The young of nelsoni are apparently all born before the last of April. None of the numerous females taken in the vicinity of Bakersfield between April 27 and May 12 were found to contain embryos. A male one-fourth grown was taken eight miles northeast of Bakersfield on May 7, 1911, and a half-grown young one was taken at McKittrick on May 18, 1911. On May 9, 1918, two immature individuals, weighing 100 and 103.3 grams, respectively, were taken at the mouth of San Emigdio Creek. These, male and female, were thus over two-thirds grown and were at this time foraging for themselves. These two youngsters were extremely playful and on several occasions they were seen to stand upon their hind legs and with their front paws braced against one another's shoulders they wrestled and pushed each other about energetically. The parents of these young squirrels had evidently cast them off to shift for themselves.
Because the California and Fisher Ground Squirrels have increased and profited by the farming activities of man in parts of the San Joaquin Valley, it has been suggested that possibly this increase has tended to crowd out Ammospermophilus nelsoni and therefore restrict the range of the latter (Taylor, 1916, p. 20). At the mouth of San Emigdio Creek both nelsoni and fisheri were found in numbers. Old colonies of fisheri, as shown by their extensive workings, were found between colonies of nelsoni. The Antelope Squirrels occupied the sandy washes and the areas covered by the salt-bush, while the Digger Squirrels occupied the more open tracts which were covered by a low growth of foxtail. While there must be a certain degree of competition as regards food supply between the two kinds of squirrels, this competition is probably no greater than that which exists between the Nelson Antelope Ground Squirrel and, for example, each of the two species of kangaroo rats which forage at night for similar food over the same ground used by the Nelson Squirrels in the daytime. We found no evidence, in this case, that the Digger Squirrels were driving out the Antelope Squirrels.
The badger is one of the chief enemies of the Nelson Ground Squirrel. Many squirrel burrows were found that had been dug out by this animal, and, since in their refuge burrows these squirrels have no back door of escape, capture in such cases must be more or less certain.
On May 19, 1918, a pair of Nelson Squirrels was observed to remain out in the open and watch a pair of Golden Eagles go through a series of aerial evolutions overhead, in which, with talons tightly locked together, the birds looped the loop three times. The eagles were obviously seen by the squirrels, and the swish of their wings was plainly heard by the observer, yet the squirrels were not in the least alarmed. However, when a Red-tailed Hawk flew over, the squirrels hustled at once into their holes. It was therefore inferred that the hawks and not the eagles were the active enemies of these small squirrels. Coyotes and kit foxes also dig out the squirrels in their burrows and probably pounce upon a few individuals during the daytime.
In foraging, these squirrels slip along close to the ground, often stopping in the shelter of a bush or pausing in the open and searching quietly, with body extended, for small seeds upon which they feed. On May 6, 1918, an old female which was nursing young was observed for several minutes at a distance of fifty feet. During this time the squirrel stood at her full height with body erect, busily munching a green head
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