愛媛大学理学部紀要 第 23 巻 1–11 ページ，2020 年
Mem. Fac. Sci. Ehime Univ. Vol. 23, p. 1–11, 2020

Intrasubspecific variations of the adult astragalar and calcaneal sizes
in living Japanese raccoon dog (Nyctereutes procyonoides viverrinus)
現生ホンドタヌキの成獣における距骨および踵骨サイズの亜種内変異

Takehisa Tsubamoto
鍔本 武久

Earth’s Evolution and Environment, Department of Mathematics, Physics, and Earth Sciences, Graduate School of
Science and Engineering, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime Pref. 790-8577, Japan
愛媛大学 大学院理工学研究科 数理物質科学専攻 地球進化学講座

Abstract.
The intrasubspecific variations of the adult astragalar and calcaneal sizes of living Japanese raccoon
dog, Nyctereutes procyonoides viverrinus (Mammalia, Carnivora, Canidae), were examined to makebasic data in considering the variations of fossil mammalian bones. The specimens consist of 63 adultindividuals (35 males and 28 females). The data consist of 12 measurements for both the astragalus andcalcaneum with a body mass and first and second molar sizes. There is no significant sexual dimorphism
in all the measurements. The coefficients of variation (CV) of the astragalar and calcaneal sizes range
from 3.7 to 5.9 and from 3.8 to 7.1, respectively, implying that the size variations of these two bones arerelatively low. These CVs of the two bones are as low as those of the first and second molars (3.4–5.8).
The correlation coefficient between the body mass and each astragalar and calcaneal measurement
ranges from -0.05 to 0.47, implying that the correlation between the body mass and the astragalar andcalcaneal sizes within N. procyonoides viverrinus is low or almost absent.
Key words: Key words: astragalus, basic statistics, calcaneum, calcaneus, Mammalia, Carnivora, talus

Introduction
Tsubamoto (2019a) investigated intraspecific(intrasubspecific) variations of the astragalar andcalcaneal sizes in living Japanese monkey, Macaca
fuscata fuscata (Gray, 1870) (Mammalia, Primates,Cercopithecidae), to make basic data in considering thevariations of fossil mammalian bones. Here, in addition,
I investigate intrasubspecific variations of the adultastragalar and calcaneal sizes in living Japanese racoon
dog, Nyctereutes procyonoides viverrinus (Temminck,1838) (Mammalia, Carnivora, Canidae). Although thecraniodental specimens of N. procyonoides viverrinus
have been well investigated (Yamamoto, 1983;
Yoshimura, 1983; Machida and Saito, 1986; Harada etal., 1989, 1992; Kauhala et al., 1998; Asahara, 2013,2014a, 2014b; Tsubamoto, 2015; Asahara and Takai,2017), its postcranial bones have been rarely studied.
The sizes of the limb bones including the astragalus andcalcaneum are usually more related to the body size of2020 年 1 月 10 日 受付
2020 年 5 月 11 日 発行

animals than the sizes of the craniodental specimens, sothat the sizes and their variations of the limb bones are
more useful for the paleoecological analyses using bodysize than those of the craniodental specimens.
Material and methods
All skeletal specimens of N. procyonoides viverrinus
examined here are housed in Primate Research Institute,
Kyoto University, Inuyama, Japan. The specimens
consist of 63 adult individuals (35 males and 28 females)(Appendix Table A1). The specimens having erupted
third molars and/or fused epiphyses of the long limb
bones were identified as of adult individuals. The
measurement positions of the astragalus and calcaneum(12 measurements for each bone) are indicated in Figure
1. For comparison, the body masses of the individuals
were taken from the data base of the institute, and thelength and width of the first and second molars of theindividuals were also measured. The units of the linear

