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Why Animals Do The Thing

How to Understand Zoo Enrichment

Rachel Garner

Sometimes, when you visit a zoo, there’s seemingly random stuff in the exhibits for animals to interact with: huge plastic balls in with the tigers, hanging wire baskets stuffed with leaves for the giraffes, sometimes even silly pinatas or cardboard boxes painted like cake if an animal is having a birthday. Something a lot of guests don’t know is that these “toys” given to the animals aren’t random - they’re part of a carefully structured facility-wide behavioral enrichment program that is geared towards keeping animals active and engaged with their surroundings. Enrichment is omnipresent in modern zoological facilities, but sometimes it’s sneaky or implemented behind the scenes. Knowing how to spot enrichment and figure out what it’s used for - or knowing what questions to ask a staff member to learn more about their enrichment program - will enhance the quality of your visit to a zoo or aquarium and help you form a more educated interpretation of the quality of care a facility provides.

Spinning feeders and a fire hose cube at Sequoia Park Zoo.  (Photo Credit: Redwood Coast AAZK)

Spinning feeders and a fire hose cube at Sequoia Park Zoo. 

(Photo Credit: Redwood Coast AAZK)


What is behavioral enrichment?

Behavioral enrichment is the practice of “enriching” a captive animal’s environment with novel stimuli to encourage engagement in species-typical natural behaviors, as well as challenging them to think, problem-solve, and cooperate (when appropriate). Enrichment items can be almost anything - basically, as long as it doesn’t pose a safety risk to the animal who gets it - and they run the gamut of different types of sensory stimulus. Common types of enrichment include but are not limited to unique ways of accessing food, novel objects or toys, scents or scented items, rearranged exhibit fixtures, audio playback, and keeper/guest/other animal observations.

A hanging vegetable feeder for the Alhambra Tortoises at Zoo Atlanta encourages these sedate animals to be more active while eating.  (Photo Credit: T. Phillips)

A hanging vegetable feeder for the Alhambra Tortoises at Zoo Atlanta encourages these sedate animals to be more active while eating. 

(Photo Credit: T. Phillips)


Why is behavioral enrichment necessary?

You won’t find this statement openly on most zoo websites, but it’s important to acknowledge: animals in captivity need behavioral enrichment because captivity fundamentally limits their range of experiences and activities. Enrichment is therefore widely recognized as a necessity - not a luxury - for providing optimal welfare in captive environments.

Zoo animals worldwide used to be considered nothing more than living dioramas, and while their physical needs were tended to in order to keep them alive, very little was done to take care of their mental health - this is the genesis of the pervasive image many people have of zoos being horrible places where bored animals pace endlessly from stress and self-mutilate as a coping method. Luckily for everyone, the field of zoo animal management has moved forward from that era. As a field, it’s been acknowledged that there is a responsibility to provide the best possible welfare for animals that have had artificial limitations imposed upon them, which includes making sure they stay mentally engaged and behaviorally fulfilled.

A Common Rhea at Sequoia Park Zoo investigates a PVC feeder tube meant for the Chacoan Peccaries it shares an exhibit with. When rolled around, pellets that are part of both species' diet fall out.  (Photo Credit: L. Miller)

A Common Rhea at Sequoia Park Zoo investigates a PVC feeder tube meant for the Chacoan Peccaries it shares an exhibit with. When rolled around, pellets that are part of both species' diet fall out. 

(Photo Credit: L. Miller)

A captive animal’s welfare in captivity is judged as satisfactory if it is able to express most or all of its natural behaviors without the addition of negative or stereotypical ones. Stereotypic behaviors are similarly defined in animals as they are in humans: seemingly aimless repetitive or ritualistic movement, posture, or utterance. What constitutes engaging in 'most' natural behaviours is to some degree inherently subjective, but the staff who work with these animals and design enrichment for them are experts in their specific care. These professionals are intimately familiar with what enrichment animals most eagerly utilize and what items they’re not into, and the staff even create calendars to make sure they’re switching it up frequently enough and encouraging different types of behaviors.

Animals in captive environments like zoos and sanctuaries have most of their daily needs provided for them - they don’t have to spend most of their time foraging simply to survive like their wild counterparts. Because they live in human care, their territory is protected from invaders, their mates and group members are provided for them, and generally any resource that a wild animal would have to travel to access (e.g. shelter, running water) is thoughtfully placed within easy reach. In some ways this is great - zoo animals have all their basic needs met - but it also leaves them with a lot of free time. Enrichment protocols aim to fill that time with activities that encourage animals to utilize the same species-specific behaviors they’d normally engage in during the day in the wild.


