The agoutis have come back to Tijuca National Park in Rio de Janeiro. The return of these rodents to one of Brazil’s largest urban forests is the result of a reintroduction project carried out by biologists and veterinarians in Rio. In the 1970s, the shy, fragile agoutis were becoming scarce in this 4,000-hectare area of Atlantic Forest nestled inside the city, and even came to be regarded as locally extinct. Since then, there has been at least one attempt to restore the park’s population of these rodents, which play a key role in seed dispersion. This time, the experiment appears to have worked, at least in the short term. The animals that were reintroduced beginning in 2010 looked at-home in the forest within a short time, feeding on their own and roaming areas far from their point of release. Eight months later, the first nature-born cub was sighted.
This initial success with reintroduction of agoutis (Dasyprocta leporina) into their native habitat is owed to a gradual-release process implemented by Bruno Cid, a biologist on the team led by Fernando Fernandez at the Federal University of Rio de Janeiro (UFRJ). The strategy encompassed two stages—quarantine and acclimatization—prior to release. In the first stage, agoutis born and raised in a park in the center of Rio were brought to the city’s zoo, where they were fed and examined by biologists and veterinarians for an average of two months. In the second stage, the healthy animals were sent to an acclimatization pen in the Tijuca Park forest. During the acclimatization period, the researchers supplemented the agoutis’ diet with seasonal fruits and seeds that they might find in the forest. After an average of three weeks in the forest, the animals were released.
Eleven agoutis were reintroduced and adapted well to life in the wild. Ten others died before they could be released, as a result of fights between males or attacks by dogs that invaded the pen during acclimatization. By monitoring the rodents’ movements, the researchers ascertained that in a matter of days after release, most of the agoutis were feeding on their own, mainly on fruits from arara nut trees and juçara palms, which are also consumed by Atlantic Forest birds. The greatest sign of success, however, is that the agoutis were able to breed, witnessed by the fact that 234 days after release, one of the agoutis was seen with a cub. Since then, the researchers have sighted 10 more cubs near the acclimatization area. The number of agoutis in the park is now estimated at 45 individuals, not yet sufficient to repopulate the entire area.
Until recently considered extinct in the park, the agoutis could help preserve the forest. Studies have shown that these rodents help disperse the seeds of several plant species. The agoutis that adapted to life in the wild buried seeds of species native to the Atlantic Forest such as the arara nut tree, as well as seeds of exotic species such as the jackfruit tree. “The reintroduction of seed-dispersing animals could be an important tool for recovering degraded Atlantic Forest segments,” says Bruno Cid.
Like other animals, agoutis eat some seeds and bury others for times of shortage. Since they move around the forest constantly, they forget some seeds, which then germinate and become new plants. “These buried seeds have a higher chance of germinating,” says Caio Kenup, a master’s student in biology at UFRJ who studies the population dynamics of the agoutis in Tijuca Park. Sometimes agoutis will also steal seeds from each another, thereby increasing dispersion. “The soil need only appear to have been disturbed for the agoutis to look for seeds in that spot,” says biologist Paulo Roberto Guimarães of São Paulo State University (Unesp), who has studied seed dispersal by agoutis for over 10 years.
A difficult return
The experiment in Tijuca Park underscores the idea that wild animals born in captivity and nature-born captives do not easily adapt to life in the wild. When returned to their natural habitat, some cannot feed on their own, so they lose weight and become easy prey for predators. Others are unable to return to the places where they lived prior to capture. One reason for this is that forested areas are shrinking, particularly when they are close to large cities.
The fact is that known attempts at reintroduction in Brazil have yielded a high rate of failure—except in the case of the golden lion tamarin, whose population in reserves has increased as a result of conservation efforts.
Although phased reintroduction may explain the successful return of the agoutis to Tijuca Park, the procedure still needs to be refined, according to Bruno Cid. The acclimatization period, for example, may be stressful for the animals, but it is necessary nonetheless. “If we do away with any stage, there is an increased risk that the animal will not adapt to life in the wild. The important thing is to establish a protocol that prescribes how long the individuals should spend in each stage,” says Cid, who is working on his PhD under the guidance of Fernando Fernandez at the Ecology and Population Conservation Laboratory at UFRJ. Fernandez and his group plan to use the same strategy to reintroduce howler monkeys into Tijuca Park and tapirs into an area yet to be determined, as part of the Refauna project, which seeks to re-establish ecological interactions and restore populations lost because of the defaunation of the Atlantic Forest.
In the state of Minas Gerais, researchers are assessing the effectiveness of gradual adaptation in the reintroduction of Red-billed Curassows (Crax blumenbachii), an endangered Atlantic Forest bird. Since 1990, they have transferred 78 animals at two years of age, when they are reaching sexual maturity, into a forested area, as part of a project coordinated by the Crax Brazil Foundation and the Cenibra company. “All of them were given medical exams by veterinarians, and they stayed four to nine months in an acclimatization vivarium before being released,” explains Joana Carvalhaes Borba de Araújo, a master’s student in charge of the research under the leadership of Professor Adriano Chiarello of the University of São Paulo (USP) in Ribeirão Preto. The objective now is to evaluate the success of reintroducing these animals 25 years into the project.
CID, B. et al. Short-term success in the reintroduction of the red-humped agouti Dasyprocta leporina, an important seed disperser, in a Brazilian Atlantic Forest reserve. Tropical Conservation Science. V. 7, No. 4, p. 796-810. 2014.