Hippos Underwater: A Conversation with Bill Dennler, Retired Director of the Toledo Zoo

During Bill Dennler’s twenty five years as Director of the Toledo Zoo, it evolved from a rundown, dysfunctional city zoo to a great zoo. It became the smallest market in the United States to have a zoo with over one million visitors a year. Dennler and his staff built transformational exhibits such a the Hippoquarium (the first filtrated hippo habitat with underwater viewing), Arctic Encounter and Africa while maintaining and upgrading the Zoo’s historic WPA buildings. He was very well-respected in the zoo field and considered a leader at an important crossroads for zoos. Here is his story.

@ Bill Dennler

Dennler was very much not a zoo fan growing up. “I did not care for zoos at all,” he recounted. “The zoos I saw were all small cages with iron bars and what we refer to in the field as postage stamp collections with no concern for breeding, conservation, education or anything zoos now stand for. I went to college and graduate school during the height of the Vietnam War and was getting an MBA at Indiana University. I was talking about how most zoos I had seen were pretty bad and someone said if you don’t like zoos why don’t you try to do something about it. I went to the Zoology Department and asked them to tell me about what jobs there are in zoos but they looked at me like I was from outer space. They said they’d never placed any graduates in zoos.”

@ Bill Dennler

“So I started writing letters to all the zoos I knew in the Midwest,” Dennler said. “Quite a few zoo directors invited me to visit them. I visited Louisville, Cincinnati, Brookfield, Lincoln Park, Indianapolis and Milwaukee. The only zoo that agreed to hire me was Cincinnati. I was told in a phone interview with the San Diego Zoo they’d give me a job as a zookeeper but when I flew out for another interview, they told me that somebody with two college degrees could not be a zookeeper - that was too much education. Most of the zoos in the U.S. those days were city or county run and the zookeeping profession was regarded as maybe a notch above garbage collecting. It was not a highly sought after position but I made up my mind that if I was going to learn about zoos, I had to start from the bottom (something I have never regretted) so I accepted the job at Cincinnati as a zookeeper. I worked in the Commissary, Bird House and Reptile House and filled in all over the zoo. After three years and no room for advancement, I was on the verge of leaving when Zoo Director, Ed Maruska, called me into his office and said there is a job for you in Toledo. The Zoo was looking for a Curator of Reptiles. That’s how I got to the Toledo Zoo and the rest is history.”

@ Toledo Zoo

The Toledo Zoo was grossly outdated and archaic when Bill Dennler arrived at the Zoo. “Toledo was a disaster,” he bluntly stated. “It was a city run zoo, 75 years old and literally crumbling. The city had not given the zoo much in resources. The grounds were bare of any landscaping (unlike Cincinnati’s) even though they had a Horticulture Department and Conservatory with greenhouses on the grounds. The reptile collection had not been curated as they had no professional staff who knew anything about reptiles. The Zoo was staffed by the City of Toledo’s Civil Service Department and the exam used was not set up with any zoo questions. I was the first out of towner hired at the Toledo Zoo and the first person they hired who knew how to care for reptiles and amphibians. So many of the animal exhibits had incorrect signage and the records were totally worthless.” However, Dennler was immediately struck by the architectural beauty of the Zoo’s buildings and their potential. “The original thirty acres are unique in the zoo world as it’s the only zoo I know of to have a Conservatory building with greenhouses, a 5,000 seat outdoor amphitheater, 500 seat indoor theater, Aquarium and Natural History Museum in addition to the typical animal exhibits all on grounds,” Dennler added.

@ Toledo Zoo

Immediately, he took it upon himself to make things better for the Zoo’s reptile collection and help the Zoo by implementing a unified signage system. This was critical to the Zoo becoming one of the first accredited zoos by the AAZPA. “We had to get rid of parasites in nearly every exhibit” he noted. “Very little was known about reptile medicine so I had to identify what an animal had and how to cure it. I was delighted to find out that Roger Conant, world renowned herpetologist and the author of The Reptiles of Ohio as well as the Peterson Field Guide Series on Reptiles and Amphibians of Eastern North America, was the first curator at the Toledo Zoo. At that point I contacted Roger and we became good friends until his death at 94. He was quite a mentor to me and also taught me a lot about the Zoo’s early history in the 20’s and 30’s when the WPA era buildings were constructed.”

