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Brookfield Zoo

Brookfield Zoo opened the first inland dolphinarium in the United States in 1961. Today, with growing concern from animal rights groups and the general public, it is one of only two zoos in the country still exhibiting bottlenose dolphins. Conjour asks Senior Vice President of Animal Programs Bill Zeigler why the zoo keeps dolphins and how it looks after its star attractions.



Brookfield Zoo - Chicago Zoological Institute - Center for the Science of Animal Care and Welfare - Conjour Zoological Review - Dolphins - Zoology - Feature Image

Dolphins - Brookfield Zoo Report - Conjour Zoology

Opened: 1934 | Size: 216 acres | Attendance: 2,183,380 | Species: 520 | Animals: 2,609+

The views expressed in this article are those of the author, and not necessarily those of Conjour magazine.

Brookfield Zoo: Committed to Care

Situated in Chicago’s western suburbs, Brookfield Zoo is dedicated to giving every animal the best possible life. Bill Zeigler, Senior Vice President of Animal Programs, tells me welfare is their top priority.

“For animals under professional care, the need for welfare management becomes more important since we have a higher ethical and moral responsibility to provide environments and health care that are conducive to their physical and mental wellbeing.”

The zoo formalised this commitment in 2008, founding the Center for the Science of Animal Wellbeing. CSAW promotes animal welfare research and turns results into routine.

Take the vets. Overseen by CSAW, Veterinary Services operates the most sophisticated radiography lab of any zoo in the world. The CT scanner is big enough for a gorilla. Not only does it generate high-resolution images for scientists, full-body scans are now so quick they can be included in regular health-checks.

And CSAW does not benefit Brookfield alone. Zeigler tells me they organise conferences at the zoo to share ideas with others across the globe. Each time, well over 100 delegates make the trip to Chicago.

Everyone is invited to these symposiums, including institutional detractors.

Dolphins - Brookfield Zoo Report - Conjour Zoology

The purpose is to educate and identify needed research and new directions we should go in further improving animal welfare under professional care.

More important than ever, CSAW is now known as the Center for the Science of Animal Care and Welfare. According to Zeigler:

“The reason for the change is based on our holistic approach to welfare that incorporates not just behavior but health care, nutrition, husbandry, and research and how those areas need to support one another in any animal management program.

“One of my objectives over the last six years has been to break down silos within departments and bring about a unified team approach to creating management plans for a species.”

These efforts are paying off. Usually an outspoken critic of zoos and marine parks, the American Humane Association certified Brookfield ‘Humane’ last June.

Visitors are supportive, too. According to a recent study, animal welfare is the zoo-going publics’ overriding concern 1. Zeigler assures me they respond positively to Brookfield’s efforts.

And one species captures the imagination of visitors like no other.

Dolphins - Brookfield Zoo Report - Conjour Zoology

Dolphins at Brookfield Zoo

Bottlenose dolphins arrived at Brookfield Zoo in January 1961. Crowds surged into the nation’s first inland dolphinarium and all but three of the first 62 shows sold out. For their part, the dolphins performed flashy-splashy tricks in a circus-style spectacle.

From the 1970s, however, the tide began to change. New insights into dolphin intelligence jarred with a growing awareness they were caught in barbaric hunts and kept with little regard for animal welfare.

Shifting attitudes and plunging profits forced many dolphinaria to close.

Brookfield Zoo moved with the times. In 1987, it unveiled the state-of-the-art ‘Seven Seas’ facility, with a capacity of 2,000 seats and one million gallons of water.

But the more profound change was ethical. The zoo recognised its responsibility to animal welfare.

I believe dolphins can be kept in captivity. However you feel about the issue, though, it is hard not to be impressed by Brookfield’s ethos, effort, and achievements.

Today, it is one of only two zoos in the United States exhibiting dolphins. They are looked after by a dedicated team of ten full-time trainers. Whilst twice-daily shows remain the most popular event in the zoo, they now inform visitors about dolphin husbandry and highlight marine conservation issues.

