Animal Diversity Web

Geographic Range

Junín red squirrels (Sciurus pyrrhinus) are found in the Neotropics. More specifically they are an endemic to Peru. Junín red squirrels have been found in habitats ranging from lowland tropics to montane foothills (300 to 1,500 m above sea level) of Madre de Dios, Peru. The geographic range of Junín red squirrels have been found throughout Peru, including Huánuco, Pasco, Junín, Huancavelica, Ayacucho, Cuzco, Ucayali, and perhaps in San Martín. They have also been found in Federico Roman, Bolivia, though the specimens found there have not been verified. An old specimen, found in 1920 near Zamora, Ecuador, suggests that the range of the species spans farther north of the eastern slopes of the Andes than expected. (Scobie, et al., 2014)

• Biogeographic Regions
• neotropical
  • native

Habitat

Junín red squirrels are arboreal forest dwellers that have been found both in low-elevation rain forests and high-elevation montane forests. They have been sighted frequently in rain forests with boggy patches of water in palm swamps. They have also been frequently found at clay licks (colpa) in terra forma forests. In anthropogenic environments, they have been reported to frequently visit family farms. They are seen in higher abundance in areas where logging has ceased compared to active logging cites. Surprisingly, Junín red squirrels are found in 120 % relative abundance in comparison to Bolivian squirrels (Sciurus ignitus) at inactive logging sites. At active logging sites, the relative abundance of Junín red squirrels compared to Bolivian squirrels was found to be 240 %, demonstrating the ability of Junín red squirrels to tolerate relatively high levels of anthropogenic disturbance. (Haugaasen and Peres, 2005)

• Habitat Regions
• tropical
• terrestrial

• Terrestrial Biomes
• rainforest

• Wetlands
• swamp
• bog

• Other Habitat Features
• agricultural

• Range elevation

  600 to 2500 m

  1968.50 to 8202.10 ft

Physical Description

Junín red squirrels are large-bodied, arboreal sciurids (family Sciuridae). They are similar in appearance to Northern Amazon red squirrels (S. igniventris), but are smaller overall. Northern Amazon red squirrels are found in Brazil, Colombia, Venezuela, Ecuador and Peru. Due to some sympatry between Junín red squirrels and Northern Amazon red squirrels, discerning the two can be difficult. Junín red squirrels have dorsal sides that are dark agouti reddish brown, which get progressively darker from head to tail. However, the pelage of Junín red squirrels are more uniform than Northern Amazon red squirrels. Both species have contrasting orange post-articular tufts. The ventral fur of Junín red squirrels can be white, red, or red with patches of white. On the other hand, the ventral fur of Northern Amazon red squirrels is either orange or white. The tails of Junín red squirrels are bicolored with orange tips and almost black bases. The dorsal sides of their forearms and hands are light orange in color and the ventral sides of their forearms are white and trimmed orange. Both the dorsal and the ventral surfaces of their hind feet are orange in color. (Allen, 1915; Amori, et al., 2016; Lee and Brant, 2014)

Measurements taken from a tag of a Junín red squirrel specimen collected from Peru and stored at the American Museum of Natural History (AMNH 60507) are as follows: total length, 536 mm; tail length, 275 mm; hind foot length, 65 mm. A reproductive female specimen from Peru had the following measurements: total length, 448 mm; head and body length, 240 mm; tail length, 208 mm; hind foot length, 59 mm. (Allen, 1915)

Junín red squirrels have short broad rostra. Their sphenopalatine vacuities average 2 mm. These are smaller or completely absent in Northern Amazon red squirrels (S. igniventris). The skull measurements of the type specimen for Junín red squirrels are as follows: greatest length of skull, 52 mm; zygomatic breadth, 33.5 mm; interorbital breadth (at the supraorbital notch), 18 mm; nasal length, 16.5 mm; diastema, 15.2 mm; maxillary toothrow, 9.6 mm. The skull measurements of the specimen at the American Museum of Natural History (AMNH 60507) are as follows: greatest length of skull, 60.64 mm; zygomatic breadth, 34.72 mm; interorbital breadth (at the supraorbital notch), 19.41 mm; brain case breadth (posterior to the zygomatic arch), 24.41 mm; nasals, 19.84 mm; diastema, 16.36 mm; maxillary toothrow, 9.67 mm; orbit size (supraorbital flange to the zygomatic arch) is 13.72 mm. (Allen, 1915)

