Redesigning the Captive Polar Bear (Ursus maritimus) Exhibit to Prevent Stereotypical Behavior and Promote

Positive Visitor Experience

Table of ContentsCindy HoangApplied Animal Behavior in Captive PopulationsNSCI 579 – 001December 4, 2012Semester Project Proposal

Terminology, Guidelines, and Regulations……………………………………. 3

Project Overview………………………………………………………………. 4

Stereotypical Behavior…………………………………………………………. 5

Enrichment……………………………………………………………………... 6

AZA Recommendations and Requirements…………………………………… 9

Creating an Enrichment Plan…………………………………………………... 10

Ethogram Summary……………………………………………………………. 11

Polar bear Exhibit Redesign Layout…………………………………………... 15

Conclusion……………………………………………………………………… 16

References……………………………………………………………………… 17

Terminology, Guidelines, and Regulations

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Conservation: careful preservation and protection of something (merriam-webster, 2012).

Endangered: threatened with extinction (merriam-webster, 2012).

Enrichment: animal husbandry principle which is used to improve the quality of captive care by providing sensory stimulation via environmental, feeding, visual, olfactory, auditory, etc. (Sherperdson, 1998; Wells, 2009; Swaisgood and Shepherson, 2005; Fischbacher and Schmid, 1999; Newberry, 1995).

Enclosure/Habitat: area in view of the public, which the animal is enclosed (AZA, 2009).

Housing Den: area out of public viewing, where the animals will be housed, fed, and veterinary care, etc. (AZA, 2009).

Maternity Den: used only by the females during maternal care.

Off-Exhibit Area: any area within the exhibit, which the public is not permitted access.

Stereotypical Behavior: repetitive behavior induced by frustration, repeated attempts to cope, or possible brain dysfunction (Mason et al., 2007).

Guidelines and Regulations:Association of Zoos and Aquariums (AZA, 2009)USDA Animal Welfare Act and Animal Welfare Regulations (AWR, 2005)Marine Mammal Protection Act (MMPA, 2007)Manitoba Polar bear Protection Act (PBPA, 2002)Endangered Species Act (ESA, 1973)

Project Overview

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Project Site The Denver Zoo – Denver, COSite Description The organization wants to secure a better world for animals through human

understanding. They want to transform into a conservation center for all animals. They envision a world where people can appreciate, respect, and conserve animals and their habitats. All animals, big and small, from all over the world are valued and careful management of the environment is very important.

Identified Problems and Potential Changes

During my visit to The Denver Zoo, the Director of Public Programs identified the stereotypical behavior of pacing in the Polar bear and suggested a potential solution of enclosure rotations. Envisioning the future of the Polar bear enclosure, the Director imagined a more interactive/personal experience for the visitors and decreasing the pacing behavior. In addition, the awareness of conservation and education of the species need to be implemented.

Project Description and Objectives

The Polar bear exhibit redesign will be presented using the AZA guidelines and published peer-reviewed articles. In order to create the new layout of the exhibit, an ethogram was made at the present-day enclosure. The new design is necessary to increase the welfare of the subject and promote positive visitor experience; this will be addressed by: Preventing the stereotypical behavior of pacing by increasing the usage

of enrichment Providing a more stimulating and appealing enclosure for both the

animal and the visitors Providing an educational experience to visitors without stressing the

animal

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Stereotypical Behavior

Stereotypical behaviors, commonly observed in captive animals, is a concern for many groups and organizations interested in animal welfare including individuals with personal awareness of the issue. The observation of stereotypical behavior may be used to identify the well-being of the animal; in the presence of the repetitive behavior, it raises awareness of potential frustration and lack of sensory stimulation (Swaisgood and Shepherdson, 2005). The most studied species to contribute to stereotypy research are felids followed by the ursids and hominids (Swaisgood and Shepherdson, 2005). The three families are one of the top zoo animals that display the behavior (Swaisgood and Shepherdson, 2005). It is important to be aware of the different forms of stereotypy such as pacing, oral, regurgitation, and repetitive movement (Swaisgood and Shepherdson, 2005). Out of the stereotypical behaviors, pacing, which is defined as “more than three traverses of a definite path, such as the back wall of the exhibit or the edge of the pool,” was found to be the most common (Swaisgood and Shepherdson, 2005).

