Enrichment is the practice of improving the living conditions of animals in human care, such as in shelters, zoos, farms, laboratories, and homes. The goal of enrichment is to promote natural behaviors, reduce boredom or stress, and improve overall health and happiness by allowing the animal to make choices to engage with the enrichment tools (LaFollette et al., 2023). Enrichment can include items for play, new smells, different sounds, puzzles to solve, and interactions with other animals or people. The idea of enrichment was first explored in the 1920s; it was not until the 1980s that enrichment began to be widely used in animal care settings (Babitz et al., 2023). Today, it is considered a vital part of managing animals in human care. Social enrichment involves allowing animals to interact with others, including members of their own species or humans. Animals that are naturally social, such as monkeys, horses, or canines, often need companionship to thrive. Housing these animals alone can lead to stress and behavioral problems, while providing social housing or contact with other animals can greatly improve their well-being (LaFollette et al., 2023; Veissier, 2024). Social animals like horses, primates, and dogs can experience significant behavioral improvements, such as increased grooming and playing and fewer stress-related behaviors, when able to live in groups or interact with caretakers (LaFollette et al., 2023; Veissier, 2024; Vicino et al., 2022). For horses, even physical or visual contact with neighboring animals through open walls can reduce signs of stress (Cooper et al., 2000). Even among animals of the same species, enrichment needs can vary from one individual to another. Just as in humans, animals differ in traits such as exploratory tendency, motivation, and engagement style, which can influence how they interact with their environment (Vicino et al., 2022). As a result, the same enrichment item may be highly stimulating for one individual and uninteresting or even stressful to another. This variability is illustrated indirectly by Rault et al. (2018), who found substantial inter-individual differences in serum BDNF concentrations among pigs provided with identical foraging enrichment and suggested the variability may be due to how the individual pigs interacted with the enrichment. Although enrichment use was not directly measured, these findings support the idea that individual characteristics shape how animals respond to enrichment, reinforcing the importance of considering individual preferences rather than assuming a uniform benefit across a species. It is also essential that caretakers are aware of the animal’s current state of well-being so that the enrichment tool or exercise challenges the animal at an appropriate level. If an animal is over-stimulated, additional stressors may be detrimental to the animal’s normal functions; however, if an animal is under-stimulated and does not receive enough stimulation or the correct type of challenges, the animal may also lose normal functions (Clark, 2017). Summary
What Is Enrichment?
Why Is Enrichment Important for Animals?
Different Types of Enrichment
Physical enrichment
Cognitive Enrichment
Sensory Enrichment
Social Enrichment
Different Species Have Different Preferences
Individual Differences Matter, Too
Giving animals choices is one way to handle individual differences. When animals are offered multiple types of enrichment and allowed to choose what they want to interact with, they are more likely to engage in meaningful and beneficial behaviors and also provide opportunities for the caretakers to learn more about the animal such as their communication styles, trust cues, and welfare indicators (e.g., calm response to particular tone of caretaker voice; reduced avoidance behaviors during routine procedures; or increased use of enrichment source like nesting material, shelter, or puzzle feeder)(LaFollette et al., 2023).
Conclusion
Discussion and Reflection Questions
Bibliography
IAABC Articles
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Enrichment enhances the quality of life for animals in human care by providing them with experiences that support their natural behaviors, mental stimulation, and emotional well-being. Enrichment aims to reduce stress and boredom by providing animals with choices and engagement through various tools and activities.
The practice of enrichment became a widely accepted animal management strategy by the 1980s. It fulfills three main goals:
Unhealthy behaviors, such as pacing or excessive grooming, can develop if animals are over- or under-stimulated. Understanding the individual animal’s needs and managing their enrichment accordingly can improve their learning, emotional resilience, and health outcomes. These positive metrics can be linked to several factors related to improved welfare, including greater coping mechanisms in response to stressors and biochemical changes like an increase in the production of brain-derived neurotrophic factor (BDNF), a protein that supports the survival, growth, and maintenance of neurons as well as promoting brain plasticity.
Enrichment comes in several forms:
Different species have unique enrichment needs based on their inherited adaptations. For instance, dogs and cats often benefit from scent-based enrichment, whereas birds tend to be most stimulated by visual and auditory activities. Even within a species, individuals have varying preferences and needs based on their personalities (e.g., curious, sensitive) and mental states (e.g., over-stimulated). Therefore, personalizing enrichment and allowing animals to choose between multiple options may enhance engagement and well-being more than a generalized enrichment program.
In conclusion, enrichment is not one-size-fits-all; it depends on an understanding of species-specific traits, individual differences, and the environment. Thoughtfully designed enrichment makes animals healthier, happier, and better able to cope with challenges, making it an essential part of responsible animal care.
