Craniometric variations in Central European populations of Ondatra zibethica (Linnaeus, 1766)

Abstract

of Ondatra zibethica (Linnaeus, 1766) [ With 8 Tables & 11 Figs.]Examination was made of the degree of population differentiation in skull measurements and also in the formation of the skull during individual development, on the basis of a collection of muskrat skulls (n=352) from three Polish populations and one Czech population, divided into four age classes. The muskrats from the three populations differ significantly by reason of their larger dimensions and different proportions of the skull, and also the statistical distances of shape and size, from animals from the central part of Bohemia. Differentiation was also found in the correlation structures of skull dimensions of muskrats from different populations. The number of differences found increases with the animals' age, and also with increasing distance in both space and time from the population closest to the place in which the muskrat was originally introduced into Europe. The skull of the muskrat is distinguished by a slight degree of sex dimorphism in dimensions which increases with the animals' age. Intensive increase of the majority of its dimensions ends in the second calendar year of the animals' lives. Age changes in skull dimensions of the muskrat are also reflected in changes in correlation structures corresponding to periods of isometric and allometric growth.

Skull variability of Mustela putorius Linnaeus, 1758

“…The results are therefore similar to the differences found in correlation structures, observed in the case of 8 species of voles of the genus Microtus (K a n e p, 1967), two species of hedgehogs of the genus Erinaceus (Ruprecht, 1972) and also 4 Central European populations of muskrats (Ruprecht, 1974).…”

“…While at an early age (class 2) population differences in skull proportions related mainly to indices based on values of linear measurements, at a greater age (classes 3 and 5) the participation of indices based on capacity and weight parameters became plain. A similar increase in the degree of differences with age also took place in Ondatra zibethica (Linnaeus, 1766) (Ruprecht, 1974).…”

“…5.7; 7.6 and 7.7). It is, incidentally interesting that the index success fully applied by Rossolimo (1958), aged coypu skulls as w ell as house sparrows and muskrats (Ruprecht, 1968 and1974), but was less applicable to the common polecat. In it, considerable overlapping of extreme age classes occurred (Fig.…”

“…subject to the influence of various additional factors -and thus the application of groups as uniform as possible with respect to sex and age -may importantly eliminate undesirable influences. Obser vations o f certain regularities in the age Changes in correlation structures which are accompanied by alternation of periods of more (isometric growth) or less (allometric growth) synchronous growth of the skulloccurring both in the case o f M. putorius, Lepus europaeus Pallas, 1778 (Caboń-Raczyńska, 1964), Clethrionomys glareolus (S c h r e b e r, 1780) (Gerasimov, 1969) and also O. zibethica (Ruprecht, 1974) -shows that this is one o f the more promising growth study methods. The occurrence of certain differences in correlation structures depending on the sex of M. putorius is, in our opinion, an additional proof of the existence of subtle manifestations of sex dimorphism which were also observed by Gerasimov (1969) in the bank vole.…”

“…There have, however, been no studies of this type on more numerous material from Poland which permit comparisons of species character istics based on the correlation structure of dimensions of different types of mammal skulls, similar to those by Cabon-Raczynska (1964) and Ruprecht (1972 and1974). This study is therefore aimed at making the most possible comprehensive analysis of variations, chiefly craniometrical, in the common polecat, Mustela putorius Linnaeus, 1758 from Poland.…”