RELATION OF SHEEP TO CLIMATE 1 
By Everett L. Johnson 2 
Department of Animal Husbandry, University of Illinois 
INTRODUCTION 
For many years sheep breeders have 
contended that breeding, feeding, and 
management are the chief factors in¬ 
volved in the further selection and 
development of the various breeds of 
sheep. But evidence from literature, 
together with the records of the univer¬ 
sity flock of the University of Illinois 
(at Urbana, Ill.), indicates that cli¬ 
matic conditions should also be con¬ 
sidered. 3 The data here presented 
seem to support the following: (a) 
Sheep are limited to certain climatic 
conditions; (b) some breeds are better 
suited to certain climates than to 
others; (c) sheep are especially sensitive 
in lambing time and rutting seasons; 
( d ) rutting season comes with falling 
temperature and varies from year to 
year; (e) high temperature with high 
humidity is detrimental to the growth 
of lambs; (/) some years are more 
favorable than others for lambing, 
growth of lambs, rutting season, and 
gestation period; (g) housing has ex¬ 
tended the limits of sheep production; 
(h) some shelter types are more desir¬ 
able than others. The climatic diagram 
methods used here were applied to 
tropical crops by Taylor (25)* The 
writer is not aware of a previous appli¬ 
cation of this method to a critical period 
by months and to good and bad years. 
WILD SHEEP 
The ancestry of domestic sheep is 
not definitely known. It is most prob¬ 
able that the Mouflon, or European 
wild sheep, and one of the races of 
Asiatic urial (Ovis cycloceros ) have 
formed the chief parent stocks (Lydek- 
ker, 17, p. 27). The Mouflon (Ovis 
musimon) is still found in Corsica and 
Sardinia. That at one time it had a 
wider distribution is evidenced by the 
remains of wild sheep in the superficial 
deposits of various parts of south Eu¬ 
rope. The breeding or rutting season 
occurs in December and January. The 
gestation period is about 145 days, and 
the lambs (generally two) are born in 
April or May. The wild Mouflon inter¬ 
breed with the domestic sheep and the 
offspring are fertile. The body covering 
of hair has to a minor degree the 
serrated scales which give to wool its 
felting property. The cry of the adult 
is a bleat very similar to that of 
domestic breeds (17, 18, 19). Sheep 
in the wild state are essentially moun¬ 
tain animals. They shun forests, live 
in the open, and feed upon the moun¬ 
tain grasses. The climatic conditions 
in such regions as the higher parts of 
Sardinia and Sicily are probably most 
suitable for sheep. The days are hot, 
the nights cool, the winters mild, with 
more or less rainfall; and the summers 
are dry (2). The sheep avoid the heat 
in the valleys by moving up the moun¬ 
tains, where it is cooler and where the 
grazing is less affected by the dry 
weather. 
PRESENT DISTRIBUTION OF DO¬ 
MESTIC SHEEP 
Sheep are not uniformly distributed. 
There is dense sheep population in 
some localities and none in others (6). 
These areas of dense population have 
similar climates. The ideal climates 
here represented for sheep (fig. 1) are 
based upon these dense centers. The 
radical way in which such climates dif¬ 
fer from others is emphasized by com¬ 
parison with Taylor’s 1919 diagrams. 
Each locality probably, though not 
necessarily, has the breeds which 
1 Received for publication Apr. 2,1924—issued February, 1925. Contribution from the Department of 
Animal Husbandry and from the Zoological Laboratory (No. 252) of the University of Illinois. 
2 The writer desires to express his appreciation to Dean W. C. Coffey, of the University of Minnesota, 
for suggesting the problem. He is indebted to Prof. H. P. Rusk and to W. G. Kammlade for many 
courtesies extended during the course of the investigation, especially in the securing of equipment and in 
giving access to the records of the university flock. The assistance from the graduate school research funds 
for the purchase of hygrothermographs to carry on a part of the work was invaluable. Thanks are es¬ 
pecially due to Dr. V. E. Shelford for his encouragement and for suggesting and supervising the work 
with the graphic methods employed. 
1 A summary of the more important literature reviewed is contained in a manuscript in the library of 
the University of Illinois (master’s thesis), where important sections are quoted from the original sources 
and full citations given. 
* Reference is made by number (italic) to “ Literature cited, ” p. 500. 
Journal of Agricultural Research, 
Washington, D. C. 
( 491 ) 
Vol. XXIX, No. 10 
Nov. 15, 1924 
Key No. I11.-20 
