A greater bamboo lemur. Photo credit: Malee Oot.

By Malee Oot

Rising temperatures have been charged with driving some of the planet’s most devastating natural disasters, but sometimes the impacts of climate change appear more subtly – as in the case of the greater bamboo lemur. Thought to be extinct in the wild just a few decades ago – until researchers discovered a remnant population in 1986 — Madagascar’s largest bamboo-noshing lemur still faces challenges like habitat loss and subsistence hunting. And now, climate change could gradually push the already critically endangered lemurs over the edge.

Greater bamboo lemurs are aptly named, the primates spend 95 per cent of their feeding time feasting on a single species of bamboo. While the lemurs prefer to chomp the plant’s succulent shoots, during the dry season they consume the bamboo’s woody trunk, a less nutritious and far less tender option, known as culm. Research conducted in eastern Madagascar suggests with projected climactic shifts, this feeding behaviour could drive the species to extinction.

A study published last year in the journal Current Biology analyzed the anatomy and diet of greater bamboo lemurs, along with fossil records and climate models, finding as the planet continues to warm, the primates will be forced to rely on bamboo culm for longer periods. Ultimately, this dietary shift may cause the lemurs to slowly starve.

Greater bamboo lemurs have highly-specialized teeth, endowed with groves and ridges which allow the primates to subsist on bamboo trunks for part of the year. The only other mammal on the planet with teeth able to grind down bamboo culm is China’s giant panda. But, researchers monitoring the lemur’s feeding behaviour over an 18-month period in Ranomafana National Park observed bamboo culm was only consumed as a last resort, during the dry season lasting from August to November.

Even with highly-adapted teeth, gnawing on bamboo trunks for an extended period takes a toll. Not only is culm a less-optimal food source for greater bamboo lemurs, but subsisting on the tough bamboo trunks for a prolonged period would also lead to increased tooth wear, making it difficult for the primates to consume their principal food source the following dry season. In short, a prolonged or more intense dry season could prove a critical tipping point for the lemurs.

To assess the impact of relying on bamboo culm for an extended period, the study looked at the distribution of fossil remains and historic climate data showing the duration of the dry season in regions across Madagascar. The researchers found greater bamboo lemurs were once much more widely distributed on the island, but are now confined to the east coast, found only in places where the dry season is comparatively brief. This more limited range suggests a shorter dry season may be critical for the bamboo-chomping lemurs. However, climate models indicate regions across Madagascar will experience longer and harsher dry seasons, including the rainforests on the east coast, the last stronghold for the island’s greater bamboo lemurs.

A prolonged dry season could also impact the reproductive cycle of greater bamboo lemurs. Over the centuries, the lemurs have evolved with their beloved food source. The life cycle of greater bamboo lemurs mirrors the growth cycle of their favoured bamboo. Young lemurs are born during the rainy season when tender bamboo shoots are abundant.

Greater bamboo lemurs aren’t the only primates in Madagascar potentially staring down the barrel of extinction. Just this summer, an assessment conducted by the International Union for Conservation of Nature’s Primate Specialist Group found that 95% of Madagascar’s endemic lemurs may qualify as critically endangered, endangered, or vulnerable to extinction in the wild.