Genetic analysis helps to map populations of large carnivores

Study of the DNA present in samples of hair or droppings helps researchers to discover information about the species remaining in fragments of Atlantic Forest and Cerrado biomes.

By Karina Toledo

Agência FAPESP – Non-invasive methods of DNA analysis are helping researchers linked to Brazil’s National Biodiversity Research System (Sisbiota) to monitor populations of large carnivores living in the Atlantic Rainforest, the Cerrado, and transition areas between these two biomes in and near São Paulo State.

The data collected will be used to enhance population viability models and will contribute to the development of conservation plans, explained Pedro Manoel Galetti Junior, a professor at the Center for Biological & Health Sciences (CCBS) of the Federal University of São Carlos (UFSCar) in São Paulo State and coordinator of the Sisbiota Apex Predator Network, supported by FAPESP.

“These animals, especially the predators at the apex of the food chain, have very elusive habits. They’re rarely sighted in the countryside, so ecologists have to study them by following their spoor, meaning visible traces like hair, tracks or scat (droppings). Now we have genetics, a powerful new tool in this identification effort,” Galetti said.

Analysis of mitochondrial DNA from a sample of animal scat, the researcher explained, can enable the depositing species to be identified and can help to calculate the size of a population and the area that it occupies.

“Using a method similar to the DNA paternity test procedure with neutral molecular markers such as microsatellites, we can individualize each sample,” Galetti said. “We have geographical data, so we can use GPS to determine where the individual was when it defecated. If a new sample from the same individual is collected later at the same location, we’re able to work out roughly how it’s moving about.”

The method standardized by the Sisbiota group can also be used to calculate the proportions of males and females in a given population, study the genetic variability of the population, and analyze the flow of genes between distinct populations from different fragments of native forest.

Studies of felines have focused to date on populations of puma (Puma concolor), ocelot (Leopardus pardalis), margay (Leopardus wiedii), jaguarundi (Puma yagouaroundi), and oncilla (Leopardus tigrinus).

In canids, the highlights are the maned wolf (Chrysocyon brachyurus), crab-eating fox (Cerdocyon thous), and bush dog (Speothos venaticus).

Jaguar detected in Serra do Mar

Although they are focusing on São Paulo State, the researchers have also studied the entire Atlantic Rainforest continuum that extends to northern Minas Gerais state as well as the Cerrado down to southern Goiás state.

“First of all, we want to find out how many of these animals still live in these remnants,” Galetti said. “We don’t have that information, simple though it may seem, because of the difficulty of performing this kind of analysis.”

Population estimates are still being concluded. According to Galetti, the process takes a long time because tests must be repeated between two and five times to confirm the results.

However, preliminary findings already point to the presence of jaguar (Panthera onca) in some parts of São Paulo State where it was believed to be extinct, such as the Santa Virgínia unit of Serra do Mar State Park.

“We want to extend our research so that we can run population viability models. These models consider several characteristics of habitat quality to calculate the probability of persistence for a given species in a given environment for the next 100 years. The analysis will become more reliable once we’ve succeeded in introducing genetic data into the model,” Galetti said.