How do zoos decide what enrichment to give animals?

Every area in a zoo is going to have a well-stocked collection of items that are appropriate for the animals in their care. Decisions about what enrichment is appropriate for which animals are made based off of  a number of different factors, such as what behaviors they facilitate, safety, individual animal preferences, and caloric density.

The enrichment item closet at Aquarium of the Bay.  (Photo Credit: D. Estes)

The enrichment item closet at Aquarium of the Bay. 

(Photo Credit: D. Estes)

The most important consideration for any enrichment item is how safe it is for the animals to have; it’s important to consider if an animal could damage or destroy an item and what might happen with the pieces. Animals with a lot of bite strength won’t be given any sort of plastic or rubber unless it’s specially designed for them (such as the large “boomer balls” or barrels often seen in big cat and bear exhibits). Paper and cardboard are ideal items for animals that like to shred things for fun or to build nests because they’re fairly harmless if ingested by animals that are used to digesting high-fiber diets.  

Streamers make up a large part of the birthday enrichment for Kiki, a Western Lowland Gorilla, at Franklin Park Zoo. Visually novel and fun to destroy, they encourage all sorts of investigative behavior.  (Photo Credit: S. McCann)

Streamers make up a large part of the birthday enrichment for Kiki, a Western Lowland Gorilla, at Franklin Park Zoo. Visually novel and fun to destroy, they encourage all sorts of investigative behavior. 

(Photo Credit: S. McCann)

Some enrichment is generally appropriate for a species across the board, but may have to be adjusted at each facility for the needs of their specific animals. North American River Otters at some facilities are approved for plush toys because they’re mostly utilized for snuggling, but other facilities have found it necessary to ban giving them to that species because their animals love tearing out the stuffing.

Other enrichment items are banned because they could hurt the animals if dropped on them or used as a weapon by other animals. Sometimes items are no longer approved for enrichment because the animals are too good at figuring out how to utilize them in ways that could compromise the security of their enclosures or the safety of nearby guests. Ape enrichment must be vetted to make sure it can’t be used as a tool to short out hot wire or breach moats, items must not be of a size and shape that is easily picked up and thrown into guest viewing areas, and the Vancouver Aquarium no longer allows its sea otters to open their own clams for dinner (for which they use rocks as tools) after one resident learned she could utilize the rocks as a battering ram and crack the glass on her exhibit.

Once an item is considered to be safe for an animal, it’s entered into the rotation of items that can be used. Staff make sure to not use any type of enrichment too frequently in order to keep them exciting. Some food enrichment items can be very calorie dense, so they’re used infrequently to ensure that animals stay at a healthy weight. New enrichment is carefully monitored during and after use to determine if its presence has any side effects: if the animals are stressed or over-excited, how it influences the social dynamic of a group during use, if anyone appears to be allergic to a new food enrichment, or if any animals show signs of gastrointestinal distress after use.  

A gorilla-style cake is part of Kiki's birthday celebration at Franklin Park Zoo. Fruit, rice cakes, and colored yogurt comprise a healthy but tasty treat.  (Photo Credit: S. McCann)

A gorilla-style cake is part of Kiki's birthday celebration at Franklin Park Zoo. Fruit, rice cakes, and colored yogurt comprise a healthy but tasty treat. 

(Photo Credit: S. McCann)


Who gets behavioral enrichment items?

In an ideal world, every animal would get access to some sort of behavioral enrichment every day - however, in the hectic world of non-profit zoos, that’s often not possible. Instead, zoos continually assess which animals require the most behavioral enrichment in order to stay psychologically healthy and create systems that prioritize their needs while encouraging staff to go above and beyond that when resources allow for it.

In general, daily behavioral enrichment is required for all elephants, felines, primates, parrots, birds of prey, and equines. It is strongly suggested that behavioral enrichment be provided as much as resources allow for canids, rodents, small carnivores, large birds, and odd-toed ungulates. Enrichment should be provided as frequently as possible for even-toed ungulates, marsupials, fish, reptiles, and invertebrates.