2020 年 4 月 20 日 受理

Received: 10 January, 2020; Accepted: 20 April, 2020
Published: 11 May, 2020

-1-T. Tsubamoto 鍔本武久

Figure 1. Measurement positions of the astragalus and calcaneum of Nyctereutes procyonoides viverrinus (Mammalia,Carnivora, Canidae) (after Tsubamoto, 2014, 2019a, 2019b; Tsubamoto et al., 2016). A, left astragalus: A1–A2, dorsal (anterior)
view; A3, distal view; A4, lateral view; A5, medial view. Linear measurements.—AS1, medio-lateral width of the tibial trochlea;
AS2, proximo-distal length of the lateral trochlear ridge of the tibial trochlea; AS3, proximo-distal length of the medial
trochlear ridge of the tibial trochlea; AS4, medio-lateral width of the astragalus; AS5, proximo-distal length of the astragalus;
AS6, proximo-distal length of the central part of the tibial trochlea; AS7, medio-lateral width between the medial and lateraltrochlear ridges of the tibial trochlea; AS8, dorso-ventral thickness of the lateral part of the astragalus; AS9, dorso-ventral
thickness of the medial part of the astragalus; AS10, neck-head length; AS11, width of the head; AS12, thickness of the head.
B, left calcaneum: B1, dorsal (anterior) view; B2, lateral view; B3, distal view. Linear measurements.—CA1, calcaneal length;
CA2, calcaneal width at the astragalar articular surfaces; CA3, width of the posterior astragalar articular surface; CA4, widthof the posterior calcaneal body; CA5, width of the tuberosity; CA6, length of the posterior calcaneal body; CA7, length of theposterior astragalar articular surface; CA8, width of the articular surface for the cuboid; CA9, height of the articular surface
for the cuboid; CA10, height at the posterior astragalar articular surface; CA11, height at the posterior calcaneal body; CA12,
height at the tuberosity.

-2-Size variations of astragalus and calcaneum in Japanese raccoon dog ホンドタヌキの距骨と踵骨のサイズ変異

measurements and body mass are millimeter (mm) andgram (g), respectively. The linear measurements weretaken to the nearest of 0.01 mm using digital calipers
and were taken mostly on the left side when available.
The analyses were carried out mostly using Excel(Microsoft) and JMP (SAS Institute Inc.), with VISUALSILVERMAN (Kusuhashi and Okamoto, 2015) for
Silverman’s test (Silverman, 1981, 1983).
Abbreviations.—AS1–AS12, measurement positionsof the astragalus shown in Figure 1A; CA1–CA12,measurement positions of the calcaneum shown inFigure 1B; CV, coefficient of variation (unbiased); M1–M2/m1–m2, upper/lower first/second molars.
Results and remarks
The basic statistics and distributions of all themeasurements of the specimens are shown in Tables 1–4,Figures 2–5, and Appendix Figures A1–A2.
Size distribution and sexual dimorphism
According to Welch’s t test (5% significance level),there is no significant difference between males andfemales (sexual dimorphisms) in all measurementsof the body mass, astragalus, calcaneum, and molars(Appendix Figures A1–A2). Each size distribution of
the adult measurements including the body mass andM1–M2/m1–m2 is superficially unimodal generally(Figures 2–5). The tests of the normality for the linear
measurements and log-normality for the body mass (5%significance level) were applied to the measurements.
Most of the measurements could not reject the nullhypothesis, but some measurements rejected it (Table5). To test the multimodality of each adult measurement,

Silverman’s test (5% significance level) (Silverman,1981, 1983) was applied. All the measurements except
the body mass could not reject the unimodal hypothesis,
and the body mass rejected the unimodal hypothesis andcould not reject the bimodal hypothesis. The distributionof the body mass can be identified as bimodal according
to Silverman’s test and also the histogram (Figure 2):
the main peak at 3,000–3,250 g and the second peakat 4,500–4,750 g. This is not caused by the sexual
dimorphism (Figure 2; Table 1). The reason for thisbimodality is unclear.
Coefficient of variation
To see and compare the degree of variation, CV iscalculated. CVs of the astragalar and calcaneal sizes
range from 3.7 to 5.9 and from 3.8 to 7.1, respectively(Tables 2–4), implying that the size variations of these
two bones are relatively low and are lower than thoseof Japanese monkey (CVs: 6.5–9.1 and 6.9–10.8,
respectively; Tsubamoto, 2019a). These CVs of the twobone sizes are as low as those of the first and second
molar sizes (3.4–5.8). If we calculate CV separating
the specimens into males and females, CVs of theadult astragalar and calcaneal sizes range as follows:
astragalus (male), 3.9–6.1; astragalus (female), 3.4–6.2;calcaneum (male), 3.3–7.2; calcaneum (female), 3.8–7.5.
These CVs of the two bones (separating males andfemales) are as low as those of the subspecies (unitingmales and females).

Table 1. Basic statistics of the body mass (in gram). SD,standard deviation (unbiased); V, variance (unbiased); Max,maximum value; Min, minimum value; N, sample size; SE,standard error (unbiased).

