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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 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.

Dehiwala Zoo, Sri Lanka Report

February 19 – 24, 2017


The purpose of the visit was to reintegrate a six-year-old infant orangutan with his parents after a four–year separation, follow up on the chimpanzee and elephant programs, and provide suggestions for improvements to the basic husbandry, enrichment, training and/or behavioral issues for all species in the collection.


Ufo 18-year-old adult

Aki 19-year-old adult

1.0 Sakifo six-year-old juvenile

Sakifo was separated from his parents at the infant stage (age 2) in hopes to induce breeding between the adult pair. He spent four years as an infant in a solitary confinement house in an adjacent exhibit with his parents.

Fig. 1 Photo by Hilda Tresz
Fig. 2 Photo by Hilda Tresz

After consulting with the Dehiwala Zoo management, it was decided that Sakifo needed to be reintroduced with his parents in order to provide a family environment – especially his mother from whom he could still learn normal social skills and species-appropriate behaviors since he was still in a juvenile stage.

The zoo had already introduced him to his mother without any help but asked for the consultant when it came to introducing him to the large adult male.

The introduction went well. Father and son were very affectionate towards each other, playing, hugging, examining each other’s body parts and hardly leaving each other’s sight. By the second day, all animals were released onto the exhibit so the visitors could enjoy the family as well. However, they wouldn’t leave their inside holding areas for a few days. I believe the night houses were very comfortable to the animals, being well lit, full of substrates and food, and away from the public – a great compliment to Dehiwala Zoo management.

Fig. 3 Photo by Shamal Samaranayake, Dehiwala Zoo

Enrichment suggestions

The Dehiwala Zoo has two extremely large, green exhibits for orangutans with fairly good, stable furniture but lacking flexible furniture.
Fig. 4 Photo by Anoma Priyadarshani, Dehiwala Zoo

Suggestions: Animals living in homogeneous enclosures with large, inflexible continuous supports exhibit different patterns of locomotion than those in more naturalistic and complex environments with smaller, interrupted, flexible supports. Flexible ladders, swings, ropes, barrels (hung) and other structures can be made of many materials. Wood, plastic and fiber have the advantage of not being thermo-conductive, which is helpful outdoors. Resting baskets or platforms should be installed to the highest parts of exhibits in order to elicit proper nest building behaviors.

All orangutans need more, and more complex types of enrichment considering their incredible cognitive skills such as puzzle feeders, paint or chalk, electronic devices, etc.

Fig. 5 Photo by Amy Dietz, Phoenix Zoo
Fig. 6 Photo by unknown, Phoenix Zoo

Fig. 7 Photo by Denise Wagner, Phoenix Zoo
Fig. 8 Photo by Jim Hughes


There were many primates held alone due to the loss of their mates or kept in solitary due to old age without any hope to get a mate for them in the near future. In order to follow United State Department of Agriculture (USDA) laws and Association of Zoos & Aquariums (AZA) guidelines, it was agreed to try introducing different species together to eliminate solitary confinement.

Due to lack of time, the consultant was only able to introduce the female sooty mangabey with the older female Hamadryas baboon.

Fig. 9 Photo by Hilda Tresz


Solitary primates need to be able to see, smell and touch other primates – even if it is a different species – until they are paired up with conspecifics.

The institution should try introducing the squirrel monkey with the capuchin monkey, the solitary ring-tailed lemur with the red–ruffed lemurs and the solitary male Hamadryas baboon with the young pair of baboons.


  1. African Bush Elephant

Name :- Joa

Age :- 26 yrs

Sex :- Male

  1. Asian Elephant

Name :- Bandula

Age :- 69 yrs

Sex :- Male

Elephant management consultation continued during the second visit as well. Simple foraging ideas such as rice scattered in hay, or basic puzzle feeders were given to the animals to decrease boredom and to increase foraging time.

Fig. 10 Photo by Hilda Tresz

Fig. 11 Photo by Hilda Tresz

Fig. 12 Photo by Hilda Tresz

Suggestions: Large (5-6 feet [1.5-1.8m]) pile of sand needs to be placed by each elephant to provide resting and skin care especially for the Asian male, Bandula, who is now 69-years-old and needs to be able to lie down comfortably.

Also, zoo management, as per their request, was put in touch with Heather Wright, Elephant Manager of the Phoenix Zoo, to discuss changing elephant management techniques.

Domesticated Hoofstock

Many animals (donkeys, horses, etc.) were kept in barren environments with no opportunities for the animals to interact with furnishings or enrichment. One horse and a donkey were kept in solitary confinement. They were later introduced to each other and are now doing well.

Fig. 13 Photo by Anoma Priyadarshani, Dehiwala Zoo      

I would like to thank the Dehiwala 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 establishing such a wonderful working relationship between the Jane Goodall Institute, the Phoenix Zoo and the Dehiwala Zoo.

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.