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. The social environment, as well, is highly structured and ever-changing. Exhibiting animals in large 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 activity levels 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).

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 of flight 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).

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 on either 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.

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 of being 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 an essence 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 by visitors and animals will be influenced by visual illusions and psychology.

Fig. 6: Apenheul Primate Park, Apeldoorn, The Netherlands
© Carlyn Worstell, 2003

Fig. 7: Two separate enclosures for sloth bears appear to be one, due to clever use of a moat and vegetation. Hannover Zoo, Germany
© Carlyn Worstell, 2003

Fig. 8: Foreground features help the gorillas at Zoo Atlanta feel less-threatened by groups of visitors.
© Jon Coe, 1988

Fig. 9a: The gorilla space at Burgers Zoo appears to be endless. Arnhem, Netherlands
© Carlyn Worstell, 2003

Fig. 9b: Due to lush vegetation, the barrier of Hannover Zoo's gorilla exhibit is not visible. Hannover, Germany
© Carlyn Worstell, 2003