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Gorilla Exhibits as a Case Study

Reconciling User Needs in Animal Exhibit Design Gorilla Exhibits as a Case Studyby Carlyn Worstell, 2003

Introduction1. Insight into natural behaviors and habitats2. A question of space: striking a balance between animal and visitor needs3. Conceiving animal-visitor relationships4. Exhibit features: benefiting animals, benefiting visitors5. Plants: Why use them?6. Plant Selection7. Plants: How to use them8. Conclusion9. Plant ListReferences

Introduction

In the zoological park setting, there is the unique situation of bringing animals and plants into the realm of people. Unlike an ecotourism destination, where people are brought to natural habitats and are expected to conform to nature’s ways, zoos possess the strength, and the responsibility, to bring close-up nature experiences to a large and broad audience.Here, nature and architecture must meet and natural elements must be manipulated for thesake of accessibility. Zoo visitors have very unique design needs, as do captive animals. The needs of these two audiences are often thought to be in conflict with one another.

The foremost goal of most zoological institutions is to use the entertainment value of live animals and re-created foreign worlds to draw people into an educational situation, in which they will learn about and gain respect for the animals they are observing, as well asnature in general. Encouraging visitors to lengthen their stay in the park is important to increase these educational opportunities, as well as increase the institution’s income (from concessions sales, for example) so that it can continue to thrive and carry out its work.

Carlyn Worstell, 2003 1


Visitors spend the most time at an animal exhibit when the animals are close-up and active (fig. 1). Most animals however, prefer to keep their distance from their human observers, if space allows. When space doesn’t allow, i.e. they are in a small enclosure with no visual cover, these animals suffer psychologically, resulting in their being inactive, or in their performing unnatural and undesirable behaviors. Unnatural behaviors detract from the educational value of the exhibit, as they do not accurately represent wild animals. The sight of an unhealthy or unhappy animal will not instill in visitors a sense ofawe for the natural world and may contribute to a poor reputation of zoos.

However, give animals vast, heavily-planted spaces in zoos, in which they can lead a natural lifestyle in relative privacy, and visitors will not be able to benefit from observingthem, as the animals will too often be out of view. This is why designing animal exhibits that are truly based on wild situations, and considering only the absolute needs of the animals, is often secondary in zoo exhibit design.

In investigating gorilla exhibits at 17 European and North American zoos over the past year, discussing animal keeping with numerous professionals, and learning about how people learn in casual settings, I have found that satisfying the needs of both captive gorillas and visitors in the zoo setting are not mutually exclusive. Rather, when an exhibitis designed with the natural needs of gorillas in mind, the visitors’ needs are simultaneously supported.


fig. 1


Gorillas have great attracting power – visitors are usually eager to see the large, mysterious animals that are so human-like (fig 2). However, gorillas are very elusive animals and not particularly active, decreasing their holding power, or their ability to hold the attention of visitors. Holding power can be increased by encouraging animal activity (through supporting natural behaviors) and increasing their viewability by visitors (Seidensticker & Doherty). The recommendations in this paper all support one of these objectives, with an emphasis on solutions reached through horticultural means. I hope that the ideas I have generated about designing for gorillas can be applied to other species as well.

1. Insight into natural behaviors and habitats

Western lowland gorillas inhabit secondary forests with widely-spaced trees and a semi-open canopy (Lash, et al.) (fig 3). The widely-spaced, slender trunks of the trees in these forests allow the large, mostly ground-dwelling animals to easily move about their large home ranges in search of resources. The semi-open forest canopy allows a limited amount of sunlight to reach the forest floor, supporting the over 50 species of herbaceous plants that are so critical to the gorilla’s diet (Harcourt).


fig. 2


Gorilla troops in nature are territorial, occupying vast territories and traveling up to five kilometers per day (Harcourt). They are subject to constant change in their surroundings. This nomadic lifestyle contributes to the well-being of the animals. These intelligent animals thrive in an environment that changes daily and seasonally (fig 4).

These large territories in nature provide animals with visual, olfactory, audible, and tactile stimulation (Hutchins et al.). In the captive setting, plants, topography, and exhibit features can provide various stimuli. Gorillas’ natural habitats are varied both spatially (multi-dimensional surfaces of varying textures) and temporally (daily and seasonal changes in light, temperature, and humidity). Ever-changing stimuli and access to choices


fig. 3

fig. 4


directly improve animal well-being and reduce stress in captivity. Light, temperature, andhumidity can be technologically controlled to replicate the natural situation (Fortham Quick). These elements also play an important role in plant growth and flowering, as wellas in the visitor immersion experience.

Gorillas usually sit and sleep in nests on the ground, which they spend much time building each day out of plant material. Daily allotments of nesting material will allow them to express this important behavior in captivity. A soft substrate, such as grass, is desirable for animal comfort. Floors of indoor gorilla enclosures tend to be of hard concrete, which is easily cleaned, but denies animals a pleasant tactile experience and is unnatural in appearance (fig 5). A “Bio-Floor” – a metal grate that allows drainage covered in about .5 meters of mulch - offers a soft and movable substrate. Natural bacteria will develop in the mulch, keeping diseases at bay and, because the mulch is not often changed, there is no added maintenance (van der Beek).

Gorillas do not spend much time playing in the wild or in captivity, though young ones play more than adults. Much play among gorillas in a zoo enclosure is likely a symptom of boredom, caused by inadequate choices and stimulus (Goerke et al.). Traveling, eating, and nest-building make up most of gorilla activity. About 50% of the day is spent


fig. 5


foraging for food (Cousins). Animals in captivity should be encouraged to move about their space and spend time performing these natural activities as much as possible.

The Rotterdam Zoo has developed a unique feeding system that keeps the gorillas moving about their island all day long and eliminates routine feeding, which offers no variation for the animals. Twelve metal boxes with electro-magnetic closing devices wereplaced in the ground throughout the island. Food is placed inside each box in the morning, before the animals enter the island and timers are set by a digital pad indoors to unlock the boxes at different times throughout the day. By setting the opening times in a different pattern everyday, the animals are constantly moving around in search of available food (de Vries).

Resources besides food should also be distributed throughout the space (Coe, 1999). The presence of several shady, high-up, and hidden areas allows animals to choose where they want to be and ensures that more than one animal has access to a certain element at any given time.

2. A question of space: striking a balance between animal and visitor needs

The physical environment is not all that makes gorillas’ lives complex and enriching. Thesocial environment, as well, is highly structured and ever-changing. Exhibiting animals inlarge groups adds immediate complexity to their lives – more so than additional space ever could. Studies have shown that there is a strong positive correlation between activitylevels and numbers of animals in captive gorilla groups (Wilson).

