48

Tce remains in Athabaska lake until about the middle of June, in parts of
Great Slave lake until the early part of July, and in Great Bear lake until some-
what later, In the autumn, ice begins to form in the bays and sheltered parts
of the great lakes early in October, but on account of storms the main bodies

of the lakes remain open for several weeks after. The small inland lakes and:

muskegs are frozen by the end of October in the southern part of the basin and
about a month earlier in the northern part. There is a difference, also, of about
a month, between the southern and the northern parts of the basin, in the
disappearance of the winter snow in the spring and the breaking up of the ice
in the streams.

FAUNA

Because of its wide range in latitude and the diversity of its topographic
features the basin of Mackenzie river contains a great variety of game and fur-
bearing animals and birds, besides several species of food fishes,

Moose (Alces americanus) are found throughout the whole region north-
ward to the mouth of the river and eastward to the limit of trees. They are,
however, more numerous in the central and mountain portions of the region
than in the rocky Laurentian plateau to the east.

Barren-ground caribou (Rangifer arcticus) are abundant at different seasons
of the year in different parts of the eastern border of the basin, both in the
Barren grounds and the forested country bordering them, They are in the main
migratory in their habits and travel southward to the shelter of the woods in the
autumn and north again in the early spring. |

Woodland caribou (2. caribou) are not abundant anywhere and their range
extends northward only to about latitude 62 degrees, but the mountain caribou
(R. curibow montanus) are found in the Rockies and in the Mackenzie mountains
as far north as Gravel river. , :

Mountain sheep of three varieties (Ovis canadensis, O. stonet, and O. dalli)
oceur throughout the Gordilleran region, Ovis dalli, however, being confined ta
Mackenzie mountains, Ovis stonei to the Rockies about the head of the Liard
river, and Ovis canadensis to the south of this.

Mountain goat (Oreamnos montanus) range throughout the Rocky
mountains and are said to be found also in the southern part of Mackenzie
mountains. |

Muskox (Obivos moschatus) are confined to the barren grounds and are
now even being restricted to the more inaccessible parts of that region. Within
the Mackenzie watershed they occur now only about Aylmer and Clinton-Colden
lakes.

Wood bison or buffalo (Bison athabascw) formerly ranged over much of

the country from Athabaska river to the Liard, but are now restricted to a few -

herds embracing some hundreds of individuals which inhabit the region west
of Slave river (Plate VII) and north of the Peace.

The black bear (Ursus americanus) occurs more or less abundantly
throughout the whole region and its range is coextensive with the forest,

Grizzly bears (Ursus horribilis) are found throughout Rocky, Mackenzie,
and Richardson mountains as far north as the delta of the Mackenzie.

The barren-ground bear (Ursus richardsoni) frequents the Barren grounds,
but is not uncommon in the wooded country on the north and south shores of
Great Bear lake.

15850—4