Confirmation of the occurrence of Andean cottontail, Sylvilagus andinus (Thomas, 1897) (Leporidae, Lagomorpha), in Peru

Sylvilagus andinus (Thomas, 1897) is a highland lagomorph from the Ecuadorean Paramos. Its distribution was tentatively believed to extend to northwestern Peru on the basis of ecological niche modeling and the inclusion of the Peruvian S. capsalis Thomas, 1913 as a synonym. Here, we confirm the occurrence of S. andinus in Peru by a morphological examination of seven new records from northwestern Peru and one new record from Ancash department in central Peru.


Introduction
Cottontail rabbits of the genus Sylvilagus Gray, 1867 are highly speciose, with about 30 valid species (Ruedas et al. 2017. Sylvilagus is endemic to the Americas and is widely distributed from southeastern Canada to northern Argentina (Chapman and Ceballos 1990;Silva et al. 2019), occupying temperate, tropical, and subtropical habitats (Schai-Braun and Hackländer 2016).
Sylvilagus andinus (Thomas, 1897), commonly known as the Andean Cottontail, occurs in highlands in Venezuela, Ecuador, and Peru (Ruedas et al. 2017, but currently its presence in Peru is based only on the type specimen of S. capsalis Thomas, 1913, which has been considered a synonym of S. andinus, and on ecological niche modelling (Ruedas et al. 2017). To improve the resolution of this model and confirm the occurrence of the species in Peru, Ruedas et al. (2017) recommended examining additional specimens from the country and tentatively treated S. capsalis (type locality "San Pablo, Cajamarca [Peru]"), as well as other highland taxa from Ecuador and Venezuela (S. meridensis Thomas, 1904; S. andinus chimbanus Thomas, 1913; S. a. canarius Thomas, 1913;S. a. carchensis Hershkovitz, 1938;S. a. chotanus Hershkovitz, 1938;S. nivicola Cabrera, 1913;S. kelloggi Anthony, 1923;and S. chillae Anthony, 1923) as junior synonyms of S. andinus based on their elevation and habitat.
Thus, previous records of the Andean cottontails from Peru published as S. brasiliensis and other associated names are now allocated to S. andinus. These Peruvian records of S. andinus include the one reported from Cutervo, Cajamarca (Thomas 1882, as Lepus brasiliensis), from San Pablo, Cajamarca (Thomas 1913, as S. capsalis), and from La Libertad and Cajamarca (Osgood 1914, as S. capsalis). Grimwood (1969) reported this species at 1500-3000 m from Piura, Cajamarca, and La Libertad but as S. brasiliensis. No additional records of northern Peruvian populations of Sylvilagus were published until Jiménez et al. (2010) recorded S. brasiliensis from Pagaibamba Protected Forest, Cajamarca department, based on indirect records (Table 1). More recently, Pacheco et al. (2020) tentatively recognized the Grimwood's (1969) historical records from northwestern Peru as S. andinus (sensu Ruedas et al. 2017).
Sylvilagus andinus has an important ecological role as a pervasive herbivore, consuming a wide variety of plant species (García et al. 2016). The species is also an important food source for several predators such as the Andean Fox Lycalopex (Pseudalopex) culpaeus (Molina, 1782) (Trujillo and Trujillo 2007;Cadena-Ortíz et al. 2020), Long-tailed Weasel Neogale frenata (Lichtenstein, 1831) (García et al. 2016), Mountain Lion Puma concolor (Linnaeus, 1771) (Hernandez-Guzman et al. 2011, and Black-chested Buzzard Eagle Geranoaetus melanoleucus (Vieillot, 1819) (Jimenez and Jaksic 1989). Despite this, S. andinus is still a poorly known rabbit and is currently classified as Data Deficient by the International Union for Conservation of Nature because distribution data are scarce compared to other cottontail species (Ruedas and Smith 2019).
Here, based on a direct examination of eight new specimens from eight localities, we confirm by our own morphological examination the presence of S. andinus in northwestern and central Peru.

Methods
We examined eight specimens housed in the mammal collection of the Museo de Historia Natural de la Universidad Nacional Mayor de San Marcos (MUSM), Lima, Peru. We took external measurements from specimen tags. We also estimated the head and body length (HBL) by subtracting the tail length (TailL) from the total length (TotalL). External measurements are reported to the nearest millimeter (mm). We took the cranial and mandibular measurements to the nearest 0.1 mm using dial calipers mainly following Ruedas et al. (2017): greatest length of skull (GLS), basilar length (BL), greatest rostrocaudal length of nasal bone (NL), greatest width across left and right nasal bones (NW), zygomatic breadth measured at zygomatic spine (BZS), zygomatic breadth (ZB), zygomatic length (ZL), dorsoventral depth of zygomatic arch (DZ), breadth of braincase (BB), width of cranium at exoccipital bones (WX), length of auditory bulla (LB), width of auditory bulla (WB), interorbital breadth (IOB), height of rostrum (HR), width of rostrum (WR), rostrocaudal length of incisive foramina (LIF), width of incisive foramina (WIF), palate length from henselion (HPL), rostrocaudal length of palatal bridge (PBL), width of choana at first upper molar (WCH), breadth of alisphenoid constriction (BAC), alveolar length of maxillary toothrow (ATL), alveolar length of upper diastema I2-PM2 (DL), dentary toothrow length (DTL). We followed the age classification of Hoffmeister and Zimmerman (1967), and the taxonomic identification followed Thomas (1897), Hershkovitz (1938Hershkovitz ( , 1950, and Ruedas et al. (2017. Our samples also included one photograph and two sighting records with accurate coordinates housed in a separate database (MUSM2). Finally, we present a map ( Fig. 1) based on vouchers and indirect records for Sylvilagus andinus from Peru and Ecuador (Table 1).

