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98 JOURNAL OF MAMMALOGY 
band of does and kids by a larger and stronger buck. Usually the 
contests do not develop into a battle; the weaker animal gives up 
after a pass or two and is chased off by the victor. Where a fight does 
develop the two bucks come together head on, then each strains hard 
to push his rival back. After a minute or two, one suddenly springs 
away, turns, and is off like a shot with the other in hot pursuit for a 
half mile or more. At other seasons they seem even more peaceable, 
and I can only attribute the fact that almost every shed horn found is 
marked with scars, to the fact that the sheath is comparatively soft 
and that they are shed so soon after the rut is over. 
The period of gestation is a little over eight months or slightly longer 
than with deer. Late in May, or early in June, the doe retires to some 
secluded spot and there the kids are born, usually two at a time. Com- 
pared with deer and elk of the same age, a prong-horn baby is unusually 
strong and reliant. True it trusts largely to hiding to escape its enemies, 
but if necessary, it can run quite fast. If the mother has any chance 
at all to fight for her youngsters, she will attack at once and fight with 
great intrepidity. She uses her sharp hoofs with fine effectiveness, 
striking a quick, downward blow with her fore feet that easily disables 
a coyote or similar foe. There being no rattlesnakes in the Yellowstone, 
I cannot confirm of my own knowledge that she can cut one to pieces 
before he can strike, but I do believe it probable. That the young are 
efficient in their fight for existence is shown by the number that survive 
the first year. In the spring of 1921, I found by careful count that 
almost 19 per cent of our herd were young ones approaching one year 
old, this figure being much higher than for our other large animals. I 
remember well a little fellow found one fourth of June; I did not see 
his twin until later, and the mother, not at all. He w^as unseen until 
I almost stepped on him; when he ran, he started at once at full speed, 
and so astonishing was his speed he seemed fairly to fade from sight 
into the misty rain that was falling. He was somewhat lighter in color 
than the adults, and with markings nowhere near as distinct, but his 
coat served him well, protectively, among the gray glacial boulders of 
his native bench land. Later I found his brother in the lee of one 
of these same boulders. Judging from what I have seen, new-born 
kids are capable of withstanding quite severe cold spells, and storms of 
snow and hail. 
Sometimes I find old bucks off by themselves; but there are enough 
exceptions, so that I would not feel safe in saying either that hermitage 
was usual for the old fellows, or that it was not. As I have said before, 