Many animal keepers now disregard the belief that gorillas should be housed in individual enclosures at night (Webster, van der Beek). In fact, there is no reason not to allow the animals to remain in a group all of the time. (A separation enclosure is important to have, however, to accommodate sick animals or new arrivals).



Size of space is in fact not as important to animal activity and well-being than other animals (of the same or different species) and exhibit features. To successfully allow for group living and social interaction, design of the space is of utmost importance (fig 6).

Many animals are territorial. Even in nature, they restrict their movements to specific, bounded areas. A complex space that provides cover, food, and other comforts is more important to most animals than a large space, in which they feel exposed or bored. The minimum space should, however, allow the group to spread out as they do while eating, sleeping, or socializing in nature. Gorillas in nature leave 8 - 15 meters between one another when sleeping and 10 – 20 meters during feeding (Lash, et al.). Thus, the minimum amount of usable space required by a gorilla group in captivity will be the number of individuals multiplied by 10 square meters (realizing also that group size will change over time). However, there are other factors to regard as well, and this number will undoubtedly be insufficient. It may even be desirable to have two or more separate enclosures, for housing multiple groups or allowing for separation and flexible sub-grouping when needed. Moats and plantings can be used to create the illusion that two spaces are actually connected (fig 7).


fig. 6


Flight distance is important to consider when laying out animal enclosure space. Again, size of space is not the most important factor. The shape of the space, its orientation to visitor spaces, and the features it contains all affect the animal’s psychological concept offlight distance. Space should be allowed, so that at any one time, at least some animals can be comfortably set back from viewers. The exhibit should be designed wide, rather than deep, so that animals are given ample space, but are never too far away from the viewer, assuming the depth is at least equal to the flight distance. The length of the flight distance can be lessened with topography, vegetation, and other features which provide visual cover, or at least a perceived barrier between the animal and visitors. (fig 8).


fig. 7


A separating feature can replace a large amount of distance, as can be observed in human behavior. At train stations, benches and standing space along a platform are often broken up by planters or lamp posts. Individual people will normally leave a space of 3 - 4 people between them and the next person on a bench or while standing. However, in the presence of a planter, for example, people will sit or stand a mere 1 person-width apart oneither side of the planter, because a physical element separates them from another. The breaking up of space in this way can be employed in an exhibit in the visitor area (allowing the viewing space to accommodate more visitors comfortably, encouraging longer stay times), in the animal area (allowing animals to separate from one another in a minimum amount of space), and in the relationship between visitors and animals.


fig. 8

fig. 9a , 9b


Enclosures should encompass a size and shape that will have the essence of a true wild habitat from the visitors’ perspective, as the image of unrestrained animals gets peoples’ attention (Coe, 1985) (fig 9a, 9b). The shape of an exhibit should include various angles for a more organic appearance. However, barriers should avoid angles of 90 degrees or less. Gorillas have been known to use tight angles to climb up enclosure walls. Also, small angles make it easier for a dominant animal to trap a subordinate animal (Hancocks).

Small enclosures, even when appropriate for the size and number of animals on display, will appear as a cage rather than a natural environment, unless they possess the illusion ofbeing an undeterminable space. There are many ways to do this and some will be discussed below.

In the design of animal exhibits, the optimal size for the animal enclosure achieves a perfect balance between animal comfort, animal proximity to visitors, and portrayal of anessence of habitat. However, the relationship of the animal to the visitor, as well as enclosure features, influence the perceived space. The perception of the enclosure size byvisitors and animals will be influenced by visual illusions and psychology.

3. Conceiving animal-visitor relationships

Perhaps the most demanding architectural element in a zoo is enclosure barriers, because of their critical function, as well as their need to remain inconspicuous. Barriers should beobscured as much as possible and visitor views should be controlled to avoid barriers being obtrusive in the view. Often, plantings are used in an attempt to obscure barriers. However, plantings on the visitor side of barriers actually emphasize the barrier further if they contrast with the plants used inside the exhibit. The plant palette of an exhibit shouldapply to both animal areas and visitor areas, to help visitors feel as though they are sharing the same space as the animals (fig 10). This facilitates a more exciting encounter, and can increase visitors’ respect for the animals, as it gives the impression of standing inthe animals’ territory, rather than the impression of an isolated animal enclosure within an urban park.



Wet and dry moats are commonly used as barriers for great apes. Often, moats are constructed as concrete-lined ditches, which are extremely obtrusive and unnatural in appearance. Moats can, however, be designed to be discreetly out of view. When the ground plain slopes up before dropping into a moat, the moat will essentially be hidden (Hancocks, 1995). This technique can be employed at the front of the exhibit, however it requires a large amount of space and results in the animals being more set-back from the visitors. This technique is very effective to disguise moats at the back of the exhibit or between adjacent exhibits, as the space will look continuous. Plantings on the opposite side of the moat will be protected from the animals, ensuring a lush backdrop.


fig. 10


Moats, particularly in front of the exhibit, can also be made appear as a natural part of thehabitat, when constructed with varying width, and appropriately planted with the same planting characteristics on either side (fig 11). Moats allow for an unobstructed view of the animals, without blocking-out sound or smell. Animals at a distance appear bigger, and therefore, closer, when viewed across a moat barrier than across another type of barrier (Kortlandt). However, moats take up considerable space and may restrict the use of vertical elements in the enclosure, as a large distance must be maintained between a climbable structure and the moat, to prevent the animal from jumping down over the moat and escaping. Thus, too small a land space can be further compounded by limited use of the vertical space when a moat barrier is used (Maple and Hoff).

The exhibit should contain the maximum number of viewpoints for visitors without introducing cross-viewing and without shortening the animals’ flight distance at any point. Ideally, visitors should not be able to see the whole space from any one viewpoint, maintaining the illusion of an undeterminable space. A series of smaller, more intimate viewpoints is more affective than one large viewpoint. Smaller groups of observers will be less stressful to the animals (Coe, 1999) and a sense of immersion is more easily created at smaller viewpoints that handle less traffic.

