Behavioral enrichment

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An Asian elephant in a zoo manipulating a suspended ball provided as environmental enrichment.

Behavioral enrichment (also referred to as environmental enrichment) is an animal husbandry principle that seeks to enhance the quality of captive animal care by identifying and providing the environmental stimuli necessary for optimal psychological and physiological well-being.[1] Environmental enrichment can either be active or passive, depending on whether it requires direct contact between the animal and the enrichment. A variety of enrichment techniques are used to create desired outcomes similar to an animals individual and species' history. Each of the techniques used are intended to stimulate the animal's senses similarly to how they would be activated in the wild. Provided enrichment may be seen in the form of auditory, olfactory, habitat factors, food, research projects, training, and objects.[2]

Purpose[edit]

Environmental enrichment improves the overall welfare of animals in captivity and create a habitat similar to what they would experience in their wild environment. It can aims to maintain an animal's physical and psychological health by increasing the range or number of species-specific behaviors, increasing positive interaction with the captive environment, preventing or reducing the frequency of abnormal behaviors, such as stereotypies, and increasing the individual's ability to cope with the challenges of captivity.[3]

Environmental enrichment can be offered to any animal in captivity, including:

Environmental enrichment can be beneficial to a wide range of vertebrates and invertebrates such as land mammals, marine mammals, and amphibians.[9] In the United States, specific regulations (Animal Welfare Act of 1966) must be followed for enrichment plans in order to guarantee, regulate, and provide appropriate living environments and stimulation for animals in captivity.[10] Moreover, the Association of Zoos and Aquariums (also known as the AZA), requires that animal husbandry and welfare be a main concern for those caring for animals in captivity.

Passive enrichment[edit]

Passive enrichment provides sensory stimulation but no direct contact or control. This type of enrichment is commonly used for its potential to benefit several animals simultaneously as well as requiring limited direct animal contact.[11]

Visual enrichment[edit]

Visual enrichment is typically provided by changing the layout of an animal's holding area. The type of visual enrichment can vary, from something as simple as adding pictures on walls to videotapes and television. Visual enrichment such as television can especially benefit animals housed in single cages.[12]

Mirrors are also potential form of enrichment, specifically for animals that display an understanding self-recognition, such as non-human primates. In addition to using mirrors to reflect the animal's own image, mirrors can also be angled so the animal is able to see normally out-of-sight areas of the holding area.[12]

Enclosures in modern zoos are often designed to facilitate environmental enrichment. For example, the Denver Zoo's exhibit Predator Ridge allows different African carnivores to be rotated among several enclosures, providing the animals with a different sized environment.

Auditory enrichment[edit]

In the wild, animals are exposed to a variety of sounds that they normally do not encounter in captivity. Auditory enrichment can be used to mimic the animal's natural habitat. Types of nature-based auditory enrichment include rainforest sounds and conspecific vocalizations.[12]

The most common form of auditory enrichment is music, whose principal stems primarily from it's benefit on humans. The benefits of classical music have been widely studied in animals, from sows.[13] to non-human primates.[14] Studies have also looked at various other genres, such as pop and rock, but their ability to provide effective enrichment remains inconclusive.[14][15][16] Most types of music that are selected for enrichment are based on human preferences, causing anthropomorphic biases that may not translate to animals.[16] Therefore, music that is specifically attuned to the animal's auditory senses could be beneficial.[17] Species-specific sounds require further research to find what pitch, frequency, and range is most suitable for the animal.

Active enrichment[edit]

Behavioral enrichment – Feeding
Active enrichment during feeding session

Active enrichment often requires the animal to perform some sort of physical activity as well as direct interaction with the enrichment object. Active enrichment items can temporarily reduce stereotypic behaviors as their beneficial effects are usually limited to the short periods of active use.[11]

Behavioral enrichment – Sensory
Inanimate tactile enrichment with paper bag

Inanimate tactile enrichment[edit]

Inanimate tactile enrichment encourages the animal to explore and manipulate various kinds of inanimate objects, behaviors that the animal would naturally display in the wild. Most inanimate tactile enrichment occurs in the context of searching for food, such as cracking open a nut or digging holes in tree trunks for worms. Other common manipulable tactile objects include rubber toys stuffed with treats. Instead of providing the food directly, foraging devices are useful in increasing the amount of searching and foraging of food, comparable to the amount of time they would spend in the wild.[12] Elaborate systems of food presentation have also been developed (e.g. presenting dead rats for wildcats in a Swedish zoo)[citation needed] and computer programmed devices which allow the animals in the enclosure to search for prey as they would in their natural environment.[citation needed]

Inanimate tactile enrichment can also be beneficial without the association with food. For example, stones has shown to encourage exploratory behavior in Japanese macaques. Interaction with the stones exhibited behaviors such as gathering, rolling in hands, rubbing, and carrying.[12]

Other common forms include cardboard, forage, and even the texture of the food (i.e. hard, smooth, cold, warm).[18]

Olfactory enrichment[edit]

Olfactory enrichment can stimulate naturalistic behavior, enhance exploration, and reduce inactivity.[19] This type of enrichment is most commonly used for wild felines, both large and small. Exposure to different odors has been shown to influence behavior, resulting in increased activity and exploration.[20] Odors can be smeared or sprayed on an object such as a ball or a tree branch. Types of odors can include catnip, odor of conspecific, or perfume.

