The Role of Architectural Design in Promoting the Social Objectives of Zoos

A Study of Zoo Exhibit Design with Reference to Selected Exhibits in Singapore Zoological Gardens

by Michael Graetz

PART 2 - PHYSICAL ELEMENTS OF ZOO DESIGN

2.3 Mesh and Fence Barriers

Steel mesh is a material applied to fences and cages for its relative transparency and for economy of materials. Mesh is ubiquitous in Singapore Zoo, as in most zoos, being used as side and rear fence barriers, in cages in lieu of bars and in off-exhibit situations. Alternative viewing barriers are rapidly replacing mesh. For a decade of Singapore Zoo's history, mesh has replaced bars on cages only to be replaced in turn by glass in the next development cycle. (See the ‘Cat Country’ case study).

Fences around otherwise open enclosures require considerable attention to detail, as a much greater risk of escape exists. Fence barriers have a psychological element as much as do moats. They are unnatural features both to animals and visitors, but while ways of avoiding their use (rear moats and islands, for example) exist, these are expensive options. They are not always possible, due to space constraints. Thus, Singapore Zoo has explored several techniques to reduce the impact of fences. Harrison[1] discusses some of these applications and the issues of animal responses and maintenance. the specific options available to Singapore may differ from those open to other zoos.

Fences in exhibits must achieve: security; safety for the animals; durability; and unobtrusiveness, if not invisibility to the visitors. The last is arguable if aesthetics is just question of beauty and not of emotional response. Evidence exists that fences and other out of place elements do affect visitors' perceptions of animals[2]. Thus, while the aesthetic question to an architect might amount to a consideration of whether the fence is ugly or can be made attractive in its own right, it is largely accepted in zoos, backed up by some scientific evidence, that the only aesthetically acceptable treatments of fences are those with the aim of reducing their impact. It has to be accepted that the fence is simply not part of the expressive vocabulary available to the designer.

It should be mentioned that this attitude applies to fences with only a utilitarian role. The deliberate use of man made elements in exhibits to make a point--about Man's relationship to an animal for example--are not precluded if they incidentally serve as barriers. The caveat of the effect on visitor perceptions would still apply, however.

Functional and Aesthetic Aspects

The contribution of fences to the social objectives of zoos seems rather small. However, functional requirements--security, safety, and durability--may easily put fences into conflict with these aims. As with planting, the designer is forced to deal with compromises.

Security, safety and durability. As has been mentioned fences are not normally found in animals' natural habitats and animals may not recognise them as barriers at first. Like moats, fences work best when animals do not have any desire to escape; they then will not perceive fences so much as physical barriers, but as the limit of their territories within which they feel secure. Never-the-less, the very alien-ness of fences, unlike moats which do resemble natural features, means that a failure will be quick to be exploited. Furthermore, animals have to be protected from sometimes aberrant, sometimes oblivious behaviour towards fences, such as excessive rubbing, charging or entanglement.

The diversity of animal species that are contained by fences means every application has to be thought through with equal care. Table III summarises some of the areas of concern a curator will have with fences in relation to some of the major animal groups. This table is not intended to be thorough and it should not be misconstrued as suggesting that the items not checked for particular groups are not relevant to these animals: height and strength are a concern to some extent in every case, for example.

Durability is also an animal related issue. Decisions about fences as with other built elements in Singapore Zoo have been influenced by a desire to extend maintenance cycles. Maintenance requirements in the zoo context are influenced by serviceability, appearance and the need to prevent situations hazardous to animals or likely to permit escapes. Rust, especially of welds and bolts in the short term and of the mesh itself in the long term, and wear and tear are the principle dangers.

