NO. 3597 RODENT ETHOLOGY — EISENBERG 23 



ceding examples the primary aggressive or sexual drives are not con- 

 summated, and the male switches suddenly to an apparently meaning- 

 less pattern of digging and kicking back, often while orientated toward 

 the female. 



Species-specific Patterns of Mating Behavior: In a previous 

 publication (Eisenberg, 1963b), a series of heteromyid rodents was 

 compared in order to demonstrate the differences between species and 

 genera when the frecj[iiencies of the various mating behaviors were 

 compared. It was found that the same basic components were present 

 in almost all forms studied, but the relative frecjuencies were cjuite 

 different. Table 17 presents a comparison of mating patterns for 

 eight rodent species. All data were taken from behavioral records 

 that had terminated in a successful series of mounts. Again the 

 conclusion is unavoidable that, although the potential exists for 

 expression of the same motor units by almost all species, the relative 

 frequency of occurrence of any given unit exhibits unic[ue character- 

 istics for the species in cj[uestion. Little information can be gained on 

 taxonomic relationships from such an analysis since, in all probability, 

 the quantified movements are not critical releasers as is the case with 

 many birds and fishes. The role of chemical releasers that must act in 

 part to promote sexual isolation in small rodents (Godfrey, 195S) 

 renuiins to be investigated more thoroughly. 



AlthcHigh complete mating in the dipodids luider study was not 

 observed, certain characteristics of their precopulatory ritual render 

 it unique. Males of Allactaga elator and Jacvlvs orientalis exhibit 

 the following courtship patterns: As the female sits stationary, the 

 male approaches and touches his nose to hers. The male may then 

 groom the female on the head. If the female remains stationary, 

 the male will hop to the rear and sniff the base of her tail or, if her 

 rump is raised, he will perform an anal-genital snifi'. If the female 

 continues to remain stationary, he will straddle her tail and m.ount; 

 however, she may initiate washing or sandbathing behavior or move 

 away. In the former case, the male will pause and then hop around 

 her to begin again with naso-nasal contact. On the other hand, if 

 she moves away, he will follow and commence driving. While driving, 

 the male Allactaga emits a buzzing sound followed by an audible 

 squeak, whereas the male Jaculus emits only the buzz. This buzzing 

 sound is unique among all the species studied. The mating behavior 

 of J. jaculus has been described in part by Lewis (1965). It appears 

 that the maleJ-jaciz/ws utters a "chirping" call when driving the female. 

 During the mount, which lasts less than a minute, the male employs 

 a neck grip with his incisors. In the example cited, Lewis reports 

 that the couple fall to one side during the terminal phases of the 

 mount. (Compare with Dipodomys in Eisenberg, 1963b.) 



