Adsersen, Anne

Adsersen, Henning

English

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THE MYSTERY OF THE FERNANDINA "MOUSE".
by
Anne and Henning Adsersen,
¡nstitute 01 Plant Ecology, University 01 Copenhagen
In oticias 44, Fritz Trillmich contributed an artic\e on the danger to the endemic rice rats of Fernandina
(Na borough) Island if alien black rats should be introduced. He pointed out that two species had been
rec gnized,Nesoryzomys narboroughi,whichwas present in goodnumbers,andN.lernandinae, a smaller
spe ies which was known only from skulls recentIy found in fresh owl pellets. No mouse has hitherto been
ide ified on Fernandina, an island still considered free from introduced species. Dr. Trillmich's artic\e has
pro oked comment - which is just what he intended. Ed.
De bie Clark's chapter on the native mammals in the Ga:apagos volume in the Key Environments series
(Pe gamon Press, Oxford) and Fritz Trillmich's recent pIea in Noticias for captive breeding of the
Fer andina endemic rat have revived memories of observations we made 13 years ago.
In 1 te May 1974, Beagle III set us ashore at Cape Hammond, together with the Belgian malacologist, Guy
Co pois. There we had plenty of opportunity to get acquainted with rice rats, not only at night but even
in t e morning when we had to drive them out of the tents. After some days on the coast, we had to begin
the wearisome task of carrying supplies of water to our secondary camp at the base of the main slope ofthe
vol ano. On one of these shuttles we found it convenient to stay the night in the middle of a vast lava field;
it as an area where large lava plates offered a rough but even surface for spending a night under the stars.
A ~ w tall Jasminicereus cacti stood guardia n over us. One ofthem had lost one of its cylindrical segments,
an this lay on the lava as a hollow tube as the soft tissue inside had decayed. During our frugal breakfast
we uddenly noticed a small rodent probing around the dead cactus tube. We were immediately convinced
th it was not the same species as our furry tent-mates at the coast. Then it ran into the hollow cactus and
we were able to catch it by holding our hands on both ends of the tube. Its capture presented problems
be ause we were only equipped to collect plants and snails. While we were considering what to do, it
es ped and disappeared into a fissure in the lava. To cut down weight on these tiring water treks we had
br ught no camera and so we cannot produce any proof of our observation. In view of this and of the
pa sage of 13 years, the following description should be treated with great caution.
T e animal had adistinctly mousy appearance and was only halfthe size ofthe rats we knew at the coast. It
was more slender; its fur was less dense, more grey and lacked the brown tinge of the other. Its ears were
larger and they were naked; we are fairly certain that it was this last fact which immediately persuaded us
that this was a different kind of animal. It did not seem particularly scared of us and we believe that it
disappeared into the lava crack to avoid the sunlight rather than to escape from us. Our immediate
reaction was to think that Fernandina had got its first introduced mammal but, on further consideration,
it struck us as unlikely that recently introduced mice would have traversed the several kilometres of sterile
lava that separated us from the coast. It seemed more likely that this little animal had come from one of the
cIumps of vegetation that occur in the south-western part of Fernandina's lava fields.
When we returned to the CDRS and reported our observation, we were met with solid scepticism and
ended up by concluding that what we had seen must have been an immature Fernandina rat. However,
now that there is recent evidence of another species of rodent on the island, we are left with little doubt in
our minds that this was the animal we actually saw alive. Furthermore we believe that there should be a
fair chance of capturing a specimen in, or cIose to, the islands of vegetation in the sea of lava that covers
south-western Fernandina.
26
Noticias de Galapagos v.45 1987
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The mystery of the Fernandina "mouse"

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The mystery of the Fernandina "mouse"

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