Biogeographical variation on craniomandibular morphology in pallas’s squirrel \(\textit{Callosciurus erythraeus}\) (Pallas, 1779) (Rodentia: Sciuridae) in Vietnam

Different forest vegetations provide herbivorous small mammals with different resources, forcing adaptation since food habits depend on available resources. We expect differences in vegetation to be reflected in the size and shape of the skull and mandible as a result of potentially different feeding resources. Therefore, we analyzed the craniomandibular characteristics of Pallas’s squirrel (Callosciurus erythraeus) in Vietnam. This species commonly occurs in different vegetations in Vietnam, making it a good model for examining morphological adaptation to vegetation type. We analyzed morphologically the skulls and mandibles of 156 specimens collected from 31 localities in Vietnam from 1960 to the present. Principal component analysis showed that females occurring in the tropical lowland evergreen rain forest were clearly separated from those in other vegetations.

Prevalence and Molecular Characterization of the Zoonotic Enteric Protozoans Cryptosporidium spp., Enterocytozoon bieneusi, and Blastocystis from Pallas’s Squirrels (Callosciurus erythraeus) in Kanagawa Prefecture, Japan

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.

Habitat selection of invasive alien Pallas’s squirrels (Callosciurus erythraeus) in an urban habitat with small fragmented green spaces

The distribution of invasive alien Pallas’s squirrels (Callosciurus erythraeus) has expanded mainly toward the southeast with continuous forest in Kanagawa Prefecture, Japan. Recently, however, squirrels have been sighted in residential areas with only a few green spaces. We examined the habitat selection of squirrels in a city with small fragmented green spaces by censusing the animals along a 6.7 km route. Twenty-three presence data were obtained in 10 grids, which were much larger than the mean home ranges of the species, suggesting that a squirrel population had already been established in this area. Although woods of <5 ha were reported to be unsuitable squirrel habitats, the study area only had two green spaces with >5 ha, and 90% of presence data were obtained in green spaces with <5 ha. This indicates that squirrels can establish a population even in areas with small fragmented green spaces. The squirrels selected areas close to evergreen and deciduous woods, but they avoided those closer to residential areas. Since small fragmented woods, such as evergreen trees, are widely distributed in the central parts of Kanagawa Prefecture, the squirrels may use them as stepping stones to expand their range.