Visitors tend to be quieter and more focused on the animals in small, immersed spaces (Lee & Coe). This is especially desirable in indoor areas, where noise is often compounded by echoing, disruptive both to visitors and animals (fig 12). Sound absorbing materials and exhibit elements that create sound (such as a waterfall) are helpful. However, encouraging visitors to observe in quiet awe is the ideal solution, as lack of distraction is one element in creating a memorable experience (Coe, 1985).


fig. 11


Multiple view points, placed on more than one side of the exhibit, diminish the common two-dimensional scene that visitors are typically presented with (Polakowski) and also allow animals to be observed more often, as people can change their position according to where the animals are. When visitors can even be surrounded by the animal enclosure on more than one side or even pass through the enclosure, as at the Bronx Zoo’s glass tunnel through its gorilla enclosure, visitors will gain a better sense of immersion and respect for the animals, who will be dominant in the scene (fig 13).

Gorillas will socialize with one another more when they are not surrounded by large, glass windows, or overwhelmed by crowds looking down upon them (fig 14). Belfast Zoo has completed a study that compared the behavior of their gorillas before and after the large windows into their space were partially covered by camouflage netting (fig 15).


fig. 12

fig. 13


It demonstrated that when animals are provided with more privacy they are more likely tospend their time focused on one another and their own social relationships, than on the visitors who are observing them, and they also demonstrate lower levels of stress (Stronge) (fig 16). Netting and paintings over glass panels are two ways zoos are retrofitting exhibits, but plants would be an even more natural medium (fig 17).


fig. 14

fig. 15


When visitors must “peek” through vegetation in the foreground, in order to spot the animals, it enhances the excitement of the experience – as though they are in the wild andspotting an animal by chance. The exhibit automatically becomes more participatory, increasing the sensory and emotional impact of the exhibit, which, in turn, enhances its educational and recreational impact (Polokowski). At the Blackpool Zoo, peeking through small windows at the great apes while standing in a themed environment is exciting for the visitor, as well as beneficial to the elusive animals, who enjoy more privacy (fig 18). After all, of what good is a large viewing window, when the animals areinactive or not behaving naturally? The Blackpool Zoo used to have a series of large windows, angled in towards the animals, along a straight hall for viewing gorillas and orangutans indoors. After a simple, but effective, renovation, the windows are partially covered with bamboo walls, about .5 meters out from the windows. Small holes, of different sizes and shapes and at different heights, allow controlled views into the animal space. Visitors now stand on a wooden boardwalk, surrounded by wood chips and potted plants. These, along with the dim lighting, create a sense of atmosphere. Light comes only from doors at each end of the hall and a few spotlights highlighting signage. Crowding at the windows is generally not a problem, as high-attendance generally coincides with nice weather, when the animals choose to be in their outdoor exhibit. This technique should only be applied in indoor exhibits, where the number of animals is dense for the amount space, to ensure that many windows enjoy a view of an animal at a


fig. 16fig. 17


given time, better accommodating large groups of visitors. A system of small windows is employed to view the outdoor exhibit at Burgers zoo where the animals have a vast spacein which to spread out. The result is that the animals are often visible in only one or two windows, and the crowd must compete to see the animals. Outdoors, trees and plantings, rather then walls, should be used to obscure the bodies of visitors.

In the indoor exhibit at the Cologne Zoo, exotic plantings between the visitor pathway and the glass windows into the animal space immerse the visitor in the animals’ environment and also serve the added purpose of preventing visitors from tapping on the glass – a benefit to the animals (fig 19). Foreground elements, such as plants, increase thesense of depth of the exhibit for the viewer (fig 20), making a more interesting view and causing small spaces to appear more vast.


fig. 18


The Munich Zoo’s indoor ape enclosures are viewed through floor-to-ceiling glass windows, which expose the entire space (fig 21). Because all walls of the enclosures can be seen, they appear to truly be enclosures, even smaller in appearance than they actually are. At the same time, the animals do not have any view to the outdoors, and visitors viewthe animals against a very architectural, mural-painted wall (fig 22). The same amount of glass, when placed behind the animals would give the animals a view to the outdoors, as


fig. 19

fig. 20


well as a green, seemingly endless backdrop in the visitors’ view. The visitors could then have a solid wall between them and the animals, with a series windows, placed at different heights, to look through. The animals’ well-being would be improved, as peoplewould appear smaller from the animals’ perspective, which reduces stress. Visitor views could be dictated through window placement, to avoid exposing the entire space at once. A glass background would allow live plants, hills, and sky to be “borrowed” as part of theview.


fig. 21


Skylights in the ceiling prevent the animals from being backlit, as is a problem in the Paignton Zoo’s indoor gorilla viewing area, where animals are silhouetted against windows behind them, and thus difficult to view (fig 23).

When visitors appear smaller to the gorillas, stress may be decreased. In addition to keeping visitors’ bodies from being fully exposed, visitors can stand below the animals,


fig. 22

fig. 23


which will cause them to appear smaller. It has also been observed that apes become anxious when approached from above (Cousins). Thus, visitor viewing areas should be placed at eye level with the animals, or slightly below, or else the space directly below the visitors view will go unutilized (as at the indoor exhibit at Paignton), resulting in wasted space. It is also believed that people’s impressions of the animals will be more respectful when the animal is placed in the higher position (Coe, 1985). Raising the animal space above the horizon line of the visitors, automatically aids in hiding barriers and buildings (Hancocks, 1995) (fig 24).When visitors are placed in a high position, it is more likely that they will be able to view over the entire enclosure, making it appear smaller than it is, or even over the entire zoo, extracting any mystery or surprise from the visit experience (Polakowski).

In off-exhibit holding areas, attention should be paid to the animal-human relationship as well. Animal enclosures should be raised above keeper space, so that the animals are generally at eye-level with keepers. It has been observed in sloth bears, that the animals will not lie down in their holding areas when a keeper is nearby, because it makes them lower than the person. The floors of Leipzig Zoo’s sloth bear holding rooms are .5 metershigher than the floor of the keeper gangway, to help the animals feel unthreatened by passing keepers (Schulman).


fig. 24


4. Exhibit features: benefiting animals, benefiting visitors

Many animal species, including gorillas, benefit from living in a group. While a larger group of animals may require slightly more space for appropriate accommodation than a smaller group, the relative density of animals within the space can be increased, by effectively breaking-up the space. A high density of animals in the space increases the likelihood of visitors seeing at least one animal and of at least one animal being near the visitor viewpoint at a given time. The animals will also be more active, when they are a social species, such as gorillas, because of their interactions with one-another. The entertainment and educational value of the exhibit is thus improved, as visitors will enjoywatching animals interact with each other and will gain an impression of the animals’ natural behaviors.