Discussion and Reflection Questions
Enrichment is critical for animals because it can:
A well-enriched animal is more likely to remain resilient and adapt in the face of challenges (refer to Figure 1). Studies have shown that animals living in enriched environments perform better on learning and memory tasks, have positive biochemical changes, and are more resilient to stress. For instance, Korholz et al. (2018) determined that mice housed in enriched cages supplemented with partitions, toys, tunnels, and hideouts had improved fitness and coordination, enhanced exploratory behaviors, and positive changes in brain morphology and neurogenesis compared to mice in standard housing. Another study demonstrated that piglets housed in environments with foraging blocks had increased serum levels of brain-derived neurotrophic factor (BDNF) compared to those living in a barren environment (Rault et al., 2018). Increased serum BDNF levels have been correlated to higher levels of BDNF in the brain, and BDNF is a protein that supports the growth and maintenance of neurons. Elevated BDNF levels promote higher stress resilience and enhance learning and memory (Rault et al., 2018).
Multiple studies indicate that animals actively choose opportunities for problem-solving and social interaction, even when simpler, low-effort behaviors are available. For instance, when shelter cats were trained to have paw-to-hand contact, the cats began jumping out of their enclosure and freely walking to the training room (Gourkow and Phillips, 2016). In another study, monkeys who learned to solve puzzles to access food rewards sometimes chose to do more puzzles rather than eat the freely available reward (Clark, 2017). The choice of these animals to voluntarily work through mental challenges suggests that there is something rewarding in the mental task itself.
There are many types of enrichment, and each serves to enhance welfare in a different way. The standard categories are physical, cognitive, sensory, and social. It is important to note that some enrichment tools can fall in several of these categories and can trigger other enrichment activities (e.g., foraging for food can be physical and sensory via olfactory then gustation engagement). Refer to Table 1 for additional examples of enrichment for birds, cats, dogs, and horses.
Physical enrichment changes the animal’s space to make it more complex. This could include tunnels, platforms, climbing structures, or additional space for movement. Adding physical features can encourage animals to explore, exercise, and interact with their environments. For instance, hamsters housed in complex cages with added partitions showed greater engagement with their surroundings and they used more environmental cues to solve tasks compared to those in standard cages (Thinus-Blanc, 1981). To maximize the benefits of an enrichment activity, the type should reflect the animal’s evolved survival strategies. For instance, goats like to climb and solve problems, so providing them with raised platforms and objects that require effort to access may be more rewarding than simple treats (Aschwanden et al., 2009).
Cognitive enrichment provides animals with mental challenges that encourage thinking, learning, and problem-solving, thereby reducing boredom and building confidence. This type of enrichment includes puzzle feeders with hidden treats, training exercises, and interactive tasks (Clark, 2017). For example, goats learned to discriminate between shapes on a screen to get water, and monkeys showed reduced over-grooming and aggressive behaviors when given the opportunity to play with computer-game-task joysticks (Clark, 2017). One study showed that shelter cats that were initially frustrated showed signs of increased contentment and reduced boredom after participating in human-led training tasks, suggesting they valued the challenge and interaction (Gourkow and Phillips, 2016).
Sensory enrichment stimulates the five senses. Examples of enrichment for each of these senses are as follows:
Animals from different species have different responses to enrichment. These variations usually reflect their natural lifestyles and sensory strengths. In a 2009 review, Wells described examples of this: birds rely heavily on sight and sound and thus may benefit more from visual or auditory enrichment, while cats and dogs have strong senses of smell and may respond best to scent-based enrichment like essential oils or pheromones. This review also reported that zoo-housed tigers increased their scent-marking behaviors in response to a synthetic cat facial pheromone, whereas lions did not show the same behavior change. Yet, zoo-housed lions showed increased activity and social behaviors when exposed to scents of prey, indicative of a simulated natural hunting experience triggered through smell. Sheep and cattle became more anxious and ate less when exposed to the smell of dog feces, highlighting how predator cues may be harmful rather than enriching for prey species. Another example of the variable effects one enrichment tool can have is that mirrors helped reduce weaving in stabled horses, but mice avoided housing with mirrors and rabbits were initially more disturbed and spent more time looking alert in the presence of a mirror. Overall, it is critical to use species-specific tendencies to predict the effect an enrichment tool will have and then to monitor individuals with the tool to ensure they do not show signs of distress.
Proper enrichment can improve the lives of animals in human care by providing experiences that support their natural behaviors, mental stimulation, and emotional well-being. Used in settings like zoos, shelters, homes, and laboratories, enrichment reduces stress and boredom by offering animals choices and engaging activities tailored to their needs. Over the past century, enrichment has evolved to become a key animal management strategy, aiming to meet basic needs, foster positive emotions, and promote long-term adaptability. Without adequate stimulation, animals may develop unhealthy behaviors, while those in enriched environments experience better learning, resilience, and health. Thoughtful physical, cognitive, sensory, and social enrichment should be personalized to each species and individual and be managed as an essential part of the animal’s health.
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