For the sake of comparison, measurements taken from the four specimens of Northern Amazon red squirrels (S. igniventris) from the American Museum of Natural history (AMNH 68258, 73385, 73388, 73892) are as follows: greatest length of skull, 63.7 – 65.28 mm; zygomatic breadth, 36.61 – 36.76 mm; interorbital breadth (at the supraorbital notch), 19.54 – 22.68 mm; brain case breadth (posterior to the zygomatic arch), 23.88 – 25.17 mm; nasals, 20.54 – 22.25 mm; diastema, 17.89 –18.61 mm; maxillary toothrow, 10.23 – 10.56 mm. orbit size, 13.71 – 14.33 mm. (Lee and Brant, 2014)

• Other Physical Features
• endothermic
• homoiothermic
• bilateral symmetry

• Range length

  448 to 536 mm

  17.64 to 21.10 in

Reproduction

There is no available information regarding reproductive behaviors of Junín red squirrels. A similar South American tree squirrel species, Red-tailed squirrels (Sciurus granatensis), shows sexual dimorphism, with females 5.5% larger on average than males. Mating chases in red-tailed squirrels involving 6 to 8 individuals have been observed in the field. Another South American arboreal species, neotropical pygmy squirrels (Sciurillus pussilus), have shown similar behavior, where several males have been observed to chase a single estrous female during mating season. (Emmons and Feer, 1997; Nitikman, 1985)

Female Junín red squirrels are known to lactate in January. Other than that, there is little available information regarding the reproduction of Junín red squirrels. However, another South American arboreal sciurid, southern Amazon red squirrels (Sciurus spadiceus), have been reported to give birth in early June in Peru. This suggests that breeding occurs in autumn in the southern hemisphere and in august in Bolivia. Litter sizes average 2 to 4 pups. The breeding season of red-tailed squirrels (Sciurus granatensis) starts at the beginning of the dry season, from late December to early January. Female red-tailed squirrels start their estrous cycles roughly at the same time. Females can carry roughly 2 to 3 embryos. The gestation period of red-tailed squirrels is reported to be 44 days. Young are born with closed eyes and no hair and they weigh around 9 to 10 g. Red-tailed squirrels can produce 2 to 3 litters a year. Yet another South American arboreal sciurid, neotropical pygmy squirrels (Sciurillus pusillus), have been reported to be pregnant and lactating in June with litter sizes of 1 or 2 pups. Generally, the litter sizes of Neotropical tree squirrels are reported to be 2 to 5 pups. (Anderson, 1997; Emmons and Feer, 1997; Nitikman, 1985; Thorington, et al., 2012)

• Key Reproductive Features
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• viviparous

Female Junín red squirrels have been documented to lactate in January. Other than that, there is little available information regarding their reproduction. Other neotropical tree squirrels have been reported to build nests out of leaves and twigs among tree vines, branches, and cavities. Another neotropical tree squirrel species, red-tailed squirrels (Sciurus granatensis) have been reported to lactate during May and June. Interestingly, it has been observed that this mating season (December to August) coincides with the availability of fresh fruits. When fruits are scarce and the species becomes dependent on nuts, there is a reduction in mating activity. This is to make sure that there is a rich source of nutrition for mothers while they are lactating, which in turn maximizes the survival of offspring. It has been observed that litters conceived during fruiting season grow faster and are more likely to survive. (Emmons and Feer, 1997; Glanz, et al., 1982; Heaney and Thorington Jr., 1978; Thorington, et al., 2012)

Lifespan/Longevity

No information was found regarding a specific lifespan for Junín red squirrels, either in captivity or in the wild. An individual of a similar South American squirrel species, red-tailed squirrels (Sciurus granatensis), was captured as a juvenile and again after 6 years. It is possible that Junín red squirrels have similar lifespans.

Behavior

Junín red squirrels are diurnal and arboreal. They have been observed to forage and socialize in small groups in non-breeding seasons with an average of 1.6 individuals per group. They do not seem to be territorial. A similar South American arboreal species, Amazon red squirrels (S. spadiceus), are documented to be solitary animals, but have been observed to forage in groups of fewer than four individuals. Amazon red squirrels have been observed to cache nuts in the ground, much like other South American sciurids of the area. Neotropical pygmy squirrels (S. pusillus) have been reported socializing and feeding together at every layer of the canopy. However, they are mostly seen around 10 m above the forest floor. Aggressive chases are commonly seen. Adults and young in groups of 6 have been seen co-nesting. (Emmons and Feer, 1997; Hammer and Tatum-Hume, 2003; Jessen, et al., 2013)