This is because the dolphins are no longer kept solely to entertain.

Dolphins - Brookfield Zoo Report - Conjour Zoology

Why Does Brookfield Exhibit Dolphins?

According to Ziegler, Brookfield Zoo continues its dolphin program for two reasons.

First, education.

“Brookfield Zoo sees over 2.2 million guests a year, and while they are not near an ocean, the choices they make each day on things like the purchase of sustainable seafood and supporting legislation to reduce pollutants and define harvest methods of seafood can have a tremendous impact on the oceans.

“Through studies here at the zoo, we have found that we do impact our guests long term. We have also found that the capability to see and get close to dolphins has a much greater impact emotionally in helping us get the messaging out there than someone watching TV.”

Dolphins inspire wonder. I have visited marine parks in Europe, Asia, and the United States, and audiences are always spellbound. Brookfield Zoo goes even further. Its staff believe encountering dolphins has a ripple effect on the lives of visitors, moving them to protect wild populations and their ocean habitat.

As Baba Dioum famously wrote: “In the end we will conserve only what we love”.

Look beneath the surface, however, and published research lends little support to such optimism. Although visitors may leave with good intentions, there does not appear to be any evidence that zoos cause long-term lifestyle changes or sustained contributions to conservation2.

Zoo director-turned-critic David Hancocks stresses the point by asking an uncomfortable question: With over 700 million annual zoo visits, where is this exuberant army of converts?34

However, Zeigler argues wild dolphins also benefit directly from their cousins in Chicago.

“The work and research we do also aid in the longest ongoing study of wild dolphins in the world. The Sarasota Dolphin Research Program has been going on for over 43 years. Many of the things we are able to do with the dolphins under our care have provided the field researchers with valuable comparative tools when assessing the health and status of the wild dolphins.”

This is the second reason Brookfield Zoo keeps dolphins: research.

The zoo began supporting work in Sarasota Bay, Florida, in 1989. Now led by Brookfield’s Dr. Randall Wells, this study has collected data on everything from life histories to diving behaviour in hundreds of wild dolphins5. The most recent paper, on respiration and energy requirements, was published a few weeks ago6.

Not only does the zoo run the study, it also provides a controlled setting for complementary research. Unlike Sarasota Bay, the Seven Seas offers excellent underwater visibility and round-the-clock access to the same individuals.

This has been pivotal for research on acoustics, because captive dolphins can be trained to use the sensitive equipment in a stable environment. For example, one of Brookfield’s animals confirmed that dolphins hear through their lower jaws7. This helped scientists understand how they echolocate in the ocean.

And it is not just wild populations that benefit. The zoo also strives to improve care for its own animals.

Brookfield Zoo - Chicago Zoological Institute - Center for the Science of Animal Care and Welfare - Conjour Zoological Review - Dolphins - Zoology - Feature Image

How are the Dolphins Looked After?

Dolphins in captivity have similar lifespans89 and higher birthrates10 than their wild cousins. Zeigler tells me achieving this requires collaboration.

“What is very important to us is the holistic approach we take by incorporating all aspects of husbandry into the welfare equation, including nutrition, preventative health care, behavioural enrichment, and research.”

Nutrition, for instance. Dolphins need up to 33,000 calories per day, but captive animals often suffer from excessive iron levels11. To combat this, scientists at Brookfield compared iron content in wild prey to the fish their dolphins eat. They hope tweaking captive diets will improve welfare.

Or the zoo’s preventative health program. Keepers have taught the dolphins to perform a range of husbandry and medical procedures. Weight and blubber thickness are measured weekly; length and girth are recorded monthly. More comprehensive checkups are carried out every few months, including blood tests, faecal analysis, and ultrasounds. All this information means care staff catch problems early.12

Behavioural enrichment is another strength. The zoo recently created a standalone Enrichment Department for R&D on enrichment and enrichment devices. Training is fun, too. When they cooperate, the dolphins are rewarded with pats, rubs, and fish. They seem to enjoy shows as much as the visitors.13


What matters most

Research, though, is where Brookfield Zoo really excels. For the dolphins, that means learning from nature. Not only do field scientists benefit from Brookfield’s support and leadership, but findings on wild dolphins are applied back in Chicago.