@ Toledo Zoo

The Zoo’s future became uncertain when the Zoo’s Director retired in 1980. “Toledo was in an economic crisis and the city was laying off a lot of people,” Dennler recalled. “The Zoo was probably the last priority for the city and over the course of a year we saw our city employees drop from 63 to 15. You can’t run a 30 acre zoo with hundreds of animals with 15 people. They advertised the Director job and with my wife’s urging, I threw my hat in the ring thinking I never had a chance.” Surprisingly he was hired as Director but had a lot of work cut out for him. “The word on the street was the Toledo Zoo was doomed because the city wasn’t in a position to fund it,” he explained. “My predecessor put word out that if the Zoo closed, the animals were available for sale so I got all kinds of calls asking if they could buy this or this animal.. It was a real struggle the first year- we had hardly any staff left to care for the collection.”

@ Toledo Zoo

"All the office staff were gone," Dennler continued. "We had to close the Museum and the Conservatory and lay off all their staff. We were left with a handful of animal keepers and maintenance personnel. With the help of several volunteers that I had trained when I was Curator, I took care of the reptiles and was also the director. I honestly don’t know how we did it but the animal collection did not suffer. The grounds were another story!"

@ Toledo Zoo

To rebound, the Toledo Zoo needed help from outside. “We had one dynamic person on the Board of Directors named Tom Anderson, who was from the most philanthropic family in Toledo and was highly respected in the community,” Dennler remembered. “Tom and I sat down and tired to find a way to save the Zoo. We got a group of concerned people to study the Zoo and other zoos to find a better way to fund it. I said we couldn’t continue as a city zoo and needed to find a way to get a broader base of financial support. We became one of the first zoos to be operated by a nonprofit. Because of Tom Anderson’s stature in the region, people listened to him and he got a number of people and businesses to support us. Tom got each of the major companies to kick in $20,000 each, which was enough money to hire a couple more zookeepers and keep the place open.”

@ Toledo Zoo

Next the Toledo Zoo would find a revenue source in an operating tax levy. “We took a real gamble in 1982 by going to the county commissioners and putting a property tax levy on the ballot for operations,” Dennler noted. “My predecessor had succeeded in putting a capital levy passed in 1980 that generated a million and a half a year but we couldn’t use that money to hire staff or cover operations.” Fortunately, the operating levy was a success. “We passed the first operating levy on April Fools Day 1982 and we were able to hire another fifteen people,” Dennler stated. “We started to fix the place up.”

@ Toledo Zoo

One major problem that stood in the Zoo’s way during Dennler’s early years as Director was working with the union in Toledo. “We struck a deal with the city union, the most powerful entity in town, because they were upset so many of their people had been laid off,” he explained. “In 1978, Toledo became the only entire city to go on strike, including the police and fire departments and the Zoo employees. The city was in chaos and violence reigned. The Curators went over the fence to feed the animals and prevent them from starving. We were discovered in the daylight and were threatened if we didn’t leave the Zoo. When our union zookeepers heard what was happening, the union finally allowed us to feed the animals as long as the gates were closed to the public. Clearly we needed a different type of operation in the future. We struck a compromise with the city union and the Zoo’s union became a separate entity not controlled by the city. We went to work hiring people who were skilled at their jobs. Gone were the days when the guy who pumped gas at the city garage was suddenly a gorilla keeper.”

@ Toledo Zoo

The Zoo union led to an entirely new era for the Zoo staff. Now almost all of the staff members were new. “I hired a horticulturalist who was a real professional named Nancy Bucher and she and her staff are responsible for how the Zoo grounds look now,” Dennler noted. “I hired two new curators who had experience with the animals in their charge. In the Reptile House I hired all my former volunteers and all except one of them is still at the Zoo. One of them, Don Red Fox, became our lead elephant keeper for 25 years.” As the Zoo began to come together, Dennler began to think of ways to make its exhibits better for animals as well as visitors. The idea for the Hippoquarium was born.

