New hair emergence phenology in the Pallas’s squirrel Callosciurus erythraeus inhabiting Kanagawa prefecture

The Pallas's squirrel (Callosciurus erythraeus) has invaded fragmented woodlands in urban areas of Kanagawa Prefecture, where frequent human contact occurs. We examined 538 squirrels in Hayama-machi, Kanagawa Prefecture, for ectoparasite infestations. A total of 1,164 lice, 877 fleas, and 231 ticks were retrieved from 297 (55.2%), 338 (62.8%), and 135 (25.1%) squirrels, respectively. The identified ectoparasite species were Neohaematopinus callosciuri, Ceratophyllus anisus, Haemaphysalis flava, Haemaphysalis hystricis, and Ixodes turdus. The prevalence of N. callosciuri and C. anisus was significantly higher in adult males (N. callosciuri 63.6%, C. anisus 70.4%) than that in adult females (N. callosciuri 36.1%, C. anisus 49.0%; P<0.0001). Such information on the dynamics of host-ectoparasite relations is crucial for evaluating the risk to public health.

ABSTRACTPallas’s squirrel (Callosciurus erythraeus) was introduced in Japan in the 1930s and has since established itself in several areas across the country. Although wild Sciuridae populations have been demonstrated to be potential reservoirs for zoonotic enteric protozoa, epidemiological studies of such pathogens in Japan are scarce. Here, we examined 423 fecal samples from Pallas’s squirrels captured in Kanagawa Prefecture, Japan, using PCR and DNA sequencing to determine the occurrence of Cryptosporidium spp., Enterocytozoon bieneusi, and Blastocystis. The overall prevalence of Cryptosporidium spp., E. bieneusi, and Blastocystis was 4.3% (18/423 samples), 13.0% (55/423 samples), and 44.0% (186/423 samples), respectively. The prevalence of Blastocystis and E. bieneusi was significantly higher in spring (60.1% and 17.4%, respectively) than in winter (27.6% and 8.6%, respectively [P < 0.01]). Sequence analysis of Cryptosporidium spp., targeting the partial small subunit ribosomal RNA gene (SSU rDNA), showed 100% identity (541/541 bp) to Cryptosporidium ubiquitum, and analysis of the gp60 gene showed 99.76% (833/835 bp) identity to C. ubiquitum subtype XIIh. The sequences of the ribosomal internal transcribed spacer region of E. bieneusi and the partial SSU rDNA of Blastocystis were identified as E. bieneusi genotype SCC-2 and Blastocystis subtype 4, respectively. This study confirmed the presence of C. ubiquitum, E. bieneusi, and Blastocystis in Pallas’s squirrels in Kanagawa Prefecture. Because Pallas’s squirrels inhabit urban areas, living close to humans, the species may serve as a potential source of infection in human populations.IMPORTANCE Pallas’s squirrel is designated a “regulated organism” under the Invasive Alien Species Act in Japan, and municipal authorities are introducing control measures to reduce its populations. It has been suggested that wild mammals may play a role in contaminating the environment with zoonotic pathogens. The present study detected the enteric pathogens Cryptosporidium ubiquitum, Enterocytozoon bieneusi, and Blastocystis in the feces of Pallas’s squirrels inhabiting Kanagawa Prefecture, Japan. These pathogens persist in the environment and contaminate soils and water, which may potentially infect humans. Because Pallas’s squirrels in Kanagawa Prefecture are found in urban areas, where they are in close contact with human populations, continued monitoring of zoonotic diseases among squirrel populations will be important for evaluating the significance of wildlife in pathogen transmission.

A species of sucking louse, Neohaematopinus callosciuri, was found for the first time in Japan. The species was found on an invasive species of squirrel, Pallas squirrel, Callosciurus erythraeus, in the Kamakura district, Kanagawa Prefecture, Japan. A total of 52 lice were obtained from 22 of 104 squirrels captured. The lice were about three times more prevalent in male squirrels than in females and were detected most frequently in the winter. As N. callosciuri has never been reported on wild animals in Japan, this species probably was introduced into Japan along with their host, Pallas squirrels.

Nest site and materials of the alien squirrel, Callosciurus erythraeus, in Kanagawa Prefecture

Characteristics and annual reproductive patterns of breeding female Pallas’s squirrels (<i>Callosciurus erythraeus</i>) in Kanagawa Prefecture, Japan

The Pallas squirrel (Callosciurus erythraeus; common name in Japan: Formosan squirrel) was introduced in the 1950s and has established populations throughout southeastern Kanagawa Prefecture, Japan. Some tree species in natural forests, parks, and gardens in residential areas have been intensively debarked by the squirrels, especially in winter and spring. The amounts of chemical components, such as polyphenols, resins, flavanols, and sugars, in the bark were compared among species and individual trees collected in the forest of Yokohama Nature Sanctuary. Interspecific differences in the extent of stripping were not related to the amounts of the four chemical components. For individual trees, the bark with feeding scars tended to contain more sugar than that without scars.

Ectoparasites of the Pallas squirrel, Callosciurus erythraeus, introduced to Japan.

Dominant-subordinate relationships in the Formosan squirrel, Callosciurus erythraeus thaiwanensis , were studied in the woods of Kamakura City, Kanagawa Prefecture, Japan from April 1982 to May 1985. Home ranges of adults overlapped, but the extent of overlap was less among females than among males. The mean number of squirrels with overlapping home ranges was 12.6 among males and 2.3 among females in the winter-spring season, and 8.7 among males and 1.6 among females in the autumn-winter season. When a squirrel encountered another, chasing occurred only once in three times; indifference was exhibited in most cases of proximity between individuals. A dominance hierarchy was apparent at a feeding stand in the study site. This hierarchy included both sexes and was correlated with age. The dominance hierarchy detected among males at the feeding stand reappeared in mating bouts. In a mating bout, nine-seventeen males assembled near an estrous female and four-eleven males successively mated in accordance with their rank. Compared to northern species in which dominant males guard the estrous female against lower-ranked males, in the Formosan squirrel, successfully mated males guarded the female for less than 70 min from the other males regardless of their rank. However, high ranking males mated with more females per year than low ranking males. This difference among species may relate to the number of males assembled for mating and the frequencies of mating bouts.