The social make-up of a gorilla group in nature, gives us an important clue as to how their space should be formed. Different individuals interact with one-another differently and subordinate individuals often seek to visually separate themselves from other individuals (Fossey). In the wild, natural barriers allow primates to escape aggression within their group, spend time in pairs or subgroups to bond, or to breed out of sight of dominant individuals (Blount). In captivity, a series of distinct, differing spaces, rather than one open space, will allow these natural social behaviors, as well as offer choice – both enhancing animal well-being (fig 25). There should be a wide variety of spaces, to compensate for the overall lack of space in the captive setting.


fig. 25


According to gorilla keepers at Apenheul Primate Park, a single space of 180 square meters for their indoor enclosure would not be big enough to house their large group, however this same amount of space, broken up into 10 different spaces of varying shapes and sizes, houses them very well and allows for lots of complex movement within the space (van der Beek) (fig 26). This concept applies both to indoor holding rooms, as well as to outdoor spaces. Both should be designed in such a way that there are no dead-ends, i.e. there is a circuitous route throughout. This will prevent an individual from being trapped by another animal and allow for continuous chase games. Apenheul and Bristol Zoo accomplish this in their indoor facilities by arranging them in a two-leveled “C” shape around the visitor viewing area. A corridor running over the heads of visitors completes the shape into a full circle.

Structures, topography and plantings, can be used in outdoor areas as architectural elements to separate distinct spaces (fig 27). The breaking up of an outdoor space with hills and vegetation proved to lessen aggression in a large gorilla group at the Jersey Zoo (Redshaw & Mallinson) (fig 28). The use of plants to form translucent barriers between spaces allows animals to separate from one another as they desire, while allowing them toremain aware of the other individuals in the exhibit (fig 29).


fig. 26


How does this benefit the visitor? The breaking up of a single space into multiple, overlapping spaces makes the exhibit appear deeper to the visitor and obscures the edges of the exhibit (fig 30). Placing darker-colored and finer-textured plants near the back will enhance this even more, as they will appear to eyes as being further away, due to their smaller size and more shadowy appearance. When the edges of the exhibit are undeterminable, visitors can easier believe they are looking at nature. However, because the enclosure is, in fact, not as large as it appears, the animals will never be too far away from observing visitors.


fig. 27

fig. 28



fig. 29

fig. 30


Varying topography and climbable elements also increase the number of unobstructed views the visitor will enjoy. Male gorillas are very often seen in zoo exhibits standing or sitting on raised areas that afford a view over the entire enclosure and beyond (fig 31). Another common habit of silverbacks is placing themselves near the front of the exhibit, facing back towards their other group members, as if keeping guard over their family and placing themselves as a barrier between visitors and their custodies (fig 32). These observations suggest the importance of providing high spaces on top of rocks, logs, or hills, with expansive views of the rest of the exhibit and beyond, allowing animals (especially males) a sense of control over their territory (fig 33). High spaces offer great


fig. 31

fig. 32


opportunities for visitors to get an unobstructed view of the animal, and should be placed in ideal viewing locations.

Gorillas at the Blackpool Zoo are often seen standing on top of the enormous hill in the middle of the island, making a superb view for visitors. The rocky hills of the island ensure that there is no cross-viewing over the island, though visitors can move around and view it from all sides. The side that visitors encounter first is completely natural in appearance with features such as trees, boulders, and waterfalls (fig 34). The built climbing structure is located on the opposite side of the island. While the first impression of the gorillas is a scene of magnificent nature, visitors can observe the animals climbing


fig. 33

fig. 34


abilities after walking around the island. The animals spend about equal time on both sides of the island.

The natural terrain of the rainforest can serve as an example for topography design in gorilla exhibits. Hills in the rainforest are usually rolling, and gently-sloped. Dried-up river and stream basins are often present. The shallow soil of the forest floor leaves rockyoutcroppings and large tree roots exposed (Weigel), however, large rock walls or cliffs are rarely seen.

An understanding of what kinds of spaces gorillas like to inhabit suggests where in the exhibit the animals will spend most of their time. This helps bringing them closer to visitor viewing areas to be easily viewed in even a large, complex enclosure. In a gorilla group, the dominant male is the leader. The other group members follow his lead, and tend to occupy space relatively near to him, particularly young and their mothers (Hoff &Maple; Box). Therefore, designing an exhibit with the dominant male’s habits in mind, can result in the entire group being more visible.

Gorillas prefer to occupy spaces that are flat, with some kind of element in the space (Lash, et. al.). They especially enjoy features that they can sit and lean their back against, while viewing out in three directions (fig 35). This is called “refuge and prospect” and is a concept that humans have carried with them throughout evolution – the desire to watch for predators while having their backs covered (fig 36). While an animal can use any element to sit or lean on, trees and logs are natural items that visitors will associate with the forest, emphasizing the animals as wild and part of an intricate ecosystem. The animalwill also enjoy the tactile access to natural textures. Young ones use raised areas to play


fig. 35


“king of the hill” and often center their chase games around a central object, such as a logor a boulder. Thus, both adults and juveniles utilize dead logs, which are prevalent in a natural forest, and these should be incorporated into the space.

Tree trunks appear natural and allow animals to peel the bark and drum on the surface. However, they rot quickly and must be changed often. For climbing structures, pressure-treated poles last longer - up to eight years (less in areas near the sea with salty air) and ropes generally last 2 – 3 years (Webster). Metal holders in the ground can be used to hold dead tree trunks and poles vertical, allowing old ones to be slipped out and new onesslipped in easily. Gorillas are quite agile climbers and climbing opportunities increase theamount of available space in an enclosure, by utilizing the vertical plane. Platforms placed in trees or on poles have shown to be favorite spots for sitting and sleeping, particularly for females (Shulman) (fig 37). Climbing structures and ropes should be designed to be easily changed, allowing the environment to be modified periodically so that animals are exposed to novelty (Maple & Perkins). The enclosure space should be accessible to trucks and cranes to easily facilitate the changing of logs, rocks, etc. Gorillas have been known to move unattached logs and place them up walls or over moats to escape (Cousins) so the length of introduced logs should be monitored. Gorillas have also been known to throw rocks at glass windows or out of the enclosure, so all rocks inside the enclosure should be substantial enough that a gorilla could not throw them.


fig. 36


Artificial trees may look more natural in appearance then poles, when mixed with live trees, as is done in the Bronx Zoo’s Congo Gorilla Forest. Here, constructed replicas of African rainforest trees include heating and cooling systems, pipes for food-hiding, and parallel branches that create a “couch” for comfortable sitting (Ehmke). Artificial trees can be built around poles or beams that should be hidden from view.


fig. 37

fig. 38


Many recent gorilla exhibits have incorporated caves into their features, usually heated and facing a visitor view point, to provide gorillas with a warm place to rest while encouraging them to spend time in view of visitors (fig 38). However, caves are not natural spaces for gorillas to inhabit, as they nest primarily among vegetation on the ground or on low branches in trees, and few captive gorillas have shown a preference for these spaces. Furthermore, unnatural heat in concentrated locations, such as in caves, often leads to illness in winter, as the animals change abruptly from warm to cold when moving about (van der Beek). Caves in exhibits usually end up being used as raised areas, from which to view out. This emphasizes once again the need for raised areas in gorilla exhibits, including raised platforms to facilitate nesting when the ground is wet.

