735.

Yellow-rumped Leaf-eared Mouse

Phyllotis xanthopygus

French: Phyllotis a croupe jaune / German: Gelbsteil 3-Blattohrmaus / Spanish: Raton orejudo de trasero dorado

Other common names: Patagonian Leaf-eared Mouse, Yellow-rumped Pericote

Taxonomy. Mus (Phyllotis) xanthopygus Waterhouse, 1837, “ Santa Cruz,” Argentina .

Holotype of P. xanthopygus was secured by Darwin probably in the vicinity of Puerto Santa Cruz, a small city located near the mouth of the Santa Cruz River. Therefore, type locality of xanthopygus can be confidently restricted to this area. Phyllotis xanthopygus was left behind from earlier concepts of P. darwin, particularly that of O. P. Pearson in 1958, after P. bonarienss, P. limatus, and true P. darwinii where recognized as distinct species. Several molecular approaches with considerable geographical coverage suggest that current alpha-taxonomy of P. xanthopygus needs refinement. For example, R. E. Palma and colleagues in 2005, based on molecular evidence, suggested that chilensis, restricted to higher elevations in the Altiplano, should be raised to full species. Six subspecies recognized.

Subspecies and Distribution.

P.x.xanthopygusWaterhouse,1837—fromNWPatagoniainArgentinaandChile,StotheStraitofMagellanandAndeanrangesinextremeSChileanmainland,andreachingthecoastinSantaCruzProvince,Argentina.

P.x.chilensisMann,1945—AltiplanoW&SWofLakeTiticacainPeruandBolivia,andthehighAndesbetweenTarapacaRegion,Chile,andBolivia,atelevationsabove3300m.

P.x.posticalisThomas,1912—C&SPeru,onbothslopesoftheAndestoelevationsaslowas1800m.

P.x.ricardulusThomas,1919—C&EAndesinNW&NCArgentina,atelevationsof500-4800m;isolatedpopulationsinSantiagodelEstero,Cordoba,andSanLuisprovincesprobablybelongtothissubspecies.

P. x. rupestris P. Gervais, 1841 — Bolivian Plateau, extending down the E Andean slope into Jujuy Province, Argentina, and at intermediate elevations on the W slope in N Chile and S Peru.

P x. vaccarum Thomas, 1912 — both sides of the Andes, from Atacama, Chile, and Catamarca Province, Argentina, S to Talca, Chile, and Neuquén Province, Argentina, at elevations of 800-4000 m.

Descriptive notes. Head-body 90-143 mm, tail 80-141 mm, ear 20-31 mm, hindfoot 25-32 mm; weight 30-92 g. The Yellow-rumped Leaf-eared Mouse is highly variable geographically. It is medium to moderately large, with tail almost always longer than 90 mm and usually longer than 90% of head-body length. Ears are large, sometimes as long as hindfeet. Dorsal fur is denser at high elevations or under hostile climatic conditions and less fluffy elsewhere. Vibrissae are elongated and luxuriant. Dorsal color varies greatly geographically from pale buff through gray and darker tones, depending upon elevation and latitude. Venter is whitish, grayish, to buffy; pectoral streak is variably present within and among populations. Tail typically ends in a tuft. Chromosomal complements in Argentinean individuals from Catamarca, Jujuy, and Mendoza provinces is 2n = 38, FN = 70-72.

Habitat. Typically rocky microhabitats on arid Andean slopes of boulder fields, rock slides, cliffs, small shale outcroppings, stone walls, and stone huts from sea level up to elevations of 5570 m (record for nominotypical rupestris where volcanic activity warmed immediate vicinity). In Patagonia, the Yellow-rumped Leaf-eared Mouse is found in rocky outcrops and basaltic tablelands in Monte and Patagonian steppes. In central Patagonia, it is widely distributed beyond its clear affinity for rocky areas. Near the end ofits distribution in southernmost Santa Cruz Province, Argentina,it occurs in dense scrublands of Schinus (Anacardiaceae) and Berberis (Berberidaceae) associated with rivers and far from rocky areas.

Food and Feeding. Diets of Yellow-rumped Leaf-eared Mice are highly variable but with a marked tendency toward omnivory or folivory. In north-western Patagonian, individuals are mostly folivorous, similar to those in northern Chile, where ¢.10% of diets contain insects. In high Andean areas of central Chile, Yellow-rumped Leaf-eared Mice ate six species of plants with tendency toward herbs, in particular Cristaria andicola ( Malvaceae) and Acaena magellanica ( Rosaceae, ¢.82%); shrubs and insects were eaten in small amounts. Extensive dietary variation was recorded in populations reported as subspecies rupestris, with insectivory surpassing 50% ofdiets. Apparently, consumption of insects and arthropods increased toward high elevations, and females consumed more insects than males. In Peru, the Yellow-rumped Leaf-eared Mouse tends toward omnivory, eating plants, fungi, and arthropods. In an elevational gradient in the central Andes of Argentina (Mendoza Province), individuals alternate between omnivory and granivory/frugivory. Richness, diversity, and quality of available resources resulted in a relatively low-quality nutrient-wise at high elevations. Nevertheless, diets from individuals at diverse elevations lacked differentiation in quality or diversity. The Yellow-rumped Leaf-eared Mouse seems to behaviorally compensate for environmental variation relative to its nutritional requirements by changing dietary composition and relative proportion of foodsit eats.

Breeding. In the southern Peruvian Altiplano, pregnant Yellow-rumped Leaf-eared Mice were caught on 28 July and 1 August at Santa Rosa but not until 5 October at Caccachara. Pregnant females and breeding males were caught frequently between 5 October and 19 December, and immature individuals were caught on 9 December. Average number of embryos was four. In all six cases where necessary data were recorded, there were more embryos in the right horn than in the left. Sex ratio was 64 males:44 females. In Chilean Patagonia, individuals trapped in March were mostly young without reproductive signals; males had scrotal testes in November—December, and pregnant females or those with reproductive signals were caught in November—March (austral spring/summer). In Central Patagonia, the Yellow-rumped Leaf-eared Mouse breeds in December—February, and no individuals are reproductive by May.

Activity patterns. The Yellow-rumped Leaf-eared Mouse is terrestrial and strictly nocturnal.

Movements, Home range and Social organization. When trapped, Yellow-rumped Leafeared Mice are docile and rarely bit. One individual survived 40 months in captivity.

Status and Conservation. Classified as Least Concern on The IUCN Red List.

Bibliography. Albright (2004), Alvarez (2016), Chebez et al. (2014), Hershkovitz (1962), Kelt (1994), Kim et al. (1998), Kramer et al. (1999), Labaroni et al. (2014), Lopez-Cortés et al. (2007), Mann (1945, 1978), Munoz-Pedreros & Yanez (2009), Musser & Carleton (2005), Osgood (1943a), Palma, Marquet & Boric-Bargetto (2005), Pearson (1951a, 1958), Pearson & Patton (1976), Pizzimenti & de Salle (1980), Riverdn (2011), Sassi et al. (2017), Silva (2005), Steppan & Ramirez (2015), Steppan et al. (2007), Tirado et al. (2008), Walker, Rojas et al. (1999), Walker, Spotorno & Arrau (1984), Walker, Spotorno & Sans (1991), Waterhouse (1837 1839).