@ Toledo Zoo

“The best viewing of hippos anywhere in the world was Mzima Springs in Africa [which includes an underwater viewing window],” Bill Dennler remarked. “Hippos in the wild spent most of their time underwater so no one knew how a hippo acts in the wild. All people could see of a hippo in a zoo were the ears, eyes and back.” The idea came to do a state-of-the-art filtrated hippo habitat that would let visitors see them underwater. “People told us we were crazy and that no one could filter hippo poop because of the large amount of particulate matter in their droppings” Dennler said. “We challenged top filtration people and they developed a very complex filtration system that employed ozone to kill off bacteria that cloud the water. This was the first one in the world.”

@ Toledo Zoo

“The old hippo exhibit was absolutely awful containing two big concrete pits inside and outside,” Dennler remembered. “they were dump and fill pools and all you saw was the back of the animal. When we moved the hippos, they would not come out of the water to eat for a week because they were afraid they’d have to go back to where they had lived all their lives. That’s how we knew it was going to be successful.” The exhibit led to the first videotaped hippo birth in the world. “I’m one of the few people in the world who has seen three hippos being born,” Dennler remarked. “I’ll always cherish that, seeing three baby hippos born underwater an then bob up to the surface for their first breaths. Most zoos felt in those days that when the mother was pregnant they’d have to separate her from the male to keep the baby safe but that never made sense to me since they were together in Africa. The interactions between our male and his baby were incredible and that was all happening underwater. The father would bounce the baby up and down as it hung on his bottom jaw! The baby would even ride around on Dad’s back as he swam through the pool. Incredible!!”

@ Toledo Zoo

In 1986, Hippoquarium opened and blew expectations out of the water. “ It’s still one of the most successful zoo exhibits ever and zoos everywhere have copied it,” Dennler noted. "Today I’m proud to say our model has been copied in major zoos throughout the world - San Diego, St.Louis, Disney’s Animal Kingdom; and Berlin, Germany to name a few."

@ Toledo Zoo

The Hippoquarium was followed up by the African Savanna (redone recently as Tembo Trail), which featured a wide variety of African animals including elephants, lions, white rhinoceros, giraffes, zebras, impalas, meerkats, Nile crocodiles, small clawed otters and and several African birds species. “We cranked out a lot of meerkats back then since a lot of zoos didn’t have them and they replaced the ever popular prairie dogs,” Dennler commented. “The African Savanna was the first exhibit where we had a terrific graphics presence. We had an African museum that talked about different cultures and how they interacted with wildlife.”

@ Toledo Zoo

However, it took awhile initially for the Hippoquarium and African Savanna to become noticed by the wider zoo community. “What really launched us was the panda loan in 1988,” Bill Dennler commented. “That brought in one million people in one hundred days. People came because they thought they’d never get a chance to see a panda if they didn’t come see them. Everyone who came to see the pandas saw the Hippoquarium and the African Savanna and was blown away by the new exhibits. That’s when our attendance started to go up.” However, the panda loan led to some controversy. “We were sued by the World Wildlife Fund since the panda was their logo,” Dennler explained. “We had agreed to partner with them to sell their merchandise but they sued us when the pandas were leaving China. That was a very dark period in my life - the WWF had denied were part of the original plans deciding they could get more members from the publicity if they sued us. They were suing us for doing a short-term loan but we had gotten a verbal commitment from China about keeping the pandas and hopefully, breeding them in the U.S. The Chinese were embarrassed by the publicity so they pulled all the panda loans. Also, San Diego, Bronx and Toronto already had done panda loans and no one criticized any of them. They had some pretty heavy hitters on the boards of those three zoos and I’m sure WWF was afraid to take on so they’d thought they’d make an example of Toledo.”

@ Toledo Zoo

Around this time, the Toledo Zoo began emptying all of its outdated animal exhibits. However, Dennler felt it was important to preserve the old WPA buildings and not tear them down. “I feel one of the things that’s special about the Toledo Zoo is it has the largest collection of WPA buildings on one site anywhere in the nation and we tell the story of how those buildings were built in the Great Depression,” he elaborated. “I saved those buildings because they are gems. All these skilled artisans, craftsmen, and architects who were out of work put their hearts and souls into the construction of these incredible structures. We repaired and replaced the gutters, roofs, plumbing and electrical systems, etc. to keep them around for future generations."

