[Illustration:  PLATE IX.  FIG. 1.—­KANGAROO RAT NEST AND YOUNG.

Nest and the two young, the ordinary number in the litter, of Dipodomys s. spectabilis, taken from den on January 31, 1920.]

[Illustration:  PLATE IX.  FIG. 2.—­YOUNG OF THE KANGAROO RAT.

The same young as shown in Figure 1, above.  They were probably about two weeks old, the pelage being short but with the white markings of the adult; the tails are relatively short and with scarcely any hair.]

COMMENSALS AND ENEMIES.

COMMENSALS.

It is doubtful whether any animals live in a truly commensal relationship with spectabilis, but of not unfriendly associates there are a great number.  It is the experience of Bailey, corroborated by observations of Vorhies on living animals, that these kangaroo rats are active in defending their caches of food, and will even fight individuals of the same species savagely and to the death.  One moonlight night a strange individual was liberated on a mound.  It deliberately entered one of the openings, but after about two minutes’ time made an exceedingly rapid exit, running rapidly out of sight as if pursued, though the owner of the home did not appear outside of the burrow.  There can be little doubt that the stranger was precipitately ejected by the owner.  We suspect, though this is a point difficult to prove satisfactorily, that merriami does not always store food supplies for itself, but visits the burrows of spectabilis regularly to pilfer the seed stored therein.  The observed facts thus far recorded which suggest this are that in no merriami burrow examined has a store of food been found, and also that in trapping for spectabilis on its own characteristic mounds one catches a large percentage of merriami.

On two separate occasions Vorhies has observed the smaller species running over the mounds of the larger, actually carrying away the grain which had been placed to entice the larger when it might appear. (In these cases the larger species did not put in an appearance until near morning.) Furthermore, the dens of merriami are often connected by distinct runways with those of spectabilis, indicating much traveling or visiting.  That this is probably not friendly visiting is suggested by the certainty with which an individual of the larger species will strike and kill one of the smaller when they are placed together in the same inclosure.  The word “thief” expresses this suspected relationship better than would the term “parasite.”

It is not to be expected that such obvious shelter retreats as the mounds of spectabilis should fail to attract the attention of other animals.  We have found a small gecko (Coleonyx variegatus), scorpions of two or three undetermined species, and certain insects (of the Order Orthoptera) to be very common inhabitants of the dens.  With the exception of the parasitic insects the most common are wingless locustids (Ceuthophilus spp.) and the peculiar wingless females of a species of cockroach (Arenivaga erratica).  These two are seldom absent when a burrow is excavated, the female cockroaches being abundant, although the winged males have never been taken in the burrows.