Results
After a morphological revision of Sylvilagus specimens housed in the MUSM, which were previously identified as S. brasiliensis following Hershkovitz (1950) and Hoffmann and Smith (2005), we confirm the presence of S. andinus in seven different localities in northwestern Peru and one record from central Peru (   Table 1.   Identification. Sylvilagus andinus is a medium-sized species (HBL 326-353 mm) with a small tail (6-7% of HBL) and long hindfeet (64-81 mm) (Table 2), characterized by the following combination of external and craniodental characters: pelage long, soft, dusky in appearance; forehead suffused with brownish; small nostril patches white; ears rather short, gray basally; cheeks and sides of neck ashy gray; back awns hairs long, colored warm buff to clay color irregularly streaked with black presenting a saturated general appearance; rump with a reddish suffusion which passes down on the legs to the heels; chin and belly whitish; underhairs woolly gray; upper surface of fore and hind feet pale, with more white than ochraceous; soles of feet thickly furred, brown; tail a mere stump colored like the rump (concurring with Thomas 1897 andHershkovitz 1950). The skull is large and robust, the dorsal surface of the cranium is smooth and lacks pitting; fenestrated rostrum short and broad; braincase concave; antorbital process minute; postorbital process relatively short not coalescing with the frontal; tuberculum frontoparietale prominent and smooth; zygomatic arch dorsoventrally slender; zygomatic fossa barely perceptible; frontoparietal suture weakly interdigitated with no fusion between the bones; frontonasal suture sharply V-shape; single craniopharyngeal foramen in basisphenoid; premolar foramen present (concurring with Thomas 1897 andRuedas et al. 2017). Crown enamel pattern of third lower premolar (p3) with multiple, deep anteroflexid invaginations into rostral aspect of anterior lobe; rostral aspect of p3 hypoflexid heavily crenellated from anteroconid to paraflexid; deep, crenellated paraflexus, with generally conspicuous hypoflexus in second upper premolar (P2) (concurring with Ruedas et al. 2017). As mentioned by Hershkovitz (1950), S. brasiliensis s.l. (lowland Peruvian population) can be differentiated from S. andinus by the following external characters: S. brasiliensis has ochraceous-buff back, ochraceus-tawny rump, and warm buff cheeks, while S. andinus has warm buff back and rump and ashy gray cheeks. No other revision has included the Peruvian lowland population of Sylvilagus. Ruedas et al. (2017) identified the following craniodental features that distinguish S. brasiliensis s.s. (Brazilian population) from S. andinus (Ecuadorean population): S. brasiliensis s.s. has longer postorbital processes ending broadly rounded and fused to the frontal; U-shaped frontonasal suture; single simple shallow anteroflexid, paraflexid and protoflexid; smooth hypoflexid; absence of hypoflexus; and simple deep paraflexus; in contrast, S. andinus (Ecuadorean population) has shorter, V-shaped postorbital processes not coalescing with the frontal; V-shaped frontonasal suture; multiple invaginations in the anteroflexid, paraflexid and protoflexid; crenellated hypoflexid; presence of hypoflexus; and crenellated paraflexus. Following Ruedas et al. (2017), our specimens correspond to S. andinus because of the aforementioned characteristics for the species (Fig. 2). We also extend the current distribution range of the species by about 169 km southeast from San Pablo, Cajamarca department (type locality of S. capsalis; Fig. 1) to Ancash department in central Peru (MUSM 23254). Records of this species are rare because it seems to avoid commonly used traps; nonetheless, the records presented here show that it is more widely distributed than previously thought. Little is known regarding the natural history this species, but it is known that lowland tropical forest cottontails have been trapped in Tomahawk traps set in native gardens and baited with yuca (Voss and Emmons 1996). Two specimens, which were determined as juveniles based on general size and cranial features, were trapped using Victor ® mouse traps with standard bait (Pacheco et al. 2007), probably because of their inexperience.

Discussion
Although the phenotype of our specimens matches the diagnostic characters of S. andinus, we observed morphological variability in three adult specimens: the premolar foramen and the antorbital process of the interorbital region were present only in MUSM 55249 (Fig. 3). Also, a smooth braincase was seen only in MUSM 46735 and MUSM 55796. These characters were indicated as diagnostic for S. andinus, but our observations suggest they could be individual or geographic variation. Documented morphological data for this species are scarce (Thomas 1897(Thomas , 1913Ruedas et al. 2017Diersing and Wilson 2017), which limits our understanding of age, sex, and population variability. Therefore, pending a thorough revision of the Andean forms, we tentatively follow the latest revision of the genus (Ruedas et al. 2017. Although our study improves the current distribution of S. andinus, we acknowledge that a larger set of samples is needed to properly assess intraspecific variability. While this contribution considerably extends the southern range of the species and provides important natural history information, we recommend that additional studies be undertaken to fully assess the taxonomic, distribution, and conservation status of S. andinus. comments on the manuscript and improving the English. The non-profit organization Idea Wild donated equipment necessary for this work. This research was supported by the Universidad Nacional Mayor de San Marcos (RR no. 2020-01686 and project number B20100321, RR no. 2021-05753 and project number B21100031), and the Asociación de Mastozoólogos del Perú (Carta no. 002-AMP-2020 and code VP002).