Wolf Skulls Research Articles

Traumatism of Grey Wolf (<i>Canis Lupus</i>, Canidae, Carnivora) Skulls in the Center of the European Part of Russia

A total of 297 wolf skulls from the collection of the Central Forest State Biosphere Reserve were studied for the presence of injuries. Of these, 129 (43.4 ± 2.9%) skulls had traumas of various origins or a deformed sagittal crest. Aside from the sagittal crest, the rate of traumas was 32.3 ± 2.7%. Based on the causes of origin, the traumas were divided into three groups: those received when hunting moose, as a result of aggressive intraspecific contacts, and accidental. Complicated fractures of dental crowns predominate among accidental traumas. Moose hunting traumas and intraspecific aggression are more common in subadult wolves than in adults, this being explicable by the elimination of injured animals. The incidence of accidental traumas, on the other hand, was increased with age. The level of traumas serves as a population characteristic indicating tension in the predator-prey system and the degree of intraspecific aggression.

ON THE PATTERNS AND CAUSES OF CHRONOGRAPHIC VARIABILITY OF MORPHOLOGICAL CHARACTERISTICS IN SOME MAMMALS: THE ORDERS RODENTIA AND CARNIVORA

Chronographic variations in some craniological features in the Spotted ground squirrel, the Red fox and the Wolf in the middle of the 20th to early 21st centuries have been established. They represent their temporary deviations from the average size towards an increase which, after several generations, is replaced by a return to the original values. The influence of trophic and climatic factors, parasites, diseases and population densities during the development of young individuals is considered. Chronographic changes in the condylobasal length and zygomatic width of the skull are established as temporary and reversible, increases in their values being replaced by their decreases. Increases in the size of the skull of the Spotted ground squirrel and the Red fox occur “suddenly” in individuals of one generation, and their return to the initial values occurs gradually in individuals of several subsequent generations. Chronographic variations in the size of the skull of the Spotted ground squirrel and the Red fox correlate with changes in reproduction rates and some other varying factors. They correspond to certain phases of population abundance. Increased sizes of the Red fox and Wolf skulls are observed in the phases of quitting a depression to the beginning of a population growth. The probable causes of chronographic changes lie in somatic heterosis, caused in natural habitats by the alternation of the prevailing mating types (inbreeding or outbreeding), these being due to massive rearrangements of individuals as a result of deep population reductions from natural or anthropogenic impacts.

Malocclusion in an Arctic Wolf (<i>Canis lupus arctos</i>) from northeast Greenland

I document the first case of malocclusion in an Arctic Wolf (Canis lupus arctos) from Greenland. All canine teeth of a wolf found dead on the tundra of northeast Greenland showed evidence of heavy anterior wear resulting from occlusion with the opposite teeth. Additional heavy wear on the incisors indicated a level bite. No cases of malocclusion were found in the largest museum collection of Arctic Wolf skulls (n = 11) from Greenland. However, the collection consisted exclusively of specimens from a northeast Greenland wolf population extirpated ca. 1939; thus, it provided no information on the incidence of malocclusion in more contemporary wolves. A finding of malocclusion in the more recent wolf population could be important because the condition is genetically based and the trait is expressed more frequently with increased inbreeding. The small, geographically isolated wolf population that this wolf was a part of disappeared for reasons unknown after 2002 and genetic conditions cannot be excluded as a contributing factor. Future study of the prevalence and severity of this abnormality in Arctic Wolves from Greenland will be problematic because of the difficulty of acquiring comparative material, but could be conducted on other populations of Arctic Wolves.

