14 - Size change in North American Quaternary jaguars

Summary

The jaguar (Panthera onca), largest of the New World felids, was formerly widespread in the Neotropical and Nearctic regions. In North America, pre–Wisconsinan jaguars ranged farther north than did those of the Wisconsinan. The present–day range of this species is far to the south of its Wisconsinan range (Figure 14.1). This illustrates a gradual restriction in the range of this species, though this general trend probably was influenced by a sequence of glacial–interglacial shifts in range (Kurtén and Anderson, 1980). The earliest jaguar may have been conspecific with the middle Pleistocene P. gombaszoegensis of Eurasia (Hemmer, 1971) that probably dispersed across the Bering land bridge to reach North America at that time (Kurtén, 1973). If that is true, the living species can be considered a relict population of a once more widely distributed Holarctic form (Kurtén and Anderson, 1980).

Concurrent with this restriction in range was a reduction in size. According to Kurtén (1973), size reduction proceeded gradually from the Blancan (Curtis Ranch, now known to be Irvingtonian) (Kurtén and Anderson, 1980; Schultz, Martin, and Schultz, 1985) to the present, although it may have accelerated during the Holocene (Kurtén and Anderson, 1980). Also, there was a gradual shortening of the limbs, especially the metapodials. Hence, the earliest North American jaguar lacked some of the living jaguar's specializations – its limbs were longer and their distal portions were less shortened (Kurtén, 1973).