Dallas Zoo tackles Giants of the Savanna and more

Imagine a herd of elephants trampling your turf and a group of giraffes stripping the leaves from your trees. Those are just a few of the daily challenges facing Cindy Wahkinney, horticulture manager for the Dallas Zoo. Founded in 1888, the Dallas Zoo now has 106 developed acres, and is the largest zoological park in Texas. Their mission is connecting people and wildlife, and that is met in their newest exhibit, Giants of the Savanna, which opened to the public on Memorial Day weekend 2010. It transformed 11 acres to an African adventure so realistic that visitors are immersed in what looks and feels like a safari. The habitat provides that same return to the wild experience for the animals.

Dallas Zoo Horticulture Manager Cindy Wahkinney shares a quiet moment with one of the giraffes in the Giants of the Savanna exhibit.
Photos courtesy of the Dallas Zoo, unless otherwise noted.
This view from inside the south habitat section of the Giants of the Savanna exhibit looks toward the public viewing area across the water from the giraffes.

Typical of zoo exhibits, three main elements are involved: the animal habitat, an exclusion area that serves as a buffer zone between the animals and human visitors, and public spaces.

For the Savanna, the habitat design process was extremely complex to meet the varying needs of the different animals. Each species requires space that provides the protection and stimuli of their native environment with opportunities for both interaction and seclusion. Wahkinney says, “The process involved developing multiple smaller habitats within the larger area. We wanted to mimic the Savanna look using plants that were adaptable to the Texas environment, including many native trees, shrubs and grasses. We’re very conscious of conserving water, so drought tolerance was a major issue, as was ease of long-term maintenance.”

Planning was a collaborative effort between zoo experts in all departments and outside specialists in wildlife research, animal behavior, and exhibit design and construction. Incorporating this with his own expertise, Rob Halpern of New York-based Zoo Horticulture Consulting and Design developed the actual design and specifications.

Because of their detailed daily tasks and other smaller projects, Wahkinney and her staff were not directly involved in the installation. That was handled by local contractors, with oversight by Halpern. The entire area became a construction zone, first with demolition of existing structures and paved areas and tilling of the compacted soil, then with work on the new buildings, roadways, hardscape features and habitat proceeding in tandem.

Within the 11 acres, 5,700 shrubs and ornamental grasses were planted, along with over 300 trees, ranging from honey locust, to mimic the African acacias, to cedar elm and live oak.

While those numbers reflect the size of the exhibit, specific details point out the complexity. Wahkinney says, “The design called for high and low areas to capture the rolling terrain of the larger habitats along with an expansive area of grasslands for grazing. To create that and provide an adequate base for plant growth while resisting compaction from the weight of the animals took nearly 19,000 cubic yards of soil mix consisting of small stones, topsoil and compost.”

Dallas Zoo Horticulture Manager Cindy Wahkinney, pictured at far right, and some of her staff work with the plants in one of the exclusion areas within the Giants of the Savanna exhibit.

When the earthwork was completed, the grazing area was seeded with 500 pounds of a warm-season grass seed mix combining nine species of native and turfgrasses. Wahkinney says, “The mix consisted of buffalo (Bouteloua), bermuda (Cynodon), blue gramma (Bouteloua gracilis) Hachita, weeping lovegrass (Eragrostis curvula), Willmans lovegrass (Eragrostis superb), switchgrass (Panicum virgatum) and Big Sacaton (Sporobolus wrightii). Some of these species are natural food sources that appeal to our grazing animals, while others were selected because they are not typically considered as palatable, and should be left uneaten, preventing total stripping of the turf, but the animals will do what they want to do. We can’t tell an elephant ‘you’re not supposed to eat that.’ So, none of the species will harm the animals if they do eat it. We’ll just have to adjust the mix to include a few less-tasty choices.” Overseeding with a cool-season grass, Endo-Free Kentucky 31 (Poa pratensis), from mid-September through the first of November will provide color and a grazing source during the winter season.

