Out with the Old, In with the New

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Some changes have been in the works for the Nature Center's bison herd.
Two bison eating from a bale of hay
The Nature Center’s former bull loves to rough up a new bale of hay. Photo by FWNC&R Staff.

With all things in life, maintaining a balance is essential to being able to prosper, a tenet that also applies to management of the Fort Worth Nature Center & Refuge’s natural resources. The Nature Center is one of the nation’s largest urban natural expanses, and, as our mission states, we “stand as an example in the preservation and protection of natural areas.” We must be intentional and deliberate in our activities and management practices.

That also is true of the Nature Center’s bison herd. Most entities that keep a bison herd do so for three primary reasons: ecological purposes, exhibit/educational purposes, and species conservation purposes. The Nature Center’s herd falls into all three categories in some form or fashion, and maintaining a good balance is crucial for the herd’s overall health and wellbeing.

The Nature Center tries to maintain a smaller 10-cow to one-bull ratio to help reduce grazing pressure on the land and lessen the amount of stress that both the animals and staff experience.

If you were to break down our herd dynamics several years ago, you would have found that we had one mature bull and nine aging mature cows. Most of the cows at that time were estimated to be 15 years old or older. As the herd manager, I knew it would be only a matter of time before we started losing cows due to age. Several of these cows came to the Refuge as adults, so their exact age was unknown. The average lifespan for bison is said to be 10 to 20 years, potentially longer in captivity. Without knowing the exact age of our animals when we received them, it was hard to predict how much time we had left with each cow. Our plan at the time was to allow the herd bull a few more years of breeding, keeping all the heifers that were born before swapping him for a younger, unrelated, immature bull.

Adding an immature bull to the herd would allow the cows to have a two-year break from having calves and also allow us to know the sire of all calves born afterward since there would be no overlap of breeding between bulls.

By the beginning of 2023, the herd had grown to 21 animals, with one mature bull, six aging mature cows, one 4-year-old cow, three 3-year-old open (non-pregnant) heifers, one 2-year-old open heifer, three bull yearlings, two heifer yearlings, two bull calves, and two heifer calves.

This spring, we reduced the herd by six animals, removing the herd bull, three yearling bulls, and two bull calves. During the same time period, we introduced a new immature bull to the herd that will serve as the future herd bull. We were able to obtain a genetically pure (within the limits of current testing technology) bull from the Texas State Bison Herd, which will diversify our genetics while maintaining a “pure” bison herd.

As we strive to maintain a good balance for the Nature Center’s bison herd, know that the changes will help us achieve our bison husbandry management goals, while maintaining our ecological, exhibit, and species conservation herd status. By ensuring that we have a diverse age group of females, we will continue to be able to have bison on display and produce calves that will be available to others for conservation purposes. Our long-term goal is to continue to maintain a smaller herd to be used for rotational grazing throughout the five bison pastures. As we say goodbye to our current bull, know that he will have the potential to resume his breeding efforts for another herd.

By Daniel Price, Pineywoods Ecosystem Project Leader, Texas Parks and Wildlife Department. Please note: Daniel, in his role as Natural Resource Manager, Fort Worth Nature Center & Refuge, contributed this article before moving to Texas Parks and Wildlife.

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A very special thank you to those who helped the Friends honor Bob O’Kennon and celebrate our 50th anniversary at Fort Worth Wild 2024.