I’m
not really into frogs. I love their croaking – especially in misty conditions
on the mountain, when it lends an air of mystery to the landscape – but otherwise
I am not particularly impressed by them. That all changes when it comes to Heleophryne rosei, commonly known as the
Table Mountain ghost frog, one of 19 frog and toad species on the mountain.
So
what makes the ghost frog so special? Primarily, its distribution: it lives
only in the swift-flowing sections of seven perennial streams on Table Mountain
(all on the south and east side), nowhere else on earth. That’s an area of
about eight square kilometres. One of only two vertebrates endemic to the Cape
Peninsula (the other also a frog), the ghost frog can truly be called a child
of Table Mountain.
Heleophryne (Latin for ‘the one who is
afraid of the sun’) rosei is one of
the most ancient frog species, having split off from its closest ancestors more
than 160 million years ago. Its solitary evolution on Table Mountain spans
millions of years and gave it the niche habitat of swift-flowing streams by
endowing it with suction pads on their toes, tiny skin projections that grip
like Velcro, flattened bodies and highly webbed feet. Even the tadpoles are
adapted to life in the fast lane, possessing sucker-like mouthparts that prevent
them from being swept away by the current.
One
of the coolest things about ghost frogs is their translucent belly through which the
innards can be seen. This together with its scarcity and secretive nature
accounts for its name. In fact, you’re almost more likely to
come across a real ghost on Table Mountain than one of these guys. Two decades
of hiking the mountain and I’ve only ever chanced upon one. They spend much of
the day underwater, ensconced in crevices, only emerging at night to feed on
insects.
So
how will you recognize one? If you find yourself along a fast-flowing stream on
the south or east side of Table Mountain at dusk – or at night with a headlamp –
and you come across a frog five to six centimeters long with enlarged toes and a striking skin coloration (pale green
with purple spots) perched streamside on a mossy rock, then you’re most likely looking at a ghost frog. Congratulations.
However, non-breeding adults occasionally do stray from streams and
venture into bogs and caves.
Sadly,
the ghost frog is set to become even more elusive, and might even face total extinction.
Tadpole numbers in Skeleton Gorge (one of its habitats) have dropped by an
estimated 50% since 1980. Not surprising that it’s listed as Critically
Endangered. With an area occupancy of less than 10 square kilometers and a
continuing decline in the extent and quality of its habitat, extinction is a
very real possibility. In fact, it has already become extinct in some parts of
the mountain. The main threats are the spread of invasive alien
(non-indigenous) vegetation, frequent fires and reservoirs (affect the
consistency of stream-flow). Furthermore, poor forestry practices also
contribute to the clogging of streams.
On
a brighter note, Table Mountain National Parks is committed to the eradication
of alien plants on the mountain – an ongoing programme that will benefit not
only the ghost frog, but many other native plant and animal species.
We
at Hike Table Mountain actively
involve ourselves in the fight against aliens (of the terrestrial kind!) through
the cutting down of cluster-pines (saplings), one of the most invasive aliens on the
mountain. Please feel free to contact us should you wish to join our next
outing.
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