Table III IMPACT OF ANIMAL TYPE ON FENCE BARRIERS

ANIMAL TYPE	JUMPING (height)	STRENGTH	DIGGING	CLIMBING	MESH SIZE (aperture)	YOUNG (precautions)	CONTACT	URINE
BIG CATS
DOGS
BEARS
GREAT APES							(testing)
DEER / ANTELOPE							(rubbing)
WILD CATTLE							(rubbing)
PIGS		(rooting)
CROCODILIANS					(gharial)
Notes: ‘Jumping’: some deer and cattle are capable of considerable standing vertical leaps. ‘Strength’ refers to that required of both mesh and the supporting structure in respect of the animals. All mesh must be appropriate to the species; cats are a concern due to safety, while gharials risk damaging their slender jaws. The presence of young (next column), adjacency to other animals and risk of predation by endemic species cause mesh size to be a concern in these particular circumstances. ‘Contact’ refers to purposeful contact by animals. The result may be harm to animals or damage to fences. Urine and scent marking are special cases which causes corrosion to metal work.

In Singapore Zoo chainlink has largely fallen out of use due to the problem of corrosion. The gauge of the mesh wire, whether chainlink or welded mesh is the critical factor in humid tropical conditions. With all but the strongest animals--big cats, bears, great apes--this question of durability should be the deciding factor in specifying mesh. The choice of material is in the end governed by construction economics and whereas many of the earlier fences in Singapore Zoo were made from heavy gauge (around a quarter of an inch) chainlink, this type of mesh is no longer made locally.

Also, the use of stainless steel became restricted to only the most critical areas from the mid 1980s due to the rising value of the Japanese Yen. Thus, mild steel mesh (coupled with a good corrosion protection system) with a wide range of standard gauges and formats is the automatic choice at this time. This may not always be the case, but any change will be brought about by a re-evaluation based on the principles.

Aesthetic treatment. Fences may be concealed by the contours of the exhibit in relation to the sight lines or screened with plants. There are, however, circumstances where this is not possible nor entirely desirable: animals may also be hidden by the contours; space may not permit planting a thick enough screen; screening plants may offer an avenue of escape; and finally, the planted screen may simply delineate the area to which the animal is confined--a more agreeable fence.

Harrison[3] discusses the importance of colour in allowing mesh to blend with its surroundings. Black is better than green, even against vegetation. Much depends on the quality of light (see Chapter 2.13) and it obviously helps for fences to be overhung with plant growth. Even this is not always possible: in one old antelope exhibit in Singapore Zoo a secondary rail was placed a metre inside the fence line as the lesser of two evils to prevent the antelopes from eating the plants through the mesh. Now displaying nyalas and wildebeest, the rear fencing is (mostly) out of view behind a slope and a drain, making use of a borrowed view of the lake beyond (see figures 26 and 27).

Mesh can be played down in other ways. The maximum allowable spacing of vertical and horizontal mesh rods is used but, while one or other dimension may be a control, the combination of the two--the area--is also important. (It should be noted that escape is one thing but getting heads/horns stuck is another). Thus, within limits, there is some discretion on the proportions of the mesh aperture. Mesh with a greater vertical spacing is less visible than other formats. Polakowski cites evidence suggesting that this is because of the extra effort required to raise our eyes compared to moving them horizontally[4], making the horizontals appear wider spaced. Why verticals are less noticeable than horizontals is possibly due to the presence of natural verticals--grass, trees, etc.--in the field of view so that the artificial becomes confused with the natural.

The Cage

For many, the image of caged animals is still synonymous with zoos. Although compared to the total number of exhibits in Singapore Zoo cages are few, it cannot be denied that their continued use does nothing to dispel this association. The dilemma for most zoos is the choice between maintaining certain species in cages or not all; and since big cats are tremendously popular, it is a brave zoo that would do without them.

The rationale for keeping cats in cages in a so-called ‘open zoo’ is twofold. First, very dangerous animals such as big cats must be handled and displayed with extreme caution, not only for the public, but also for the keepers. Before opting to display any animal in any kind of open enclosure, the consequences of it escaping must be seriously considered. ‘Open’ does not have to involve the possibility of escape, for even these types of enclosures can be made increasingly secure until it is reasonably escape proof. The question is whether such measures for some species are worth it.

