The holotype of gabbii is USNM A14214, an unsexed adult skull (with dimensions, in this sexually dimorphic species, that indicate that the specimen is female). The holotype skull, collected by William Gabb, was figured by Allen (1908). No specific locality other than Costa Rica was given in the original description (Allen 1876), but Allen (1877) later specified its origin as “Talamanca” (i.e., the Talamanca Mountains of southeastern Costa Rica; see also Allen 1908:667). The skin associated with the specimen was lost before the species was described (Allen 1876). Allen (1877) later incorrectly associated the skin of a coati, Nasua narica, with the holotype skull, but corrected this mistake soon after (Allen 1879).

The holotype of richardsoni is AMNH 28486, an adult female (skin and skull), from “Rio Grande (altitude below 1,000 feet), Atlantic Slope”, Nicaragua (Allen 1908). The skull of the type was figured by Allen (1908).

The holotype of lasius is UMMZ 64103, an adult male (skin and skull), from “Estrella de Cartago… six to eight miles south of Cartago near the source of the Rio Estrella, … about 4500 feet”, Costa Rica (Harris 1932).

The holotype of pauli is ANSP 17911, an adult male (skin and skull), from “between Rio Chiriqui Viejo and Rio Colorado, on a hill known locally as Cerro Pando, elevation 4800 feet, about ten miles from El Volcan, Province de Chiriqui”, Panama (Enders 1936).

This is the largest olingo, measuring larger than all other taxa in most measurements, and is the most sexually dimorphic species of Bassaricyon in cranial characters and measurements (Table 3). It can be distinguished externally from other olingo species by its coloration, which is grayish-brown (less rufous than in other Bassaricyon), with the face usually dominated by gray, the belly fur cream-colored (sometimes washed with orange), and the tail showing a faint banding pattern (Figures 3, 20). Fur length on the dorsum varies noticeably with elevation (longer at higher elevation). The tail is similar in length to the head-body length, averaging shorter relative to total length than in other olingos (Table 5), perhaps an indication of less complete arboreal habits than in other Bassaricyon (an aspect unfortunately not captured well in our Figure 3).

The skull is large compared to other Bassaricyon (Table 3), with the zygomata more widely splayed, particularly in males (Figures 4–5, Table 3), and a wide rostrum. Uniquely in Bassaricyon, a sagittal crest develops in older males. The cheekteeth and auditory bullae are proportionally quite small compared to the size of the skull, relatively smaller than in Bassaricyon medius and Bassaricyon alleni, and the postpalatal shelf tends to be broadened relative to Bassaricyon medius and Bassaricyon alleni. The canines are more massive than in other Bassaricyon. The first lower molar (m1) is distinctively shaped relative to other Bassaricyon, with the paraconid usually situated right at the midpoint of the front of the tooth and often jutting out anteriorly (the m1 paraconid is less prominent and/or situated more antero-medially in other Bassaricyon).

This species occurs in the central portion of Central America, in montane and foothill forests, from northern Nicaragua to Costa Rica and into the Chiriqui Mountains in western Panama, possibly also extending north into Honduras and Guatemala (Reid 2009; see below). Northern olingos are recorded at elevations as low as sea level, but are most commonly encountered in forests above 1000 m, and extend elevationally at least as high as 1700 m (USNM 324293), and probably as high as the upper limit of forest on the highest peaks in Costa Rica. Forested areas above 1000 m in Central America can be understood to be the core distribution of this species. Vouchered records are from the north-central mountains of Nicaragua (Allen 1908, AMNH, USNM); the mountains of Costa Rica, including the slopes stretching down to the Atlantic coast (Allen 1877, Allen 1908, Harris 1932, Goodwin 1946, Wilson 1983, Timm et al. 1989, Reid 1997, Timm and LaVal 2000, de la Rosa and Nocke 2000, Wainwright 2007, Reid 2009) and a few records of observations from the Pacific slopes (Puntarenas Province: Daily et al. 2003; Guanacaste Province: González-Maya and Belant 2010); and in the Chiriqui Mountains of western Panama (Enders 1936, ANSP, USNM). Reid (2009) included the Azuero Peninsula of Panama in a distribution map for Bassaricyon, but we can trace no record from this region and the basis of this record is unclear (F. Reid, R. Samudio, J. Pino, in litt., 2012–2013). The eastern limits of occurrence for this species are not yet firmly established, but the boundary of occurrence between Bassaricyon gabbii and Bassaricyon medius orinomus apparently lies between 81 and 80 degrees longitude in central Panama. Ours is the first study to document the marked taxonomic distinction between Bassaricyon gabbii of (especially montane) central Mesoamerica, including western Panama, and Bassaricyon medius orinomus of eastern Panama, the Central American member of a group of closely related lowland taxa that also includes Bassaricyon medius medius (of northern South America west of the Andes) and Bassaricyon alleni (of South America east of the Andes). The nature of the interactions between Bassaricyon gabbii and Bassaricyon medius orinomus at this boundary (whether involving, e.g., parapatry, sympatric overlap, or limited hybridization) is unknown and a priority for field study (see Figures 11–12).