Endocranial volume increases across captive generations in the endangered Mexican wolf

Endangered animals in captivity may display reduced brain sizes due to captive conditions and limited genetic diversity. Captive diets, for example, may differ in nutrition and texture, altering cranial musculature and alleviating constraints on cranial shape development. Changes in brain size are associated with biological fitness, which may limit reintroduction success. Little is known about how changes in brain size progress in highly managed carnivoran populations and whether such traits are retained among reintroduced populations. Here, we measured the endocranial volume of preserved Mexican wolf skulls across captive generations and between captive, wild, and reintroduced populations and assessed endocranial volume dependence on inbreeding and cranial musculature. Endocranial volume increased across captive generations. However, we did not detect a difference among captive, wild, and reintroduced groups, perhaps due to the variability across captive generations. We did not find a relationship between endocranial volume and either inbreeding or cranial musculature, although the captive population displayed an increase in the cross-sectional area of the masseter muscle. We hypothesize that the increase in endocranial volume observed across captive generations may be related to the high-quality nutrition provided in captivity.

The canine counts! Significance of a craniodental measure to describe sexual dimorphism in canids: Golden jackals (Canis aureus) and African wolves (Canis lupaster)

Sexual dimorphism is a widespread phenomenon among mammals, including carnivorans. While sexual dimorphism in golden jackals (Canis aureus) has been analysed in the past, in the related and apparently convergent canid, the African wolf (Canis lupaster), it is poorly studied and showed to be relatively small. Previously, sexual size dimorphism (SSD) research in these species was mostly based on skull and body measurements. In our study, we also included dental measurements, namely the diameter of the canine. We used 11 measured sections of 104 adult specimens, comprising 61 golden jackal and 43 African wolf skulls. Data analyses were carried out through logistic regression and conditional inference trees (CIT). To compare the results of SSD to other species, sexual dimorphism indices (SDI) were calculated. Golden jackals and African wolves show significant sexual size dimorphism, both in cranial and dental size. The logistic regression revealed that the mesiodistal diameter of the upper canine is most effective in discerning the sexes. The difference in the calculated SDI of the canine diameter between the sexes amounted to 8.71 in golden jackals and 14.11 in African wolves, respectively—with regional diversity. Thus, the canine diameter is an important measure to investigate SSD as well as an easy tool to apply in the field.

Endocranial Development in the Coyote (Canis latrans) and Gray Wolf (Canis lupus): A Computed Tomographic Study

The purpose of this study was to examine the pattern of postnatal brain growth in two wild canid species: the coyote (Canis latrans) and gray wolf (Canis lupus). Adult regional and total brain volume differences were also compared between the two species as well as within each species by sex. Three-dimensional virtual endocasts of endocranial airspace were created from computed tomography scans of 52 coyote skulls (28 female, 24 male; 1 day to 13.4 years) and 46 gray wolf skulls (25 female, 21 male; 1 day to 7.9 years). Age was known in coyotes or estimated from dentition patterns in wolves. The 95% asymptotic growth of the endocranium is completed by 21 weeks in male and 17.5 weeks in female coyotes and by 27 weeks in male and 18.5 weeks in female wolves. These ages are well before age at first reproduction (coyote – 40.4 weeks; wolf – 91.25 weeks). Skull growth as measured by centroid size lags behind endocranial growth but is also completed before sexual maturity. Intra- and interspecific comparisons of brain volumes in the adult wolves and coyotes revealed that relative anterior cerebrum (AC) volume was greater in males than females in both species. Relative brain size was greater in the coyote than in the wolf as was relative cerebrum volume. However, relative AC volume and relative cerebellum and brainstem volume was greater in the wolf than coyote. One explanation for the increased AC volume in males compared to females may be related to the role of social information processing. However, additional data are needed to determine the correspondence between regional volumes and functional differences either between or within these species. Nonetheless, these findings provide important baseline data for further studies on wild canid brain variations and development.