Figure 2. Histogram and box plot of the body mass (BM).
The box plot shows quartiles with arithmetic mean (diamond)
and whiskers from minimum to maximum with 2.5th, 10th,90th, and 97.5th percentiles. Green line indicates the fitting
for log-normal distribution. F, female; M, male.

-3-T. Tsubamoto 鍔本武久

Table 2. Basic statistics of the astragalar measurements (in mm). CV, coefficient of variation (unbiased); AS1–AS12,measurement points of the astragalus shown in Figure 1A. Other abbreviations are indicated in Table 1.

-4-

Size variations of astragalus and calcaneum in Japanese raccoon dog ホンドタヌキの距骨と踵骨のサイズ変異

Figure 3. Histograms and box plots of the astragalar measurements. Red line indicates the fitting for the normaldistribution. The explanations of the box plots are shown in Figure 2. Abbreviations are shown in Figures 1–2.

-5-T. Tsubamoto 鍔本武久

Table 3. Basic statistics of the calcaneal measurements (in mm). CA1–CA12, measurement points of the calcaneum
shown in Figure 1B. Other abbreviations are indicated in Tables 1–2.

-6-

Size variations of astragalus and calcaneum in Japanese raccoon dog ホンドタヌキの距骨と踵骨のサイズ変異

Figure 4. Histograms and box plots of the calcaneal measurements. The explanations of the box plots are shown in Figure
2. Abbreviations are shown in Figures 1–2.

-7-

T. Tsubamoto 鍔本武久

Table 4. Basic statistics of the molar measurements (in mm). M1–M2/m1–m2, upper/lower molars; L, maximum length; W,maximum width. Other abbreviations are indicated in Tables 1–2.

-8-

Size variations of astragalus and calcaneum in Japanese raccoon dog ホンドタヌキの距骨と踵骨のサイズ変異

Figure 5. Histogram and box plot of the measurements of M1–M2/m1–m2. The explanations of the box plots are shownin Figure 2. L, maximum length; W, maximum width. Other abbreviations are shown in Figures 2–3.

Correlation with body mass
The correlation coefficients between the body massand the astragalar and calcaneal measurements are
generally higher than those between the body mass andthe molar measurements (Table 6; Appendix Figure
A3). The correlation coefficient between the body massand each astragalar measurement ranges from 0.01 to0.42; that between the body mass and each calcaneal
measurement ranges from -0.05 to 0.47; and thatbetween the body mass and each molar measurement
ranges from -0.04 to 0.17 (Table 6). These results imply
that the correlation between the body mass and the adultastragalar and calcaneal sizes within the subspecies N.
procyonoides viverrinus is low or almost absent.
Concluding remarks
Here, I investigated intrasubspecific variations of
the various astragalar and calcaneal sizes in the adultspecimens of living N. procyonoides viverrinus. The
sizes of the two bones of this subspecies did not show
any sexual dimorphism. The results will be additional
basic data in interpreting the variations of mammalianastragali and calcanea discovered in paleontological andarchaezoological sites.

-9-T. Tsubamoto 鍔本武久

Table 5. Goodness-of-fit tests of the fittings for thenormal and log-normal distributions. The normal test is forthe linear measurements, and the log-normal test is for thebody mass. The Shapiro-Wilk and Kolmogorov-Smirnov
tests were used for the tests of normality and log-normality,respectively. *, p-value < 0.05. Abbreviations are shown inFigures 1–2 and Tables 1–4.

Table 6. Pearson’s correlation coefficient between thebody mass and each measurement. Abbreviations are shownin Figure 1 and Tables 1–4.

Acknowledgments
I am grateful to Masanaru Takai, Takeshi Nishimura,and Naoko Egi (Primate Research Institute, Kyoto
University, Inuyama, Japan) for graciously providing
access to the specimens examined. This manuscript
was improved by the reviews of Masaya Matsuura andNao Kusuhashi (Ehime University, Matsuyama, Japan).
This research was partly supported by the Cooperation
Program (2014-B-2) of Primate Research Institute (KyotoUniversity, Inuyama, Japan).
References
Asahara, M., 2013: Shape variation in the skull andlower carnassial in a wild population of raccoon dog(Nyctereutes procyonoides). Zoological Science, 30:205–210.

