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Reconciling User Needs in Animal Exhibit Design Carlyn Worstell
Content - Introduction - Chapter 1 - Chapter 2 - Chapter 3 - Chapter 4 - Chapter 5 - Chapter 6 - Chapter 7 - Chapter 8 - Chapter 9 - References

6. Plant Selection

Animals need plants for shelter, cover, and tactile stimulation (fig 45). Important for their needs 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 as to 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 habitat is 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, rather than the actual species.

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).

Rainforest plants in Africa differ greatly from those in Asia and South America. Differing plant 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).

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 grow lushly 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 (should a 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 are many 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 evergreens are generally not translucent, and are thus good when a severe visual screen is needed. Placed in the center of an exhibit, however, the animals may find them very good to 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 professional sports 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 may fare 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 are often 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 in a 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 many gorilla 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.

Fig. 45: Pampas grass survives the handling of gorillas at Bristol Zoo, England
© Carlyn Worstell, 2003

Fig. 46: Slender, straight tree trunks surrounded by low herbaceous plants mimic the make-up of the West African rainforest. Duisburg Zoo, Germany
© Carlyn Worstell, 2003

Fig. 47: The gorilla exhibit at the Bronx Zoo is lushly planted - accurately representing the rainforest. New York, USA
© Rob Halpern, 1999

Fig. 48: Many gorilla exhibits are bare in comparison to the rainforest, or even the zoo space surrounding them. Belfast Zoo, Great Britain
© Carlyn Worstell, 2003

Fig. 49: Laurel in Chimpanzee exhibit, Chester Zoo, England
© Carlyn Worstell, 2003

Fig. 50: Evergreens provide cover during the winter months. Blackpool Zoo, England
© Carlyn Worstell, 2003

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Revised 2017-05-17
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