Chinchilla lanigera, Bennett, 1829

Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Chinchillidae, Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona: Lynx Edicions, pp. 462-481 : 478

2.

Chilean Chinchilla

Chinchilla lanigera

French: Chinchilla a longue queue / German: Langschwanz-Chinchilla / Spanish: Chinchilla de cola larga

Other common names: Coastal Chinchilla, Common Chinchilla, Long-tailed Chinchilla

Taxonomy. Chinchilla lanigera Bennett, 1829 ,

“Coquimbo, Chile.”

This species is monotypic.

Distribution. N Chile (Coquimbo and Atacama regions), extant wild populations are restricted to Las Chinchillas National Reserve, 24 km N Auco, and surrounding areas (Quebrada Curico and Quebrada El Cuyano), and the new colony recently reported in La Higuera, ¢.100 km N Coquimbo; it was also reported in the Atacama region during the first part of the 20" century, particularly around Vallenar.

Descriptive notes. Head-body 220-240 mm, tail 140-170 mm, ear 45-48 mm, hindfoot 54-58 mm; weight 369-493 g (wild males), c.600 g (domestic males), 379-450 g (wild females), and c.800 g (domestic females). Chilean Chinchillas have round and long ears (more than 45 mm), covered by tiny hair, and long tails (more than 130 mm). Hair is 20-40 mm long, with gray, white, and black bands; it is silky, extremely soft, and firmly adhered to skin; thus, it is commercially valuable. Fifty to 75 hairs emerge from a single skin pore. Wool hairs (5-11 mm in diameter) are grouped in two lateral clusters. A single guard hair (10-15 mm in diameter) is located at the center of each cluster. Vibrissae are abundant, strong, and long (100-130 mm) and emerge from single follicles. Each group of hairs has one erector pili muscle. Guard hairs have their own sebaceous glands, whereas 3-4 other glands serve all hairs of a lateral group. Solitary hairs are found as vibrissae or on the tail as pinnae. Follicular layering is found only in vibrissae. Color of upperparts is bluish or silver gray, and under parts are yellowish white. Tail has long, coarse, gray and black hair on its dorsal surface; they are 30-40 mm near body, 50-60 mm neartail tip, and form a bristly tuft of 50 mm. Skull of the Chilean Chinchilla has very expanded auditory bullae that protrude over upper plane; it is relatively broad, with little or no ridging. Infraorbital canalis very large, without a distinct groove for nerve passage. Lacrimal canal has a large opening on rostrum side. Paroccipital process is short and attached to bulla. Jugal approaches lacrimal. Pituitary is 3-5 mg/100 g of body weight in males and 4 mg/100 g in females. Auditory bullae have three large vesicular protuberances; superior protuberance is nearly hemispherical, posterior is oblong, and inferioris pyriform. Mean total volume of middle ear is 1-5 ml. Tympanic membrane is nearly parallel to medial wall of external meatus and anchored to bony annulus; tympanic flat area is 55-6 mm?, but when its conical form is considered, average area increases 9% to a mean of 60-4 mm?. Forelimbs are much smaller in size than hindlimbs. Tibia is longer than femur, and fibula is virtually nonexistent. Short forefeet have five digits, and narrow hindfeet have three digits and a rudimentary digit with stiff bristles surrounding a small, flat claw. Other claws present but very short. Females have two pairs of thoracic and one pair of inguinal mammae, although the latter are not visible in wild females. Area around mammae is devoid of hair during lactation. Teeth are hypsodont and ever growing (rootless). Upper tooth rows are convergent anteriorly and crowns of cheekteeth are flat, consisting of a series of transverse plates. Dental formula of the Chilean Chinchilla is I 1/1, C0/0,P1/1,M 3/3 (x2) = 20. Incisors grow 50-75 mm/year. Enamel is usually dark yellow in healthy individuals; some inner radial enamel occurs close to dentin-enamel junction and in portio externa. Lower jaw has no ridge or groove on lateral surface; angular process is elongated and not deflected. Condyle is small and longitudinal, and glenoid cavity is superficial, permitting motion in anterior-posterior direction. Vertebral formula is 7 cervical, 13 thoracic, 6 lumbar, 2 sacral, and 23 caudal (51 vertebrae), with 13 pair of ribs. Radius and ulna, although distinct, are so closely applied to each otherat their carpal extremity that they appear anchylosed for one-halfoftheir length. Interarticular cartilage between clavicle and sternum is ¢.6 mm. Masseter is divided in three portions. Gluteus medius is enlarged. Temporalis is reduced and undifferentiated. Internal carotid artery is absent, and brain is supplied by vertebral-basilar artery system alone, whereas external carotid artery system has assumed entire stapedial area of supply by means of three anastomoses; internal ophthalmic artery is closed. Arterial irrigation of testicles and epididymis proceeds from testicular arteries that emerge from renal arteries, and accesorial sexual glands and ductus deferens irrigation are from externaliliac artery. Lungs are asymmetric, with three lobes in left and four in right; lower lobe is the largest and deeply bifid in the right lung. Trachea is transversely oval, with rings dorsally imperfect. Oral cavity is small and narrow. Oropharynx communicates with pharynx through palatal ostium. Stomach is pyriform and 6 mm; its greatest breadth on left is 44 mm and in middle 25 mm. Esophagus enters near middle of cavity, and pyloric portion forms an upward curve, on which beginning of duodenum makes a sudden turn. Liver has four lobes, two large and two small, with cystic and lobulus spigelii deeply cleft. Spleen is 25 mm, with a breadth of 22 mm at its lower extremity. Chromosome numberis 64, with 128 chromosome arms. Molecular genetic distance (mtDNA sequences of cytochrome-b gene) between the Chilean Chinchilla and the Short-tailed Chinchilla ( Chinchilla chinchilla ) is significant: 5-9% (4-9-6-2%).

