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

In 2012, in partnership with the Jane Goodall Institute, the Phoenix Zoo created a unique position to promote international animal welfare. Filled by Hilda Tresz, the Behavioral Enrichment and International Animal Welfare Coordinator role is responsible for developing and overseeing the Zoo’s Behavioral Enrichment program, but also extends beyond the Zoo through its international role of assisting zoos improve animal care across the world. This post is part of a series of stories that describe the significance and logistics of this position through Hilda’s travels across the globe.

In some zoos of foreign countries with limited knowledge and funding, animals are often found 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 have a variety of behavioral problems. To complicate matters further, when I visit one of these zoos, I typically have only one week to make improvements. In the remaining time, it is my responsibility to assess, negotiate and improvise to make immediate changes with limited available resources.

I 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; I 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 completely foreign by many visited institutions.


August 16 – 24, 2012

Edgar Chimpanzee Gets a New Family

Edgar was an approximately six-year-old female chimpanzee. She was confiscated from poachers by a family who tried to raise her best they could. They named her Edgar, not knowing she was a female. Once she became too dangerous to handle, she was given to the Dakar Zoo, where staff kept her separate from a pair of chimpanzees believing that if she were to be integrated, the male would kill her. She was raised by humans during her entire infancy, sitting alone in a cage. She only occasionally socialized with visitors and her keepers; therefore, she lacked most species-typical behaviors.

Female Edgar appr. 6 years old. Photo by  Hilda Tresz.
Female Sydney 12 years old and Kou (Kong) 18 years old. Photo by Hilda Tresz.
Female Sydney 12 years old and Kou (Kong) 18 years old. Photo by Hilda Tresz.

Our first meeting became one of the most memorable moments in my life. When I first saw Edgar, she was just sitting by herself. After spotting me, she reached out with both hands through the bars. Right then, I knew I would be able to walk up to her, and nothing bad would happen. She pulled me close, and hugged me for the longest time. It’s hard to describe what was in her mind without being anthropomorphic, but it seemed as she was craving love and attention, even if it came from a total stranger. That moment stayed with me for many years. The picture became my “signature picture.” I use it for my presentations, for my Facebook banner, in articles, everywhere to remind me what these infants go through once they are taken from their parents. Still, no matter how much love they get from humans, there is a much bigger need to be with their conspecifics. Chimpanzees cannot be kept alone!

Edgar held me for the longest time. Photo by: Liliana Pachero
Edgar held me for the longest time. Photo by: Liliana Pachero

The introduction took place the next day. All animals received plenty of food, browse and substrates. I never introduce animals on an empty stomach. A hungry animal is a frustrated animal, and frustration leads to anger and aggressiveness.

Above and below: All animals received plenty of food, browse and substrates. Photos by Hilda Tresz
Above and below: All animals received plenty of food, browse and substrates. Photos by Hilda Tresz

OLYMPUS DIGITAL CAMERAKong was separated from Sydney and locked inside the night house so he wouldn’t influence the behaviors by trying to support any of the females, making them braver and perhaps even starting a fight. Edgar initially was apprehensive of the adult female chimpanzee, but in less than two days they bonded. They ate, slept, played, groomed frequently and didn’t leave each other’s side for longer period of times. They became inseparable.

Edgar standing on her head while playing with Sydney. Photo by Hilda Tresz
Edgar standing on her head while playing with Sydney. Photo by Hilda Tresz

At that point, Kong was introduced. His introduction was even easier. He had great interest in Edgar and followed her everywhere, constantly prompting her to play. He was extremely gentle with her.

Edgar now had two surrogate parents, and a new family formed. She didn’t have to be alone anymore.

The family became inseparable Photo by Hilda Tresz
The family became inseparable Photo by Hilda Tresz

Another interesting note: I was told that prior to the introduction of Edgar, Kong and Sydney were mostly ignoring each other, sitting far from one another all day long and almost never interacting. That was also my impression during my short stay. Once they were separated (in order to do Edgar’s introduction to Sydney), interestingly, they constantly protested being away from each other. They tried to groom, play and comfort one another frequently though the mesh, and tried to open the door so they could reunite. After all three of them were put together, they were inseparable.

In July, 2015, I returned to Senegal to introduce their two male chimpanzees … but that’s another story. I found the chimpanzee family together, appearing in good condition and truly bonded. Indeed, I felt an immense sense of pride and happiness.

Hilda Tresz with Dr. Jane Goodall
Hilda Tresz with Dr. Jane Goodall

Born and raised in Budapest, Hungary, Hilda Treszbnow 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.


  1. Lenora Stewart
    Phoenix, Arizona
    August 23, 2016, 7:50 am

    Good work, Hilda! May God bless you for the work that
    you do.