In a comparison of 28 zoological parks with brown bears (Ursus arctos), a close relative to the polar bear, brown bears displayed stereotypical behaviors of pacing, circling or walking in a figure eight, head-tossing, and swaying (Montaudouin and Le Pape, 2005). The stereotypical behavior was performed more frequently in adults than the younger individuals; adults paced, while the young bears head-tossed. In addition to comparing the individuals, Montaudouin and Le Pape (2005) also compared the surrounding factors such as the characteristics of the enclosures, housing management, and social relationships. Taking all of the external factors into consideration, it was found that:

Circling behavior was significantly lower when the area surrounding the enclosure/exhibit was visible by the bears.

Lower levels of stereotypy was found when there was either a medium or large pool (one or more bears can move but cannot swim OR bears can swim)

Higher levels of stereotypy were found in bears that were locked inside during the night for feeding which resulted in the behavior during the afternoon.

Those fed in the morning or afternoon showed significantly lower levels than those fed at night.

After looking over the comparison performed by Montadouin and Le Pape (2005), it is recommended that changing the housing and management strategies can reduce the stereotypical behavior.

A surrounding view is more favorable. A large or medium pool is recommended. Allow the bears to have free access to the indoor enclosure during the day and not lock

them up at night. In addition to changing the feeding time to mornings, by scattering small pieces of food

around the enclosure will promote more curiosity and foraging.

EnrichmentHoang 5

Another approach in addressing stereotypical behavior is providing enrichment; this method is practiced more frequently in the zoo community today. Enrichment is a husbandry activity used to provide sensory and mental stimulation that can prevent and reduce the occurrence of stereotypical behaviors (Swaisgood and Sherpardson, 2005). Mellen and Sevenich Machphee (2001) believe the goals of enrichment should be to:

1. Enrich the captive environment that will enhance the psychological and physiological well-being of animals under care; therefore, enrichment enhances animal welfare.

2. Identify and reduce the potential sources of chronic stress and/or enhance an animal’s ability to cope successfully with acute stress.

3. Reduce and eliminate the abnormal behaviors and provide opportunities for appropriate behaviors and activity patterns.

Enrichment can be provided for the animal in different ways and can fall into two categories: feeding and non-feeding (Swaisgood and Shepherdson, 2005).

FEEDING NON-FEEDING Increase the foraging/search time by scatter

or hiding food Increase the capture time by implementing

live prey Increase extraction time such as a puzzle

feeder Change the variability of feeding times to

prevent predictability Increase the number of feeding/day

Adding non-permanent novel objects, such as inedible objects for manipulation/play

Adding scents/scented materials or auditory Husbandry behavior performed during

training to challenge cognitive skills Rotating enclosures between two or more

enclosures Constructing a new enclosure – habitat

redesign Physical structure of the environment

Within the two categories, there are subdivisions that need to be discussed in further detail. In order to provide relevant enrichment for the subject species (Polar bear), it is necessary to compare the effectiveness of the different types of enrichment.

FEEDINGUsing multiple feedings, hiding food, using devices that can be manipulated (puzzle

feeders), or offering food at different times has been found to stimulate the bears and decrease stereotypical behavior (Fischbacher and Schmid, 1999). When comparing the different types of feeding enrichment, 70 – 80% of low value foods were scattered in the enclosures in the morning, and the rest of the food was given in the housing dens at night (Fischbacher and Schmid, 1999). They compared various feeding devices such as:

Food holes – concrete tubes in the ground where food was hidden Branch racks – metal construction where fresh-cut branches can be fixed Narrow holes – filed with raisins at one end and fixed to the ground at the other end Honey trees – a dead climbing tree with a cup-like hollow at a 3.5 m height where syrup

can be pumped

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Fischbacher and Schmid (1999) found that the feeding enrichment significantly increased the foraging behavior but only during the initial release in the mornings and stopped before noon or early afternoon. This may be because the food was only scattered in the mornings prior to the release and not throughout the day. It can be concluded, although food enrichment decreases stereotypy, it has no long-term or delayed effect on the behaviors during the day (Fischbacher and Schmid, 1999). An issue using food-related objects for environmental enrichment is that the effects last only as long as the food lasts (Altman 1999). In captivity, food is predictable and always available, resulting in decreased search time and handling (Newberry, 1995). Some other methods that may reduce food-related stereotypes include smaller, more frequent meals, scattering food in unpredictable locations, increasing skill and time to get food (maybe providing live prey), and potentially increase the fiber to increase the feeling of fullness (Newberry, 1995).

