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.


By Hilda Tresz,

Hi everyone,

Some of you may remember little Dora the chimpanzee who had a snare in her neck from poachers and could not be introduced to other chimpanzees after her operation.

If you have forgotten about this story, you can read the blog again here.

I took another trip to the Rostov Zoo from October 16 – 19, 2017, and now Dora lives in a small, but functioning group . The new goal was to introduce a young couple of juvenile chimpanzees (Dora and Haus) to an early adolescent male, Mikl. 

Mikl and Haus were kept together for years up until January 2016, when Haus was separated to be introduced to Dora. Dora was hand-raised and needed to be with another chimpanzee to learn species-specific behaviors.

Dora was 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 Mikl. The plan was to slowly introduce her to six-year-old juvenile, Haus, and then later the two of them to adolescent male, Mikl who was in solitary confinement for over a year due to his separation from Haus.

The introduction was successful. As soon as the door opened, Haus ran to Mikl and jumped into his lap. They greeted each other and played for a long time. Dora was more apprehensive but tried several times to join them by swinging above them on the ropes after watching. After a few hours, she walked over to Mikl, presented to him (showing perfect submissive behavior) and in return Mikl hugged her from behind. Playing and grooming ensued afterwards. 

In regards to other species, the Rostov Zoo made some significant progress since the last visit. The animals are now on substrate, and they have movable furniture (dynamic branches). Many of the small exhibits, including the feline enclosures were demolished, and the animals are now housed in much larger enclosures. As I mentioned in my first report, the new director Sergey Gorban and his new staff (especially the primate and carnivore sections under the leadership of Victoria Costenko and Nina Dudina) are very progressive. The polar bear now has a huge enclosure with temperature-controlled water that seems to have increased his swimming frequency.

I would like to thank the Rostov Zoo’s director and staff for inviting me to improve their animals’ welfare. I would also like to thank Dr. Mary Lewis for funding this trip and the Forgotten Animals Foundation establishing such a wonderful working relationship between the Jane Goodall Institute, the Phoenix Zoo and the Rostov Zoo.

Pleased stay tuned for the next trip about the Almaty Zoo in Kazakhstan. Coming soon!

– Hilda 


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.