Weighing Greater One-horned Rhinoceros "Dekopon"

Dekopon (female), Greater One-horned Rhinoceros born at Tama Zoo on September 3, 2024, had her first weight measurement in August 2025.

Previously, we lacked the necessary equipment to perform these measurements, but we have now introduced automotive weighing scales, making it possible to conduct them.
In addition to the display unit, the scale uses a pad measuring approximately 40 x 60 cm and 2 cm thick. A board measuring approximately 180 x 90 cm and 3 cm thick is placed on top of this pad, and the rhinoceros is placed on it for measurement. The measurement takes place in the passageway connecting the bedroom and the indoor exhibition room.

Prior to the measurements, I started training on July 16th to get used to the board.
First, we set up only the board without the weighing scale, covered it with wood chips so that the board was not visible, and observed whether the animal would walk over it.
The mother, "Gopon," carefully checked the board, flicking the chips away with her breath, before slowly passing over it.

The next Dekopon tree was wary and walked along the edge of the path, avoiding the boards, but after a few days it gradually got used to it and was able to pass through smoothly.
On July 21st, even when the board was fully visible, neither the parent nor the offspring showed any significant signs of wariness, and they were able to practice staying on the board using bait without any problems.

My first weight measurement, conducted on August 20th, yielded a result of approximately 560 kg.
Although the figures are approximate because even slight shifts in the center of gravity can cause them to change, according to literature, the birth weight of an Greater One-horned Rhinoceros calf is 50-90 kg, meaning it would have gained nearly 500 kg in about a year.

We continued taking measurements once a month, and confirmed the steady growth of the Dekopon oranges, with approximately 600 kg in September, 640 kg in October, 690 kg in November, and 750 kg in December.
Greater One-horned Rhinoceros calves are said to gain 1-3 kg per day, so this rate of weight gain can be considered good.

Adult Dekopon weigh between 1,500 and 2,500 kg, and the rate of weight gain in offspring gradually slows down, with Dekopon expected to exceed 1,500 kg around 4 to 6 years of age.
In the future, I would like to measure the weight of Gopon and the male dog "Bikram," but Gopon's limbs do not fit on the current board, so I plan to prepare a larger board before doing so.

Dekopon is now over a year old and is still being nursed, but she started eating grass when she was two months old, and recently she has been mainly eating adult animal feed. It is thought that weaning will gradually progress as she approaches two years old.
Since Greater One-horned Rhinoceros live solitary lives in the wild, we plan to implement separation training between parents and offspring after weaning.

The time we can see parents and children snuggling together is limited.
Please come and visit the growing Dekopon and its mother, Gopon!

[Tama Zoo South Garden, Animal Care and Exhibition Section 2, Mitsuka]

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