The taxonomy of ruminant Trypanosoma theileri and its relatives (Kinetoplastida: Trypanosomatidae) is controversial, with recent phylogenetic studies segregating T. theileri in cattle and other ruminants worldwide into two major genetic lineages (the TthI and TthII clades) based on genetic markers. In the present study, T. theileri-like trypanosomes isolated from Honshu sika deer (Cervus nippon) in the western Japan (YMG isolate) were genetically characterized using a number of genetic markers. Sika deer trypanosomes of the YMG isolate were genetically different from the Trypanosoma sp. TSD1 isolate previously recorded from Hokkaido sika deer in northern Japan, with the former trypanosome isolate being genetically closer to European cervid trypanosomes and the bovine T. theileri TthII lineage. In contrast, the latter isolate exhibited greater relatedness to North American cervid trypanosomes and the bovine T. theileri TthI lineage, although a clear genetic distinction between these was apparent. Furthermore, trypanosomes in Honshu sika deer from the central part of Japan harboured additional genetic diversity and were closer to either TSD1 or YMG isolates, while distinct from known T. theileri-related genotypes. Importantly, cervids and wild ruminants worldwide might harbour divergent descendants of a T. theileri ancestor, which exhibit rigid host specificity to either bovines or cervid species.

Rutting calls of male and alarm calls of female red deer (Cervus elaphus), sika deer (C. nippon), and their hybrids were recorded from wild and captive-bred populations. Vocal variations between these species and their hybrids (C. elaphus × C. nippon) were examined using multivariate analysis to determine whether these groups could be successfully discriminated. There were highly significant differences between the vocalizations of each group for both sexes (males: Wilks' Λ = 0.0233, P<0.0001; females: Wilks' Λ = 0.1338, P<0.0001). The greatest differences were between analogous calls of red and sika deer. Vocalizations of hybrids from both captive-bred and feral populations were intermediate between the two parent species. The differences between the groups were most highly influenced by the pitch of calls. The results of this study indicate that the vocalizations of deer, rather than being learned or mimicked from similar species in their proximity, are strongly influenced by the genetic background of their parents.