Gorillas should, however, be provided with shelter from rain, as most apes do not enjoy getting their heads wet (Brown, et al.). A variation of the cave is a simple wooden structure enjoyed by the gorillas at Bristol Zoo (fig 39). These 4-sided, roofed shelters allow the gorilla to be covered on three sides (refuge and prospect) and choose in which direction it would like to view. It has also been used to stand on top of, for that ever-important expansive view. Adequate shade should be provided for the animals by means of shade trees.

5. Plants: Why use them?

“A lot of plants in the visitor area can compensate for few plants in the animal area.” “Formal annual beds in front of exhibits are good because they appeal to elderly people.” “Plants in the exhibit serve merely for aesthetics for the visitor.” “A few plants that are


fig. 39


placed out of reach of the animals can help in portraying a natural habitat.” “Plantings must not distract from the animal.”

All of the above statements have been written about the use of plants in zoo exhibits and show the lack of importance that has so far been placed on naturalistic plantings in the realm of animal display. I disagree with all of the above. The plant and animal worlds cannot be easily separated, in terms of education or conservation. Since most endangered animals are suffering in the wild due to habitat loss, saving habitats, rather than single animal species, should be at the core of zoos’ educational messages. When appropriate plants are used, the visitor experience becomes more real, more exciting, and the reality of an interconnected nature more evident. Plants will be the force that will help bring zoos the next step closer to becoming “Bioparks” (Robinson).

Plants can contribute so many critical elements to a successful exhibit that they should nolonger be thought of as purely decorative. Plants provide animals with enrichment, physical comfort, and even fresh food. They help direct views and control lighting and atmosphere, as well as aid in habitat immersion, screen buildings, and support education about habitats. Plants can aid in drainage and help control soil erosion, as well as create desirable animal spaces near visitor viewpoints. Plants are the key to mixed-species exhibits, as they create niches and provide cover.

Far from worrying about plants possibly distracting from the animals, animal exhibits canserve as a mechanism for raising awareness of the plant world in visitors. Exhibits shouldcontain one or two focal plants, which help establish a sense of place, as well as catch theeye of the visitor. When animals are in view, they will certainly steal the show. However,when animals are not active, visitors will still have something to catch their interest. Beautiful or interesting plants will add to the total aesthetic impact of the exhibit, an important element of memorable experiences (Coe, 1985).

As mentioned previously, it is important to enrich the animal environment with as much variety and change as possible. Plants are an ideal way to do this, because they naturally undergo change seasonally and yearly. The more textures, scents, flowers, and fruit that can be incorporated into the exhibit space, the better (fig 40). In the rainforest in which gorillas live in the wild, there is at least one species of plant in flower at any given time (Weigel). The animals, even if they cannot come in physical contact with the plants in their surroundings, will benefit from complex and changing stimulation.



Visitors will benefit from plant seasonality as well, as people tend to learn better when more than one of their senses are stimulated (Polakowski). A visit to the zoo is primarily a visual experience. However, appealing to the senses of touch (even the touch of handlesand handrails) and smell can enhance the pleasure and enlightenment of the experience. A variety of textures, colors, and forms of plants, especially when somewhat exotic for the area and especially when they extend into the visitor space, will immerse the visitor ina more complex and exciting experience – the kind of experience visitors come to the zoofor. It will also support education, as animals cannot be understood when separated from the context of their habitats. Studies have shown that visitor attitudes towards animals areheavily based on the environment in which the animals are presented (Hoff & Maple). Naturalistic, immersive environments that encompass both the visitors’ and animals’ space will promote positive behavior in both users. When people enter a world that is foreign to them, but comfortable for the animals, they tend to be more respectful, quieter, and more open to learning and reflection (Maple & Hoff).

Indoor spaces can achieve this sense of entering a foreign habitat as well, when lushly planted. Visitors at the Cologne Zoo find themselves surrounded in greenery inside the primate house, with glass windows also offering views of the nature outside. Plants fill every corner of the building, obscuring building beams and de-emphasizing the rectangular shape of the building (fig 41). Animal areas here, as well as at the Zurich Zoo, are covered by mesh below the ceiling, creating a space for plants to grow as a sort of canopy (fig 42). Dense plantings along visitor pathways are so effective in keeping people on the path, that a rope balustrade was removed.


fig. 40


The indoor primate exhibits at Munich Zoo obscure the glass panels at the front of the exhibits with plantings on the floor and hanging from above, in addition to surrounding the animals in green by means of plantings between double-paned glass walls (fig 43). The animal spaces themselves have a natural ground surface, beneficial to the animals as well as more natural in appearance for visitors. An evergreen grass native to Spain was planted on the natural ground, in the natural light provided by the transparent ceiling.


fig. 41

fig. 42


Raised areas offer comfort when the ground becomes cold. To improve further on this, the natural substrate could even continue out into the visitor space, rather than contrastingharshly with the concrete substrate on which visitors stand (fig 44).


fig. 43

fig. 44


6. Plant Selection

Animals need plants for shelter, cover, and tactile stimulation (fig 45). Important for theirneeds is just that the plants survive and can – to some extent – be interacted with. Habitat simulation – re-creating the essence of a natural habitat – is, however, very important for the visitor experience. Animals should be presented as parts of specific, intricate, and unique ecosystems. An animal exhibit should be very specifically planted for the particular species it will house, to best meet the behavioral needs of the animal, as well asto maximize the message and identity of each exhibit.

Narrowly focusing the intended message of each exhibit, will help use the zoo’s limited space wisely. Rather than try to portray all the aspects of a diverse ecosystem, an animal exhibit can focus on that animal’s specific niche and attempt to draw attention to particular physical or behavioral features. A defined message is more easily learned and retained by the casual observer. The specific educational or conservational message required should serve as the basis for the portrayed setting and layout of the exhibit. Replicating a specific location and focusing interpretation on the local culture and problems, will have more impact than showing animals in a general scene and trying to explain everything about all the habitats they inhabit.

