Posted by Elizabeth Bacher, Communications, with contributions from Al Kennedy and Chad Harmon, Rhino Keepers at the Woodland Park Zoo
“If you’ve visited our Assam Rhino Reserve recently, you might have noticed something new about Taj and Glenn’s habitat. The ground these 2-ton greater one-horned rhinos walk (and run, and play) on looks a little different than before. But the biggest change is actually beneath the surface. It took more than a year to complete and it has totally transformed the way we care for these amazing animals!
The word “substrate” refers to the kind of substance that covers the ground or surface where an animal lives—sort of like flooring. In short, Taj and Glenn have a new “floor” in their habitat. The process to plan and install it was a huge undertaking and the benefits it offers for our rhinos and for their well-being are equally huge.
The greater one-horned rhino is native to parts of Northern India, Bhutan and Nepal where swampy forests, grasslands and riverine floodplains predominate the landscape. The climate in their home range is humid and very wet—even by Seattle standards—sometimes getting around 100 inches of rainfall per year. Compare that with our average of 40 inches of rainfall per year!
This is where the new substrate—and a HUGE construction project led by many talented people from throughout our zoo—comes into play. Our challenge was to add 2 feet of just the right kind of wood chips to as much of the rhino habitat as possible—both inside and outside. This kind of “flooring” would allow their feet to sink into the chips as they walk so that their weight could be distributed onto their toes rather than their hoof pads—just the way that nature designed them to walk. This would allow us to mimic, as closely as possible, the “feel” of swampy forests, flood plains and soft ground that these rhinos naturally live in.
We wanted to provide wood chips that would not only be able to support the weight of our “big boys” but would also be easy to source and safe for them to ingest when they inevitably sampled a mouth full of fresh cut chips. After reaching out to multiple mills, our amazing rhino keepers were able to find the perfect kind of chips—made from maple and alder—from a small mill in northwest Oregon. The rhino habitat has many connected yards and an indoor barn, and we knew the process of “redoing the floors” for the entire rhino exhibit would take up to a year with a detailed construction schedule that included lots of planning, permitting, tilling, removing and compacting soil to make room for 1,100 cubic yards of wood chips! For context that’s the equivalent of 11 large truck loads or 55 large dumpsters full of chips! In other words, the “to-do” list was long and most of it could only be done with heavy machinery operated by a very dedicated outside contractor—AND with “heavy lifting” from the many outstanding people who make up our Animal Care, Exhibits, Projects, Maintenance and Horticulture teams!
At first, our rhino keepers wondered how the rhinos would react to this busy project that was changing their yards and their routines. But rather than moving away from the commotion—which they could choose to do at any time—Taj and Glenn proved to be incredibly resilient! They were very curious and seemed quite interested to watch all the construction unfold. Soon the keepers were adding new tasks to their daily routine, including playing “musical rhinos” (allowing Taj and Glenn to shift from yard to yard as they watched the work continue), troubleshooting drainage changes and managing a very busy construction team.
Finally, after many months of planning followed by nearly a year of construction work spanning from July of 2021 through May of 2022, it was time to “test” the new floor throughout the exhibit. How would Taj and Glenn move around on the new substrate? Would the ground beneath them mimic that of their wild cousins? The rhino team was amazed at what they saw: eight massive feet, each supporting 1,000 pounds of weight (yup, each of these boys weighs more than 4,000 pounds) sinking smoothly into the wood chips allowing all their toes to disappear into the soft mix. YES! This was exactly the result everyone wanted and the changed distribution of weight on their feet has added benefits for their health, too.
Rhino feet are very specialized and the kind of surface they live on can affect their hoof pads and the way their nails grow. As they age and as the seasons pass, it is typical for some rhinos in human care to show some cracks or breaks in their hooves. The best way to monitor a rhino’s foot health is to take photos and radiographs (x-rays) of their feet. But how do you “ask” a 2-ton rhino to move into place and stand still in just the right spot in order to get those images? Using positive reinforcement—including lots of high-value snacks—our animal keepers have trained Taj and Glenn to voluntarily lift their feet to be photographed and measured to monitor their foot health and to hold their feet still in a particular position for x-rays. This training took many, many months but the results were worth it; by October of 2022 our team was able to get the first x-rays of Taj’s foot. This was no small feet feat as we’re one of the only conservation institutions that has been able to do this with the animal’s voluntary participation.
We’re happy to report that at present neither Taj nor Glenn show signs of any foot issues and their overall foot health has improved with the new substrate. This is something we’re very proud of and it is of great interest to rhino experts all over North America and the world.
It is also of great interest to our Sustainability team here at the zoo because this new flooring has given a whole new meaning to the term “living room.” We have actually found a few kinds of mushrooms growing in the mulchy substrate, which is a sign of a healthy and biodiverse ecosystem in the ground surface itself. Our team has identified all the flourishing fungi as the non-toxic varieties that are typically present in composting piles, so there’s no harm to Taj and Glenn if they want to “sample” the mushrooms either.
Our Woodland Park Zoo rhino keepers are involved in an organization called the International Rhino Keeper’s Association—a group of animal care professionals, scientists, and conservationists from all over the world who share expertise and best practices for all species of rhinos that live in human care. We are very excited that we have been invited to present these last two years of research and work with Taj and Glenn at their upcoming 2023 conference at The Wilds this May. The Wilds is an Association of Zoos and Aquariums-accredited safari park and conservation center in Ohio which also happens to be Glenn’s birthplace as well as that of former astronaut and U.S. Senator John Glenn, who he was named after.
Sometimes we can predict the best environment for an animal. At other times, the animals—like Taj and Glenn—signal their own needs. For our guests, the biggest difference in the Assam Rhino Reserve might be that the ground looks a little different—and as a result of all those wood chips you may occasionally lose sight of those cute rhino toes as they sink into the substrate. But for our rhinos and all the rhinos in human care, the difference is a whole lot bigger and better.
Woodland Park Zoo is, at present, the only facility in North America to have completely revamped a greater one-horned rhino habitat at this scale with wood chips—an enhancement that was made possible through donors to our Forests for All campaign.
Taj and Glenn will turn 7 years old later this year and are just coming into maturity. They still get along great, but our rhino keepers are on the lookout for any changes in behavior showing us they’ll be ready for their own space soon. In the wild, mature males are mostly solitary so this will be a completely normal and expected development for these rhinos—and since what we’re learning will help all zoos, both of them will continue to benefit from this knowledge wherever their futures lead.”