Inspired by my Grandfather’s (Helmut) stories of adventure in identifying orchids and my Father’s (Klaus) passion for snakes, I visited REGUA as a volunteer in 2015. I want to pursue a career in biology and my focus then was on which mammals venture to and from the wetlands and which routes they choose to take, using camera traps positioned on visibly active animal trails.
I showed that trail building in an around the wetlands is almost exclusively done by the Capybara Hydrochoerus hydrochaeris, that permanently live in the wetlands though other animals would also use their trails. These animals like to use the main tourist trails, but between the wetland lakes and the major routes also exist a network of minor “social” trails.
The Capybaras’ stronghold at REGUA is the wetlands but they leave the wetlands for feeding. This was done on three major routes leading to neighbouring farmland, adjacent wetlands and into reforested rainforest with remnant pastures.
I returned to REGUA in March 2017 and observed that all the major routes still existed. There was no change in the trail network although there was an obvious change to where the Capybaras stay during daytime. The object of my stay was to determine how the Capybaras live in the wetlands.
Based on different counts I estimated that there were 50–70 Capybara living in the wetlands in March/April 2017. These numbers were less than we expected. I did not count them in 2015, but I have the feeling their numbers have declined. In 2015 there were seemingly two major groups of Capybara and they were apparently present everywhere in the wetlands. But this was not the case this year, when there was only one group left and other individual Capybara were scattered.
In 2015 I also noticed that many Capybara had wounds and cuts especially on their rear body parts. Some were seriously wounded and were noticeably limping. They seemed to be quite aggressive between each other and I could witness several moments when Capybaras bit each other. The wounds were not as obvious this year. Fighting still took place but the wounds were not as numerous and not as severe. I have the feeling there may have been over-population in 2015 and the lower numbers could have diminished social pressure in 2017.
I also observed that only the group near the volunteer houses remained and concluded that the animals also formed “Capybara nurseries”. A group of 20-30 Capybaras would gather on an island and look after the new born and young less than six months of age, guarded by three to six adults. The young were clearly protected with the adult guards looking in every direction supervising the group. This nursery island was abandoned about one hour after sunrise each day, the young guided to their day area and to other Capybara groups. The majority of Capybaras live loosely dispersed on the shores and islands all over the wetlands.
Aside from the nursery, I could not find evidence of a constant group of Capybara larger than five animals during my three week study. I could not mark any Capybara and there are no individual markings on any Capybara body to distinguish them apart. From the pictures of the camera trap I could see that there were no uniform constant groups. Capybara would go alone or form differently composed groups daily.
Over the past three years there was a noticeable relocation of the Capybara population towards human housing especially during night time. This behaviour could be the result of a clear increase of larger predators in the wetlands. We have seen at least three large Broad-snouted Caiman Caiman latirostris longer than two metres and there was a clear evidence of an increase of big cat activity in the wetlands. I had read tales from African safari camps of alternating behaviour of animals with young moving towards humans to avoid their predators.
It is possible that the whole population of the REGUA wetland Capybara are in fact a loosely connected society but their behaviour may vary seasonally. This has to be verified.
The REGUA wetland Capybaras give me the impression of a healthy population that very well adapts and regulates itself by wandering off to the adjacent habitat and perhaps also through increasing predation. For future work on the Capybara and to study their social behaviour I will have to find a way to mark individual Capybara. Radio tagging would only make sense when and if we could get funding for a major work on Capybara.
There are excellent conditions to study the life in nature of Capybaras and other wildlife at REGUA because wildlife is diverse and abundant and almost free from human pressure. I look forward to returning and conducting further research work at REGUA.