Rose petal enrichment for amphibians was part of a Valentine's Day enrichment theme at Aquarium of the Bay (the exhibit is themed around the consequences of dumping, so the bottles are permanent fixtures). Amphibians are hard to enrich but flower petals are novel and have an interesting texture.  (Photo Credit: D. Estes)

Rose petal enrichment for amphibians was part of a Valentine's Day enrichment theme at Aquarium of the Bay (the exhibit is themed around the consequences of dumping, so the bottles are permanent fixtures). Amphibians are hard to enrich but flower petals are novel and have an interesting texture. 

(Photo Credit: D. Estes)


What types of behavior does enrichment encourage?

Foraging behavior is one of the biggest categories of behavior - because it’s what most animals spend a lot of their day on in the wild - and is the easiest to encourage with enrichment. Scatting food across an enclosure or multiple surfaces works well for animals that would spend most of their day picking through bushes or leaf-litter for food, and multiple small dishes containing grubs can be hidden throughout an exhibit for rooting animals to find. Sometimes these animals are given complicated enrichment devices that randomly release more food throughout the day, encouraging intermittent but continuous foraging behavior. Hanging browse (low-quality, fibrous vegetation good for constant grazing) encourages treetop grazers like giraffes and elephants to utilize their whole bodies to stretch for food.

An African Elephant at Zoo Atlanta stretches to snag browse from a lofted feeder device. (Photo Credit: T. Phillips)

An African Elephant at Zoo Atlanta stretches to snag browse from a lofted feeder device.

(Photo Credit: T. Phillips)

Carcass feeds are great for letting predators utilize their ability to rip and tear and crunch bone; in places that discourage carcass feeding on account of the sensibilities of their guests, simulated prey made from cardboard and burlap stuffed with straw and raw bones gives predators similar satisfaction. Meat or simulated carcasses can be attached to zip lines or bungee cords to stimulate prey drive and encourage teamwork between members of a group. In facilities that allow it, some animals are given live fish in water features of their exhibits so they can stalk them and attempt fishing behaviors.

A Tasmanian Devil at the Taronga Zoo eats meat out of a simulated wallaby carcass. While it does not encourage the same behaviors as a true carcass feed, the simulated feeder is itself enriching for the devils - and educational for guests. (Click here to see a real carcass feed as enrichment - content is graphic).  (Photo Credit: Taronga Zoo)

A Tasmanian Devil at the Taronga Zoo eats meat out of a simulated wallaby carcass. While it does not encourage the same behaviors as a true carcass feed, the simulated feeder is itself enriching for the devils - and educational for guests. (Click here to see a real carcass feed as enrichment - content is graphic). 

(Photo Credit: Taronga Zoo)

Almost every species has been known to engage in problem-solving behaviors when given food items frozen in blocks of ice. Fish that graze on coral reefs in the wild are frequently enriched with food sunk into blocks of plaster they have to chip away at until the food comes free.

A menagerie of reef fish - squirrelfish, grunts, spadefish, surgeonfish, and a puffer - work to dislodge vegetables from a block of plaster at the Cameron Park Zoo.  (Photo Credit: D. Estes)

A menagerie of reef fish - squirrelfish, grunts, spadefish, surgeonfish, and a puffer - work to dislodge vegetables from a block of plaster at the Cameron Park Zoo. 

(Photo Credit: D. Estes)

Because it’s very easy for animals in zoos to be sedentary, locomotion/exploratory behaviors are important as a source of physical activity. Luckily, these can be encouraged with multiple types of enrichment; everything from new exhibit fixtures to toys can be utilized. Something as simple as putting a new rock in the way of an animal’s usual route through an exhibit can help. Hanging ropes are perfect for encouraging primates to brachiate (swing from limb to limb by their hands), while fire-hose structures make great durable beds and hides for all sorts of species. Large barrels and balls are often pushed around by everyone from carnivores to hoofstock. Kiddie pools can be introduced to encourage large birds or smaller mammals without a standing water feature to go wading or wallow. Inside of aquatic exhibits, rocks and overhangs can be moved around, new haul-outs added, or rings/fake seaweed can be added to encourage a variation in movement patterns. Even animals like reptiles can be enriched by changes in their substrate or the addition of new climbing branches or hides.

Red Pandas at the Sequoia Park Zoo nibble on browse placed throughout their fire hose climbing structure.  (Photo Credit: L. Miller)

Red Pandas at the Sequoia Park Zoo nibble on browse placed throughout their fire hose climbing structure. 

