Dinomys branickii Peters, 1873

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 : 110-111

Dinomys branickii Peters, 1873

Figure 45

VOUCHER MATERIAL (N = 1): Nuevo San Juan (MUSM 11231). In addition to our single specimen, the occurrence of Dinomys branickii in the Yavarí-Ucayali interfluve is documented by photographs of one adult and a juvenile that were killed by a Matses man at Estirón in 2013. The dead individuals were examined by D.W.F., but they were not preserved because he had no collecting permits for them. Unfortunately, the photographs are not suitable for publication.

UNVOUCHERED OBSERVATIONS: None.

IDENTIFICATION: Our single specimen of Dinomys branickii —commonly known as the pacarana—consists of the skull of an adult individual (with fused basicranial sutures). Although incomplete, this specimen exhibits all the diagnostic craniodental traits of this morphologically unique taxon ( Patton, 2015c). Selected measurements of MUSM 11231 are: condyloincisive length, 144.9 mm; length of diastema (alveolar), 35.2 mm; maxillary toothrow (alveolar), 33.3 mm; length of nasals, 54.8 mm; least interorbital breadth, 54.4 mm; zygomatic length, 57.4 mm; and zygomatic breadth, 99.0 mm. The photographs of dead individuals from Estirón are equally compelling because they clearly show the diagnostic external traits of pacaranas as described by authors ( Emmons, 1997; Patton, 2015c).

Apparently, our specimen and photographs constitute the only definite records of Dinomys branickii from Loreto department. 30

ETHNOBIOLOGY: The Matses name for the pacarana is tambisbiekkid (“one that is similar to a paca ”). A dialectal variant name is tambis inkuente chokid ( “paca that has a tail”). Despite these names, it is not considered a type of paca. No subtypes are recognized by the Matses.

Pacaranas are encountered infrequently, so not all Matses have seen them. They do not seem to occur in all parts of Matses territory, such as along the lower Río Gálvez, whereas they are more common along the upper Gálvez and the upper Quebrada Chobayacu. The Matses do not eat pacaranas, which are sometimes seen while hunting or are flushed from their burrow by hunting dogs during the day. Sometimes a hunter mistakes a pacarana for a paca when dogs chase one into a hole. When the hunter catches up, he introduces a palm frond into the burrow; if the quarry bites it (something that pacas never do), he knows that it is a pacarana.

Pacaranas can be pests in Matses swiddens. They don’t just eat some of the tubers (like pacas do), but they also cut away the stem, killing the whole plant. They return every night to the swidden until they are killed. To be rid of pacaranas that have become pests, Matses search the area around the swidden with dogs,

30 The specimen that Patton (2015c) listed from Iquitos (AMNH 98576) was part of a large collection of Amazonian vertebrates that Harvey Bassler donated to the AMNH in 1934, but the locality datum is problematic. The fauna of Iquitos and its evirons on the left (north) bank of the Amazon, has been intensively surveyed for many years (most recently by Hice and Velazco, 2012), and it is implausible that a mammal as large as Dinomys branickii (ca. 10–15 kg) should not be represented by additional specimens or observations if it really occurred there. Harvey Bassler—a petroleum geologist and amateur collector of natural history specimens throughout much of western Amazonia ( Willard, 1966; Edson, 1982; Myers, 2000)—is known to have maintained a small zoo at Iquitos, and his manuscript catalog of mammals (in the Department of Mammalogy archives) records the locality of AMNH 98576 as “Iquitos (prep.).” We infer that this specimen was captured elsewhere but died in his menagerie.

hunt them down, and kill them. However, if pacaranas are encountered far from swiddens, the Matses do not kill them.

MATSES NATURAL HISTORY: The pacarana’s head and body are like a paca’s, but it has a tail. It has longitudinal stripes on its body and has a large head.

The pacarana dens in a shallow hole in a stream headwater gully or in standing hollow trees that have a hole at the base.

It is nocturnal. During the night it forages for dicot tree fruits in the forest and comes to eat manioc in swiddens.

It is solitary.

It enters any hole for refuge when dogs pursue it. Unlike the paca , it does not plunge into streams when pursued.

The pacarana eats principally dicot tree fruits. It also eats the stems of mani pada plants ( Heliconia spp. [ Heliconiaceae ]). In Matses swiddens it feeds mostly on manioc tubers, but also on ripe or unripe plantain fruits and sugar cane.

REMARKS: The single collected specimen and both photographed individuals of Dinomys branickii from our region were killed in Matses swiddens. The skull from Nuevo San Juan was discarded and left outdoors near the village, where it was defleshed by scavengers and insects; the mandibles and missing teeth could not be found. Matses natural history observations about this species are sparse, but their assertion that it is solitary appears to contradict published suggestions that pacaranas live in pairs or small groups (White and Alberico, 1992; Saavedra-Rodríguez et al., 2012). By contrast, Matses dietary observations are consistent with published observations that this species eats tubers, succulent stems, and fruit, but not seeds ( Neto et al., 2017; González and Osbahr, 2013). Its exceptionally broad incisor teeth; convergent toothrows; and hypsodont, ever-growing cheekteeth suggest that Dinomys routinely consumes soft but abrasive items, presumably tubers and rhizomes, which we conjecture to be dietary staples of this unusual rodent.