While the turtle-jawed goose foraged the forests of Kauai
during the day, nighttime on the island brought out an entirely different, and
even weirder, character. Snuffling through the underbrush, poking its sensitive
bill through the leaf litter, something else was stirring.
Enter Talpanas
lippa, the nearly-blind mole-duck. The evolutionary origins of this bizarre
bird are still a mystery and, like the turtle-jawed goose with which it existed,
the greater age of Kauai had clearly wrought the mole-duck into a
super-specialized and unique species. T.
lippa was adapted not for a life of browsing or dabbling for water plants;
instead, it probed the detritus for worms and insects like the kiwis of New
Zealand.
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| Talpanas lippa, the nearly-blind mole-duck of Kauai. Reconstruction by Julian Hume. |
The largest mole-ducks were the size of female mallards,
though their physique was much stockier. Its legs were shorter and stronger
than those of similarly-sized ducks, and its feet probably lacked webbing, as
this was an animal clearly adapted for the terrestrial life. Though a complete
skull remains undiscovered, the holotype fossil of this species is its
braincase, revealing unique characteristics about the mole-duck beyond its
external features.
The true weirdness of the mole-duck lies beyond its stout
body. The foramina, holes through which nerves and arteries are connected to
other areas around the skull, are unlike those found in any other living
species of duck. The optic foramen, connecting the brain to the optic nerves,
is extremely reduced, and leads to equally small orbits: T. lippa had beady eyes and extremely poor eyesight. (James et. al, 2009)Now, these adaptations are
common among nocturnal insectivores, and they do not pose a problem to the
little mole-duck. But every nocturnal hunter needs a way to find its prey; if
it didn’t rely on eyesight, just how did it seek out its food?
The mole-duck, rather than using sight to find its prey,
used its sense of touch. Kiwis use whisker-like feathers to feel for worms in
the soil, but the mole-duck had a much broader, flatter bill. Connected to this
bill, however, were huge foramina through which passed the bird’s trigeminal
nerves, which are responsible for sensation in the facial region. The
mole-duck, it seems, had an extremely sensitive bill, perfect for detecting
minute vibrations and movements under the rotting leaves and logs on the forest
floors of Kauai. (James et. al, 2009)
Platypuses (platypi?) hunt their aquatic prey in a similar fashion: their bills
are extremely sensitive, and can be used like a giant, flat hand as they sift
through the substrate.
It doesn’t get much weirder than T. lippa. It really doesn’t. Over generations and generations, the
awesome powers of evolution turned an ordinary-looking duck to a stumpy,
nocturnal, platypus-billed, nearly-blind insect-hunter. It’s a shame that such
an interesting and indescribably unique species no longer scuffles through the
nighttime Hawaiian forests, where daylight saw the march of heavyset,
turtle-jawed, titanic herbivorous waterfowl. The more we discover about the
bizarre ducks of Hawaii, the more we learn about the incredible niches which
these waterfowl were so diverse to fill.
References
Cooper, A.; Fleischer, R.C.; James, H.F.; Olson, S.L.;
Paxinos, E.E.; Quinn, T.W.; and Sorenson, M.D. 1999. Relationships of the
extinct moa-nalos, flightless Hawaiian waterfowl, based on ancient DNA.
Proceedings of the Royal Society B 266, 2187-2193.
James, H.F. and Olson, S.L. 1991. Descriptions of
thirty-two new species of birds from the Hawaiian Islands, part I.
non-passeriformes. Ornithological Monographs 45, 1-88.
James, H.F.; Olson, S.L.; and Iwaniuk, A.N. 2009.
Extraordinary cranial specialization in a new genus of extinct duck (Aves:
Anseriformes) from Kauai, Hawaiian Islands. Zootaxa 2296, 47-67.
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