Cary’s observations at Monahans, Tex., and those of others at numerous localities, combined with our own, show that at various times the dens furnish protection and shelter for various species of cottontail rabbits (Sylvilagus), ground squirrels (Citellus and Ammospermophilus), wood rats (Neotoma), grasshopper mice (Onychomys), rattlesnakes (Crotalus), and most of the common lizards.  Of these the ground squirrels Citellus tereticaudus and Ammospermophilus harrisii are most often noted on the Range Reserve using the dens as a retreat, the Ammospermophilus seldom being observed to enter any other kind of burrow.  It should be added that the total observations include dens which have been deserted by their rightful owners.

NATURAL CHECKS.

The enemies of the kangaroo rat are not determined in detail, or as to relative importance, but the badger (Taxidea taxus berlandieri) and the kit fox, or swift (Vulpes macrotis neomexicana), may well be foremost.  Dens which have been deeply excavated by badgers are frequently seen, and sometimes two or three badger tunnels penetrate one burrow system.  Dens thus despoiled are probably soon reoccupied even if the original owner is captured, and in the course of a few months the reworking of the abode obliterates the signs of destruction.

Droppings of the kit fox show an abundance of bones of small mammals of kangaroo rat size, among them those of spectabilis.

Bobcats (Lynx baileyi) and coyotes (Canis mearnsi) probably are a prejudicial factor.  Skunks may sometimes be able to surprise the kangaroo rats, but probably not often.  The western horned owl (Bubo virginianus pallescens), the barn owl (Tyto alba pratincola), and perhaps others may well be among the most feared enemies, but no special investigation of owl pellets on the reserve has been possible.  In 592 barn-owl pellets from California were found remains of 230 kangaroo rats, only one other rodent being represented by a larger number (McAtee, 1921, 258).

Much more information on enemies is needed.  The relatively low rate of reproduction (see p. 18) indicates comparative freedom from inimical factors.

PARASITES.

Dipodomys s. spectabilis is regularly infested with a species of flea, Ctenophthalmus sp.  Seldom or never is a specimen taken in reasonably fresh condition without some of these parasites present on its body, though of course they desert the body of the host after it becomes cold, and hence dead specimens left too long may be free from them.  The den conditions are ideal for the breeding of this parasite, because of the great quantities of fine, dusty, organic refuse littering the tunnels and furnishing food and refuge for the larvae.  As demonstrated to us by F. C. Bishopp, of the Bureau of Entomology, a handful of this refuse taken from the floor of a burrow within arm’s length of the entrance is almost certain to contain these larvae.