Part 16

Southern Grasshopper Mouse

Grasshopper mice seemed to be partial to the more sandy parts of the Joshua tree flats where the mice were trapped regularly but not abundantly. This mouse inhabited the barren sandy channels of Mescal Wash but was rare on the adjacent juniper-clad benches. In the arid, sandy washes this typical desert rodent penetrated the high pinyon-juniper association.

Wherever grasshopper mice occurred they were outnumbered by most of the other rodent species. For example, on November 26, 1949, below Graham Canyon, 100 snap traps yielded 10 Dipodomys panamintinus mohavensis, 2 Dipodomys merriami merriami, 4 Peromyscus maniculatus sonoriensis, and 3 Onychomys torridus pulcher.

Where abandoned kangaroo rat burrows were common in the Joshua tree belt these burrows were used as retreats by Onychomys. Some traps set at the entrances to old burrows caught grasshopper mice.

Specimens examined.--Total, 7, distributed as follows: Los Angeles County: 8 mi. E and 3 mi. S Llano, 3500 ft., 1; Mescal Wash, 4200 ft., 5 (3 PC); 2 mi. S Valyermo, 4600 ft., 1 (PC).

=Neotoma lepida intermedia= Rhoads

Desert Woodrat

This species was on the Pacific face of the Mountains from 1600 feet elevation in the coastal sage belt, to 4800 feet elevation in open groves of big cone-spruce and scrub oak of the chaparral association.

The local distribution of this woodrat is determined by suitable nesting sites. Although taken in different types of vegetation, lepida, without exception, was associated with rocky areas or areas supporting patches of prickly-pear cactus. In the channels of San Antonio Wash, lepida was commonly associated with jumbles of boulders and boulder-dotted cut banks. There the vegetation is sparse, and the rats dwell among the rocks; only their droppings and faint trails indicate their presence. Among boulders lepida builds only small houses of sticks and debris, and even these only occasionally. The effect of the prickly-pear cactus on the distribution of lepida in the sageland is striking; trap lines there yielded no woodrats where extensive rock piles and patches of prickly-pear were absent, but many rats were taken where patches of prickly-pear are plentiful. On an acre supporting coastal sagebrush at the mouth of San Antonio Canyon, at 1800 feet elevation, there were fourteen patches of prickly-pear, each covering at least thirty square feet. In these patches there were thirteen occupied woodrat nests. Only one patch lacked an occupied nest, and this one contained the remains of an old nest. On this acre there were at least thirteen individuals. In the sagebrush belt only an occasional large patch of cactus lacks a woodrat house occupied by lepida. Seemingly Neotoma fuscipes does not build houses in patches of prickly-pear.

Most of the houses built by Neotoma lepida are small and simple as compared to those of Neotoma fuscipes, and often in rocky areas no nests are in evidence. The most elaborate nests are built among the pads and spines of the prickly-pear and under laurel sumac or other large shrubs growing near washes. One of three houses examined at the mouth of San Antonio Canyon was on sandy ground in a patch of Opuntia measuring approximately 11 x 14 feet. The house was 14 inches high and 41 x 37 inches at the base. It was built around the main stem of the prickly-pear and a rock about 10 inches in diameter. The house was constructed of sticks of coastal sagebrush and buckwheat, and was dotted with dissected fruits and flowers of the prickly-pear. The main chamber was arched over by the main stem of the prickly-pear and was roughly 12 x 19 inches, inside dimensions, being reached through two three-inch openings, one on the east side of the chamber and one on the north side of the chamber. Two cup-shaped nests were inside the chamber, these being constructed mostly of grasses, and each resembling a well constructed bird nest 4 inches in diameter. The grass nests were free of feces, but feces were piled up against the west side of the chamber with many snail shells and dissected fruits and flowers of prickly-pear. Thirty-five inches from the main chamber was a third grass nest on the ground beneath a cluster of cactus pads. Next to this there was a blind burrow about eight inches long, and one and three-quarters inches in diameter. No burrow led to the main chamber, in this or in either of the other houses, but all had at least one short blind burrow beneath the house.

At many houses there were one to three grass nests outside the house on the ground, within four feet of the house. From each nest a well worn path lead to the house. Traps set in these nests invariably caught woodrats.

The many prickly-pear fruits and snail shells in and around the houses of lepida probably were remnants of food. So many of the rodents caught in traps near woodrat nests were partly eaten--usually the brains were taken--that I suspect the woodrats of eating their relatives. The heads of many composite annuals were piled near woodrat nests.

Immature individuals were taken in September, October, and early November, and on September 26, 1951, a lactating female was trapped near Palmer Canyon.

An old female bobcat trapped in Thompson Canyon had masses of cactus thorns beneath her skin, especially about the forelegs. These thorns were probably received while she was foraging in growths of prickly-pear for woodrats. The other bobcats from San Antonio Wash also had accumulations of thorns under the skin of the forelegs. Fragments of the skulls of Neotoma lepida were recovered from horned owl pellets and coyote feces.

Specimens examined.--Total, 7, distributed as follows: Los Angeles County: San Antonio Canyon, 4500 ft., 2; San Antonio Wash, 1800 ft., 5 (2 PC).

=Neotoma lepida lepida= Thomas

Desert Woodrat

These woodrats were present in rocky situations along the desert slope from the lower edge of the juniper belt down into the desert. Specimens were taken in piles of boulders in Mescal Wash, and amid rock outcroppings on the steep, barren, south slopes at the base of Grandview Canyon, whereas none was found on the juniper-clad benches.

This woodrat built no nests in rocky areas; however, in the Joshua tree belt N. l. lepida often built small nests at the bases of large standing or prostrate Joshua trees. There sticks from creosote bushes, along with cow dung and small stones were favorite building materials. Judging from the large number of unused woodrat nests in the Joshua tree flats it seemed that this rat was formerly far more common than it was in the period of this study.

Specimens examined.--Total, 9, distributed as follows: Los Angeles County: 6 mi. E and 1 mi. S Llano, 3500 ft., 4; Mescal Wash, 4200 ft., 5 (3PC).

=Neotoma fuscipes macrotis= Thomas

Dusky-footed Woodrat

This subspecies was widely distributed along the coastal slope of the mountains from the coastal sage belt, at roughly 1600 feet, up to 6500 feet at the lower edge of the yellow pine forest and was most common in the chaparral association.

In the coastal sage belt these woodrats are restricted to wash areas where large chaparral plants such as lemonadeberry and laurel sumac are used as nesting sites. In San Antonio Wash the occasional large juniper trees almost invariably harbor the nests of fuscipes. The general absence of suitable nesting sites in the sage belt probably limits the spread of fuscipes in this area.

In the upper part of the chaparral belt in talus these woodrats live beneath the angular boulders and build no visible houses. Several areas of talus occupied by woodrats were examined carefully and no sign of houses was noted.

Two juveniles were found in the stomach of a rattlesnake (Crotalus viridis helleri) killed in May, 1948, at the mouth of Evey Canyon. Remains of woodrats were found in feces of the coyote and gray fox.

Lactating females of this species were taken on March 16, and October 2, 1951.

Specimens examined.--Total, 4, distributed as follows: San Bernardino County: Icehouse Canyon, 5500 ft., 2. Los Angeles County: San Antonio Canyon, 2800 ft., 2.