- 10 -Size variations of astragalus and calcaneum in Japanese raccoon dog ホンドタヌキの距骨と踵骨のサイズ変異

Asahara, M., 2014a: Evolution of relative lower molar sizes
among local populations of the raccoon dog (Nyctereutesprocyonoides) in Japan. Mammal Study, 39: 181–184.
Asahara, M., 2014b: Shape variation in the skull within
and between wild populations of the raccoon dog(Nyctereutes procyonoides) in Japan. Mammal Study, 39:
105–113.
Asahara, M. and Takai M., 2017: Estimation of diet in extinctraccoon dog species by the molar ratio method. Acta
Zoologica, 98: 292–299.
Gray, J. E., 1870: Catalogue of Monkeys, Lemurs, and FruitEating Bats in the Collection of the British Museum,viii + 137 p. Trustees of the British Museum (NaturalHistory), London.
Harada, Y., Ogawa, K., Mori, S., Kobayashi, S., Kubo, H.
and Kiyosue, T., 1989: Variation of dentition in raccoon
dogs (Nyctereutes procyonoides viverrinus T.) —Anomalies in number of the teeth—. Japanese Journalof Oral Biology, 31: 257–264. (in Japanese with Englishabstract)
Harada, Y., Ogawa, K., Mori, S., Kobayashi, S. andNagamoto, S., 1992: Anomalous teeth of the raccoon
dogs (Nyctereutes procyonoides viverrinus T.) —Shape, position and occlusion—. Japanese Journal ofOral Biology, 34: 467–480. (in Japanese with Englishabstract)
Kauhala, K., Viranta, S., Kishimoto, M., Helle, E. and Obara,I., 1998: Skull and tooth morphology of Finnish andJapanese raccoon dogs. Annales Zoologici Fennici, 35:
1–16.
Kusuhashi, N. and Okamoto, T., 2015: A nonparametricmultimodality test—Silverman’s test—and itsi n t r o d u c t i o n i n t o p a l e o n t o l o g y. F o s s i l s ( T h e
Palaeontological Society of Japan), 97: 23–37. (inJapanese with English title)
Machida, K. and Saito, T., 1986: Age structure and dental
numerical anomalies of the raccoon dogs, Nyctereutes
procyonoides viverrinus Temminck, in Chichibu District,
Saitama Prefecture. Bulletin of the Saitama Museum of
Natural History, 4: 15–20. (in Japanese with Englishabstract)
Silverman, B. W., 1981: Using kernel density estimatesto investigate multimodality. Journal of the Royal

Statistical Society, Series B, 43: 97–99.
Silverman, B. W., 1983: Some properties of a test for
multimodality based on kernel density estimates. In,Kingman, J. F. C. and Reuter, G. E. H., eds., Probability,Statistics and Analysis, London Mathematical Society
Lecture Series, 79: 248–259. Cambridge UniversityPress, London.
Temminck, C. J., 1838: Over de kennis en de Verbreiding
der Zoogdieren van Japan. Tijdschrift Voor Natuurlijke
Geschiedenis en Physiologie, 5: 273–293.
Tsubamoto, T., 2014: Estimating body mass from theastragalus in mammals. Acta Palaeontologica Polonica,59: 259–265.
Tsubamoto, T., 2015: Rare anomalous dental morphologies
found in raccoon dog (Nyctereutes procyonoides)
and their implication to dental morphology of fossilmammals. Journal of the Geological Society of Japan,
121: 185–189.
Tsubamoto, T., 2019a: Intraspecific variations of theastragalar and calcaneal sizes in living Japanese monkey(Macaca fuscata). Memoirs of the Faculty of Science,
Ehime University, 22: 1–17.
Tsubamoto, T., 2019b: Relationship between the calcaneal
size and body mass in primates and land mammals.
Anthropological Science, 127: 73–80.
Tsubamoto, T., Egi, N., Takai, M., Thaung-Htike and ZinMaung-Maung-Thein, 2016: Body mass estimation fromthe talus in primates and its application to the Pondaungfossil amphipithecid primates. Historical Biology, 28:27–34.
Yamamoto, T., 1983: A comparative morphological studyof tooth in raccoon dogs. Journal of the Kyushu Dental
Society, 37: 1–29. (in Japanese with English abstract)
Yoshimura, K., 1983: A comparative anatomical study on
the mandibulae of raccoon dogs. Journal of the Kyushu
Dental Society, 37: 663–679. (in Japanese with Englishabstract)

Appendix
Appendix (Table A1 and Figures A1–A3) is available
from http://www.sci.ehime-u.ac.jp/wp/research/bulletin/.

- 11 -