The vast majority of lemur species are threatened with extinction, experts warn. But not every lemur species faces a grim future. For example, up to 1.3 million white lemurs can occur in the wild, and mouse macaws can count more than 2 million, as a Duke-led study has shown.
"For some lemurs, healthy populations can be maintained and our conservation efforts preserve them," said lead author James Herrera of Duke University.
The results come from statistical modeling techniques that estimate the total population size and geographical distribution of 19 of the approximately 100 recognized lemur species in Madagascar by using the plants to which they depend as the proxy for counting animals.
These tree-dwelling primates eat mainly fruits, leaves and flowers such as African star apples, mangosteens, tamarinds and figs over Madagascar in the world where lemurs live in the wild.
In a study published on August 30 in the Journal of Biogeography researchers show that lemurs in areas that are not safe are less common tree species ̵
Based on this relationship, the team was able to produce the first estimates of population size for some lesser-known species, such as the dwarf lemur that Crossley created. These estimates can be critical base data for managing what's left over.
Approximately 95 percent of all lemurs are threatened with extinction due to deforestation, hunting and other factors. Since the 1950s, lemurs have lost more than 40 percent of their living space. Tens of thousands of hectares of forest are cut down each year to make way for farms and pastures, or burned and harvested as charcoal.
But finding reliable populations for these elusive animals in the remote and rugged terrain in which they live is not easy. Counting each one is impossible. An alternative statistical model-based approach uses the correlation between species densities at a subset of sites and the environmental conditions at those sites to determine how many individuals occur in larger areas.
Research teams passed between 2011 and 2016 Ranomafana National Park, Makira National Park and Masoala National Park in Madagascar in Search of Lemurs
"We woke up at 4:30 or 5:00 am, wandering six to eight Hours to look for lemurs, and then we go back with our searchlights at night to search, "said Herrera, a postdoctoral fellow in the laboratory of Duke Professor Charlie Nunn.
"Many of these species are small nocturnal animals that are active only at night," researchers rarely see them, Herrera said. "You can go for hours and see no lemurs."
Overall, they have collected data from more than 2,000 Lemur sightings and more than 3,000 sightings of the trees they eat.
With these records, along with climate data from each site, researchers identified other suitable areas for each of the 14 lemur food trees on the 225,000 square mile island.
Then they used the resulting tree maps, along with temperature, precipitation, altitude, and other data. to estimate the potential population size of each Lemur species over their range.
This technique – involving tree distributions in addition to the climate – proved to be more accurate than methods that estimate lemur numbers and ranges alone with climate.
Several species had populations that were smaller than expected.
The researchers estimated that in Madagascar in 2014 there were still 15,000 to 20,000 red-faced brown-necked macaws. That's as much as 85 percent of the app's approximately 100,000 was estimated in 2000 through a separate study based on lemurs and satellite imagery from the rest of the rainforests.
Another species, the gentle bamboo lemur, grows to about 20,000 in less than two decades 9,000 copies shrunk -10,000
The steep declines are partly due to continued habitat loss, say the researchers. Madagascar lost more than 380 square miles of forest per year between 2010 and 2014.
But the numbers for other lemur species were not as low as they feared.
This study estimated that nearly 50,000 red-bellied lemurs remained, nearly twice the number estimated 14 years earlier.
In addition, the study found that 16 of the 19 species had potential population sizes of more than 10,000 individuals, with the IUCN threshold considered to be critically endangered.
"It was actually good news for some of these species," Herrera said.
Many of these species may still be endangered for bushmeat or pet trafficking, which their models do not explain, the researchers say] but they hope that their approach, combined with hunting pressure and other threats, will lead to a more refined assessment of Endangered species for lemurs or other animals in the future.