(Photo Credit: L. Miller)

The smells and sounds of other species are always great enrichment for most animals and encourage many different types of behavior. Meerkats exposed to occasional vocalizations of predatory animals might engage in colony alerting behavior and/or perform mobbing behavior if a fake predator (like a rubber snake) is introduced. Animals that scent mark their territory will carefully inspect anything that has been sprayed with the urine of another species before remarking their exhibit to claim it as their own. Big cats are encouraged to perform flehmen responses by providing them with the bedding/exhibit fixtures/excrement from prey species. (This behavior can also be encouraged with spices and perfume).

A scent-enrichment device for giraffe at Zoo Atlanta awaits being placed on exhibit. The wiffle balls inside it can be covered in non-toxic scents and/or flavors, encouraging the giraffe to investigate them with their long tongues.  (Photo Credit: T. Phillips)

A scent-enrichment device for giraffe at Zoo Atlanta awaits being placed on exhibit. The wiffle balls inside it can be covered in non-toxic scents and/or flavors, encouraging the giraffe to investigate them with their long tongues. 

(Photo Credit: T. Phillips)

Nesting or denning behavior is often encouraged by providing animals with items to shred and add to their preferred sleeping spots. Large birds like storks are given plenty of browse and sticks scattered across their enclosures so they can search out the perfect piece to add to their nests next. Rodents and their ilk get lots of cardboard and paper they can shred to the perfect size for nesting material, whereas apes and animals less likely to shred their bedding can have fabric, like super snuggly blankets.

A favorite North American River Otter nest full of bedding and soft toys behind the scenes at Aquarium of the Bay.  (Photo Credit: D. Estes)

A favorite North American River Otter nest full of bedding and soft toys behind the scenes at Aquarium of the Bay. 

(Photo Credit: D. Estes)

Many other behaviors that enrichment encourages are less specific, because the enrichment focuses on providing novel experiences for the animals. Sometimes, objects are added just to see how the animals interact with it, like a Christmas tree, which could be a chew toy, browse, back-scratcher, or perch, depending on the species. New objects will be novel even if the animal just notices them and ignores them, so enrichment always serves at least some purpose because it changes the environment.

Individual preferences are obvious when animals are presented with varied enrichment. At Sequoia Park Zoo, some Bush Dogs prefer raw bones - but others make a beeline for their favorite fire hose.  (Photo Credit: L. Miller)

Individual preferences are obvious when animals are presented with varied enrichment. At Sequoia Park Zoo, some Bush Dogs prefer raw bones - but others make a beeline for their favorite fire hose. 

(Photo Credit: L. Miller)


Why might I not see enrichment in every exhibit when I visit?

How and when enrichment is put in an exhibit varies as much as what type of enrichment might be offered on a given day. New enrichment is often put on exhibit first thing in the morning because it’s a great incentive for animals to shift out into their enclosure so their night houses can be cleaned. Edible or destructible enrichment is often consumed fairly quickly after animals notice it, and might not be visible later in the day. Other types of enrichment, such as novel objects, are frequently visible throughout the entirety of the day.

A Chacoan Peccary with a fall-themed jack-o-lantern enrichment item at the Sequoia Park Zoo. It'll be destroyed fairly quickly once introduced.  (Photo Credit: L. Miller)

A Chacoan Peccary with a fall-themed jack-o-lantern enrichment item at the Sequoia Park Zoo. It'll be destroyed fairly quickly once introduced. 

(Photo Credit: L. Miller)

Some enrichment is only offered to animals behind the scenes because staff want to supervise its use. There are other considerations for what enrichment is offered on-exhibit versus off-exhibit based on the construction of the habitat. Large balls are often not allowed in moated exhibits to prevent animals from jumping into the moat in pursuit and getting stuck, and enrichment that could be pushed between bars or through fences must be indoors-only.

Even when a full range of enrichment devices is being offered, you might not be able to spot them. A recent trend in zoo management has been to limit on-exhibit enrichment to naturalistic objects only in order to cater to guests’ desire to see animals in enclosures that look like their natural environment. So in some cases, while a full range of enrichment devices can be offered behind the scenes, only objects that look like they could be found in nature will be placed in the public view. In this case, just because you can’t see it doesn’t mean it isn’t there - there are some pretty nifty ways to make PVC piping (a core component of many puzzle feeders) look like wood. Some zoos have the funding to build permanent naturalistic enrichment devices on exhibit that can be used in myriad ways to retain their novel effect. For instance, one might be able to deliver randomly throughout the day on a timer, or at the push of a button by staff, or when triggered by a specific interaction by the animal.