EFFECTS OF INEDIBLE, MANNIPULABLE OBJECTSThe short amount of time the bears spent engaging in food enriching behaviors motivated

the approach in using inedible objects to decrease stereotypical behavior. Altman (1999) compared the usage of inedible objects in captive bears. The polar bears in the study were given two large (61 cm long x 122 cm diameter), hollow, industrial strength white plastic drums with handles (Bonar Plastic AquaCulture Floats). One of the drums was airtight and could float, while the other had small holes allowing the other drum to fill with water. Altman (1999) found the use of the inedible objects decreased pacing, excessive inactivity, or both. The interaction of the polar bears with the objects are listed below:

Climbed out of the pool and jumped on the floating drum Flipping the drum into the air with their paws Floating on their backs with their paws wrapped around the drum Pushing the drum ahead of them with their snouts or pulling with their teeth Pulling the drum underwater to let it fill with water and pushing it back up to the surface

Altman (1999) did not observe a decline of interaction and habituation after a month. Additional ideas for enrichment “toys” include (AZA, 2009; Canino and Powell, 2010):

Plastic floats 55 Gallon barrels Boomer balls Plastic weeble Cut up rubber and canvas hose Traffic Cones

Heavy duty plastic outdoor play such as sleds, picnic tables, climbing structures

Beer kegs and plastic water cooler jugs

PHYSICAL STRUCTURE OF THE ENVIRONMENTAside from inedible objects, the physical structure of the environment can affect the

animal’s behavior. It is recommended to add complexity to the environment by adding some elevation or levels to allow different functional areas (Newberry, 1995). Having access to different areas of the enclosures such as their indoor and outdoor living space may enhance more exploration (Newberry, 1995). Providing the animal with covered shelter, ledges, and climbing

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structures can give the animal more security and awareness of its surroundings (Newberry, 1995).

SENSORY STIMULATION – SMELL AND AUDITORYWells (2009) discussed the potential effects sensory stimulation can have on captive

animals and the benefits. In recent studies, triggering one or more of the animal’s senses has been used as environmental enrichment (Wells, 2009). Studies performed in humans and auditory stimulation is well known and reported. Keeping auditory stimulation into consideration, Wells (2009) applies it to animals in captivity. Auditory stimulation can be classical or country music, playing prey sounds, or sounds of the rainforest. Visitor perception of what sounds should be played has influenced the enrichment. Studies found lowland gorillas preferred classical music, whereas the visitors preferred sounds of the rainforest (Wells, 2009). Another study found predatory species responded with higher levels of activity when they heard prey sounds from a moving object that would release treats, which contributed to appropriate species behavior (Wells, 2009). For some species, adding auditory stimulation to cover a noisy environment, may actually do worse since the animals have no option in removing the sound (Newberry, 1995).

On a similar note, the olfactory stimulation or the smelling sensation can have positive and negative impacts. Negative olfactory stimulation come from the use of disinfectants, cleaning supplies, too much animal waste, and predator smells. Elimination from species is used as an informational tool for social status, and although regular cleaning is necessary, it is recommended to clean half of an animal’s enclosure at a time (Wells, 2009). Positive stimulation can come from essential oils, plant odors, pheromones, and prey scents. The safety and toxicity of essential oils and plants have to be considered before placing them into a habitat (Wells, 2009). For some species of animals, visual stimulation may play an important role in enrichment.

WHEN ENRICHMENT BECOMES HAZARDOUSAlthough enrichment plans are meant to improve the well-being of the animal, there have

been cases where the items have been unsafe. It is highly important to consider the enrichment safety issues and potential hazards (Hare et al., 2008). Consideration of the presentation of enrichment is important (Hare et al., 2008):

Body part entrapment due to too small or too large of holes or hanging materials The materials of the enrichment Overnight and unsupervised enrichment Items can get stuck in the animal’s teeth or mouth and prevent feeding Ingestion of non-food items can cause health concerns such as irritation and blockage Disease-causing, toxic, and irritating materials and food items – ex. Salmon poisoning in

the polar bears

AZA Recommendations and Requirements

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In order to ensure the highest quality care and improvement of well-being for the polar bears, the Polar bear Care Manual from the Association of Zoos and Aquarium (2009) will also be referenced. In order to ensure well-being of the polar bear, the AZA (2009) recommends:

Temperature Hills, trees, shrubs, branches, rocks, and stumps provide shade throughout the day

Free-access to air conditioned spaces, chilled water, or ice piles Sprinklers, misters, and wind generating fans Heat stress is greater risk than the cold