It is not important that gorilla exhibits in temperate zones cannot be faithfully planted with rainforest plants. What is important is that the essence of the gorilla’s natural habitatis conveyed. This can be done with hardy plants, as habitat replication depends more on the character, growth habit, arrangement, spacing, massing, and diversity of plants, ratherthan the actual species.


fig. 45


The secondary forests that gorillas inhabit generally consist of straight-trunked, high-branching trees, creating a broken canopy above (fig 46). A few taller trees may emerge from the canopy. Ground vegetation consists mostly of a carpet of herbaceous plants. There are few shrubs to create a middle story, other than that formed by a few tree saplings. Tall grasses are not abundant, with the exception of bamboo in wetter areas. Vines, lianas, and epiphytes abound (Weigel), covering any available surface (fig 47). Most current gorilla exhibits appear bare in comparison (fig 48).


fig. 46

fig. 47


Rainforest plants in Africa differ greatly from those in Asia and South America. Differingplant palettes can be used to distinguish different areas of the zoo, aiding in visitor orientation, as well as accurately portray natural ecosystems. African rainforest plants usually have large, whole leaves that are generally dark green in color. They rarely have variegated or toothed leaves. Leaves are usually waxy and shiny and often come to a point (drip-tip) at the end (Weigel). Trees are usually single-stemmed, smooth-barked and have grayish trunks (Cousins).


fig. 48

fig. 49


Leaves on African rainforest plants, then, resemble those of laurel (Prunus larocerasus) (Clousdley-Thompson). Laurel is an evergreen and outstanding plant. It is little used in primate exhibits, because it is known to be toxic. However, it used successfully in the chimpanzee exhibit at the Chester Zoo, where the animals do not eat the plants (Sparrow)(fig 49). A plant only becomes toxic when the animals ingest it. Often, animals are naturally deterred from toxic plants, due to their bitter taste, meaning that the plants growlushly in the exhibit, undisturbed by the animals. There is variance among primate individuals and colonies in their use and eating of certain plant species. The risk of animal illness is a serious one, and very toxic plants that the animals have been known to ingest should be avoided, both in the enclosure and on the zoo grounds in general (shoulda leaf or branch reach the animals by means of wind or visitors trying to feed animals). However, a plant with desirable horticultural characteristics (such as large, lustrous, year-round leaves) that the animals will not eat and destroy, can benefit the exhibit greatly. It is worth experimenting with plants such as laurel and viburnum (the fibers on the leaves of which can cause skin irritation) (Turner), which have great simulating-capacity.

While few temperate-zone trees are truly high-branching, canopy-creating trees, there aremany that have leaves that simulate African rainforest plants and also possess desirable growth characteristics. A brief list appears at the end of this article. Indoors, tropical plants from West Africa, or plants that mimic these, that endure low-light conditions should be used.

Needle evergreens do not represent the plant palette of a tropical rainforest. However, gorillas tend not to destroy them, and for the sake of maintaining a green landscape during the winter months, they may be useful – particularly at the back of the exhibit where they are not obvious to visitors, but will make a green backdrop (fig 50). Needle


fig. 50


evergreens are generally not translucent, and are thus good when a severe visual screen isneeded. Placed in the center of an exhibit, however, the animals may find them very goodto hide behind from visitors.

Gorillas are large, heavy animals that move over the ground a great deal. It is important to prepare for soil compaction in their enclosures. A fast-draining soil should be used to minimize this, and, thus, plants that grow in well-drained soil, in addition to being somewhat compaction-tolerant, will fare best. Wear-resistant turf, as used on professionalsports fields, or pervious substrates, as used in urban plantings and horse pastures, can even be employed in this realm (Jackson).

Exhibit soils are often high in salt content, due to animal feces, so salt-tolerant plants mayfare better. Also, because chemical pesticides cannot be used in the zoo setting, plants that are pest-attracting are not ideal. However, in both visitor and animal areas, plants that attract native birds and butterflies can lead to a more stimulating environment and realistic depiction of an ecosystem. Fine-stemmed vines can be used along barriers in gorilla exhibits, as the animals are heavy enough to break them, should an animal try to escape by climbing the vines.

Because gorillas enjoy and benefit from handling plants, durability and fast growth are extremely desirable for plants that will be unprotected in the exhibit. Many plants that areoften thought of as being “invasive” (such as Hops vine or Arundo), can be used effectively in animal spaces, as the animals will naturally control them. Plants that propagate through shoots or rhizomes may be able to regenerate quickly enough to avoid annihilation by the animals. This is helpful in deflecting costs that quickly add up when plants must be constantly replaced. Choosing plants that are durable and aggressive in their growth, over-planting them, and allowing them to be well-established before the animals have access to them will reduce maintenance and costs later on.

Some plants are affordable enough that they can be replaced often, including some tropical species that can be used as annuals. Bananas, papaya, taro, sweet potato, and gunnera will all add to the tropical atmosphere of the exhibit, and create a lush landscape during the summer months, as they will grow to extreme sizes in a matter of weeks. Bananas and papaya can be easily purchased from fruit suppliers and propagated in house, making them cost-effective solutions. Ideally, the plants could be over-wintered ina greenhouse (Jackson). Corn plants resemble some species of the tropical plant Dracena,are easily available, and can be used as browse. Giant rhubarb is used effectively in manygorilla exhibits, including the one at Paignton Zoo.

Another easily-available group of plants is the Aframomum family, or gingers. These make up a substantial part of gorillas’ diet in the wild (Cousins). Naturally, a group of gorillas would be found near Aframomum growths, adding a specific touch of reality to a gorilla exhibit. Ginger tubors can be bought at most (Jackson).



Plants can be used in the visitor space to break up views into the enclosure, however, where viewing is desired, plants that grow taller than .75 meters will block the view for children and people in wheelchairs. It is better to use plants of appropriate height, than to create excess maintenance caused by plantings that must be continuously cut back. Also, plants with messy fruits can create additional maintenance when planted near pathways.

7. Plants: How to use them

A planting design should always begin with the existing conditions in mind. Full-grown shade trees are very valuable to an exhibit, the aim of which is to appear lush on opening day, if they can be salvaged. Zoo Leipzig incorporated existing vegetation into its primateexhibits, which were built on a forested site. Trees were saved in strategic locations, while others were removed to open up the space and allow an herbaceous layer of native grasses, clovers, and thistle to grow beneath. Because all plants are native, additional irrigation isn’t required.