Can skull form predict the shape of the temporomandibular joint? A study using geometric morphometrics on the skulls of wolves and domestic dogs

The temporomandibular joint (TMJ) conducts and restrains masticatory movements between the mammalian cranium and the mandible. Through this functional integration, TMJ morphology in wild mammals is strongly correlated with diet, resulting in a wide range of TMJ variations. However, in artificially selected and closely related domestic dogs, dietary specialisations between breeds can be ruled out as a diversifying factor although they display an enormous variation in TMJ morphology. This raises the question of the origin of this variation. Here we hypothesise that, even in the face of reduced functional demands, TMJ shape in dogs can be predicted by skull form; i.e. that the TMJ is still highly integrated in the dog skull. If true, TMJ variation in the dog would be a plain by-product of the enormous cranial variation in dogs and its genetic causes. We addressed this hypothesis using geometric morphometry on a data set of 214 dog and 60 wolf skulls. We digitized 53 three-dimensional landmarks of the skull and the TMJ on CT-based segmentations and compared (1) the variation between domestic dog and wolf TMJs (via principal component analysis) and (2) the pattern of covariation of skull size, flexion and rostrum length with TMJ shape (via regression of centroid size on shape and partial least squares analyses). We show that the TMJ in domestic dogs is significantly more diverse than in wolves: its shape covaries significantly with skull size, flexion and rostrum proportions in patterns which resemble those observed in primates. Similar patterns in canids, which are carnivorous, and primates, which are mostly frugivorous imply the existence of basic TMJ integration patterns which are independent of dietary adaptations. However, only limited amounts of TMJ variation in dogs can be explained by simple covariation with overall skull geometry. This implies that the final TMJ shape is gained partially independently of the rest of the skull.

Patterns of integration in the canine skull: an inside view into the relationship of the skull modules of domestic dogs and wolves

The skull shape variation in domestic dogs exceeds that of grey wolves by far. The artificial selection of dogs has even led to breeds with mismatching upper and lower jaws and maloccluded teeth. For that reason, it has been advocated that their skulls (including the teeth) can be divided into more or less independent modules on the basis of genetics, development or function. In this study, we investigated whether the large diversity of dog skulls and the frequent occurrence of orofacial disproportions can be explained by a lower integration strength between the modules of the skull and by deviations in their covariation pattern when compared to wolves. For that purpose, we employed geometric morphometric methods on the basis of 99 3D-landmarks representing the cranium (subdivided into rostrum and braincase), the mandible (subdivided into ramus and corpus), and the upper and lower tooth rows. These were taken from CT images of 196 dog and wolf skulls. First, we calculated the shape disparity of the mandible and the cranium in dogs and wolves. Then we tested whether the integration strength (measured by RV coefficient) and the covariation pattern (as analysed by partial least squares analysis) of the modules subordinate to the cranium and the mandible can explain differing disparity results. We show, contrary to our expectations, that the higher skull shape diversity in dogs is not explained by less integrated skull modules. Also, the pattern of their covariation in the dog skull can be traced back to similar patterns in the wolf. This shows that existing differences between wolves and dogs are at the utmost a matter of degree and not absolute.

Archaeological dogs from the Early Holocene Zhokhov site in the Eastern Siberian Arctic

Excavations on the Zhokhov Island yielded a small but meaningful collection of Early Holocene canine faunal remains (MNI=13). To clarify the morphological characteristics of the Zhokhov dogs' skulls, they were compared to the modern skulls of the Eastern Siberian wolves. This analysis shows, that around 9000years ago a fully formed, as a species, domesticated dog was present at the Zhokhov site and used by the inhabitants of the area while hunting and as a draft animal. Presence of a developed form of dog sledding has been securely established for this culture. The Zhokhov site osteological dog remains analysis showed that the comparison of two proportional ratios (the ratio of skull height in the cranial region to total skull length and the ratio of snout height at Рm1 – Рm2 to total skull length) is a universal and reliable criterion for distinguishing wolf skulls from wolf-like dog skulls. This method prevents the influence of any single measurement on the identification of any individual as a dog or a wolf. We propose to name them indices DD1 and DD2, accordingly (for Dog Domestication). We also show that a sled dog and hunting dog standard existed, which significantly changes the current ideas about the timing of specialized dog breed formation via directed selection. Full completion of this process marks the third stage of domestication. Two earlier stages precede it in time and space (natural selection via the feeding behavior within specific ecological niche, formed by the human activity, followed by artificial selection based on the animal's ability to be tamed). We suggest that sled dogs could have been used in Siberia around 15,000years ago.

