NO. 3597 RODENT ETHOLOGY — EISENBERG 17 



forepaws and iiose by jerking the body back and I'ortli in the vertical 

 plane while holding the forepaws rigid on either side of the nose. The 

 forepaws and nose strike the soil and serve to tamp it firmly into place. 

 Allactaga and Jaculus pack loose soil b}^ raising and lowering the head 

 in the vertical plane, thus repeatedly bringing the snout and incisors 

 against the substrate. This packing method appears to be highly 

 ritualized in the Dipodidae. The heteromyid rodents as well as Gerhillus 

 and Pachyuromys appear to employ pushing and patting with the 

 forepaws as the principal method for packing the tunnel walls. 



Assembly of foodstuffs. — Studies of Aleriones i^ersicus (Eibl- 

 Eibesfeldt, 1951) indicate a tendency to bite pieces of food (e.g., 

 vegetable matter, stalks, roots, pods) into small pieces, which are then 

 cached. This behavior pattern has been termed "Hackseln" and is here 

 translated as chopping. M. unguiculatus , M. hurrianae, and Tatei'a 

 indica all exhibited this trait. 



The caching of foodstuffs either m the burrow or in discrete loci 

 within the animal's home range is a behavioral trait shared by many 

 species of rodents. The family Heteromyidae is characterized by a 

 persistent tendency to gather and cache great quantities of grain, and 

 this behavioral trait is correlated with the possession of capacious, 

 externally opening, fur-hned cheekpouches (Eisenberg, 1963b). None 

 of the other genera in the current study exhibited such persistent 

 caching behavior, and the dipodid genera do not seem to cache very 

 much at any time during theu" annual cycle. Allactaga and Jaculus 

 will assemble dried grasses in their burrows, but this material is 

 generally used in nest building rather than as food (see table 8). 



Discussion. — Behavioral and ecological convergences appear to 

 be very close when the genera Perognathus, Gerhillus, and Pachyuromys 

 are compared. Although the genera Alicrodipodops , Dijwdomys, 

 Jaculus, and Allactaga are ecologically similar and have evolved a 

 similar morphology correlating with their bipedal form of locomotion, 

 rather profound behavioral and physiological differences separate the 

 bipedal Heteromyidae from the Dipodidae. The most basic correlate 

 appears to involve the reduced caching tendency of Jaculus and 

 Allactaga with a concomitant tendency to hibernate or exhibit periods 

 of torpor (Skvortsov, 1955, 1964). Dipodomys caches seeds and is not 

 known to hibernate. 



Since the Heteromyidae are essentially solitary rodents with a 

 ver}^ low threshold for the exhibition of agonistic behavior, this 

 tendency toward asocial behavior may correlate with the fact that 

 the genera Dipodomys and Microdipodops do cache and the fact that 

 the selective advantage of caching is related to a dispersed or solitary 

 social structure. 



242-222—67 2 