The plant palette used in the animal space should be mirrored in the visitor space. These plantings should begin to surround visitors before they even reach the exhibit, in order to set the mood and begin to take visitors into a new context (fig 51). Formal annual beds in


fig. 51


front of exhibits, only increase the contrast between people space and animal space. Visitors will feel little connection to the animals they are viewing, when they are standingin a park-like setting, simply viewing into a piece of wild African habitat. Designers can lessen perceptual clues that remind people that they are in a zoo. The setting should be free of contradictions, such as obviously man-made structures would be in a wild habitat (Coe, 1995). Plants, rocks, soil and architectural character can aid in providing visual connections across barriers.

While selecting appropriate plant species is the first step to creating a convincing landscape, the layout of the plantings is equally important (Jackson), especially in makingthe space functional, i.e. using plants as architectural elements.

Plant masses in animal spaces will serve as architectural elements – walls defining spacesof various sizes and characters, benches and raised areas for standing, sitting, or sleeping,translucent or opaque screens to direct views. Some evergreen plants can be used to ensure that the exhibit does not become too open in the winter months.

The relationship between plants and space is the first determinant in creating a sense of place or atmosphere. Space can be defined with plants in a number of different ways. An open space, such as a savanna, can be created by surrounding an open space with plants. The African rainforest, however, is made up of spaces that are seemingly cut out of an enclosed, canopied space. Single-stemmed, high-branching trees create a look of a cathedral ceiling, held up by tall, straight poles. In the rainforest, growth is always emphasized up, toward the sun. Trees are generally widely-spaced. Wide spacing and an absence of branches below the canopy are ideal in an exhibit, where visibility through thespace is desired.

Trees and other plants should be spaced and clumped in a random fashion. Rainforest plants generally grow as individuals mixed together, rather then in homogenous clumps. A clump of plants usually contains individuals of various species (Richard). Thus, speciesvariety is a characteristic of tropical rainforests and exhibits should reflect this, while including some degree of species repetition within animal and visitor spaces, to create an understandable scene. An illusion of greater depth can be achieved by placing large-leafed plants nearest the visitor and small-leafed, or fine-textured, plants in the background.

Tactile access to natural elements such as tree trunks and live plants is important for the animals. Gorillas use plants in nearly every aspect of their daily lives in the wild. Eating, nest-building, playing, leaning, viewing, and aggressing are all heavily based on plants orplant parts. Natural behaviors can be encouraged by allowing the animals tactile contact with plants. In the exhibits I have seen in the past year, I have found that a variety of plants can survive the handling of gorillas. The biggest determinants of the plants’ survival is how well they are established before animals have access to them, the ratio of



plants to the number of animals, and how much other browse they receive as part of their diet (Pacinotti).

Rotterdam and Blackpool Zoos have found effective ways to allow animals to forage for willow (Salix), while not killing the willow completely. At Blackpool, willow near the water moat is fenced off by electric wires, separating it from the animals (fig 52). The animals can reach the branches that grow over the wires, but the willow can grow uninhibited toward the water (Webster). At Rotterdam, a number of willow clumps are wired off separately. From time to time, the wires are removed from one of the clumps, allowing gorillas access. Later, the wires will be replaced, to let the planting re-grow and another clump will become accessible (de Vries).


fig. 52


Duisburg and Paignton Zoos have built innovative herb gardens in their gorilla enclosures(fig 53). A metal grate protects the roots and base growth of the herbs. In Duisburg, herbsare planted about 20 cm below ground level so that the grate unobtrusively sits on groundlevel (fig 54). Gorillas have access to the new growth that rises above the metal grate, while the roots of the plants are protected, allowing re-growth. The animals have shown great interest in the various scents and textures of the herbs.


fig. 53

fig. 54


But even plantings that the animals cannot physically touch are still valuable in an exhibit, whether they are just outside the enclosure, or inside the enclosure but protected by hot wire or some other means. Visitors will connect the animals to their forest home, and the animals may feel more comfortable – after all, numerous studies show that the presence of houseplants decreases stress in humans, so we can infer that the same might be true for one of our closest relatives, who are more intimately connected to nature than ourselves. Protecting plants from total annihilation by gorillas is challenging, but feasible.

Plant protection is achieved in many different ways. Plants can be placed between a double-paned glass wall, simply making a green backdrop, as at the indoor exhibit at Munich. Trees can be surrounded by hot wire or, like at Apenheul Primate Park, by an artificial trunk, made of hard plastic, which still allows the animals to lean against the trunk and even drum on it (fig 55).

There is discussion as to whether or not animals tend to leave a consistent distance of a meter or so between themselves and any hot wire. If this is true, the presence of hot wire in an exhibit will radically reduce the amount of usable space for the animals. Further study should be undertaken on this topic.

Shrubs and trees, if they do not have thorns already, can be surrounded by a planting of thorny shrubs, such as Cotoneaster, Berberis, or Ilex (which have the added benefit of being evergreen) (fig 56). Chester zoo uses rose whips and Pyracantha to protect trees in its chimp exhibit. Animals can later be allowed access to the trees, as they become more established, by leaning a log against the tree trunk, allowing the animals to climb over thethorny shrubs.


fig. 55


Both animals and visitors benefit from the existence of large shade trees – protected or not - in the exhibit. The essence of a broken canopy accurately represents the type of habitat gorillas inhabit in the wild, supporting visitor education of gorillas as part of a unique ecosystem (fig 57a, 57b). Shade may also make for more active animals – very important in holding visitors’ attention. In the wild, and at many zoos in varying climates,it has been observed that gorillas are more active when not in bright sunlight (de Vries). Providing shade at all times of day, and all seasons, is important for the physical comfort of the animals and can also be used to encourage the animals to spend time close to viewing spots. Zoo Leipzig provides shade at the front of the exhibit, nearest to the visitor, to entice the animals to this area (fig 58). When the animals are in the back of the exhibit, up on the hill, they are in full sun, so they are still easily visible to visitors. If an animal, especially a dark-colored one like a gorilla, is far away and in the shade, it will bedifficult for visitors to see it. Background plants can be chosen for colors that will best contrast the animal’s color, to make the animal stand out in a complex exhibit.

