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A week to Change: Phoenix Zoo and Jane Goodall Institute Join Forces to Improve Animal Welfare Around the World

BACKGROUND: In 2012, in partnership with The Jane Goodall Institute, the Phoenix Zoo created a unique position to promote international animal welfare. Hilda Tresz, the Behavioral Enrichment and International Animal Welfare Coordinator, is responsible for developing and overseeing the Zoo’s Behavioral Enrichment program, but also extends her work beyond the Zoo through an international role of...

BACKGROUND: In 2012, in partnership with The Jane Goodall Institute, the Phoenix Zoo created a unique position to promote international animal welfare. Hilda Tresz, the Behavioral Enrichment and International Animal Welfare Coordinator, is responsible for developing and overseeing the Zoo’s Behavioral Enrichment program, but also extends her work beyond the Zoo through an international role of helping zoos improve animal care. The following stories will describe the significance and logistics of this position through Hilda’s travels across the globe.

In some foreign zoos with limited knowledge and funding, animals are often housed alone in sterile environments, on bare concrete floors and with no “furniture” (climbing structures, resting platforms, visual barriers and the like). Many times they are malnourished, injured and/or have a variety of behavioral problems. To complicate matters further, when she visits one of these zoos, she typically have only one week to make improvements. In the remaining time, it is her responsibility to assess, negotiate and improvise to make immediate changes with limited available resources.

She must quickly determine how to effectively implement all necessary changes. Every zoo and every country is different when it comes to available resources. Initial doubts and fears of proposed changes by zoo staff are often evident; she must develop a working relationship with unfamiliar people in an unfamiliar setting. Suggestions that would seem to be common practices for those working in an Association of Zoos and Aquariums (AZA) facility in the United States are viewed as novel recommendations by many visited institutions.


August 16 – 24, 2012

From “baboons to warthogs” and back to chimpanzees again!

The first part of the article was about an approximately six-year-old female chimpanzee (Edgar) who was confiscated from poachers, raised by a family who gave her to the Dakar Zoo once she became dangerous where she was successfully introduced to a pair of chimpanzees as surrogate parents.

However, during these visits, much needs to be done besides chimpanzee introductions. While the chimpanzees are “howdied” (meaning, they are next to each other but separated by mesh or bars to provide semi- contact), there is time to walk around the zoo and address other issues impacting other species from butterflies to elephants. I mainly focus on enrichment, training, animal behavioral issues and basic husbandry, and when I do not know the answer, I make sure to put the zoo management in touch with other specialists at the Phoenix Zoo or with other experts from the world.

The top priority is examining proper social enrichment for all social species. There were many animals housed alone such as Guinea baboons (Papio papio), patas monkeys (Erythrocebus patas)vervet monkeys (Chlorocebus pygerythrus) and an infant warthog (Phacochoerus africanus), eliciting a prompt response on my part. Because the zoo did not have enough animals to fill exhibits and the Ministry did not permit empty enclosures, animals were scattered to fill the exhibits. As shown in Fig. 1, animals such as Guinea baboons, when chance given, tried to physically contact one another despite being separated.

unnamed-1Fig. 1   Guinea baboon trying to touch each other
unnamedFig. 2   Male patas monkey housed alone

Photos by Hilda Tresz

Once all animals that needed to be introduced were identified, logistics had to be worked out; e.g., how will animals be transferred? Is veterinary assistance available? Will animals need to be sedated or manually restrained for transfer? What kind of doors will we be working with (solid or with bars and mesh)? How will the introduction proceed if the animals have no chance to be “howdied”? What can be done if injuries occur? Transporting animals is time consuming and while the zoo management begins those transports, I am afforded  a chance to address structural and substrate enrichment, three dimensional space use, available edible plants (browse) and many more issues.

First things first!

Getting animals off the concrete is another important task. With the help of a fantastic volunteer team from Peace Corp., all animals received some type of substrate. Most of the times materials could not be placed directly inside, therefore they were put in front of the cages and the animals clawed them inside, which kept the animals even busier

unnamedFig. 3 Hyena receiving hay                                        unnamed-1Fig. 4 Patas monkey with hay


unnamedFig. 5 Guinea baboon playing with sand             unnamedFig. 6 Liliana Pachero supplying hay to vervet monkeys

unnamedFig. 7 Paula Diéguez and Silvia Casas picked grass to feed all primates

unnamed-1Fig. 8. Zoo staff and volunteers gathering fresh browse for feeding

Filling enclosures with substrates and browse is an ongoing program lasting for days. It is rewarding to observe the animals looking through the dense litter, foraging to find their general diet, insects, seeds, etc. and interacting with the new materials they have never seen before (e.g., “playing” with it, playing in them and foraging on large leafy branches). One of the most memorable moments is of a young male Guinea baboon receiving sand for the first time in his life. It was extremely rewarding both for the animal and for people.


