By Edward Carver

Lemurs in Madagascar have been under pressure from deforestation, poaching, drought and other challenges for years. Now, in the much-visited Berenty Reserve near the island's southern tip, one species faces a mysterious new threat.

In the last month and a half, at least 31 Verreaux's sifakas (Propithecus verreauxi) have died in the reserve. Most were found already dead; others were found gravely ill and later died from respiratory failure. Berenty staff and local scientists have reached out to veterinarians and primatologists across the world. The experts believe that a parasite or tick-borne disease is likely to blame, but the exact cause remains unknown.