Behavioral enrichment

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

Behavioral enrichment (closely related to 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] The goal of environmental enrichment is to improve or maintain an animal's physical and psychological health by increasing the range or number of species-specific behaviors, increasing positive utilization of 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. The purpose of behavioral enrichment is to improve the overall welfare of animals in captivity and create a habitat similar to what they would experience in their wild environment.[2]

For each animal in captivity, a goal oriented plan is outlined and created to meet the needs of that animal specifically.[2] Many different factors are included in making an enrichment outline including the needs of the species, their desired behaviors, an individual history, and the animal's current habitat. This plan is then put into action and changed based on the response and changing needs of the animal.[3]

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.[4]

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 must be followed for enrichment plans in order to guarantee, regulate, and provide appropriate living environments and stimulation for animals in captivity.[10]

Making a goal oriented plan[edit]

Creating an individual goal oriented plan for each animal in captivity is a crucial part of behavioral enrichment. Each plan is created by considering desired species specific behavior, their habitat while in captivity, and their individual history. The plan created for an animal often also includes planning in order to discourage unwanted and abnormal behaviors that are acquired from being in captivity.[2] Every plan that is created must have enrichment activities that can be well documented as a way to ensure that the animal is benefitting from the plan and activities they take part in. By creating a plan with easily documented activities, caretakers are able to adjust the plan as needed for desired behaviors of the individual animal.[3]

Each plan can be created following a set of steps. First, the animal must be identified and a team of specialized members is assembled. The team members often have specific roles, such as gathering information regarding the species, documenting and analyzing the environment, and going over the animal's individual history. The next step is to gather the information and create a plan with specific and detailed enrichment activities that will be used to help produce the desired behaviors that were agreed upon by team members. After the plan is drawn up, it is then submitted to the Animal Management team who then approves or denies the plan.[11] Once the plan is approved, the caretakers for the animal begin picking different activities off of the list of approved ideas and present them to the animal as a way to ensure varied enrichment. As enrichment activities begin, a schedule is then produced in order to document the animal's change and progression; it is at this point that the plan is reevaluated and adjusted depending on the animal's individual responses and new behaviors.[2]

Plans are created for each animal in captivity. This includes land mammals, amphibians, and even marine mammals. Dolphins, sea lions, whales, sharks, and even fish that are seen within captivity and throughout aquariums are all given goal oriented enrichment plans. Marine mammals experience training with food and positive feedback as a major form of their enrichment plans. This training helps zookeepers and trainers monitor the animal's health and veterinary care in a format that is less stressful and safer for the animal.[9]

Types of enrichment[edit]

Behavioral enrichment - Feeding
Behavioral enrichment - Feeding
Behavioral enrichment - Sensory
Behavioral enrichment - Sensory

Any stimulus which evokes an animal's interest in a positive way can be considered enriching, including natural and artificial objects, scents, novel foods, and different methods of preparing foods (for example, frozen in ice). Most enrichment stimuli can be divided into seven groups:[4]

  • Environmental; enhancing the animals' captive habitat with opportunities that change or add complexity to the environment.
  • Feeding; by presenting food to an animal in different ways, such as hidden, scattered throughout their habitat, buried, or presented differently, natural hunting and scavenging behaviors are encouraged by requiring the animals to investigate, manipulate, and work for their food as they would in non-captive environments. Feeding enrichment is the most common technique used.
  • Manipulation; providing items that can be manipulated by the paws, feet, tail, horns, head, mouth, etc. This promotes investigatory behavior and exploratory play that is often closely related to behaviors that can be seen by the species in a natural, wild habitat. It is not uncommon to see manipulation and feeding techniques combined. Many objects offered to an animal in their habitat can contain treats that require the animal to open, break apart, and/or find the treats through obstacles within the enrichment object.
  • Puzzles; requiring an animal to solve simple problems to access food or other rewards. These puzzles can include puzzle feeders that contain the animal's meal or manipulation objects that are presented.
  • Sensory; stimulating animals' senses: visual, olfactory, auditory, tactile, and taste. Olfactory senses can be activated by presenting scents that the animal would encounter while hunting and mating in the wild. Caretakers include prey, predator, and pheromone scents within the enclosure. Auditory senses can be activated by playing recordings of the animal's natural habitat, animal, and vocalizations that can be heard by the species in the wild.
  • Social; providing the opportunity to interact with other animals, either conspecifics or interspecifics.
  • Training; training animals with positive reinforcement or habituation. This technique not only helps the animal to become mentally stimulated, but also helps to create and form a bond between the animal and his/her caretaker; allowing the caretaker to get a closer look at the animal on a daily basis and allowing for easier daily and veterinary care.

Elaborate systems of food presentation have 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]

It can be argued that a stimulus may be considered enriching even if the animal's reaction to it is negative, such as with unpleasant scents, although stimuli that evoke extreme stress or fear should be avoided, as well as stimuli that can be harmful to the animal. A contrary point of view is that for environmental enrichment to be considered successful, it should promote only positive behaviours.

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 and exposing them to each other's scents.

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,[12] animals should be allowed to perform the activities or interactions they prefer, i.e. preference test studies,[13] and animals should be allowed to perform those activities for which they are highly motivated, i.e. motivation studies.[14]

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.[15]

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.[16] 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,[17][18] cognitive bias studies,[19] and the effects of frustration.[20][21] Physiological indicators include heart rate,[22] corticosteroids,[23] immune function,[24] neuorobiology,[25] eggshell quality[26] and thermography.[27]

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.[16]

Regulatory requirements[edit]

In the United States, the 1985 amendments to the United States Animal Welfare Act amendments directed the Secretary of Agriculture to establish regulations to provide an adequate physical environment to promote the psychological well-being of primates[28] and exercise for dogs.[29] Subsequent standards for nonhuman primate environmental enhancement (including provisions for social grouping and environmental enrichment) are included under Section 3.81 in the Animal Welfare Regulations (9 CFR).[30] Concepts relating to behavioral needs and environmental enrichment are also incorporated into the standards for marine, flying, and aquatic mammals.[31]

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. In order to be an AZA accredited facility, certain guidelines must be followed that pertain to the practices and techniques of enrichment in zoos. These regulations are in place in order to protect the animals overall wellbeing and to ensure the proper mental, physical, social, and biological characteristics of the animals are present when being compared to their ancestors that are found in the wild.[32]

When evaluating a facility for requirements and aspects necessary to receive accreditation as an AZA facility, all aspects are reviewed. This includes, but is not limited to, all animal habitats, diets, enrichment plans, and social groupings found at the location being reviewed. The facility is also evaluated on research done at the institution, their veterinary care in place for the animals, public education efforts, and overall involvement in wildlife conservation.[33]


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