He said he doesn’t pay attention to “tiniest” reports, but the frogs
themselves are a significant discovery.
“The discovery of two new frog species comes as great news against the
background of more prevalent accounts of tropical amphibian extinction,”
he wrote in an email.
Knowing about such tiny creatures and their ecology, he said, helps scientists “better
understand the advantages and disadvantages of extreme small size and how
such extremes evolve. Fundamentally, these tiny vertebrates provide a window
on the principles that constrain animal design.”
Mr Austin said that since these frogs hatch out as hoppers rather than
tadpoles and live on the ground, their existence contradicts the hypothesis
that evolution at large and small extremes is linked to life in water.
At least 29 species of minuscule frogs in equatorial regions worldwide live in
leaf litter or moss that is moist year-round and eat even tinier
invertebrates, creating a previously unknown “ecological guild” of
similar animals with similar life habits, he said.
“We realised these frogs were probably doing something incredibly
different from what normal frogs do – invading this open niche of wet leaf
litter that is full of really tiny insects that other frogs and possibly
other creatures weren’t eating,” Mr Austin said.
In August 2009, Mr Austin and graduate student Eric Rittmeyer were collecting
and recording the mating calls of frogs at night in a tropical forest near
the village of Amau in eastern Papua New Guinea, when they heard a chorus of
high-pitched “tinks.”
“This frog has a call that doesn’t sound like a frog at all. It sounds
like an insect,” he said. The calls seemed to surround them, and it
took a while to be sure they were coming from the ground.
Since they couldn’t locate the noisemaker, they snatched up some habitat,
expecting to find a six-legger in it.
“We found it by grabbing a whole handful of leaf litter and putting it
into a clear plastic bag and very, very slowly going through that litter
leaf by leaf by leaf until we saw that small frog hop off one of those
leaves,” he said.
Getting photos took some effort – the frogs can leap 30 times their own
length. After hopping around for a bit, they settled down long enough for a
close-up or two, Austin said.
Their expedition, sponsored by the National Science Foundation, later turned
up another new species of tiny frog, found farther west along the island’s
coast. The other is closely related, but a millimetre or so larger, and it
had a different call.
Mr Austin estimated that they found 20 previously unknown species in New
Guinea, which is such a hot spot of diversity that scientists figure they’ve
described only about six-tenths of all the species living there.
Maurice Kottelat, a Swiss scientist who found the tiny carp called Paedocypris
progenetica, wrote in an email that it’s hard to compare frogs and fish,
because they’re measured differently: frogs from nose-tip to the excretory
vent, and fish from nose to tail.
“It is not so interesting to know which is really the smallest. Tomorrow
will bring another smallest anyway,” he wrote.
He concluded a long email, “I have a great concern. It is not when will
we discover the next smallest, but whether habitats where to discover them
will still be there. Or how long will the habitats survive.
“Since the discovery of Paedocypris most of the fragile peat swamps that
it inhabits have been destroyed.”
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