Cricetidae, Fischer, 1817

Voss, Robert S., Fleck, David W. & Jansa, Sharon A., 2019, Mammalian Diversity And Matses Ethnomammalogy In Amazonian Peru Part 5. Rodents, Bulletin of the American Museum of Natural History 2024 (466), pp. 1-180 : 38-40

Cricetidae

All the cricetids known to occur in the Yavarí-Ucayali interfluve are members of the sigmodontine tribe Oryzomyini , although members of other sigmodontine tribes could also be expected in our region (appendix 5). Oryzomyine taxonomy has undergone major transformations in the past few decades, both from species-level revisionary work (e.g., Musser et al., 1998) and from phylogenetic analyses and subsequent generic reclassifications ( Weksler, 2003, 2006, 2015; Weksler et al., 2006). Among other noteworthy changes, the genus Oryzomys , a formerly polyphyletic taxon that included many Amazonian species, is now restricted to a much smaller number of mostly trans-Andean taxa. Except as noted otherwise below, oryzomyine taxonomy in this report follows Patton et al. (2015), which includes morphological diagnoses and keys to all the genera mentioned in the following accounts ( Amphinectomys , Euryoryzomys , Holochilus , Hylaeamys , Neacomys , Nectomys , Oecomys , Oligoryzomys , and Scolomys ).

Cricetid taxonomy is an active field of research, and the literature can be daunting for newcomers. Nevertheless, the following accounts assume familiarity with cricetid comparative morphology, including terminology for aspects of external and craniodental anatomy defined or referenced by Voss (1988) and Weksler (2006). Although we devote much attention to external features that might be useful for field identifications, it must be emphasized that many cricetids in our region cannot be confidently identified to species without collected voucher material.

MEASUREMENTS: We measured the following dimensions of cricetid skulls and teeth (fig. 17): CIL, condyloincisive length: from the greater curvature of one upper incisor to the articular surface of the occipital condyle on the same side. LD, length of diastema: from the lesser curvature of an upper incisor to the crown of the first upper molar (M1).

LM, length of molars: greatest crown length of the upper molar row (from M1 to M3).

BM1, breadth of M1: greatest transverse dimension of the crown of either the left or right first upper molar.

LIF, length of incisive foramen: greatest anterior-posterior dimension of either the left or right incisive foramen.

BIF, breadth of incisive foramina: greatest transverse dimension across both foramina.

BPB, breadth of palatal bridge: breadth of the palate between the crowns of the right and left first upper molars.

BZP, breadth of the zygomatic plate: least width of the zygomatic plate from its anterior to posterior margins.

LIB, least interorbital breadth: the least transverse dimension between the orbits across the frontal bones.

ZB, zygomatic breadth: the greatest transverse dimension across the zygomatic arches.

BR, breadth of rostrum: the greatest transverse dimension across the undamaged nasolacrimal capsules.

LR, length of rostrum: distance from the distal apex of an intact nasal bone to the posterior margin of the ipsilateral zygomatic notch.

AGE DETERMINATION: The last teeth to erupt in cricetids are the third molars (M3/m3), but specimens with fully erupted dentitions can exhibit statistically significant and visually conspicuous ontogenetic variation in cranial size and shape (e.g., Voss, 1991: fig. 16). To minimize the confounding effect of such ontogenetic variation for morphometric comparisons, we recorded measurement data from specimens with visible wear (exposed dentine) on all of the cusps and crests of M3. We refer to such specimens as “adults” without any intended implication of reproductive maturity.

ETHNOBIOLOGY: The cricetids that occur in our region are all small (<300 g), nocturnal, and generally inconspicuous. Not surprisingly, the Matses consistently distinguish only a few by name, either because they are occasionally trapped and eaten, or because they are semicommensal pests. The term tambisëmpi (“little paca”) can refer specifically to echimyid spiny rats ( Proechimys spp. ), but it is also used as a general term that includes all rats and mice in the families Echimyidae and Cricetidae . The term maka (“mouse/rat”) is an old word that presumably has (or had) the same meaning as the general sense of tambisëmpi, but it currently survives only as part of the names of three folk species: maka tanun (“gray rat,” for Nectomys apicalis ), abuk maka (“up rat,” for arboreal echimyids), and abuk makampi (“little up rat,” for species of the arboreal cricetid genus Oecomys ). In effect, the Matses folk classification system does not distinguish these two rodent families.

Another Matses folk-taxon name associated with cricetids is takbid umu (“gray belly”). This term apparently refers to any mouse-size rodent with grayish ventral fur (such as Hylaeamys spp. ), but it is difficult to ascertain precisely the full semantic range of this term. A regional variant name for this folk category is takbid çhëşhë (“black/dark-colored belly”). These species may also be referred to as cheka, which is a term that prototypically designates opossums, but in more general usage includes any small rodent that is not eaten (e.g., all cricetids except Nectomys apicalis ) as well as an unidentified species of climbing rat mysteriously known as yama. 13

Lastly, the Matses refer to a rodent called şhëa that we are unable to identify. Like the semicommensal species known as şhubu pekid ( Oecomys bicolor ; see below), şhëa is said to be a pest that takes up residence in Matses houses, feeds on maize and other food, and chews noisily on thatch, where it makes its nest. However, several Matses claim that they have not seen one for several decades, so it is possible that şhëa lived only in traditional Matses longhouses (which were thatched all the way to the ground) and do not enter modern Matses homes (which are built on stilts). According to the Matses, şhëa is a tiny mouse (smaller than O. bicolor ) with grayish dorsal fur, a white belly, large ears, and a long tail. Neither this physical description nor details of its alleged behavior (e.g., arboreal locomotion, foraging for fruit in the forest) are a compelling match for any local species known to us.