@ Toledo Zoo

In one particular case, Dennler turned an outdated 1920’s building into a restaurant. “I thought it would be fun if we turned the carnivore building into The Carnivore Cafe,” he remarked. “In that building, we had five species of big cats on one side of the building and gorillas, chimpanzees and orangutans on the other side. They were all on concrete 365 days a year in barred cages. To get rid of all the odors in the building, we hired a firm who does sterilization of hospitals to get all the bacteria out. Within three or four days you’d never have known there were ever animals in that building. It was a great revenue generator - groups and businesses would rent it and have dinner parties at night. It began our catering business. Eventually we had three full times chefs and were making a lot of money in after hour events.”

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The zoo also upgraded the homes of its apes. “In the 1970s, the only zoo that had the guts to put apes in a natural habitatswith soil, grass and shrubs and trees was the Woodland Park Zoo in Seattle,” Dennler explained. “When my predecessor built The Great Ape exhibit in 1978, it was not much different from the old lion house since they were still on concrete year-round. We took a lot of the garden area around the building and converted it into a gorilla habitat. We raised up the floor levels of the the old exhibits and added grass and enrichment furnishings, since the old outdoor spaces had people looking down on the apes. That’s not good psychologically for the animals and creates a bad impression for the visitors. We put nets over the enclosures and added trees for climbing. We built a big indoor room so we could rotate the animals in the winter and they wouldn’t be confined to their smaller holding areas indoors. I was proud of that too. The public started having more of an appreciation and respect for these animals.”

@ Toledo Zoo

@ Toledo Zoo

Another task Dennler took on was reopening and reimagining the zoo’s Conservatory and Natural History Museum. “I could never understand why we had greenhouses and a Conservatory but no landscaping around the Zoo at all,” he remarked. “I hired a real horticulturalist and staff and they turned the buildings around first. The greenhouses were all reglazed to be energy efficient and then they started beautifying the zoo with new trees, shrubs, grass,etc.The Museum, it was a hodgepodge of anything people wanted to donate to the City of Toledo. They had fire equipment, Eskimo art, a military section, a biplane, stamp collections,etc. Nothing fit. We even had a hall of mounted animal heads , which I thought was very inappropriate for a zoo. I took out all the fire stuff and donated it to a new museum in an old fire station.. I found Roger Conant’s collection of preserved specimens he used in writing his books in the basement, cleaned them up, and, with his blessing, sent it to the American Museum of Natural History in New York.”

Casey Cook @ Toledo Zoo

“ One of the things I saw in the Museum was this beautiful two-storied structure that would be perfect for seasonal exhibits without the expense of having to build permanent exhibits,” Dennler continued. “We were able to do a huge dinosaur exhibit and a number of exhibits that could tie in with the rest of the Zoo’s collection as well as have a permanent space for live insect exhibits.We even used it as indoor space for Christmas displays during the Lights Before Christmas. When we had the pandas, we turned it into a collection of photographs of Chinese people and rarely seen animals and exhibits highlighting some of the inventions developed first by the Chinese.”

@ Toledo Zoo

Other focuses of Bill Dennler during his tenure were building up the zoo’s education and conservation programs. “Nothing upset me more as a Curator than seeing school groups coming in and letting kids run loose,” he explained. “It was just a day off for the teachers and they were missing a great opportunity to teach. I talked to a few teachers about developing lesson plans before their visits. I hired a top notch education curator, Dave Jenkins, who had won an award with the MetaZoo in Louisville and we sat down with representatives of the ten school districts in our area. We said we need your help as we want to develop workbooks that could be used to teach math, science, english, etc before, during, and after their zoo visits. We need your teachers to help develop these books.We also added the Zoo Teen program and it has been a huge success. Now I don’t think there’s a zoo in the country that doesn’t have education programs like ours.”

