Despite their name, tree hyraxes — small, furry, nocturnal African mammals — don’t always live in trees. In Tanzania’s Pare mountains, near the border with Kenya, they’ve adapted to life on steep rocky outcrops as forests disappeared over the centuries, a recent study has found.
Eastern tree hyraxes (Dendrohyrax validus) are known to inhabit the Eastern Arc mountains, which stretch from southern Kenya across eastern Tanzania, and the Zanzibar archipelago. They prefer old-growth evergreen forests, sheltering from the heat inside the cavities of large trees. But after centuries of agriculture, mining and logging, the Eastern Arc’s Pare mountains retain less than 3% of their original forest cover.
Hanna Rosti, a conservation biologist from the University of Helsinki, Finland, and colleagues observed hyraxes and recorded more than 700 hours of their calls at 18 sites across the Pare massif. Across all sites, the researchers heard tree hyraxes calling mostly from rocky outcrops and saw them seeking shelter in rock crevices.
The team also found that the songs of Pare hyraxes, including a distinctive “strangled thwack,” resemble those of eastern tree hyraxes on Mount Kilimanjaro and in Kenya’s Taita Hills. However, Pare hyrax calls differ markedly from populations elsewhere in Tanzania traditionally classified as the same species, including those on Zanzibar and other parts of the Eastern Arc.
This suggests the eastern tree hyrax populations in places like Pare and Kilimanjaro may represent a different taxonomic unit, though Rosti said not enough analysis has been done to formally split them into separate species or subspecies.
Trevor Jones, a conservation zoologist who works in the Udzungwa mountains, an Eastern Arc massif to the southwest of Pare, told Mongabay he’s familiar with the “ping pong” call of Udzungwa’s eastern tree hyraxes but not the “strangled thwack.”
“Clear acoustic differences can indeed be a strong indicator of divergence,” he said.
The Udzungwa hyraxes Jones is familiar with do inhabit trees, but he’s also seen them in cliffs and rocky crevices, even within undisturbed forest. This, Jones said, suggests that for eastern tree hyraxes, life in rocky crevices is an adaptation that pre-dates habitat loss, but is becoming increasingly useful now.
“These special beasts are in decline and so yes, we should also be protecting these rocky habitats, especially where they have lost their primary forest.”
The study’s authors say that Pare’s high number of inaccessible cliffs also offer tree hyraxes and other species in the area safety from hunters who kill them with spears. “There is statistical evidence that the height or slope of the crevice is important, because if it’s almost vertical the people won’t go to kill them that easily,” Rosti told Mongabay in an interview.
The closely related southern tree hyrax (Dendrohyrax arboreus) has also shown flexibility in its habitat: it’s been found sheltering in human-made structures, including at the Karen Blixen Museum’s old coffee factory in Nairobi, Rosti said.
Banner image: Eastern tree hyrax in Pare mountains. Image courtesy of Hanna Rosti.
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