Zeigler tells me how they fluctuate water temperatures in the Seven Seas and provide different fish depending on the season. A natural group composition is especially crucial.

“By studying the social aspects of the dolphins in Sarasota through multiple generations, we have been able to develop our management program of our dolphins. Essentially, it mimics what dolphins in the wild experience. This in turn has provided our dolphins with a very stable social environment that promotes good welfare. We presently have three generations of dolphins at Brookfield Zoo.”

But how does the zoo ensure all this actually benefits the animals?

Dolphins - Brookfield Zoo Report - Conjour Zoology

Does Good Care Translate into Great Welfare?

Remember CSAW, the Center for the Science of Animal Care and Welfare? The titular ‘care’ covers everything provided to an animal (food, water, training, etc.), whereas ‘welfare’ describes how it is actually doing.

Good care often leads to great welfare, but not always. In humans, for instance, wealthy individuals with loving families can still suffer from depression.

This means zoos cannot take an exclusively ‘resource-based’ approach to welfare assessment, focusing on the quality of care alone. They must also use ‘animal-based’ indicators, which measure welfare directly.

In recognition of this, Brookfield Zoo launched WelfareTrak® in 2013. This is a web application that tracks weekly keeper assessments of animals’ physical and psychological states. The system then ‘flags’ any potential shifts in welfare status, both good and bad.

Says Zeigler:

“WelfareTrak® has brought into focus the ability that animal care staff have in determining the welfare status of the animals they care for through collaborative and comparative surveys and dialogues that take place during the process. By using this tool, we have been able to validate those abilities in a measurable way while applying a systematic approach to measuring the welfare of individual animals.”

The dolphins were some of the first test subjects. Each week, keepers in the Seven Seas login to WelfareTrak® and complete a survey. Developed by a panel of experts, it includes 13 species-specific welfare indicators, such as appetite, skin condition, and playfulness. Any changes to the dolphins’ routine are also recorded. The survey only takes two minutes, but allows keepers to closely track the welfare of each animal.14

And it works. According to feedback, WelfareTrak® helps identify problems proactively and evaluate efforts to improve. Zeigler tells me it is used in zoos worldwide to monitor 20 species of mammals, birds, and reptiles.

“WelfareTrak® shows us our animal care staff are actually quite in tune with their animals, and as such, they have a good sense as to when animals are ‘happy’, just as a dog owner knows when his or her dog is happy. Being able to measure the level of happiness is critical to show the level of our welfare programs.”

But it does not end there. For such popular and well-studied animals, research on dolphin welfare is surprisingly scarce.15 Until now.

In 2018, Brookfield Zoo announced it is leading the largest ever study on captive whales and dolphins. Funded by a $740,000 grant from the Institute of Museum and Library Services, it will involve 300 marine mammals at 44 facilities in seven countries.16

The plan is to record activity patterns using video footage and devices called bio-loggers (imagine a dolphin Fitbit). Combined with other welfare indicators, such as stress hormones and social behaviour, this will give a good idea of how dolphins fare in different environments.

By quantifying welfare this way, the new study should bring about a sea-change in the industry. Best practice will be established scientifically for the first time. What conditions allow dolphins to thrive? Where can improvements be made?

You can expect answers by 2020.

Dolphins - Brookfield Zoo Report - Conjour Zoology

Bill Zeigler of Brookfield Zoo

The Future

Over the last 50 years, Brookfield Zoo has earned an unparalleled reputation for excellence in dolphin care and welfare. It now leads the longest-running study on wild dolphins and the largest study of captive ones.

