Craniometric variability of Canis lupus, Carnivora, Canidae in the centre of European Russia

Abstract

The history of the co-existence of human-grey wolf (Canis lupus) is an example of competition, close interaction during domestication, persecution and extermination. The amazing plasticity and adaptations of the grey wolf ensured the sustainable survival of its populations. Being at the top of the food pyramid, Canis lupus is a consumer of the highest order. It actively regulates the abundance of its main prey, i.e. large ungulates, through their selective predation. These circumstances highlight the interest to study this carnivore species inhabiting the centre of European Russia. Using craniometric methods, we studied 326 wolf skulls obtained in Tver region, Smolensk region, Yaroslavl region, and Vologda region. We revealed a high intraspecific size polymorphism, based on the analysis of the spatial and temporal dynamics of the craniometric characters of the grey wolf collected in the centre of European Russia. These data are originated from an area of 350 × 450 km over a 65-year period. The spatial and temporal dynamics was demonstrated for measurements characterising the length of the skull, the length of the upper and lower jaw, and odontological features characterising the size of the crown of the first premolar and second molar teeth. The sexual variation of the grey wolf skull is characterised by a generally smaller size of female skulls (3.6% in average). A feature related to the functioning of the jaw apparatus, the width of the articular head of the mandible, showed the highest sexual variation (8.1%-difference between males and females). In order of increasing influence, the polymorphism factors are arranged as follows: chronographic, spatial, sex-related, and age-related. Besides the fundamental reasons caused by the sexual selection, the sexual dimorphism in size is determined by exogenous factors associated with a certain degree of segregation in trophic niches of males and females, their different social role, determined by the species life strategy. The geographic variability of the grey wolf skull has a complex and disordered nature. It is primarily caused by social organisation and strong territoriality of the grey wolf, limiting the panmixia, as well as by the stochastic intrapopulation processes due to a generally high elimination of individuals in populations. In the study area, the obtained spatial and temporal grey wolf variability could be caused by the complementary influence of a number of factors. The nature of the variability in the size of the grey wolf skull makes it possible to associate it with the dynamic parameters of the trophic ecology of the studied species, depending on the population-demographic characters of the main prey of the grey wolf, Alces alces and Sus scrofa, in the study area. In addition, it is not excluded that the temporal variability is affected by stochastic factors caused by the intensive grey wolf elimination as a result of sum death, active emigration and immigration of animals caused by anthropogenic load. By contributing to an intrapopulation polymorphism increase, the morphological heterogeneity of the grey wolf population increases the adaptive population ability, which ultimately favours the survival of this carnivore species.

Keywords

• central forest state nature biosphere reserve
• cranium variability
• european part of the range
• grey wolf
• protected area