This leads to the second reason why cages are necessary for some animals: for some cats such as leopards and jaguars, the measures necessary to prevent escape given the danger level will compromise the view too greatly. The chances of escape from a cage amount to the risk of human error, and this is the only acceptable level of risk as it is controllable and not inherent. In the case of big cats, the trade off of viewability and safety is an equation that relates size, agility and intelligence to danger. The smaller the animal is relative to it's agility, intelligence and dangerousness, the less value there is in doing away with bars or mesh. For example, a jaguar moat would be at least as wide as that for a tiger, the largest of cats, which is commonly eight to ten metres wide. In the case of leopards, their cunning, agility and strength deny even the possibility[5].

Cages in Singapore Zoo have been the subject of considerable experiment to reconcile them with the zoo's ‘open zoo’ epithet. An assessment of how successful this has been with visitors is contained in the ‘Cat Country’ Case Study in this dissertation. Cages can be regarded as a special case of the visual problem of fences. Even with the use of glass for viewing, disguising cages to avoid the connotation of imprisonment is difficult but worth attempting. Many of the techniques used to disguise fences are applied to cages in Singapore Zoo, summarised specifically as follows:

• Irregular form - The original cages were modular, standardised, almost cubic spaces. The new cages are less regular and hence less ‘readable’ to viewers used to rectilinear buildings.

• Greater cage volume - Increased, in the case of the leopard cage, 8 times from around one hundred cubic metres. Size has to be balanced by visibility of the animals.
• Mesh set in water - Again, to avoid an artificial frame to the view. The mesh also disappears unexpectedly.
• Better cage furnishing and use of the whole volume - Most cats are arboreal and restriction to the ground plane is a handicap to them. Greater freedom of movement encourages activity and draws the visitor’s eye. New branches etc. are added at intervals to further stimulate activity.
• Mesh format - After security, visual impact determined horizontal and (greater) vertical spacing of mesh rods.
• Disruption of cage outline - Views are framed by plants so that structural supports are not in the area of focus.
• Visual integration - Similar plants, water, rocks, etc. appear inside and out.
• Natural landforms - A flat cage bottom is avoided. The eye follows the ground plane, especially if it is featureless, until it meets the rear of the cage.
• Matte-black mesh paint colour - This reduces the visual impact of the mesh and structural form.
• Moving water - When animals are resting, this adds interest to the setting,. It draws the eye and keeps attention focused within.

These measures are aimed, as Ingraham says, at the “dematerialisation of the cage”[6]. In Singapore the process has probably been taken about as far as it can go with the basic material of welded mesh. The use of glass has been alluded to, but it is worth mentioning that other mesh forms are capable of extending the possibilities. These include woven meshes and ‘piano’ or ‘harp’ wire. The latter is restricted to smaller cats and birds but is particularly transparent. Woven mesh, as distinct from chainlink, is usually used with tensile structural systems as it behaves like a skin. Its chief disadvantage for large mammals and primates is cost as stainless steel is usual and being a specialised material, manufacturing costs are high. A hybrid of tensile structure and rigid mesh is used by many zoos and is used in the ‘Night Safari’. This has the advantages of being cheaper and having fewer and less visible structural members.

Two Case Study exhibits in this dissertation, the Pygmy Hippo and Crocodile, include bird aviaries which consist of nylon netting stretched over tensile cable structures. These have the advantages of being easy to design, cheap, able to be fitted to almost any site and, with some care taken with sightlines, very transparent. This technique has also been used with flying fox, >Pteropus vampyrus natunae, in the ‘Night Safari’ (in a mixed bird and gharial display).

Concluding Remarks

The fence, the cage and the aviary are the only artificial structures in large enclosures that have necessarily to be contended with in a tropical setting like Singapore. While the ideal is always to conceal or prevent their being noticed, it is arguable that efforts aimed at more humane display conditions for animals, and to see that visitors appreciate this, will also reduce the impact of such reminders of captivity. If visitors see and understand that the animals are housed in acceptable conditions, they will be less likely to point to the enclosing membrane and be disturbed by it.

This does not give the designer a free hand to be heavy-handed or expressive with the built elements of enclosures. Once cages were an opportunity for playful wrought iron creations, or to dabble in exotic architectural ornamentation. Even the austerity of Modernism can draw parallels with beautiful display cases containing rare artifacts in a museum. Zoos need to show animals in the correct context and allow visitors to filter out that which does not belong.