Prey size reflected in tooth wear: a comparison of two wolf populations from Sweden and Alaska

Ingesta leaves distinct patterns on mammalian teeth during mastication. However, an unresolved challenge is how to include intraspecific variability into dietary reconstruction and the biomechanical aspects of chewing. Two extant populations of the grey wolf (Canis lupus), one from Alaska and one from Sweden, were analysed with consideration to intraspecific dietary variability related to prey size depending on geographical origin, sex and individual age as well as tooth function. Occlusal enamel facets of the upper fourth premolars, first molars and the second lower molar were analysed via three-dimensional surface texture analysis. The Swedish wolves displayed facets characterized by higher peaks and deeper, more voluminous dales, featuring an overall rougher surface than the wolves from Alaska. Compared to females, the Swedish male wolves had a slightly larger dale area and hill volume on their facets. Upper fourth premolars are smoother and had higher values in texture direction compared to upper first molars. The upper first molars were rougher than the occluding lower second molars and were characterized by larger and deeper dales. We find evidence supporting intraspecific dietary segregation, and antagonistic asymmetry in occlusal wear signatures. The data offer new insights into the roles of apex predators like the grey wolf.

Different, but the same: Inferring the hunting behaviour of the hypercarnivorous bush dog (Speothos venaticus) through finite element analysis

Cerdocyonina is a clade composed by the South-American canids in which the bush dog (Speothos venaticus) is one of the most elusive species. Known for its unique morphology within the group, this small, bear-like faced canid is the only member of the clade adapted to hypercarnivory, an almost exclusively meat-based diet currently present only in usually large, pack-hunting canids such as the grey wolf (Canis lupus). However, much of the biology of the bush dog is poorly understood, and inferences about its ecology, hunting strategies and diet are usually based on observation of captive individuals and anecdotal records, with reduced quantitative data to offer support. Here, we investigated the craniomandibular functional morphology of the bush dog through finite element analysis (FEA). FEA was employed to model the biting behaviour and to create extrinsic and intrinsic functional scenarios with different loads, corresponding to different bites used to subdue and process the prey. For comparison, the same modelling was applied to the skull of a grey wolf and a grey fox (Urocyon cinereoargenteus). Our analysis showed that the bush dog's responses to loading are more similar to the wolf's than to the fox's in most scenarios, suggesting a convergent craniomandibular functional morphology between these two hypercarnivorous species, despite their distinct phylogenetic positions and body sizes. Differences between the three taxa are noteworthy and suggested to be related to the size of the usual prey. The modelled bite force for the bush dog is relatively strong, about half of that estimated for the wolf and about 40% stronger than the fox's bite. The results strengthen with quantitative data the inferences of the bush dog as a pack-hunting predator with prey size similar to its own, such as large rodents and armadillos, being specialised in subduing and killing its prey using multiple bites. Its similarity to the wolf also confirms anecdotal accounts of predation on mammals that are much larger than itself, such as peccaries and tapirs. These data highlight the ecological specialisation of this small canid in a continent where large, pack-hunting canids are absent.

A Morphological and Morphometric Dental Analysis as a Forensic Tool to Identify the Iberian Wolf (Canis Lupus Signatus)

Simple Summary

Attacks by Iberian wolves on farm animals routinely cause conflicts with humans and threaten their economic interests related to livestock. However, wolf predation can sometimes be confused with that caused by other carnivores like dogs. Some studies have tried to identify or differentiate canids as the predators responsible for such attacks by analysing their tooth/bite marks on bone remains. Nevertheless, most of those studies have only considered a few dental measurements, and they were carried out in a palaeoecological and zooarchaeological context. As there is still limited information on Iberian wolf‘s dental anatomy that can be used in forensic cases, this study aimed to describe the morphology of the Iberian wolf‘s teeth and to provide new morphometric characteristics, as complete as possible, to collaborate in the correct interpretation of a wolf‘s bite marks at crime scenes. Based on the morphometric dental analysis, it was possible to differentiate female and male wolves. Moreover, the dental morphometric characteristics described can be used, at least as a reference, to identify the Iberian wolf‘s tooth/bite marks or to rule out other potential aggressors.

Abstract

Depredation by the Iberian wolf (Canis lupus signatus) is currently thought to be a problem in some areas of Spain. However, there are few technically validated forensic tools available to determine the veracity of claims with a high degree of scientific confidence, which is important given that such attacks may lead to compensation. The analysis of bite marks on attacked animals could provide scientific evidence to help identify the offender. Thus, the aim of this study was to assess the morphological and morphometric characteristics of Iberian wolf dentition. This data collection would serve as a base-point for a more accurate identification of the wolves thorough their bite marks. For the first time, 36 dental variables have been studied in wolves’ skulls, employing univariate and multivariate analyses. The general morphological dental characteristics of wolves are very similar in terms of their dental formula and tooth structure to other canids, like domestic dogs. Sex differentiation was evident, principally in terms of the maxillary distance between the palatal surfaces of the canine teeth (UbC) and the width of the left mandibular canine teeth (LlCWd). New morphometric reference information was obtained that can aid the forensic identification of bite marks caused by the Iberian wolf with greater confidence.