Habitat Resting platforms, water features, and nesting sites Naturalistic landscape and functional Open/panoramic views, and pits with materials Soft substrate instead of hard Easily modified if necessary

Furniture Moveable boulders, trees, logs Climbing structures and platforms to observe distances

Nesting Materials 1350 ft2 soil, straw, woodchips, or other soft substrates for coverage

Space 5400 ft2 dry land and additional 1650 ft2 per additional bear Pool must be at least ~5-9 ft deep and 96-760 ft2 surface area Pools must be irregularly shaped with shallow and deep ends Pools suggested to have cool saltwater with live fish, smooth walls

and ledges, an island, polar themed floats, waterfalls or streams, changing currents, and wave machine

Freshwater streams in addition to the poolOff-exhibit housing Each bear must have its own area for sleeping have shift facilities

Must be at least 807 ft2 and additional 269 ft2 for each additional bear.

Maternity Dens Quiet area away from the exhibit At least 2.5 m x 2.5 m x 2.5 m Not allowed access to males

Barriers Barrier walls must be at least 5 m high/deep Glass barriers must be at least 2 inches thick Have elevated areas to avoid the pit-like effect and bears should be

allowed to see beyond their enclosures The public should be kept at least 6 m away vertically/horizontally

unless separated by a glass barrier (2 inches thick)

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Creating an Enrichment Plan

Because there are different ways enrichment may be provided, it is recommended to create an enrichment plan for each animal/group; what may work for one animal may not work for another (Mellen and Sevenich Macphee, 2001). Careful consideration of the different types of enrichment and the presentation will play a large role in the success of the habitat redesign project.

Prior to introducing the enrichment, Mellen and Sevenich Macphee (2001) have created a “framework,” which is used to create a self-sustaining enrichment program. The components of the framework include 1) goal setting 2) planning 3) implementing 4) documenting 5) evaluation and 6) re-adjusting (Mellen and Sevenich Macphee, 2001). It is recommended to use this framework when creating an enrichment plan:

1. Goal setting – what do we want this enrichment to achieve?

2. Planning – given the potential enrichment ideas, how do we decide which ones should be implemented? How do we review/approve the enrichments? How will animal care staff make sure the enrichment is routinely provided?

3. Implementing – who will implement the enrichment? 4. Documentation – what happened? Did the enrichment

work? All the observations need to be recorded.5. Evaluation – after a period of time, the outcome of the

enrichment must be analyzed. Did we like what happened? Did the enrichment achieve the goals we set?

6. Re-adjusting – adjust the plan if necessary and start the process over.

It is recommended that managers and keepers are to outline a plan to promote the behaviors and activity patterns that address the animal’s natural history within the organizations resources (Mellen and Sevenich Macphee, 2001).

For the habitat redesign, an assessment of the current polar bear enclosure at The Denver Zoo was performed.

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Before an implementation of a habitat redesign can take place, it is important to consider all factors relevant to the design such as visitor perception, zoo keeper accessibility, feeding schedules, management, the types of enrichment, and individual preference of the animal. Although visitor perception does not directly play a role in the well-being of the animal, it is important to raise awareness and educate the public of endangered species for organizations working towards conservation.

Ethogram Summary

Weather Conditions: Rain/Snow at 55°F – cold weather conditions with intermittent snow intervals, not windy, potentially small sized hail

Species Studied: Polar bear (PB) (Ursus maritimus) Age and Sex Unknown Two bears were observed in two separate

enclosures Polar bear A (PBA) is in enclosure 1 Polar bear B (PBB) is in enclosure 2 Both of the subjects were exhibited

separately during time of observation Feeding times unknown

Enclosure 1: Outdoor There is a large pool which takes up what

appears to be 80-90% of the enclosure There is a walking strip with ~5 ft width

from the pool to the wall which wraps around the pool

At the right side of the pool is a waterfall which is 8-10 ft tall which flows into the pool

At the far left side is a larger space that is ~10 ft from the pool to the wall

The enclosure is covered by ~ 10-15 ft of “rock” material around the enclosure and in front of the enclosure is a viewing glass which runs along the entire front of the exhibit (the entire length of the exhibit was not measured)

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Enclosure 2: (Outdoor) In comparison to the first enclosure, this is ~2-

3x the size of the first one, by width and length

(Image on the Left) In the enclosure is the “Polar bear

Playground,” which is featured as their enrichment for the bears to encourage natural behaviors.