But what about the next 50? I ask Zeigler whether Brookfield is swimming against the current and what the future holds for the zoo’s dolphin program.

“When our detractors try to infer that an animal is suffering psychologically simply because they are under our care, we have not amassed the amount of evidence… that we need.

“It is there and we are building up the science-based evidence for positive responses from our animals. Continuing to do so will be important to the future of the profession.”

This is what impresses me most: the insatiable desire to improve. No zoo is perfect, but the best always strive for better. Facilities across the world already ride the bow wave of Brookfield’s efforts.

I, for one, hope its dolphins inspire many more generations to come.


We would like to thank Bill Zeigler and the staff at Brookfield Zoo for this interview. All images courtesy of Brookfield Zoo.

1 Ballantyne, R., & Packer, J. (2016). Visitors’ Perceptions of the Conservation Education Role of Zoos and Aquariums: Implications for the Provision of Learning Experiences. Visitor Studies, 19(2), 193-210.
2 Marino, L., Lilienfeld, S. O., Malamud, R., Nobis, N., & Broglio, R. (2010). Do zoos and aquariums promote attitude change in visitors? A critical evaluation of the American zoo and aquarium study. Society & Animals, 18(2), 126-138.
3 Gusset, M., & Dick, G. (2011). The global reach of zoos and aquariums in visitor numbers and conservation expenditures. Zoo Biology, 30(5), 566-569.
4 Hancocks, David (2012). The Future of Zoos. Available here:
5 Wells, R. S. (2014). Social structure and life history of bottlenose dolphins near Sarasota Bay, Florida: insights from four decades and five generations. In Primates and Cetaceans (pp. 149-172). Springer Japan.
6 Fahlman, A., Brodsky, M., Wells, R., McHugh, K., Allen, J., Barleycorn, A., Sweeney, J. C., Fauquier, D., & Moore, M. (2018). Field energetics and lung function in wild bottlenose dolphins, Tursiops truncatus, in Sarasota Bay Florida. Royal Society Open Science, 5(1).
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8 DeMaster, D. P., & Drevenak, J. K. (1988). Survivorship patterns in three species of captive cetaceans. Marine Mammal Science, 4(4), 297-311.
9 Duffield, D. A., & Wells, R. S. (1990, November). A discussion on comparative data of wild and oceanarium Tursiops populations. In Proceedings of the 18th International Marine Animal Trainers Association Conference (pp. 28-39).
10 Wells, R. S. (2009). Learning from nature: bottlenose dolphin care and husbandry. Zoo Biology, 28(6), 635-651.
11 Slifka, K. A., Wells, R. S., Ardente, A. J., & Crissey, S. (2013). Comparative diet analysis of fish species commonly consumed by managed and free-ranging bottlenose dolphins (Tursiops truncatus). Internet J Vet Med, 10(1).
12 Miller, L. J., Wells, R. S., Stacey, R., Zeigler, F. W., Whitham, J. C., & Adkesson, M. Animal Welfare Management of Bottlenose Dolphins at the Chicago Zoological Society’s Brookfield Zoo. Markus Gusset1 & Gerald Dick2, 24, 14.
13 Miller, L. J., Mellen, J., Greer, T., & Kuczaj, S. A. (2011). The effects of education programmes on Atlantic bottlenose dolphin (Tursiops truncatus) behaviour. Animal Welfare, 20(2), 159-172.
14 Whitham, Jessica (2016). Monitoring the Welfare of Individual Animals. Available here:
15 Ugaz, C., Valdez, R. A., Romano, M. C., & Galindo, F. (2013). Behavior and salivary cortisol of captive dolphins (Tursiops truncatus) kept in open and closed facilities. Journal of Veterinary Behavior: Clinical Applications and Research, 8(4), 285-290.
16 Pine, Steve (2018). Chicago Zoological Society Takes Lead on Multi-Institutional Cetacean Study. Available here:

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