Staff work to build a naturalistic feeder device for the Red Pandas at Brookfield Zoo. Once on exhibit, it'll blend right in with the rest of the vegetation and be barely noticeable. (Photo Credit: Chuck Berman / Chicago Tribune) 

Staff work to build a naturalistic feeder device for the Red Pandas at Brookfield Zoo. Once on exhibit, it'll blend right in with the rest of the vegetation and be barely noticeable.

(Photo Credit: Chuck Berman / Chicago Tribune) 

If enrichment isn’t visible, it’s always fine to ask staff about it! Assuming you’re asking someone who works in the correct area (don’t expect a bird keeper to know about enrichment for the lions, most of the time) they’ll be happy to tell you about what’s in store for that day. You’re going to get the best response if you ask about what enrichment is in store for the day rather than assuming the animals are bored and miserable because you can’t see any at a given moment.


What types of enrichment are there?

Sometimes enrichment is mean to be as fun for the guests as it is for the animals. Taco Tuesday at Aquarium of the Bay was one such theme: the North American River Otters got corn tacos filled with their normal meat diet, shredded lettuce, and cheese. (These items aren't part of their normal diet, but are approved for occasional use in enrichment). (Photo Credit: D. Estes)

Sometimes enrichment is mean to be as fun for the guests as it is for the animals. Taco Tuesday at Aquarium of the Bay was one such theme: the North American River Otters got corn tacos filled with their normal meat diet, shredded lettuce, and cheese. (These items aren't part of their normal diet, but are approved for occasional use in enrichment).

(Photo Credit: D. Estes)

Meerkats at Capron Park Zoo investigate a size-appropriate ball pit - there's likely tidbits of food hidden among the balls.  (Photo Credit: S. McCann)

Meerkats at Capron Park Zoo investigate a size-appropriate ball pit - there's likely tidbits of food hidden among the balls. 

(Photo Credit: S. McCann)

Food-related:

  • Hanging Browse / Lofted food

  • Scatter feeds

  • Randomized food dispensers

  • Puzzle Feeders

  • Ice Blocks

  • Carcass Feeds

  • Faux predatory experiences

  • Bug dispensers

Olfactory:

  • Spices

  • Perfumes

  • Other animals’ scent-marked items

  • Feathers or sheds from other animals

Aquarium of the Bay brought in hundreds of pounds of snow one winter as enrichment for their North American River Otters.  (Photo Credit: D. Estes)

Aquarium of the Bay brought in hundreds of pounds of snow one winter as enrichment for their North American River Otters. 

(Photo Credit: D. Estes)

Novel Items:

  • Boomer balls

  • Cardboard boxes

  • Streamers

  • Holiday themed items

  • Bedding

  • Clothes (for primates)

  • Snow/Ice as appropriate

  • Christmas trees

A Nine-Banded Armadillo at Capron Park Zoo paints during a keeper interaction. The novel experience as well as the texture and smell of the paint are all enriching. 

A Nine-Banded Armadillo at Capron Park Zoo paints during a keeper interaction. The novel experience as well as the texture and smell of the paint are all enriching. 

Auditory:

  • Conspecific calls

  • Novel sounds

  • Music

  • Calls of other animals

Exhibit Furniture:

  • Fire hose constructions

  • Perches / Logs

  • Netting

  • Permanent installations (e.g. feeder, water features)

Keeper Interactions:

  • Training Sessions

  • Painting sessions

  • Tech - iPad Games & FaceTime for primates

  • Research Projects

Observation:

  • Guests as enrichment

  • Other animals as enrichment (e.g. elephant walks around the zoo, ambassador animal sightings, wildlife coming near the fence)

  • Novel events outside of exhibit (e.g. musicians)




 

The weird things guests do are also novel and enriching! Here North American River Otters investigate a guest's re-usable cup.  (Photo Credit: D. Estes)

The weird things guests do are also novel and enriching! Here North American River Otters investigate a guest's re-usable cup. 

(Photo Credit: D. Estes)

If we fits, we sits: Patagonian Cavies at the Sequoia Park Zoo utilize cardboard fruit boxes filled with straw as temporary beds.  (Photo Credit: L. Miller)

If we fits, we sits: Patagonian Cavies at the Sequoia Park Zoo utilize cardboard fruit boxes filled with straw as temporary beds. 

(Photo Credit: L. Miller)


Like this? Check out another article in this series:

How To Understand Zoo Accrediation


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