Functional differentiation of teeth in the wolf (Canis lupus, Canidae, Carnivora)

Vector analysis has been used to investigate the functions of incisors, canine teeth, premolars, and molars in a sample of 411 wolf skulls and to elucidate the morphological features that confer resistance to mechanical loading (pressure from the prey tissues upon jaw clenching and fracture under pressure directed along the jaw) to the teeth. Differentiation of the teeth was due to functional differences and showed only partial conformity to the anatomical nomenclature. Canine teeth and i3 serve for the infliction of wounds upon an attack. These teeth, together with I1-2/1-3, are used to tear off parts of the prey. The premolars p1-3/2-4 are used to hold, tear off, and carry parts of the prey. The carnassials р4 and m1 are used to break bones and cut the soft tissues. The rear part (talonid) of m1 and m1-2/2 serve for further disintegration of food. The anterior premolars p1/1 and m3 are undergoing a rudimentation process, as evident from higher frequency of developmental defects compared to that in other teeth. Breakage and chipping of the teeth is rare, except for cases of extreme loading, since mechanical strength of the teeth is sufficiently high.

A standardized framework for examination of oral lesions in wolf skulls (Carnivora: Canidae: Canis lupus)

Abstract Oral lesions in wolves (Carnivora: Canidae: Canis lupus) are usually reported in a nonstandardized manner, and often only a few abnormalities are indicated. This approach has likely led to underreporting of oral lesions, thus limiting our ability to interpret wolf health conditions and thus making comparisons across geographical and taxonomic groups difficult. Here, we present a standardized oral exam protocol to examine wolf skulls for their oral lesions. Using this protocol, we analyzed 40 skulls of adult wild Middle East wolves representing 1,680 teeth. Six wolves were Canis lupus arabs, 34 were Canis lupus pallipes. Only 3 skulls showed no oral lesions. We were able to identify a large range of oral lesions and refined subclasses, exceeding the variety of what has been reported on wolf oral lesions so far. No statistical differences were found in the type and number of lesions between the 2 subspecies of wolves. Therefore, the lesions were pooled in subsequent analyses. This standardized protocol should provide a useful framework to assess oral lesions in wolf skulls, facilitating rigorous comparisons across geographic and taxonomic groups.

Can orbital angle morphology distinguish dogs from wolves?

For more than a century, the orbital angle has been studied by many authors to distinguish dog skulls from their progenitor, the wolf. In early studies, the angle was reported to be different between dogs (49°–55°) and wolves (39°–46°). This clear difference was, however, questioned in a more recent Scandinavian study that shows some overlap. It is clear that in all studies several methodological issues were unexplored or unclear and that group sizes and the variety of breeds and wolf subspecies were small. Archaeological dog skulls had also not been studied. Our goal was to test larger and more varied groups and add archaeological samples as they are an evolutionary stage between wolves and modern dogs. We also tested the influence of measuring methods, intra- and inter-reliability, angle symmetry, the influence of variations in skull position and the possibility of measuring and comparing this angle on 3D CT scan images. Our results indicate that there is about 50 % overlap between the angle range in wolves and modern dogs. However, skulls with a very narrow orbital angle were only found in wolves and those with a very wide angle only in dogs. Archaeological dogs have a mean angle very close to the one of the wolves. Symmetry is highest in wolves and lowest in archaeological dogs. The measuring method is very reliable, for both inter- and intra-reliability (0.99–0.97), and most skull position changes have no statistical influence on the angle measured. Three-dimensional CT scan images can be used to measure OA, but the angles differ from direct measuring and cannot be used for comparison. Evolutionary changes in dog skulls responsible for the wider OA compared to wolf skulls are mainly the lateralisation of the zygomatic process of the frontal bone. Our conclusion is that the orbital angle can be used as an additional morphological measuring method to discern wolves from recent and archaeological dogs. Angles above 60° are certainly from recent dogs. Angles under 35° are certainly of wolves.