Junín red squirrels build ball-like nests using leaves and twigs on vines and trees. They sometimes nest in tree holes to protect themselves from predators and raise offspring. Junín red squirrels have also been observed to visit clay lick sites and ingest soil for an average of 14 minutes at a time. It has been speculated that they ingest soil to supplement their diets with minerals that they cannot obtain from their regular diet. Junín red squirrels have also been reported to frequently visit family farms in human-populated areas. They are also seen in higher abundance in areas where logging has ceased, when compared to active logging sites. However, Junín red squirrels tend to recover from moderate hunting and acclimatize easily to human disturbance when compared to Bolivian squirrels (S. ignitus). (Aquino and Torres, 2010; D’Elía, et al., 2015; Hammer and Tatum-Hume, 2003; Herbruggen and Rossiter, 2003)

• Key Behaviors
• arboreal
• scansorial
• diurnal
• motile
• solitary

Home Range

Home range sizes for Junín red squirrels are unknown. However, southern Amazon red squirrels (Sciurus spadiceus) have home ranges of 25 to 50 ha. (Haugaasen and Peres, 2005)

Communication and Perception

There is little information regarding specific communication and perception of Junín red squirrels. However, based on what is known about sciurids in general, they likely rely on visual, tactile, acoustic, and chemical senses to perceive the world and communicate with each other. Female squirrels often use pheromones and scents to indicate they are in estrous and attract potential mates.

A closely related squirrel species, Amazon red squirrels (Sciurus igniventris), emit shrill vocalizations to scare off predators or warn other squirrels. Southern Amazon red squirrels (S. spadiceus), when threatened, make alarm calls that sound like a sneeze followed by “a series of chucks and chatters”. Neotropical pygmy squirrels (Sciurillus pusillus) make alarm calls of varying intensities that sound like a cricket with “a more uncommon trill”. (Emmons and Feer, 1997; Jessen, et al., 2013)

• Communication Channels
• visual
• tactile
• acoustic
• chemical

• Other Communication Modes
• pheromones
• scent marks
• vibrations

• Perception Channels
• visual
• tactile
• acoustic
• vibrations
• chemical

Food Habits

There was little to no information available regarding the specific food habits of Junín red squirrels. However, from what is known of other South American sciurids, they have large incisors and enlarged jaw muscles that allow them to gnaw on nuts. Some are specialized to eat hard-shelled nuts of the tropics such as palms (Arecaceae) while others are omnivorous. Omnivorous sciurids eat nuts, fruits, insects, fungi, and even leaves, flowers, and bark. (D’Elía, et al., 2015)

Closely-related sciurids such as southern Amazon red squirrels (Sciurus spadiceus) specialize in eating thick, hard-shelled nuts that are available to many of the sciurids in their ecosystem. Fruits from large-seeded genera such as Astrocaryum, Attalea, Scheelea and Dipteryx make up the majority of their diet. Much like Junín red squirrels, southern Amazon red squirrels are also known to ingest clay to supplement their diets with minerals. Studies on red-tailed squirrels (Sciurus granatensis) suggest that these organisms specialize in eating hard-shelled nuts as well. The majority of their diet consists of Astrocaryum standleyanum, Dipteryx panamensis, Scheelea zonensis, and Gustavia superba. When fruits are out of season, red-tailed squirrels rely on cached nuts such as palms in the genus Scheelea and various fleshy, small-seeded fruits such as those in the genera Coccoloba, Eugenia, Protium, and Spondias. This is not their ideal diet, which is evident by correlated declines in average weight and trapping success and higher rates of mortality. However, red-tailed squirrels are opportunists and eat anything that provide some level of nourishment. They have been observed to eat fungi and tree gums. In human-populated areas, they have been observed to feed on cultivars such as mangoes, guavas, coconuts, avocados, banana, maize, and cacao, among others. Reportedly, red-tailed squirrels have been observed to eat insect larvae and frog eggs and they are notorious for destroying bird nests and eating eggs. Considering red-tailed squirrels are closely related to Junín red squirrels and inhabit similar geographic areas, the diets of these two species may have significant overlap. (Glanz, et al., 1982; Gwin, et al., 2012; Nitikman, 1985)

• Primary Diet
• herbivore
  • granivore

• Animal Foods
• insects

• Plant Foods
• leaves
• roots and tubers
• wood, bark, or stems
• seeds, grains, and nuts
• fruit
• flowers

• Other Foods
• fungus

• Foraging Behavior
• stores or caches food

Predation

The dark agouti reddish-brown dorsal coloration of Junín red squirrels helps them camouflage against tree bark. Their ventral fur consists of white, red, or red with patches of white and, although it mostly faces away from potential predators, it does provide some camouflage. Other than that, very little has been observed regarding the anti-predatory behaviors and adaptations of Junín red squirrels. Capuchin monkeys (Sapajus paella), and both medium and large felids (family Felidae) are considered to be the primary predators of other South American sciurids (see detailed list below). Ocelots (Leopardus pardalis) and jaguars (Panthera onca) are known to be predators of southern Amazon red squirrels (Sciurus spadiceus). Known predators of red-tailed squirrels (Sciurus granatensis) include Capuchin monkeys and other carnivorous mammals, such as boa constrictors, raptors, and various arboreal snakes. (Emmons, 1987; Lee and Brant, 2014; Nitikman, 1985)

