Weighing Greater One-horned Rhinoceros "Dekopon"

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

Until now, we were unable to measure the weight of the rhinoceros due to a lack of specialized equipment, but with the introduction of a car weighing scale, it is now possible to carry out such measurements. In addition to the display, the weighing scale uses a pad measuring approximately 40 x 60 cm and 2 cm thick, on top of which a board measuring approximately 180 x 90 cm and 3 cm thick is placed, and the rhinoceros is then asked to stand on it to measure the weight. The measurement takes place in the corridor connecting the bedroom and the indoor exhibition room.

Prior to the measurements, training began on July 16th to help the kittens get used to the board. First, we set up the board without the scale, then placed chips on the board so that the board was not visible, and watched them walk over it. The mother, Gopon, carefully checked the board, blowing the chips with her nose, and slowly walked over it.

The next Dekopon was wary and walked along the edge of the walkway to avoid the board, but over a few days it gradually got used to it and was able to pass through smoothly. On July 21st, even when the board was completely visible, neither the parent nor the offspring showed any significant wariness, and they were able to practice staying on the board using food without any problems.

The first weight measurement, conducted on August 20th, came in at approximately 560 kg. This is only an estimate because even the slightest movement in the center of gravity can cause the weight to fluctuate, but according to literature, the birth weight of Greater One-horned Rhinoceros calf is between 50 and 90 kg, so this means that the calf has gained nearly 500 kg in about a year.

Monthly measurements were continued thereafter, confirming the steady growth of the Dekopon, which reached approximately 600 kg in September, 640 kg in October, 690 kg in November, and 750 kg in December. It is said that baby Greater One-horned Rhinoceros gain 1-3 kg per day, so this rate of growth can be considered good.

Adults weigh between 1,500 and 2,500 kg, and the weight gain rate of the young gradually slows, with Dekopon expected to exceed 1,500 kg at around the age of 4 to 6. In the future, we would like to measure the weight of Gopon and the male "Bikram", but the current board does not fit Gopon's limbs, so we plan to prepare a larger board before doing so.

Dekopon is over one year old and is still nursing, but he started eating grass when he was two months old and has recently started eating mostly adult food. It is thought that he will be gradually weaned as he approaches the age of two. Since Greater One-horned Rhinoceros live alone in the wild, we plan to begin training the mother and calf to separate after weaning.

The time to see the mother and child together is limited, so please come and meet the growing Dekopon and its mother Gopon.

[Mitsuka, 2nd Section of the South Zoo Animal Exhibit Section at Tama Zoo]