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“When I became Director, I hired Peter Tolson, our first and only PhD in herpetology, to replace me ” Dennler recalled. He took my old job for a few years but eventually became our first Conservation Biologist. He had been studying snakes on the verge of extinction in the Caribbean. He successfully reintroduced a number of species on several uninhabited islands and worked extensively on our U.S.base in Guantanamo on Cuba. ”Tolson was responsible for setting up the Toledo Zoo’s conservation initiatives. “One program I didn’t see coming was Peter became aware of the plight of several butterfly species native to Ohio and said I’d like to do a greenhouse to breed these rare butterflies now extinct in Ohio,” Dennler said. “We had to plant the vegetation for these animal to feed on and raise the young for eventual release. This created a model for butterfly work in the entire U.S.. A lot of these little obscure species of butterfly have now come back.”

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Even the gift shop became completely transformed during Dennler’s leadership. “We had a gift shop that was really tacky with rubber animals and junk,” he said. “We had things that kids would throw into animal exhibits. We got rid of all that stuff and brought in educational things like books and games. We hired gift shop managers who brought in new merchandise like some really nice Christmas ornaments and exotic stuffed animals like Colobus monkeys, We improved the food service as well. Before we were basically selling circus food. By upgrading our food quality we not only brought in new sources of revenue but people appreciated it and started eating at the Zoo.”

@ Toledo Zoo

The Toledo Zoo would end up getting the National Exhibit award from the AZA for the renovation of its Aviary. “The reason we got the award for the birdhouse is we did something no one else thought we could do. Rather than raze the building with its tiny bird cages, we gutted the building’s interior space, saved the beautiful woodwork and carvings and made the public area the bird area,” Dennler elaborated. “We did netted mixed species flight exhibits, some of which visitors actually walk through with the birds flying around them in trees and plantings. The public walkways were where the old cages were. I thought it was kind of neat to highlight the fact Toledo is one of the most important parts of the United States for birders. Every spring people come from every state and even other countries to Toledo just to see the warbler migration, something most Toledoans weren’t even aware happens in the early Spring.” The Aviary is still regarded as one of the best in the nation today and does a brilliant job at staying true to its historic architecture and providing modern habitats for birds. A separate off exhibit breeding area has allowed the Zoo staff to breed dozens of rare species of birds.

@ Toledo Zoo

@ Toledo Zoo

One of the biggest accomplishments of Dennler’s career was almost doubling the footprint of the Zoo by buying up and developing land of the other side of a six lane highway that splits the Zoo. “It used to be the only way you could get to the Zoo from the old parking lot (now the Arctic Encounter and Africa exhibits) was to walk through a damp, and often wet, tunnel under the highway and then go up and down four flight of steps ,” he explained. .”The Zoo was completely inaccessible to people with disabilities and it was very difficult for parents with small children in strollers to navigate the steps.”

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The first exhibit built on the new land was Arctic Encounter, a fantastic facility for polar bears, Gray seals, harbor seals and Arctic wolves that opened in 2000. “The polar bears were one of the last animals on concrete and not in a very nice habitat,” Dennler recalled. “They had to go back into these dungeon like cages when off exhibit. All along during our renovations we had to make difficult decisions about which species we were going to create new habitats for. This is one of the reasons the Aquarium waited so long to be redone is we had to pick and choose. If we were going to do polar bears, we had to do it right.”

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“We did something I don’t know if anyone else had done at the time in that we built a freshwater stream going through the polar bear exhibit,” Dennler stated. “The pools in the bear and seal exhibits were salt water. The bears could drink out of this stream and we “injected” live trout into it at one end. We thought it was great that we could show the visitors how they catch fish and catching the fish would provide enrichment for the bears However,we had a male polar bear who was a cut above your average bear and found out if he did a belly flop in the stream, the fish would be flushed up onto the bank and he could pick up the fish at his leisure.” The Arctic Encounter also featured top notch interpretive graphics and an air-conditioned cave for Toledo’s hot summer. “It could be 95 degrees outside and the polar bears could be sleeping in a cool 65 degree cave.” A glass viewing window allows guests to see the bears lounging in the den. “Kids could climb up in there and get really close to them,” Dennler added.

