The science behind well-being

How endocrine research guides animal care

Past a gate marked staff only, up two flights of stairs and through a maze of small offices is an area many Oregon Zoo employees don't know about, never mind zoo visitors. Here, at the zoo's wildlife endocrinology lab, a small group of researchers and grad students is attempting to answer a question at the heart of the zoo's mission: How do we know whether an animal is living its best life?

The lab - one of about a dozen such facilities at AZA-accredited facilities across the U.S. - is part of a growing movement as zoos and aquariums refine the tools and measures needed to assess animal wellbeing.

"Animals can't tell us what they're feeling," said Dr. Nadja Wielebnowski, the zoo's animal welfare and research director. "But they do communicate their needs in other ways. Our research team monitors a variety of indicators that, collectively, can show us what an animal is experiencing."

Hormones are chemical messengers in the bloodstream and tissues that trigger a wide variety of bodily processes. Some, such as glucocorticoids - aka "stress hormones" - can provide insight into an animal's psychological state. Tracking glucocorticoid levels over time and under varied circumstances helps reveal how an animal is responding to its surroundings and activities.

And stress, Wielebnowski is quick to note, is not inherently bad.

"Stimulating and challenging activities - like meeting another animal for the first time or interacting with a new enrichment item - can be stressful in a good way," she said. "To understand whether stressors are positive or negative, we need to interpret our data carefully and use multiple measures. We combine hormone data with physical health assessments, notes from animal keepers and behavioral observations."

The hormone data can provide animal-care staff with a more well-rounded understanding of each animal's physical and mental wellbeing.

"If a keeper notices a behavior that's out of the ordinary and it coincides with a jump in hormone levels, our care team can catch issues sooner," she explains. "This is key because many animals have evolved to hide when they are sick or hurt."

Much of the hormonal data comes through fecal samples, which are easy to collect and reflect an animal's state of being over an entire day rather than a single moment in time. This method is also non-invasive - meaning scientists can measure stress without causing stress in doing so.

"We're able to collect all kinds of information without the animals even knowing," says Dr. Laurel Westcott, an animal welfare monitoring specialist. "They just plop a sample down and walk away."

It helps to have a sense of humor about the work, Westcott says, and the team doesn't shy away from scatological jokes. Poop-emoji plushies and magnets fill the work area alongside lab coats, rubber gloves, pipettes and centrifuges.

"I've been referred to as a 'poopologist,' and that's not completely wrong," she laughs. "Studying fecal samples accounts for about 90% of my job. We have fun with it, but we're serious about the science, and the work is important."

And fecal samples are a great source of information.

"It's like a gold mine for us," Wielebnowski says. "Wildlife biologists might be lucky to collect a single fecal sample from an animal they're trying to study, whereas we literally get hundreds of them - often from animals it would be difficult or impossible to approach in the wild."

Amur tigers, for example - the largest of the nine tiger subspecies. With only around 500 of these critically endangered cats remaining in the wild, one threat to their survival is lack of genetic variation, and AZA-accredited zoos are helping. Though the Oregon Zoo lacks the denning space needed for tigers to raise cubs, it plays a critical role by housing tigers not currently recommended for breeding - like Dmitri and Luka.

At 4 years old, these young males are starting to reach sexual maturity, and the lab is monitoring their testosterone levels to assess when they might be ready for mates or other social opportunities.

"Each animal has a unique history and set of life experiences," Wielebnowski said. "We can establish the basic standards of care for every animal, but we still need to adapt the setting and daily routine to the needs of each animal. Regular hormone and behavior monitoring can help us establish some of these needs."

The team places a high priority on measuring hormones during significant life events, such as a pregnancy, an introduction to a new mate, a move to a different habitat, or construction work taking place nearby.

"We want to know how animals react and adapt to these events," Wielebnowski says. "And we want to measure their resilience."

She cited the example of cheetah brothers Strike and Ranger. As the pair reached the median life expectancy for their species, the lab watched their hormone levels closely. When Ranger died, keepers were concerned about how Strike would respond. Hormone analysis confirmed a big jump in his stress response immediately afterward, but it did not last long. Keepers gave the surviving cheetah lots of extra attention and the stress response lessened as he adapted to his new circumstances.

Sometimes the results are unexpected. Several years ago, red panda Mei Mei and her cub, Pabu, were scheduled to move to another zoo while the father, Moshu, was to remain in Portland. Concerned about how Moshu would respond to their departure, the team measured his stress hormones pre-move to establish a baseline level. After the move, though, they were surprised to find his actual baseline was lower. From this, care staff concluded Moshu might prefer living by himself.

Beyond the wellbeing of zoo residents, data from the lab has applications for wildlife - especially when it comes to supporting species recovery efforts.

"There's a lot to learn from animals living in zoos," Wielebnowski says. "Reproduction research and monitoring like this help to illustrate the important role that zoos can play in learning how to maintain a sustainable population."