Once addition of substrate to enclosures has begun, I then circle back to the status of the primate introductions. All primates were immobilized and introduced to one another and the zoo agreed to break the walls between cages for shifting doors to increase areas.

unnamed-3Fig. 9 Patas monkey immobilized for introduction  unnamed-1Fig. 10  Hilda Tresz overseeing patas monkey transfer form one cage to another

unnamed-2Fig. 10 Vervet monkey grooming after introduction

unnamed-3 Fig. 11 Paired up Guine baboons

Common Warthog (Phacochoerus africanus) piglet

There was a suckling warthog piglet of unknown age in an empty enclosure by itself. He was overheated due to poor housing and was fed dry bread and water. The animal also had some skin problems. Milk powder was purchased and the piglet was fed immediately. Additionally, a much larger enclosure was found in fairly good shape. The enclosure was originally for birds and required some serious mesh repair, but after these modifications and adding plenty of soil, browse, barks, logs, hay and a wallow, it was perfect for the tiny piglet. Separate dishes were added for water and milk.

unnamedFig. 12 Patrick fixing an old but good enclosure for the infant warthog

unnamed-1Fig. 14 New baby warthog cage with substrate and furniture

unnamed-2Fig.15 Happy warthog piglet in the new enclosure

unnamed-3Fig.16   After several feedings of fresh milk the piglet was up and looking healthier Photo by: unknown


Hyenas (and other carnivores) received substrate and keepers were shown to feed hooves and skulls as enrichment.

unnamedFig. 17 Hyena receiving bones in the Dakar Zoo

unnamed-1Fig. 18 The ” A “Team of Peace Corp Volunteers  Photo by: Unknown

Left to right: Paula Diéguez, Hilda Tresz, Ashleigh Baker, Silvia Casas, Liliana Pacheco, Patrick Hair 

Second chimpanzee introduction

July 22 – July 28, 2015

Three years later, I was invited back to introduce two individually-housed male chimpanzees (Pan troglodytes verus) to one another. Tali (29 years old) and Movuli (22 years old) were hand raised by a keeper and kept in solitary confinement their entire lives because of a misconception that they would kill each other if introduced.

unnamedFig. 19 Tali and Movuli lived more than two decades next to each other, yet never had seen one another

The two enclosures had no doors or windows between them. Therefore, the chimpanzees could only hear or smell each other. After creating a door between the two enclosures and assessing some safety measures, we proceeded with the introduction. The door was bent a little and hard to move. In some places of the exhibit there were larger gaps under the fence, but they did not pose a serious threat and could be fixed later.

unnamedFig. 20 The door was bent a little and was hard to move

unnamed-1Fig. 21 There were larger gaps under the fence

The introduction went well and the animals were immediately engaged in play behaviors with each other. I was told; the keeper cried because of happiness. Later he told me this was one of the happiest days in his life. All I could think of was that it was certainly one of the happiest days for me too!


unnamedFig. 22 Tali and Movuli became instant friendsz

unnamed-1Fig 23. Movuli (left) laughing while Tali is initiating play

There is much to be done and so our work continues. I just returned from the Dehiwala Zoo of Sri Lanka. Look for an upcoming story highlighting this trip too!

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Meet the Author

Hilda Tresz
Born and raised in Budapest, Hungary, Hilda Tresz now resides in Mesa, Arizona, where she has lived since 1989. After graduating high school, she began working as a zookeeper and has been working with animals ever since as a caregiver, enrichment specialist, trainer, educator and behavioral manager, focusing on chimpanzees and general behavioral management for all species for over 28 years. She holds a triple-major degree in Biology, Geography and Education.Hilda Tresz changes the lives of animals, the people that work with them, and institutions that house them. She is currently the Behavioral Enrichment and International Animal Welfare Coordinator at the Phoenix Zoo; as well a mentor for the Jane Goodall Institute. She has worked with numerous international zoos (in India, Israel, Qatar, Egypt, UAE, Mexico, Paraguay, Argentina, Chile, China, and other countries) to enhance the psychological wellbeing of chimpanzees and other species. Many international institutions in developing countries have become overwhelmed with the financial and physical demands that are required to care for these animals; too often, many of these animals are left in barren, isolated situations with meager subsidies. Hilda finds solutions by collaborating with these institutions, and their staff to create productive, healthy, mentally stimulating conditions for their animals with little to no funding. She utilizes past experiences to educate her temporary teammates about animal diet and natural behavior to enhance their understanding and encourage ongoing improvement of their husbandry techniques. Because of her passion to leave no chimp isolated, no elephant chained, or no tiger malnourished, she embraces those who may not know and teaches them that they are the voices for those who cannot speak, the guardians for those who cannot step away, and the saviors for those who cannot save themselves.