It is placed ~ 10 ft from the fencing The playground consists of fish tubes, rope,

floats and bouys, grooming brush, burrow, digging/foraging area, and browse receptacles.

Fish tubes: used to hold fish and other treats to encourage sense of smell Rope: allows keepers to add or remove objects Floats and Bouys: for pushing, pulling, and bouncing behaviors Grooming Brush: for bears to rub and scratch Burrow: to explore, escape, or take a nap Digging/foraging area: hole in the floor for bears to explore and find hidden treasures Browse Receptacles: used for scratching and chewing on

(Image on the Right) This is the midsection of the habitat which

consists of a large pool which is fairly deep and can be viewed in a “cave” underneath the exhibit.” This provides an “underwater” experience for the visitors.

Towards the back of the exhibit is a large cave/den which the bear can lay under for shelter

(Image on the Left) This is the far right of the habitat and shows

the rest of the pool The pool uses 70-80% of the space in the

habitat In the pool is a floatation platform which is

potentially used to replicate “sea ice” In the far right corner, seems to be an access

door either to the indoor facility or to the neighboring enclosure

Enclosure #1

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Pros: It allowed the visitors to come close to the

PBA with a barrier PBA seem comfortable and very interested

in the visitors and stayed along the viewing glass

Cons: Although there was a large pool, it took up

a lot of space in the enclosure. There was also no provided cave/den area as the other enclosure

The appearance of the viewing glass in enclosure #1, which covered the entire enclosure, was not as appealing because it did not feel as like an “open-concept” as the other enclosure

Gives a small appearance and a negative impression on animal welfare and comfort

Does not seem to have many areas for foraging behavior

Enclosure #2Pros: It had a very large open-concept, which

gave a visitor impression of positive animal welfare

Provided many areas and activities of enrichment such as the playground, pool, a flotation “sea ice,” and a cave/den area for shelter and rest

Has areas available for foraging Provides an “underwater” experience for

the visitors when the animal is in the pool. This is a good source of education

Cons: The enrichment playground was too close

to the fence line, I think the polar bear would feel uncomfortable to use it with people nearby

Observation summary: Both PB were not interested in the pool or exploring the area during my time of observation. This may be due to weather, lack of visitors (no human interaction), or they may have previously been fed prior. Although I am aware of the adaptations of these animals in inclement cold weathers, I am unsure if it is favorable for displays of active behavior. I overheard a comment from a visitor when observing PBA in the enclosure #1 (with the viewing glass). She stated, “Oh look, he’s laying down. I hope you’re happy in there.” I took this response to the animal as a state of concern and worry.

In addition to observing their behaviors, I analyzed the structure of the enclosure. I thought it was strange for both enclosures to differ in size and presentation. One enclosure seems more pleasing to the visitors than the other. Personally for myself, I felt the enclosure with the open concept was much more appealing than the enclosure that was surrounded by rock and a viewing glass. Especially since PBA kept sniffing and positioning his head in an upward behavior.

Personal Comments:

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Because I am not observing the whole day or even 3-4 hours, PBB may be using the playground, just not at the time of my observation.

I think PBB will feel more comfortable with the playground if it wasn’t so close to the fencing. It is the closest site of “enrichment” compared to the other areas.

If there were a combination/compilation of the two enclosures, it would provide a better experience for both the animals and the visitors.

If the open-concept of the fencing in combination with a smaller viewing glass in one enclosure, would provide a more positive experience. It would benefit for those who want to get really close to the animals (if the animal chooses) and the animal would look more natural and comfortable.

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Polar bear Exhibit Redesign Layout

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Figu

re 1

(Cont.)

The Polar bear Exhibit Re-design was created using the studies and comparisons enrichment tools and the occurrence of stereotypical behaviors. Shown in Figure 1, the exhibit is designed with an outdoor/indoor perspective for the visitors and with an open concept for the polar bears. Surrounding each enclosure are either rail barriers or viewing windows. This allows the polar bear to see the surroundings without being completely sheltered from its environment. It is also recommended for the land to have a softer surface than the traditional “grotto” and “rock-like” structure. The land should also be built on a slant/level instead of a flat surface, this is recommended to prevent the “pit-like” effect in addition to a climbing structure that allows the polar bear to view its surroundings at different levels. In addition, the enclosure should provide a naturalist, yet functional living space.

