Regularly weighing animals not only helps in understanding short-term changes and providing useful information for health management, but also provides crucial data for determining the dosage of anesthetics and medications for treatment. As veterinary medicine advances and the number of elderly animals in zoos will continue to increase, accurately knowing their weight will become even more important, considering the expected rise in age-related diseases.
　
At Tama Zoo, since they began keeping Przewalski's Horse 's horses in 1981, weight measurements were mainly taken during anesthesia or transport. As a result, of the 10 horses currently being kept there, weight records exist for only two.

Therefore, we started a program to regularly weigh all of the horses. To ensure the scale could withstand the weight of Przewalski's Horse 's horse, which can weigh over 300 kg as an adult, we used a load meter, the kind used to measure the load capacity of trucks.

When Przewalski's Horse 's horses move from the paddock (small exercise area) to the enclosure, they normally pass over a rubber mat placed in front of the gate separating the two areas. Instead of requiring them to perform a special action to get on the scale, we decided to leverage their existing habits and place the scale under the rubber mat. Ultimately, the goal was to have them pass over the layers in the order of "plywood, scale, plywood, rubber mat" from bottom to top. We gradually introduced them to the layers to prevent them from becoming wary of the unstable footing, the smell of the plywood, or the sound. The measurement procedure is as follows:

1. Keep one animal still on the rubber mat with the door closed.


2. Open the door and release one animal into the enclosure.


3. Repeat the above steps.

It looks like a road meter has been installed.	A plywood board and rubber mat have been placed on top of the road meter.

We attempted the first weight measurement once all the dogs were able to pass through the rubber mat with a scale without any problems.
Normally, the horses were let out all at once with the door open, so Domestic Horse weren't used to standing still in front of a closed door and stopped approaching the scale. Therefore, along with getting them used to the scale, we decided to get them used to waiting one by one in front of the door when letting Domestic Horse out of the paddock. After about three weeks of training, on the second attempt, five out of seven horses were able to stand still on the mat for several seconds.


Weight measurement of Przewalski's Horse
During this experiment, we observed some unexpected reactions. Older individuals are usually more wary of humans, while younger individuals tend to be less so, so we expected the younger individuals to step onto the scale without any hesitation. However, it was the younger individuals who took longer to get used to stepping onto the scale and to being let out of their enclosure one by one. While this cannot be generalized due to individual differences in temperament, it suggests that wariness towards the surrounding environment and customs may differ from wariness towards humans.

Through weighing the horses, we reaffirmed the difficulties of individual management in herd rearing and the strong wariness of wild horses, as well as noticing personality traits we had not seen before. We will use this experience to continue our efforts until we can consistently weigh all of the horses.

[Ito, Animal Care and Exhibition Staff, South Tama Zoo]

◎Related articles
・ Management of Przewalski's Horse 's hooves (May 21, 2021)
・ Two new Przewalski's Horse join the "Bachelor Group." (July 5, 2019)
・ Przewalski's Horse becomes the first "Bachelor Group" horse. (July 13, 2018)


(July 18, 2025)