Is black coat color in wolves of Iran an evidence of admixed ancestry with dogs?

Melanism is not considered a typical characteristic in wolves of Iran and dark wolves are believed to have originated from crossbreeding with dogs. Such hybrid individuals can be identified with the combined use of genetic and morphological markers. We analyzed two black wolves using a 544 base pairs (bp) fragment of the mtDNA control region and 15 microsatellite loci in comparison with 28 dogs, 28 wolves, and four known hybrids. The artificial neural networks (ANNs) method was applied to microsatellite data to separate genetically differentiated samples of wolves, dogs, and hybrids, and to determine the correct class for the black specimens. Individual assignments based on ANNs showed that black samples were genetically closer to wolves. Also, in the neighbor-joining network of mtDNA haplotypes, wolves and dogs were separated, with the dark specimens located in the wolf branch as two separate haplotypes. Furthermore, we compared 20 craniometrical characters of the two black individuals with 14 other wolves. The results showed that craniometrical measures of the two black wolves fall within the range of wolf skulls. We found no trace of recent hybridization with free-ranging dogs in the two black wolves. Dark coat color might be the result of a natural combination of alleles in the coat-color-determining gene, mutation in the K locus due to past hybridization with free-ranging dogs, or the effect of ecological factors and adaption to habitat conditions.

Morphometric variations of the skull in the Gray Wolf (Canis lupus) in Iran

The Gray Wolf is a wide ranging carnivore in Iran, absent only in the central deserts and Dasht-e Lut. This study was carried out to verify whether, despite their high mobility, individual wolves belonging to different populations show morphological variations in the skull. We collected 48 skulls from various regions of Iran and measured 24 variables on the cranium. These primary variables were then used to generate six indices to examine any variations in the shape of the skulls collected in different regions of the country. Although the largest skulls collected for this study originated in the mountainous regions of the northwest, northeast, and west, principle component analysis (PCA) did not result in a meaningful difference in the size and shape of wolf skulls in different regions of Iran. Our results confirm that the minor morphological variations of the skull in wolves of Iran are not an evidence for the separation of wolf populations in different regions or the existence of various subspecies in the country. This uniformity can be explained by the strong gene flow among populations as well as high mobility of the wolf that facilitates movement of individuals between populations.

Use of cranial characters in taxonomy of the Minnesota wolf (Canis sp.)

Minnesota wolves (Canis sp.) sometimes are reported to have affinity to a small, narrow-skulled eastern form ( Canis lupus lycaon Schreber, 1775) and sometimes to a larger, broader western form ( Canis lupus nubilus Say, 1823). We found that pre-1950 Minnesota wolf skulls were similar in size to those of wolves from southeastern Ontario and smaller than those of western wolves. However, Minnesota wolf skulls during 1970–1976 showed a shift to the larger, western form. Although Minnesota skull measurements after 1976 were unavailable, rostral ratios from 1969 through 1999 were consistent with hybridization between the smaller eastern wolf and the western form. Our findings help resolve the different taxonomic interpretations of Minnesota skull morphology and are consistent with molecular evidence of recent hybridization or intergradation of the two forms of wolves in Minnesota. Together these data indicate that eastern- and western-type wolves historically mixed and hybridized in Minnesota and continue to do so. Our findings are relevant to a recent government proposal to delist wolves from the endangered species list in Minnesota and surrounding states.