While the design of the exclusion areas ties into the look and feel of the habitat, much more is involved. “The setup varies for each segment of the zoo’s exhibits based on the animals and what potential danger they could pose to the public. In a few cases, visitors walk right up to a barrier that allows up-close viewing. A café within the Savanna exhibit features floor-to-ceiling windows adjacent to Predator Rock where lions lounge, sometimes watching the watchers. More frequently, that pattern is similar to the rhino area in a different exhibit where a barrier, in that case a concrete moat, is masked by a small landscaped buffer zone. The landscaped exclusion areas in most of the Savanna incorporate the plants used within the habitat, drawing visitors into the safari experience while protecting them. Sometimes, the exclusion areas also are designed so that zookeepers can be stationed within them to conduct interactive sessions with visitors. We did that within the Savanna,” Wahkinney says.

Initially, some of the public areas within the Savanna were planted with the same grass seed mix used within the habitat. Due to weather conditions within the short time between planting and the Memorial Day opening, buffalograss sod was later installed on the berms. “It’s a low-maintenance alternative that looks great and is performing well,” Wahkinney says.

Typical to most contracted plant installations, maintenance of the Savanna during grow-in was the contractor’s responsibility. The transition to staff maintenance is another challenge. Wahkinney says, “With hundreds of different microclimates across those 11 acres, we’ll be tracking our irrigation and management practices closely and making frequent adjustments. I communicate with Rob, as do those within our other departments, to make sure all is working as anticipated based on his expertise.”

Wahkinney’s staff includes a senior irrigation specialist, who is a Texas-licensed certified backflow inspector, and an irrigation assistant. They have been working closely with the contractor during the transition. With the combined focus of plant survival and water conservation, the Savanna irrigation system encompasses over 150 zones operated from three controllers: one serves the habitat, another the exclusion area, and the third the public landscape. Irrigation coordination within any area of the zoo is complex, as it must be adapted to animal presence within the habitats, personnel involved with animal care or facility maintenance, and visitors, as well as changeable weather conditions. Wahkinney says, “Our irrigation duo is excellent. They’ve been able to run zones in tandem and tighten run cycles to provide adequate coverage within the Savanna.”

The Dallas Zoo is open every day but Christmas, with summer hours 9 a.m. to 5 p.m. and winter closings at 4 p.m. Special events and rental functions fill many evening hours and the education department frequently holds overnight campouts. Working around that scheduling is another challenge for Wahkinney and her horticulture staff of four. So, with the addition of the Savanna, Wahkinney brought in an outside contractor for the first time this year, which handles the mowing, edging, seeding and fertilization of the turf areas within the north section of the zoo, along with maintenance of the north and south parking lots, the plaza areas at the entrance and two small turf areas inside the plaza. They also apply corn gluten as a preemergent to the inground color beds once a year. All other horticultural maintenance is handled in-house. The staff tackles the remainder of the mowing, seasonal color in beds and containers, shrub and hedge trimming, horticultural maintenance along the service roads and service areas, cleanup of leaves, fallen branches, etc., fertilization and pest control and assistance with special projects. Wahkinney says, “We just opened a new pavilion where we needed to design the landscape to include a turf area and a raised bed with ornamental plants and seasonal color, design the irrigation system to serve it, and do all the installation. With so much area, new projects pop up almost weekly.”

One staff member oversees the greenhouse (which is used primarily for cold weather storage for the tropical plants integrated in seasonal displays) and focuses on the color change-outs of in-ground beds and containers.

Wahkinney also oversees two members of the zoo’s environmental team. Part of their tasks include the chipping and windrow composting operations that convert the zoo’s green waste to useable mulch or compost. “These processes save us thousands of dollars each year,” Wahkinney says.

With the small staff and big workload, it’s not possible to keep all work out of the sight of zoo visitors. The staff starts at 7 a.m., concentrating on tasks requiring heavy equipment or projects that would be disruptive to the public before the zoo opens. Wahkinney says, “The safety of our visitors, the animals and our zoo personnel are primary concerns in everything we do.”

Suz Trusty is a partner in Trusty & Associates, a communications and market research firm in Council Bluffs, Iowa. She has been involved in the green industry for over 40 years.