Cognitive enrichment[edit]

Lack of cognitive stimulation could cause boredom and frustration which are manifested in behavioral disturbances. Because most cognitive enrichment is reinforced with food, it activates reward-related circuits in the brain that can directly affect emotional processes of appraisal.[21] Puzzle feeders are a common method of providing cognitive enrichment, as it makes food harder to access than during routine feeding. Some consider training to be a form of cognitive enrichment, since it requires animals to use their cognitive skills to respond to cues.[22]

Computerized tasks are growing in popularity as it provides feedback as to whether an animal is cognitively enriched.These tasks are designed to test a specific cognitive skill and are standardized so that performance can be compared within and between subjects. It is important to ensure that the task provided is not too easy for the animal, nor too difficult that they get discouraged.[22]

Social enrichment[edit]

Social enrichment can either involve housing a group of conspecifics or animals of different species that would naturally encounter each other in the wild. Social animals in particular (i.e. most primates, lions, flamingos, etc.), benefit from social enrichment because it has the positive effect of creating confidence in the group.[23] Social enrichment can encourage social behaviors that are seen in the wild, including feeding, foraging, defense, territoriality, reproduction, and courtship.[24]

Human-interaction enrichment[edit]

The most common form of human-interaction enrichment is training. The human and animal interaction during training builds trust, and increases the animal's cooperation during clinical and research procedures. In addition, training sessions have been shown to benefit the welfare of both individually housed animals and communally housed animals by providing cognitive stimulation, increasing social play, decreasing inactivity, and mitigating social aggression during feeding.[25]

Amount of enrichment[edit]

A survey of over 200 staff working with mammals at 60 zoos in 13 countries found that all forms of enrichment were considered important for mammals, but several of them were rarely available, because of lack of staff or other priorities.[26]

Type of Enrichment Percent of Staff Ranking This Important or Very Important for Mammals Percent Never Giving This*
Social 56% 76%
Visual 98% 75%
Auditory 81% 74%
Olfactory 85% 32%
Structural 71% 28%
Human-animal interaction 98% 16%
Tactile 96% 3%
Feeding** 41% 1%

* time span over a one week period

** feeding enrichment sessions differ from routine feeding sessions

Assessing the success[edit]

A range of methods can be used to assess which environmental enrichments should be provided. These are based on the premises that captive animals should perform behaviours in a similar way to those in the ethogram of their ancestral species,[27] animals should be allowed to perform the activities or interactions they prefer, i.e. preference test studies,[28] and animals should be allowed to perform those activities for which they are highly motivated, i.e. motivation studies.[29]

Environmental enrichment is a way to ensure that an animals natural and instinctual behaviors are kept and able to be passed and taught from one generation to the next. Enrichment techniques that encourage species specific behaviors, like those that are discovered in the wild, have been studied and found to help the process of reintroduction of endangered species into their natural habitats, as well as helping to create offspring with natural traits and behaviors.[30]

The main way the success of environmental enrichment can be measured is by recognizing the behavioral changes that occur from the techniques used to shape desired behaviors of the animal compared to the behaviors of those found in the wild.[31] Other ways that the success of environmental enrichment can be assessed quantitatvely by a range of behavioral and physiological indicators of animal welfare. In addition to those listed above, behavioral indicators include the occurrence of abnormal behaviours (e.g. stereotypies,[32][33] cognitive bias studies,[34] and the effects of frustration.[35][36] Physiological indicators include heart rate,[37] corticosteroids,[38] immune function,[39] neuorobiology,[40] eggshell quality[41] and thermography.[42]

It is very difficult for zookeepers to measure the effectiveness of enrichment in terms of the stress due to the fact that animals that are found in zoos are oftentimes on display and presented with very abnormal conditions that can cause uneasiness and stress. Measuring enrichment in terms of reproduction is easier because of our ability to record offspring numbers and fertility. By making necessary environment changes and providing mental stimulation, animals in captivity have been seen to reproduce at a more similar rate to their wild ancestors in comparison to those provided with less behavioral and environmental enrichment.[31]

Issues and concerns[edit]

Habituation[edit]

Although environmental enrichments can provide sensory and social stimulations, it can also have limited efficacy if not changed frequently. Animals can become habituated to environmental enrichments, showing positive behaviors at onset of exposure and progressively declining with time. Environmental enrichments are effective primarily because it offers novelty stimuli, making the animal's daily routines less predictable, as would be in the wild. Therefore, maintaining novelty is important for the efficacy of the enrichment. Frequently changing the type of environmental enrichment will help prevent habituation.[6]

Training[edit]

Usage of more highly advanced enrichment devices, such as computerized devices, requires training. This can lead to issues as training often consists of food as a reward. While food encourages the animal to participate with the device, the animal could associate the device with food. As a result, the interaction with the enrichment would bring about behaviors that are associated with training instead of the desired playful and voluntary behaviors.[43]

Time and resources[edit]

The process of producing and providing environmental enrichment usually require a large allocation of time and resources. In a survey,[26] "time taken by animal care staff to complete other tasks" was the most significant factor influencing environmental enrichment provisions and scheduling. Therefore it is important to develop appropriate environmental enrichment programs that can be effectively carried out with the size of staff and time available.

References[edit]

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