To protect themselves from predators, Junín red squirrels build spherical nests using leaves and twigs or they nest in tree holes. In order to protect themselves from predators, closely-related southern Amazon red squirrels (Sciurus spadiceus) emit shrill vocalizations and find cover in the forest. Then they vocalize from a distance until the threat has passed. Southern Amazon red squirrels do not use the canopy to make their escape when threatened. Instead they flee to the ground. When threatened, they make an alarm calls which sound like a sneeze followed by a series of chucks and chatters. On the other hand, neotropical pygmy squirrels (Sciurillus pusillus) can make alarm calls of varying intensities that sound like a cricket with “a more uncommon trill”. Similar anti-predator behaviors have observed in southern Amazon red squirrels and neotropical pygmy squirrels. (D’Elía, et al., 2015; Emmons and Feer, 1997; Jessen, et al., 2013)

• Anti-predator Adaptations
• cryptic

• Known Predators

  • Capuchin monkeys (Sapajus paella), and felids such as mountain cat (Puma concolor), Geoffroy’s cat (Leopardus geoffroyi), jaguar (Panthera onca), kodkod (Leopardus guigna), margay (Leopardus wiedii), ocelot (Leopardus pardalis), oncilla (Leopardus tigrinus), Pantanal cat (Leopardus colocola braccatus).

Ecosystem Roles

There is no available information regarding the ecosystem roles of Junín red squirrels. Their ecosystem roles have not been evaluated. Speculating from what is known, they may play a role in seed dispersal of the plant species in their diet. Junín red squirrels are also a likely source of nutrition for Capuchin monkeys (Sapajus paella), and both medium and large felids, listed in detail in the “Predation” section. (D’Elía, et al., 2015)

• Ecosystem Impact
• disperses seeds

Economic Importance for Humans: Positive

There is no available information regarding the economic importance of Junín red squirrels. It can be speculated that, by dispersing nuts and seeds, they play a role in building up the local flora from which people can benefit. Like many sympatric sciurids, Junín red squirrels likely carry nuts across their home ranges and cache them into the ground. This can lead to germination and successful dispersal of flora. Junín red squirrels may also play a role in sustaining predators such as Capuchin monkeys (family Cebidae) and various felids (family Felidae). By contributing to the overall floral and faunal diversity of the area, Junín red squirrels may benefit locals financially through ecotourism. (Emmons and Feer, 1997)

• Positive Impacts
• ecotourism
• research and education

Economic Importance for Humans: Negative

There are no known adverse effects of Junín red squirrels on humans.

Conservation Status

The IUCN Red List categorizes Junín red squirrels as “data deficient”. However, the Peruvian government classifies them as “vulnerable”. No other list contained the species name due to it being rare and only endemic to Peru. No information was found regarding the current population or distribution of the species. However, they have been stated to be relatively common and frequently encountered within their distribution. Due to the lack of information and awareness, coupled with the effects of logging, Junín red squirrels might be of future conservation concern. As of now, no conservation efforts are in place specifically for this species. (Amori, et al., 2019; Aquino and Torres, 2010; Herbruggen and Rossiter, 2003; Quintana, et al., 2009)

• IUCN Red List

  Data Deficient

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special status

Other Comments

Order: Rodentia Suborder: Sciuromorpha Family: Sciuridae Subfamily: Sciurinae Genus: Sciurus Subgenus: Hadrosciurus/ Mesosciurus (Allen, 1915)

The genus name, Sciurus means squirrel in Latin. It came from the Greek word “skia” (shade) and “oura” (tail). The origin of the species name “*pyrrhinus*” is unknown, however it is speculated to have come from the Greek word “pyrrhos”, meaning flame colored, referring to the copper tinge of its dorsum (Brown, 1954).

Common names: Ardilla, Ardilla Colorada, Ardilla Rojiza, and Ardilla Rojy (Scobie, Palmer and Koprowski, 2014).

Originally the specimen of S. pyrrhinus were mistakenly named as Sciurus varianbilis (Central American species) by Johann Jakob von Tschudi in 1844 (Hershkovitz, 1987). Later on, this mistake was corrected (Thomas, 1898).

There have been no fossil records of the species in South America. But evidence seems to suggest that tree squirrels have been around in South America since the Pleistocene (Simpson, 1980).

Contributors

Asif Mortuza (author), Purdue University - Fort Wayne, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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