In the wild male capybaras would leave the herd when they become sub adults, between one and two years of age. They are too closely related to the females in the herd to be able to mate with them. These young males would usually join another herd as subordinate males, hoping to become the dominant male one day.
As subordinate males they play a very useful role on the outskirts of the herd keeping a vigilant eye out for danger. Subordinate males give more warning calls than other capybaras in the herd. They also collectively secure more matings than the dominant male, although the dominant male mates more often than each subordinate male. As female capybaras are only receptive for the last eight hours of estrus, the dominant male may well be the father of most of the offspring in the herd as he can guard the female in estrus for this short period and chase away subordinate males who wish to mate at this time. Dominant males will sometimes interrupt a mating which is taking place between a subordinate male and a female.
Female capybaras seem to prefer to mate with the dominant male and if a subordinate male tries to mate with them, or is mating with them, they sometimes vocalise loudly to attract the attention of the dominant male, in effect asking him to come over and break up her liaison with the subordinate male…..And then mate with her.
Sometimes the young males leaving the herd will form their own herds. If they fail to join a herd or establish a new herd, the outlook for a solitary capybara in the wild is often bleak. They may easily succumb to attacks by predators. There is safety in numbers as the more capybaras there are being vigilant in the herd, the more likely it is that a predator will be noticed by at least one of the members of the herd of capybaras who will give a warning call.
Capybaras in captivity live a very different life. At Nagasaki Bio Park, in Kyushu, Japan, Choco and Doughnut, Momiji’s sons who were born in 2013, were neutered at age 6 months so that they could remain in the herd. If they had not been neutered Choco and Doughnut would have had to be removed from the herd and as there are too many male capybaras in Japan their future would not have been very happy. They would either have had to spend their lives alone in a separate small enclosure, probably with a concrete floor, and with at best a tiny pond. Very likely they might only have had a small plastic tub barely large enough for them to sit in, which is quite unacceptable for these very active and graceful, semi-aquatic animals. Or they might have been sold to China, whose zoos have a dreadful reputation.
What I find very interesting is the way that the senior capybaras in the female hierarchy react to these neutered male capybaras as they grow older. They don’t like them! At first I thought this was because, as neutered males, they smelt different and wrong. But then I realised that instinctively the senior capybaras knew that these males should have left the herd.
This was why Hinase frequently chased Choco and Doughnut. Even wise and peaceful Donguri didn’t want them in her Onsen, although she never chased them. She just gave them a very powerful look and raised her nose to indicate her dominance and her wish that they would move away, which Choco and Doughnut completely understood. Even their own mother, Momiji, is often aggressive towards them. Capybaras are very sensitive emotionally and Choco and Doughnut could sense the mood of these senior capybaras, and whether, at any given time, they were likely to encounter aggression. Choco and Doughnut would then give these females a wide berth, thus avoiding any direct aggression.
Choco, possibly the cleverest capybara I have ever met, came up with a very clever strategy to gain acceptance by the female capybaras. Either that or he was a little confused about his sexual identity. He joined the female capybaras every time they went to visit Toku the male. Toku leads a life of endless frustration in a separate enclosure separated, by a metal fence, from the females who long to be with him. (In 2016 the only female capybara who was allowed in to mate with him was Zabon, and she was only allowed in for 30 minutes on the first occasion and 20 minutes on the second occasion. Toku and Zabon’s frustration at being separated so quickly was palpable and very upsetting to watch.)
Choco acted just like the females when the herd went to visit Toku and Toku was never aggressive towards him though he seemed very curious about Choco’s presence, no doubt sensing that Choco was not female! Choco often went right up to the gate of Toku’s enclosure along with the most senior females and Toku often spent a long time sniffing him which was quite amusing to watch, especially the expression on Choco’s face! There was just one occasion when I saw Toku react aggressively to Choco. On this occasion Choco visited Toku without the other females and Toku got very upset by Choco’s presence and became quite aggressive.
Choco’s demeanour, perhaps his fearlessness, and his general behaviour gained him greater acceptance by the female capybaras than Doughnut, his brother. Doughnut is a much more emotional and openly sensitive capybara then brother Choco, and much more hardwired to be aggressive. He is always alert to the danger posed by Hinase. Whenever she looks likely to come anywhere near him Doughnut will get up and move away. Choco, ever fearless, by contrast, only moves when Hinase begins to run towards him with that mischievous gleam in her eye and her ears pricked. Capybaras don’t often prick up their ears, but it is quite a characteristic pose for Hinase. She does this frequently and looks very cute and it is usually a sign that she is either planning to chase someone, or she has noticed some food and is amazed that other more junior capybaras think they are entitled to it!
When Choco does run away from Hinase, he usually outruns her and stops at the earliest opportunity. He then moves back to where he was, quite fearlessly, and Hinase rarely chases him again.
When Doughnut visits Toku, Toku gets very upset and aggressive, as does Doughnut.
One of the advantages of being a neutered male and being allowed to remain in the herd with the females is that you may have the opportunity to mate if one of the females will let you. Choco and Doughnut frequently mate with Maple but she is the only fairly senior capybara who is interested in mating. Choco and Doughnut both also sometimes mate with Butter, one of Maple’s three-year-old daughters, but never with Butter’s sister, Cookie. Hinase and Momiji are not at all happy about Choco and Doughnut mating with any of the females and sometimes they will swim over to break up the liaison.
One of my very favourite capybaras at Nagasaki Bio Park was Syu, whose mother Aki (Donguri’s sister) tragically died five days after giving birth to him and his sister Autumn. Syu was exceptionally affectionate and when I petted him he would put his face up to mine and gently rubbed his morillo affectionately across my lips.
Syu the Most Affectionate Capybara in The World カピバラは私にキスをしました。シュー世界で最も愛情カピバラ:
Syu was also a neutered male and for the first year he and Donguri were very friendly. The second year the keeper, Shoko Ono, who took great interest in observing the capybaras and knew everything about their lives and relationships, told me that Donguri and Syu no longer seemed to be friends. I now realise this was simply because as a male capybara Donguri knew Syu should have left the herd by now. At the time it surprised me that Donguri, being such a wise and compassionate leader and capybara, would cease to be friends with a sweet capybara like Syu. Especially as she always liked the male capybaras and was the favourite of all the males.
The relationship that neutered male capybaras have with the senior female capybaras in their herd is complex and not entirely satisfactory. However, if they can remain in the herd by being neutered that is easily the best life for them.