On December 9, 2020, a female Greater One-horned Rhinoceros named "Gopon" arrived from Yokohama Municipal Kanazawa Zoo with the aim of forming a new pair and breeding.

This time, we'll be talking about Gopon's estrus cycle after arriving at the zoo and how she's living with two males.

On December 18th, nine days after Gopon arrived at the zoo, we confirmed that she was in heat for the first time since coming to Tama. Greater One-horned Rhinoceros have several signs of estrus, including a decrease in appetite and restlessness. In this case, we confirmed it by a specific call known as a "whistle call," which is characteristic of the estrus period. We also collected feces and examined hormones to check the estrus pattern and whether or not ovulation occurred.


[Video] Gopon's whistling
She continued to go into heat at intervals of 41 or 42 days, but due to the cold weather, we prioritized letting her get used to the environment at Tama Zoo.

During the estrus cycle on April 21, 2021, the male "Vikram," who was in the opposite enclosure, also showed signs of estrus, so it was decided to house them together.

When Greater One-horned Rhinoceros are kept together, it is expected that there will be fierce horn-to-horn contact and the male will chase the female. However, when they actually started living together, Gopon would slowly approach, and Vikram would run away, repeating this cycle. Throughout their cohabitation, Gopon approached Vikram many times, but Vikram neither attacked nor ran away; instead, he would freeze, run away, or eventually sit down.


Gopon approaches Bikram, who has sat down.
Also, I lived with "Tar" twice after that, but both times it was a relaxed atmosphere and nothing happened.

A significant change in breeding behavior occurred during estrus on September 4th. Based on previous observations, we determined that cohabitation with Vikram would be beneficial. Vikram had been increasingly dominant over Gopon with each cohabitation, and during the September cohabitation, he showed positive signs such as chasing Gopon and resting his head on top of him when butting horns.

After running around a few times, Vikram finally placed his forelegs on Gopon's waist and assumed a mating position. He mounted Gopon several more times that day, but mating did not occur. However, the fact that he was able to place his forelegs was a big step forward for both the rhino and the handlers.


The appearance when the front legs are placed on the ground.
However, during her estrus cycle in October, perhaps due to the temperature and other factors, she did not exhibit any particularly active behavior.

We will continue to carefully assess the condition of each individual, their relationship with Gopon, and other factors, and strive to contribute to the breeding of Greater One-horned Rhinoceros. We would appreciate your continued support and encouragement.

[Tama Zoo Tama Zoological Park]

◎Related News
・ Gopon, Greater One-horned Rhinoceros, will be arriving from Yokohama Municipal Kanazawa Zoo. (December 1, 2020)
・ Until Greater One-horned Rhinoceros "Gopon" came to Tama (December 25, 2020)

(November 12, 2021)