Habitat. Steep and dry equatorial-facing slopes, with refuges in rock crevices and boulder piles. The Chilean Chinchilla coexists with a diverse assemblage of rodents such as Bennett's Chinchilla Rat ( Abrocoma bennettii), the Olive Soft-haired Mouse (Abrothrix olivacea), the Long-haired Soft-haired Mouse (A. longipilis), the Common Degu ( Octodon degus), and Darwin’s Leafeared Mouse (Phyllotis darwini). The Atacama colony is located 44 km from the coast, in the middle of a very arid hill and surrounded by extensive dunes of the Atacama Desert. Vegetation includes Eriosyce aurata ( Cactaceae ), Gymnophyton flexuosum ( Apiaceae ), Heliotropium sclerocarpum ( Boraginaceae ), Nolana sp. (Solanaceae) , and Tetragonia microcarpa ( Aizoaceae ).

Food and Feeding. The diet of the Chilean Chinchilla in the Las Chinchillas National Reserve included the succulent bromeliad Puya berteroniana, but the main plant species eaten was the perennial graminoid Nassella chilensis and secondarily the fern Adiantum chilense, Bridgesia incisifolia ( Sapindaceae ), Heliotropium stenophyllum ( Boraginaceae ), and Lobelia polyphylla ( Campanulaceae ). The Atacama colonies eat E. aurata cactus, which is probably the main source of water and food, with 87% of cacti gnawed on by rodents.

Breeding. Information about reproduction in wild populations of Chilean Chinchillas is very limited, but births apparently occur during austral winter in May—-November. In captive individuals, gestation is 105-118 days, with litter sizes of 1-6 young but usually 2-3 young. Lactation normally lasts 6-8 weeks, and minimal period of suckling necessary for survival is 25 days. Sexual maturity of both sexes occurs at c.8 months but may occur as early as 5-5 months. Domestic females have a long estrous cycle (38-1 days + 0-7 SD, range 16-69 days). A postpartum estrus usually occurs at 57-4 days + 2-6 SD, whether or not the litter is lost. Vaginal closure membrane of anestrous female may open and close in c.12 hours, but it usually takes 2—4 days. Ovulation in captivity is usually spontaneous. Copulatory plug is usually visible after mating. Single-cell zygotes have been found in fallopian tubes 1-2 days postcoitum (after mating). Fertilization is difficult to detect because some eggs show no traces of polar bodies, sperm, or pronuclei, although some show a single polar body and sperm in the zona pellucida, or a single polar body and second maturation spindle at 2-5 days postcoitum. Polyspermy has not been observed. Preimplantation blastocysts have been detected at 3-5 days postcoitum. Implantation occurs at 5-5 days postcoitum, and it is completely interstitial. Amniotic cavity is formed at 15 days postcoitum, allantois at 25 days, and chorioallantoic placenta at 30 days. Fetal reabsorption occurs frequently and may take place at any stage of pregnancy. Reabsorption occurs even in late stages when skeletal tissue of fetus has formed. Neither placental nor fetal tissue can be recognized in the necrotic mass, but a central blood-filled cavity is typical. Parturition usually occurs in early morning, and the female eats the placenta.