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“We also built a large outdoor pit in the back of the exhibit where the bears could go off exhibit and dig in the dirt, which they loved,” Dennler continued. “The polar bears would turn brown from the dirt and become a white polar bear again when they jumped in the pool. We also built a middle section between the two exhibits where the seals could swim underneath and the polar bears could look down on them. We didn’t count on the fact that polar bears that were born in captivity would no idea what a wild bear does to hunt seals. They didn’t pay any attention to each other since they weren’t familiar to the” I’m the predator you’re the prey thing”. We hoped that would be further enrichment but the polar bears never bother to look through the glass.”

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Dennler’s last project at the Toledo Zoo was Africa, which opened in 2004. The centerpiece of the area is the five-acre savanna featuring giraffes, zebras, wildebeests, impalas, greater kudus, guinea fowl, vultures, cranes and now ostriches. What is unique about it is it can be best viewed by a train ride that goes around the outside of the exhibit. “We moved the old train from the other side of the Zoo where there was no animal viewing," Dennler remarked. "To add to the live animals we added fiberglass copies of smaller animals found in the savanna like monitor lizards, crocodiles, bats, birds and their nests, etc. The train narrator’s script was never the same as they’d talk about whatever the animals in the area were doing at the time. We even had a carcass of a lechwe up in the tree, which is exactly where a leopard in Africa would hide it. We took a fun ride and put an educational component to it. We also moved the wild dogs [since replaced by cheetahs] next to the savanna animals’ exhibit since we needed a bigger area for them.”

@ Toledo Zoo

@ Toledo Zoo

“One other idea that came from another zoo was The Lights Before Christmas which today accounts for 15 to 20% of the Zoo’s yearly attendance," Dennler said. "Winter was always a down time with little visitation in zoos in the northern part of the country. Remembering my childhood in the 50’s and 60’s I recalled how much everyone enjoyed putting up light displays on their houses. Obviously, others had fond memories too because now most zoos have followed suit and our staff has trained a lot of zoos around the country on putting up these displays.”

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In 2005, Bill Dennler retired from the Toledo Zoo leaving behind a transformed zoo and rich legacy. “I was very fortunate to be able to hire one of the best staffs in the country,” he stated. “I was a firm believer that the Zoo Director shouldn’t be the only front person for the zoo. Most of the time, I had the staff - Curators and Keepers - do the interviews with the media. We had a very successful TV show and I made sure I was never on it. As it turned out, everyone still knew who I was. I got to know just about every influential person in town. We were very successful in passing all of our operating and capital levies during my tenure and I’m very proud of that. Without the support of the people of Lucas County, we would have never been able to accomplish what we did.”

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“In the future,I think we’re going to have more effort from zoos in preventing many of the endangered species of the world from becoming extinct,” Dennler reflected. “For example, most people don’t realize how many turtles are critically endangered right now. I serve on the Board of the Turtle Survival Alliance which is committed to ending turtle extinctions. I see zoos working with countries no matter what species you’re talking about and finding ways for the conservation of animals in their habitat to pay off for the people that live there too. Conservation works best if people can also benefit from saving the species around them. Education to me should be our number one priority and our justification for keeping animals in captivity. If we don’t educate today’s children , it’s not going to happen. One of my earliest successes at the Zoo was implementing a no feeding policy. We sponsored a poster contest with all the schools on why it’s bad to feed animals at the Zoo and had over 4,000 entries. As a result it was the children who educated their parents.”

@ Toledo Zoo

“I was fortunate to be part of a group of zoo professionals that made much needed changes in how zoos operated,” Bill Dennler concluded. “We’ve come a long way from the old barred cages but we still have a ways to go. Apart from what we were able to accomplish in Toledo in terms of education, research, and conservation of many species, I also want to be known as someone who saw these beautiful buildings and preserved them. Hopefully, future generations of visitors to the Zoo will appreciate the pride and craftmanship that went into creating the WPA era structures and realize that even during one of the darkest periods in our country’s history, something positive came from it."

@ Bill Dennler

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