The Chile Otter was originally described by Mr. Bennett from a specimen
presented to the Zoological Society by Mr. Cuming, but as this specimen
is a young animal, scarcely half-grown, it does not present some of the
characters of the species in so marked a manner as the adult. I have,
therefore, availed myself of an adult specimen in Mr. Darwin’s
collection, to draw up the above description.
Compared with the Common Otter (_Lutra vulgaris_, Auct.) the most
striking difference consists in the character of the fur: the hairs
instead of being adpressed as in that species, are here semi-erect, and
appear as if they had been clipped at the extremity. The fur is of a
deeper colour, but has a slightly grizzled appearance, owing to the tip
of each hair being of a much paler colour than the remaining part.
In the young animal described by Mr. Bennett, (which in weight was
probably not more than one-third of that of the present animal) the
hairs of the body are of an uniform deep brown colour; hence, if I am
right in considering Mr. Darwin’s animal as the same species, it would
appear that the grizzled character of the fur is dependent on age.
The semi-erect fur will also serve to distinguish the present species
from the _Lutra Platensis_; the fur is likewise longer, the tail is
shorter, and the feet are smaller in proportion. The most important
distinctions, however, are furnished by the skulls; I will, therefore,
compare them.
The skull of _L. Chilensis_ compared with that of _L. Platensis_, (Plate
35, figs. 4.) when viewed from above, presents but little difference in
general form; it is, however, smaller in all its proportions, and the
zygomatic arch is a little less convex: the palate is proportionately
shorter; the tympanic bullæ are much smaller, less elevated, and wider
apart, in which respect there is a greater approximation to the skull of
_L. vulgaris_ than to that of _L. Platensis_; but here, the tympanic
bullæ are larger than in _L. Chilensis_. Both in _L. Chilensis_ and
_Platensis_, the sub-orbital foramina are kidney-shaped, the emarginated
portion being downwards, whilst in _L. vulgaris_ they approach somewhat
to a triangular figure, the apex being external. In _L. Chilensis_,
however, this foramen is comparatively larger than in _L. Platensis_,
and the outer portion of the foramen forms the segment of a larger
circle than the inner one, whilst in _L. Platensis_ both portions are
equal.
The principal difference in the dentition of the La Plata and the Chile
otters, consists in the comparatively smaller size of the posterior
molars, both of the upper and lower jaws, of the latter species. In the
upper jaw, the “carnassière” has its inner lobe, approaching somewhat to
a triangular form, whereas in _L. Platensis_ it is broader and almost
semicircular. In the lower jaw, the last molar but one has the inner
lobe much smaller than the middle outer lobe, whilst in _L. Platensis_
these two lobes are of nearly equal size and elevation. Other points of
dissimilarity will be perceived in the annexed table of admeasurements.
_L. _L.
Chilensis._ Platensis._
In. Lines. In. Lines.
Whole length of skull 3 9¾ 4 2½
Greatest width 2 6⅓ 2 10⅓
Width of skull from the apex of one mastoid
process to the opposite 2 3¼ 2 8¼
Length of palate 1 6 1 10
Breadth of palate between the posterior molars 7¾ 7¾
Length from last molar to posterior margin of
palate 3⅓ 5½
from base of canine to hinder part of
last molar 11⅔ 1 1⅓
of carnassière 5 5⅔
Width of do. 5 6¼
Length of last molar 2¾ 3½
Width of do. 4⅓ 5⅔
Length of ramus of lower jaw 2 4½ 2 8¾
from canine to hinder portion of last
molar (lower jaw) 1 2¼ 1 4¼
of last molar but one (lower jaw) 5¾ 6⅔
Width of do. 2⅔ 3½
“These animals are exceedingly common amongst the innumerable channels
and bays, which form the Chonos Archipelago. They may generally be seen
quietly swimming, with their heads just out of water, amidst the great
entangled beds of kelp, which abound on this coast. They burrow in the
ground, within the forest, just above the rocky shore, and I was told,
that they sometimes roam about the woods. This otter does not, by any
means, live exclusively on fish. One was shot whilst running to its hole
with a large volute-shell in its mouth; another (I believe the same
species) was seen in Tierra del Fuego devouring a cuttle fish. But in
the Chonos Archipelago, perhaps the chief food of this animal, as well
as of the immense herds of great seals, and flocks of terns and
cormorants, is a red coloured crab (belonging to the family _Macrouri_)
of the size of a prawn, which swims near the surface in such dense
bodies, that the water appears of a red colour. This specimen weighed
nine pounds and a half.”—D.