Activity patterns. The Chilean Chinchilla is nocturnal, but it is sometimes crepuscular. In the Atacama region, one individual was seen at midday between large cracked rocks.

Movements, Home range and Social organization. The Chilean Chinchilla is a social and colonial species. There are ¢.700 individuals in Aucé, with densities of 4-4— 72-9 ind/km? in the Quebrada El Cobre. Some colonies have been identified outside the Auco reserve in the areas of Quebrada Curico and Quebrada El Cuyano, with 17-5-82-6 ind/km?® and 12-3-58:-3 ind/km? respectively. Isolated colonies form a metapopulation, with frequent local extinctions and colonization of suitable habitat patches. In the Atacama region, the population seems to be small, with densities of 24-7-115-4 ind/km? Main predators of Chilean Chinchillas in the Coquimbo region are the Culpeo (Pseudalopex culpaeus) and the South American Gray Fox (Lycalopex griseus). The Magellanic horned owl (Bubo magellanicus) is also a predator of the Chilean Chinchilla .

Status and Conservation. CITES Appendix I (wild populations). Classified as Critically Endangered on The IUCN Red List. The Chilean Chinchilla is also classified as critically endangered by the Evolutionary Distinct & Globally Endangered Program ofthe Zoological Society of London. It is considered extinct in the Antofagasta and Atacama regions of Chile and endangered in northern and central Chile because of drastic past and ongoing population declines, estimated to be more than 90% during the past three generations (15 years). The Chilean Chinchilla occurs in only a small part of the original distribution; it was once widespread in the hills and low mountains between 26° S and 35° S latitude, and isstill pressured by illegal hunting and reduced habitat quality. A conservation plan was formulated for the Chilean Chinchilla by CONAF (the National Wildlife Service of Chile) in 2004; the main goal ofthis conservation plan is to develop scientific research and management of the wild populations in situ and ex situ and to develop a program of education.

Bibliography. Albert (1900, 1901), Bernal & Silva (2003), Bidlingmaier (1937), Cabrera (1960, 1961), Cabrera & Yepes (1960), Cofré & Marquet (1999), Cortés et al. (2003), Espejo et al. (2004), Glade (1988), Grau (1986), Iriarte & Jaksic (1986), Jiménez (1996), Lagos et al. (2012), Miller et al. (1983), Munoz-Pedreros & Gil (2009), Parera (2002), Redford & Eisenberg (1992), Spotorno & Patton (2015), Spotorno et al. (2004), Tamayo & Frassinetti (1980), Tirado et al. (2012), Valladares (2002), Valladares, Espinosa et al. (2012), Valladares, Zuleta & Spotorno (2014), Woods & Kilpatrick (2005).

Figures

1. Plains Viscacha (Lagostomus maximus), 2. Chilean Chinchilla (Chinchilla lanigera), 3. Short-tailed Chinchilla (Chinchilla chinchilla), 4. Ecuadorean Mountain Viscacha (Lagidium ahuacaense), 5. Common Mountain Viscacha (Lagidium viscacia), 6. Wolffsohn’s Mountain Viscacha (Lagidium wolffsohni)

Distribution. N Chile (Coquimbo and Atacama regions), extant wild populations are restricted to Las Chinchillas National Reserve, 24 km N Auco, and surrounding areas (Quebrada Curico and Quebrada El Cuyano), and the new colony recently reported in La Higuera, ¢.100 km N Coquimbo; it was also reported in the Atacama region during the first part of the 20" century, particularly around Vallenar.