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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 the first of a series of stories that will 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.


January 22-28, 2016

Photo by Chloe Rossman
Photo by Chloe Rossman

Doroty (Dora) chimpanzee

Five-year-old female chimpanzee, Doroty, was living by herself at the Rostov Zoo. She was separated from the other chimpanzees because she appeared to be stunted in her growth. She looked like she was approximately two-years-old, didn’t appear to use her legs very well and had limited social skills. Consequently, staff was concerned about her not being able to protect herself from her brother. Doroty was loaned to the Rostov Zoo. She was hand-reared by the primate manager and her family in a cage modified to be a nursery inside the chimpanzee building.


Figure 2 Photo by Polina Aksenova
Photo by Polina Aksenova


Although her caregivers loved her very much, and she seemed to be in good spirits, it was imperative that she be with her own species. Chimpanzees, especially infants, should not live in solitary confinement. In fact, until they reach about eight years of age, they learn survival skills and social behaviors from their mothers and group members. Just as humans, keeping them isolated takes a toll on their mental and physical health. The Rostov Zoo management was concerned about her development and decided to seek consultation about the possibilities of introducing her to other chimpanzees.

Haus, a six-year-old male, was the best choice with which to pair her. He was hand-reared, friendly and similar in age.

However, the introduction couldn’t procced because Doroty had a piece of wire in her neck (under her skin) – a possible remnant from a snare or capturing/restraining device of the poachers. Indeed, it was necessary to remove the wire prior to any introductions to avoid probable injury in the future.

Every morning on the visit, Haus was separated from his cage mate (an early adolescent male Mikl) and walked by hand next to Doroty. He spent 30-40 minutes per day “greeting” Doroty, and then put back with Mikl in the afternoon. Haus could approach Doroty through a small tunnel and she could climb up and meet him sitting on a metal bench. Staff needed to stay with the infants at all times to monitor the two chimpanzees.


Photo by Victoria Kostenko
Photo by Victoria Kostenko
Photo by Chloe Rossman
Photo by Chloe Rossman                                                           

Since the tunnel that connected the two cages was about five feet high (1.5m), Doroty was forced to use her limbs extensively. By the second day, she was clearly holding the bars with her feet and was able to thrust her body upwards.

In April 2016, Dora was operated on, and the wire was removed from her neck. With summer approaching, she was frequently let outside to a much larger enclosure that also encouraged her to climb and use her legs.

The Rostov Zoo with the supervision of the Primate Manager, Victoria Kostenko, has already started to integrate Doroty into a group so she can live a happy and healthy life as a chimpanzee. Dora is now together with Haus in full contact. The next step will be introducing both infants to their new surrogate parents.

Photo by Victoria Kostenko
Photo by Victoria Kostenko
Hilda Tresz with Dr. Jane Goodall
Hilda Tresz with Dr. Jane Goodall

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.


  1. Laura Healy
    Los Angeles
    August 18, 2016, 12:38 am

    Please help me learn the status of Rostov Zoo chimpanzee brothers Kumi and Joma. They were hand-reared at London Zoo, where I visited them. This inspired me to arrange several London lectures for Dr. Jane Goodall in the 1990s.

  2. Laura Healy
    Los Angeles
    August 18, 2016, 12:31 am

    I helped Dr. Jane Goodall arrange several of her London fundraising lectures back in the 1990s and was close to two hand-reared chimpanzee brothers at London Zoo, Kumi and Joma. They were sent to Rostov Zoo in 1997 and I would love to know how their lives are. Thank you for the good work you do!

  3. Laura Healy
    Los Angeles
    August 18, 2016, 12:28 am

    I am eager to learn about Kumi and Joma at Rostov Zoo — they were born in London and hand-reared before being moved to Whipsnade Zoo, and later, in 1997, moved to Rostov Zoo. I was thrilled to read this story. My husband and I helped the Jane Goodall Institute in the UK by helping arrange several of Dr. Jane’s London fundraising lectures at the London Marriott Hotel Grosvenor Square. I would love to know how my old friends have fared at Rostov Zoo.

  4. Laura Healy
    August 18, 2016, 12:21 am

    I saw this story because I was searching for two chimps, Kumi and Joma, who were hand-reared at London Zoo and re-located to Rostov Zoo in 1997. I would like to contact Hilda to find out about them. I worked on some London fundraisers for Dr. Jane Goodall in the 90s. Cheers, and keep up the good work! Happy to read about Doroty and Haus.

  5. Laura Love Wymore
    August 8, 2016, 2:00 pm

    Dearest Hilda, you are, as always, such an inspiration. I love the work you have done for so many animals around the world. I miss having our conversations while I worked for the Zoo. Congratulations, on continued victories in your position with the Jane Good all Institute!

  6. Laura Love Wymore
    August 8, 2016, 1:47 pm

    Dear Hilda, you are such an inspiration. I love the work you do for animals in our care. Great job, My friend. And I miss seeing you daily at the Phoenix Zoo.

  7. Sue Thurman "Safari Sue"
    Cave Creek, AZ
    August 8, 2016, 11:08 am

    Hilda, So nice to learn you are continuing your great work, now on an international level. All the best.