Morphological Adaptation of the Skull for Various Behaviors in the Tree Shrews

Abstract

ABSTRACT. Skull size and shape were examined among 14 species of the tree shrews (Tupaia montana, T. picta, T. splendidula, T. mulleri, T. longipes, T. glis, T. javanica, T. minor, T. gracilis, T. dorsalis, T. tana, Dendrogale melanura, D. murina, and Ptilocercus lowii). The bones of face were rostro-caudally longer in T. tana and T. dorsalis, contrasting with T. minor and T. gracilis, D. melanura, D. murina and P. lowii which have smaller facial length ratios. The arbo-terrestrial species (T. longipes and T. glis) were similar to terrestrial species in length ratios of bones of face unlike the other arbo-terrestrial species (T. montana, T. picta, T. splendidula, and T. mulleri). We propose that T. longipes and T. glis have adapted to foraging for termites and ants as have T. tana and T. dorsalis. Additionally small body size in T. javanica may be the result of being isolated in Java. We separated the species into 5 groups from the measurment values of skulls: 1) Terrestrial species; T. tana and T. dorsalis, 2) Arboreal species; T. minor and T. gracilis, 3) Arbo-terrestrial species group 1: T. montana, T. splendidula, T. picta and T. mulleri, and T. javanica, 4) Arbo-terrestrial species group 2: T. glis and T. longipes, 5) Arboreal species of Dendrogale and Ptilocercus. Principal component analysis separated species into 8 clusters as follows: 1) T. tana, 2) T. dorsalis, 3) T. montana, T. splendidula, T. picta and T. mulleri, 4) T. glis and T. longipes, 5) T. javanica, 6) T. minor and T. gracilis, 7) D. melanura and D. murina, and 8) P. lowii. We suggest that these clusters correspond to behavioral strategies and peculiarities observed in foraging, feeding and locomotion in each species.

Proportion and Cluster Analyses of the Skull in Various Species of the Tree Shrews

“…We examined 337 skulls of 14 species of the tree shrew (Tupaia montana, T [8]. The specimens have been stored in Muséum National d'Histoire Naturelle (Paris, France), the Mammal Division of the Smithsonian Institution (Washington DC, U.S.A.), The University Museum, Kyoto University (Kyoto, Japan), the Raffles Museum of Biodiversity Research, National University of Singapore (Singapore), the Department of Wildlife and National Parks (Kuala Lumpur, Malaysia), and Bogor Zoological Museum (Bogor, Indonesia).…”

“…Measurements are defined in Table 2, and were based on Driesch [3]. In the present analysis we used the same osteometrical data as those in the previous study [8]. The mean measurement values were shown in each species [8].…”

“…In the present analysis we used the same osteometrical data as those in the previous study [8]. The mean measurement values were shown in each species [8]. The skull proportion indices were obtained as quotients of each measurement value divided by the geometric mean of all measurement values.…”

“…Since the skulls have been functional-morphologically adapted to each style of locomotion, we previously examined the 4 species of Tupaia, and suggested that T. tana, T. javanica and T. minor have evolved different behaviors [7]. Using the skull specimens of 14 species of Scandentia, we compared the skull size and shape among the species to confirm the relationships between the skull characteristics and the locomotion strategies [8].…”

“…Although we compared the measurement data among the species and applied the principal component analysis to the osteometrical data to discuss the adaptational patterns of skull form [8], the skull proportion indices should be actually obtained and the similarities of skull shape among tree shrews should be quantitatively examined to elucidate the morphological adaptation in various types of skull form in these tree shrews.…”