In accordance with AZA (2009), the visitors should be at least 6m away either vertically or horizontally, unless separated by a two-inch thick viewing window. Between the two enclosures is an elevated indoor walking bridge which contains a viewing window for an aerial view. Since the polar bear prefers a softer walking surface, placing a concrete or hard like surface near the doors may prevent pacing near the doors. In addition, if the polar bear chooses, the doors should be open for indoor/outdoor access.

The size of the pool is also important in the layout of the enclosure. Both pools have various levels of shallow and deep water and should be large enough to swim in. In addition, one enclosure has a waterfall and the other will have an island. A representative from The Denver Zoo also liked the idea of having a “swimming experience with the polar bears,” which is also incorporated into the layout. The indoor swimming for the visitors is a wading pool that is directly next to the bear pool which is separated by a two inch thick viewing window. This may also be a form of visual stimulation for some of the animals that like the human interactions.

When looking at Figure 1, the enclosure to the right consists of a waterfall, pool, and a freshwater stream. For foraging and feeding enrichment, there will be live fish in the stream that will be released randomly throughout the day. Since previous studies have found feeding enrichment only lasts as long as the food lasts, it will not be the only source of enrichment and feeding is recommended to be done in the mornings to prevent stereotypical behavior in the afternoon. Other forms of enrichment have been discussed throughout the proposal and it is recommended to have various inedible objects for manipulation that can be rotated daily and safety hazards should be taken into consideration. Adding different scents into the enclosure such as prey scents or food items can encourage foraging behavior and exploration.

In order to provide a positive visitor experience, the indoor portion of the exhibit will contain the indoor wading pool, an Imax/Dome, and several informational slideshows throughout the exhibit. Providing an Imax/Dome inside the exhibit can be used for visitor education and awareness regarding conservation, global warming, and what they can do to help the cause. This may also increase the viewing time of the polar bears and create a stronger connection to the species. The first step to conservation is providing education and awareness.

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References

Alman JD. 1999. Effects of inedible, manipulable objects on captive bears. Journal of Applied Animal Welfare Science 2: 123-132.

Animal Welfare Regulations (AWR). 2005. Animal welfare Act, 7 U.S.C. Animal Welfare Regulations, 9 CFR Chapter 1, Subchapter A. Parts 1-4.

Association of Zoos and Aquariums. 2009. Polar bear (U. maritimus) care manual. www.aza.org.Canino W, Powell D. 2010. Formal behavioral evaluation of enrichment programs on a zookeeper’s

schedule: a case study with a polar bear (Ursus maritimus) at the bronx zoo. Zoo Biology 29: 503-508.

Endangered Species Act (ESA). 1973. Endangered species act. Department of the Interior U.S. Fish and Wildlife service, Washington DC. http://www.fws.gov/laws/lawsdigest/esact.html

Fischbacher M, Schmid H. 1999. Feeding enrichment and stereotypical behavior in spectacled bears. Zoo Biology 18: 363-371.

Hare VJ, Rich B, and Worley KE. 2008. Enrichment gone wrong! The Shape of Enrichment, Inc., San Diego, USA.

Mason G, Clubb R, Latham N, Vickery S. 2007. Why and how should we use environmental enrichment to tackle stereotypical behaviour?. Applied Animal Behaviour Science 102: 163-188.

Marine Mammal Protection Act (MMPA). 2007. The marine mammal protection act of 1972 as amended 2007. Marine Mammal Commision, Bethesda, MD. Pg. 113.

Mellen J, Sevenich MacPhee M. 2001. Philosophy of environment enrichment; past, present, and future. Zoo Biology 20: 211-226.

Montaudouin S, Le Pape G. 2005. Comparison between 28 zoological parks: stereotypical and social behaviours of captive brown bears (Ursus arctos). Applied Animal Behaviour Science 92: 129-141.

Newberry RC. 1995. Environmental enrichment; increasing the biological relevance of captive environments. Applied Animal Behaviour Science 44: 229-243.

Polar bear Protection Act (PBPA). 2002. Polar bear protection act. C.C..S.M c. pg 94.Shepherdson D.1998. Tracing the path of environmental enrichment in zoos. Second nature:

environmental enrichment for captive animals. Washington: Smithsonian Institution Press. p 1–12.

Swaisgood RR, Shepherdson DJ. 2005. Scientific approaches to enrichment and stereotypies in zoo animals: what’s been done and where should we go next?. Zoo Biology 24: 499-518.

Wells D. 2009. Sensory stimulation as environmental enrichment for captive animals: a review. Applied Animal Behaviour Science 118: 1-11.

Website References:http://www.merriam-webster.com/

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