6 The Mammals of Colorado 
were more or less migratory, moving north in the spring two 
hundred to four hundred miles, and south again in the fall. 
When the Union Pacific Railroad was built across the plains 
in 1 867-1 870, it seemingly split the herds into two parts, 
which became known as the northern and the southern herds. 
This separation was probably caused by the great amount of 
hunting along the railroad. In 1874 the southern herd was 
practically exterminated, though a few individuals and small 
FIG. 6. BUFFALO BULL 
Photographed in the Goodnight Herd, Texas, by Donald DeWitt 
bands lingered until 1889. The last one in southeastern 
Colorado was killed near Springfield, Baca County, in 
1889. 
The northern herd lingered longer, but was gone in 1885. 
A few scattered ones remained, as in the case of the southern 
herd, but every man's hand was against them, and they have 
followed their friends. The last bull in the Pike's Peak 
