An illustrated key to the mandibles of small mammals of eastern Canada

Abstract

Skulls are often used to identify small mammals, and most identification keys to small mammals have been developed on the assumption that whole skulls will be available. however, the skulls of small mammals are seldom found intact in predator pellets or nests, and the bones of several individuals are often scattered and mixed, making counting impossible without the use of a specific cranial part. In addition, only a few keys include all the species found in the eastern provinces of Canada.Mandibles readily resist degradation by the gastric acids of both avian and mammalian predators and are often found intact in food caches of mustelids and in bat hibernacula. We therefore designed an illustrated dichotomous key to small mammals (mean mass <5 kg) of eastern Canada based on diagnostic mandible characters (including the teeth and one dentary bone). We identified and confirmed diagnostic characters to distinguish 55 species from the orders lagomorpha, rodentia, Soricomorpha, Carnivora, and Chiroptera. these diagnostic characters are based on a review of the literature and were confirmed by measurements performed on both museum and trapped specimens. In order to facilitate identification, photographic illustrations are provided for each couplet of the key.the ability to identify small mammals using their mandibles will reduce the number of skull components needed and has proven to be a useful tool in the study of the diet of predators. this key may also be helpful in identifying bats in the genera Myotis, Perimyotis, and Eptesicus, which are presently affected by the spread of white-nose syndrome (caused by Pseudogymnoascus destructans) throughout the eastern part of Canada.

Geometric Morphometrics of Dentaries inMyotis: Species Identification and Its Implications for Conservation and the Fossil Record

“…In North America, only Corynorhinus and Lasionycteris have a lower alveolar formula similar to Myotis (dental formula 3-1-3-3, with a single-rooted p2 and p3 and a double-rooted p4; Czaplewski et al 2002). Fortunately these genera can easily be distinguished by dental and dentary morphology (Czaplewski et al 2002, Fauteaux et al 2014, Gaudin et al 2011. For instance, Corynorhinus has a more laterally directed angular process, no lingual cingulum on the molar trigonids, a broad talonid, and mandibular foramen typically exposed.…”

“…Fauteaux et al (2014) were able to distinguish among Myotis in eastern Canada, in part because only 3 species occur there. However, identification of fossils based on geographic criteria must be done with caution, because geographic ranges may have changed over time (Bell et al 2009).…”

“…However, identification of fossils based on geographic criteria must be done with caution, because geographic ranges may have changed over time (Bell et al 2009). Several authors have noted characteristics that distinguish Northern Long-eared Bats from other members of the genus, including strong lingual cingula around the protocones of the upper molars, a rectangular p3 with anteroposterior length greater than labiolingual width, and middle labial cusp of i3 small (Czaplewski et al 2002, Fauteaux et al 2014, Gaudin et al 2011. Gray Bats and Eastern Small-footed Bats can sometimes be distinguished on the basis of size (Fauteaux et al 2014, Gaudin et al 2011).…”

“…Several authors have noted characteristics that distinguish Northern Long-eared Bats from other members of the genus, including strong lingual cingula around the protocones of the upper molars, a rectangular p3 with anteroposterior length greater than labiolingual width, and middle labial cusp of i3 small (Czaplewski et al 2002, Fauteaux et al 2014, Gaudin et al 2011. Gray Bats and Eastern Small-footed Bats can sometimes be distinguished on the basis of size (Fauteaux et al 2014, Gaudin et al 2011). Menzel et al (2005 were able to distinguish among these 6 species using cranial characters, though they did not analyze morphology of the dentary in detail.…”

Improving diet assessment of Arctic terrestrial predators with the size of rodent mandibles

“…Counting and identifying prey remains in pellets or scats has been done in the past to assess the diet of avian and mammalian predators (Maser & Brodie, ; Redpath et al , ; Buidin, Rochepault & Savard, ). Identification keys using skull parts or mandibles can be used to determine the species consumed (Carraway, ; Glass & Thies, ; Naughton, ; Fauteux et al , ). Mandibles are particularly useful because of their high resistance to gastric degradation.…”