Wolf body mass, skull morphology, and mitochondrial DNA haplotypes in the Riding Mountain National Park region of Manitoba, Canada

Two types of wolves, gray ( Canis lupus L., 1758) and eastern ( Canis lupus lycaon Schreber, 1775 or Canis lycaon ) or Great Lakes wolves, representing Old World (OW) and New World (NW) mitochondrial DNA (mtDNA) haplotypes, have been reported in eastern Canada and the Great Lakes region. Both haplotypes were found in Duck Mountain Provincial Park and Forest, Manitoba. Only OW haplotypes have been reported from the isolated Riding Mountain National Park (RMNP), 30 km to the south. Wolves with NW haplotypes hybridize with C. lupus and coyotes ( Canis latrans Say, 1823) and could mediate gene flow between canids. We examined available data on wolf body mass, skull morphology, and mtDNA from the RMNP region, as well as mtDNA from Manitoba and Saskatchewan, to assess the occurrence of NW haplotypes in wolves and possible canid hybridization. Mean body mass of female (n = 54) and male (n = 42) RMNP wolves during 1985–1987 was higher than that of females (n = 12) and males (n = 8) during 1999–2004. Thirteen skull measures from 29 wolf skulls did not suggest significant differences between RMNP and Duck Mountain wolves. Nineteen of 20 RMNP samples had OW haplotypes, whereas one clustered together with NW haplotypes.

Changes in the skull morphology of the Arctic wolf, Canis lupus arctos, during the twentieth century

Measurements of a large series of skulls of the Arctic wolf, Canis lupus arctos. have shown that since 1930 there has been an overall reduction in the size of the skulls, together with widening of the cranium, shortening of the facial region, and reduction in size of the teeth. This suggests that hybridization and subsequent introgression occurred with huskies (Canis familiaris) during the 1930s, which is consistent with historical accounts. Since 1950 there has been a reversion in skull morphology to a more ‘wolf‐like’ form, suggesting that hybridization is no longer occurring.The skull of a wolf/dog hybrid is intermediate in size between the skulls of wolves and huskies but its shape is allometrically dissimilar. Skulls of wolves from the period 1930–50 are moi‐e similar to the skull of this hybrid than in the other time periods.The skull of a male canid from a carcass collected on Ellesmere Island and presented to the Natural History Museum. London, in 1986 was at first thought to be from a wolf/dog hybrid but analyses of the measurements show that it is more likely to be from an Arctic wolf with severe abnormalities to the jaws.

Tooth losses and anomalies in the wolf (Canis lupus)

We observed tooth losses (and subsequent alveolar resorptions) and other cases of anodonty and polydonty and anomalies in the shape and occlusion of the teeth in skulls of wolves from the former Soviet Union. Resorptions increase in number with age, but do not seem to have much of an effect on individual survival (they probably do not affect hunting), and are found in half of individuals over 8 years of age. The highest numbers of resorptions, as well as cases of polydonty and dental anomalies, were in the premolars. This suggests that the premolars are not greatly subject to selective pressure. At least 6.8% of the skulls have malformed teeth or malocclusions.

Identification of Pups and Yearling Wolves by Dentine Width in the Canine

One hundred and thirty-nine wolf (Canis lupus) skulls and mandibles were collected from hunters and trappers of northern Quebec and Labrador during the winters of 1980-81 through 1983-84. The maximum width of the dentine-cementum wall in wolf canine teeth was used to separate pups killed late in their first year from yearlings killed early in their second winter of life. Both age classes may have a closed foramen at the apex of the root and a clear deposit of cementum with no opaque annulus.Key words: wolf (Canis lupus), canine teeth, dentine width, pups versus yearlings

Zmienność uzębienia oraz asymetria czaszek u wilka

Analysis was made of teeth in 234 wolf skulls obtained from Polish territory and from eastern part of the Białowieża Primeval Forest (USSR). Authors describe three groups of deviations from typical tooth pattern in wolves: polydonty, oligodonty and others types of tooth anomalies occuring when the normal number of teeth was presented.