The proposed conceptual framework can be a nice starting point to develop your enrichment program. Frequency is defined as how extensive enrichment is utilised for each species. This can be as frequent as at least one enrichment session a day as sometimes is needed by severe behavioural problems and stereotypes. However, only the frequency is not enough. A certain level of variety is essential too. When animals are confronted with the same environmental stimulation or challenge each time, it will habituate and adapt to this situation what conclude in boredom, predictability and in worst case continuation of stereotypes. Novelty within a certain interval keeps challenges challenging and stimulates a level of exploration. Therefore it is required that periodically newly developed enrichment is added to the already established enrichment collection.
What desired behaviour needs to be encouraged?
Besides determining the effort of enrichment for each species, it is very essential to consider which behavioural stimulation is most desirable. When we scope this thought only to the feeding regime, there are multiple aspects to consider. It is generally known that appetitive and consummatory behaviours are insufficiently stimulated in most captive animals. The time animals spend on these behaviours in captivity in comparison with their wild conspecifics is generally enormous. Where we frequently offer their food ready-made, the perspective of hunting, finding, exploring, reaching and consuming is completely lost. There is a huge quick profit to make when we stop providing 'free food'. Ironically, animals tend to have the behavioural need to work for their food. This concept is called contrafreeloading. Following the food-based behavioural system, there are seven more behavioural systems to consider to stimulate: Sleep & resting behaviours, self-maintaining behaviours, exploratory behaviours, sexual behaviours, play behaviours, and social behaviours. You only use enrichment's full potential when examining all behavioural systems. Behavioural "needs" can even be more confirmed with the 'behavioural needs hypothesis': this theory states that some animals may need the chance to perform certain behaviours even if they do not need the outcome. This is illustrated, as of one example, by many animals that will continue to eat and even hunt when satiated. Similarly, some animals will continue to build nests even if presented with (multiple) fully formed nests. While above is mostly about the intrinsic motivation of behaviour, it is also crucial to consider the variation in the animals' environment to stimulate its exploratory behaviour. Every animal has some sort of fundamental need to gather information about its surrounding. In some studies, it is even stated that animals need an environment that provides them with a constant source of new and relevant information. Enrichment can assuredly be used to fulfil this need of information seeking. To conclude, it is therefore important for each species, especially the species categorized with a high priority, to list behaviours you want to encourage and/or discourage. When these behaviours are listed, you can start developing enrichment devices and ideas.
Final thoughts to consider
We continuously speak about wild-type and natural species-specific behaviours. Behaviours of species have evolved to provide their needs in their natural environments. Therefore, it seems a good strategy to recreate these natural stimuli in their captive environment, and indeed, the performance of natural behaviours is a central tenet of much animal welfare legislation and professional guidelines. However, it is not always helpful to recreate these natural stimuli for a couple of reasons. Consider that not all "wild-type" behaviours are indicative of good well-being. Fear, stress, disease and death are frequent experiences that wild animals come across to. Simply mimicking nature is therefore not acceptable as a conceptual outline to base on your enrichment initiatives.
Another consideration is the extent of environmental complexity. Extremes could prove to be detrimental to individual animals, at least, initially. Where sterile enclosures could lead to boredom and atypical behaviours, highly complex and novel enclosures could (initially) induce anxiety and stress when not use to it. Gradually transitions from understimulated to full-stimulated environments may, therefore, be necessary.
Furthermore, enrichment is just like husbandry routine subject to control and predictability. Enrichment typically increases control by allowing to perform behaviours from their wild-type repertoire to obtain some of the things they want and need, and control itself is critical to an animals' well-being. Predictability is to some degree a good thing as well. Many studies have shown that being able to predict an unpleasant event reduces the degree of stress. However, predictability can also result in high levels of anticipatory arousal, which in itself can cause stress and has often been implicated in the formation of stereotyped behaviours. This can occur especially when a predicted event does not happen or is delayed.
A point often overlooked is the necessity to consider what to do with the periods outside the normal working hours of staff, as this can be a relatively large proportion of the day. Although staff only spend several hours at the zoo, animals are there 24/7, all year round. As captive animals are reliant on humans to provide conditions to meet their needs, the absence for two-thirds of the day is likely to impact on the choices available to the animals, and their perceived control. The idea of the '24/7 enrichment recipe' is promoting good welfare with the provision of enrichment outside staff working hours.
- A Conceptual Framework to Determine Enrichment Needs and Priority (document)
- Thirty Years Later: Enrichment Practices for Captive Mammals (article)
- Effects of Predictability on the Welfare of Captive Animals (article)
- The S.P.I.D.E.R. Framework (article)
- The 24/7 Approach to Promoting Good Welfare for Animals housed under Human Care (website)
- Second Nature - Environmental Enrichment for Captive Animals (book)