Also, the contrast between the light and shady areas will make the bright area appear closer to the visitor than it actually is, much like a bright stage in front of a darkened audience (Polakowski). The opposite will be true for the animals. As they look back, visitors standing in shade will seem farther away, increasing the sense of privacy and flight distance for the animals. This is often achieved by placing visitors in a cave or shelter as they view into a sunny enclosure (fig 59). The same effect can be reached with shade tree plantings in and near the visitor area (fig 60). In areas with glass windows, it isessential that the visitor area be darker than the animal area, in order to avoid distracting reflections and glare on the glass.


fig. 56



fig. 57a, 57b

fig. 58


There are many good reasons to set aside budget for moving and protecting mature trees when building new exhibits. In addition to what I have already mentioned, large trees in an exhibit also create multiple niches, offering the opportunity for mixed-species exhibits(fig 61). By utilizing different niches, such as the terrestrial, arboreal, and aquatic, more species can enjoy the same area, thus using the zoo’s space in the most efficient manner. For example, while gorillas are mainly terrestrial, Guerzza monkeys utilize the canopy


fig. 59

fig. 60


space, making them a logical mix in terms of education. Mixed –species exhibits also contribute to the enrichment of the animals’ lives by adding variety and complexity to their environments and contribute to visitor education by showing ever more holistic pictures of ecosystems. They also aid in holding visitor attention because when one animal species is inactive, another may be very active, giving visitors reason to stay at theexhibit.

In areas of limited water, planting beds should be constructed to retain water. They should always be deep and wide enough to allow for a stable root system to develop and to encourage fast-growth – both will aid them in self-defense from animals. Compost andmulch will reduce the amount of water needed, though mulch should not be used in areas where the public can see it, as it is unnatural in appearance. Mulch can be used within planting beds, when kept away from visitor pathways. Drip systems of irrigation, aimed at specific plants and irrigating at night will help conserve water. Also, waterfalls should be able to be easily turned off at night, which saves water and also offers the animals a quieter atmosphere.

8. Conclusion

A survey conducted by the Cunningham Group in 1999, showed that nearly every zoo questioned mentioned that their greatest conflict is providing for animal welfare within the framework of having the animals on display. I hope this paper has offered some ideas that will help alleviate this conflict.


fig. 61


Observing successful, as well as unsuccessful, built exhibits is essential to understand how to create more successful exhibits in the future (Seidensticker & Doherty). I believe designers can learn a lot from the examples of existing exhibits mentioned in this paper, in the quest to further develop design techniques that help achieve the fullest potential of a zoo exhibit for all of its audiences.

I have shown examples of how exhibits can provide their visitors with an exciting experience that appeals to multiple senses, easier viewing of animals even in a large and complex enclosure, and a more accurate portrayal of the natural habitat of gorillas. At thesame time, these design techniques provide the animals with privacy, physical comfort, and the space and means with which to carry out natural activities and social interactions.Design can directly aid in fulfilling a zoo’s educational goals, as animals who lead an enriched lifestyle in an appropriate habitat will display natural behaviors that can be observed and better understood by visitors.

9. Plant List for moderate climate

Botanic Name NotesActinidia arguta vigorous, fast-growing, adaptable vine with dark green leavesAilanthus altissima tough, durable, tree that thrives in compacted and conditions, endures salty soils,

interesting flowers and fruit – may be messy in visitor areasAristolochia durior vine with huge leaves, very fast-growing and adaptableAsimina triloba large, shiny leaves, tasty fruitBerberis fast-growing, use for screening, thorns may prevent animals from destroyingBuddlea fast-growing, attracts butterflies, survives in gorilla exhibit at BelfastCatalpa speciosa a very adaptable tree with large leaves and prominent flowers, tolerates

compacted and salty soilsCedrela sinensis straight-trunked tree with peeling bark that tolerates extreme soil conditions and

self-propagates through suckers (which animals will control)Celtis occidentalis* grows in tough conditions including salty soil, grey barkCladrastis kentukea grey bark, fragrant flowers, tolerates most soilsCornus alba or sericea large leaves, interesting stems in winter, propagates through suckering, tolerant

of a variety of conditionsCrataegus x lavallei does well in well-drained soils and is more disease resistant than other

hawthorns, fruits may be messy in visitor areasGymnocladus dioica endures great stress, rich blue-green leaves, interesting bark, quite fine-textured,

so best if placed near backLeocothoe evergreen, interesting - unpleasant scent, lustrous leaves, purple color in winter Liriodendron tulipifera large, glossy leaves, can grow very large, columnar growth habit, a well-

established one has survived un-protected in Leipzig’s gorilla enclosure very well

Lonicera* many species of durable vines, salt tolerantMagnolia many species, especially macrophylla, have very large leaves, interesting bark,

extremely adaptable, may tolerate salty soilsMahonia aquifolium evergreen, glossy leaves, fragrant flowers, abundant fruit, can be used in shady



areas, chimps at Chester Zoo pick leaves (Sparrow)Myrica pensylvanica* tolerates salty soils, propagates readily through suckeringPaulownia tomentosa large dark green leaves, used to re-vegetate strip-mined land because of its

adaptability and fast growth rate, interesting fruits and fragrant flowers, tolerates compacted soils

Platanus x acerifolia large, dark green leaves, tolerates nearly all soilsPyracantha coccinea stiff, thorny branches may deter animalsPyrus ussuriensis large, glossy leaves, somewhat salt-tolerantRhus glabra spreads easily, difficult to destroy, interesting texture, tolerates salty soilsRibes alpinum fast-growing shrub, very adaptable, can be used for screeningSalix* quickly regenerates, tolerates salty soils, interesting stems in winterSambucus fast-growing shrub, tastes bitter so gorillas tend not to eat it, although at

Blackpool they enjoy the berries, has been said to be toxic - probably depends onindividual populations (Stronge, Webster)

Syringa reticulata tree-like form of lilac with fragrant flowers, very adaptable to difficult conditionsTilia Americana large, lustrous leaves, fragrant flowers, and small, hard fruit, columnar growth

habit, adaptable to rough conditions, including salty soilsVitis collected in nearby woods for use in gorilla exhibit at the Houston Zoo, anchored

by eye-bolts to ceiling on wall beams making them favorite swinging and climbing structures, animals also eat the bark so they must be replaced periodically ( Maple & Hoff)

Yucca exotic appearance, thrives in poor soils, adds interesting texture, salt tolerant(Dirr)

*this plant is a favorite food of gorillas. It should be protected from animals or placed in visitor areas, and regularly cut for browse material.

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mailto:[email protected]


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carlyn worstell, 2003 - zoolex · gorilla exhibits as a case study reconciling user needs in animal...

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