There are unverified records of olingos occurring north of Nicaragua, in Honduras and Guatemala, and these records may represent Bassaricyon gabbii. Ordóñez Garza et al. (1999–2000) reported a night sighting of an olingo in Honduras at “La Picucha, Montaña de Babilonia, 1380 m, Parque Nacional Sierra de Agalta, Departamento de Olancho” and discussed a museum specimen of an olingo (later apparently lost) obtained from hunters in Guatemala near the Honduras border at “Montaña Cerro Negro Norte… Río Bobos… 300–500 m” in the Sierra del Merendón, Departamento de Izabal” (Ordóñez Garza et al. 1999–2000, McCarthy and Pérez 2006). Neither of these localities is immediately adjacent to large contiguous areas of Bassaricyon gabbii occurrence as predicted by our range modeling analyses (Figure 11), but both areas could represent relevant habitats for the Northern Olingo, and verifying the occurrence of olingo populations in Honduras or Guatemala should be considered an important goal in Mesoamerican mammalogy.

The nominal taxa richardsoni, lasius, and pauli, synonymized here with Bassaricyon gabbii, were all originally diagnosed based on distinctions in pelage coloration and fur length, in small samples (Allen 1908, Harris 1932, Enders 1936), and their taxonomic status has never been closely reviewed.

Specimens from northern Nicaragua have fur that is slightly more suffused with orange tones than animals from Costa Rica or western Panama. Nicaraguan populations may deserve recognition as a distinct subspecies, Bassaricyon gabbii richardsoni, as sometimes classified (e.g., Goodwin 1946, Hall 1981), but specimens from Nicaragua are too rare in collections for a detailed assessment, and Nicaraguan animals are otherwise very similar to specimens from Costa Rica and Panama. A young adult female specimen of Bassaricyon gabbii from Almirante in Panama’s Bocas del Toro Province (USNM 316320) is one of few low-elevation records for Bassaricyon gabbii, and is notable in having much smaller teeth than specimens from higher-elevation forests in the adjacent Chiriqui Mountains, and deserves close study in the future. We have carefully examined the type series of the nominal taxa Bassaricyon lasius and Bassaricyon pauli, the morphological attributes of which clearly fall into the range of variation seen in series we refer to Bassaricyon gabbii. We confidently relegate these names, often previously recognized as distinct species known only from the type localities (e.g., Hall 1981, Nowak 1999, Wozencraft 2005), to the synonymy of Bassaricyon gabbii, although we note that the only specimen of gabbii that we have seen from the area of the type locality, the Talamanca Range, is the holotype, which is an adult with worn teeth and no accompanying skin. Without further investigation, ideally involving the compilation and study of greater number of museum specimens from throughout the range of this species, we do not yet advocate recognizing subspecies of Bassaricyon gabbii, though we note that names are available for several of the major sections of the Middle American Highlands (Cordillera de Talamanca: gabbii, Chiriqui: pauli, Cordillera Central: lasius, Nicaraguan Highlands: richardsoni).

This is the olingo speciesmost commonly seen and photographed by visitors to the Neotropics, especially because it is present at Monteverde and several other protected areas in Costa Rica that are frequently visited by both tourists and biologists (e.g., Forsyth 2008, Kays 2009, Reid 2009). It is larger, more sexually dimorphic, and has a shorter tail than other olingo species, suggesting a different ecology and behavior compared to the slightly better studied Bassaricyon medius and Bassaricyon alleni (see accounts below). Bassaricyon gabbii has been reported feeding on fruit and nectar in rainforest trees, but no details have been published on its diet. Olingos in Monteverde, Costa Rica, are often seen during the day, typically as solitary animals; it is unclear if diurnal activity is typical for the species or if this is in response to being fed by humans at the tourist lodge (Reid 2009, Kays 2009). Relevant field notes associated with Bassaricyon gabbii include: “fruit in stomach” (ANSP 18851); “shot in fruit tree at night” (ANSP 18852); “lactating” on 4 June 1937 (ANSP 18894); “shot at 8:00 pm in small trees” (ANSP 17911); mother with accompanying young on 20 August 1909 (AMNH 30748).

Costa Rica: AMNH 140334, LACM 26480, 64837, UMMZ 64103 (holotype of lasius), 112321, 112322, USNM A14214 (holotype of gabbii). Nicaragua: AMNH 28486 (holotype of richardsoni), 30748, 30749, USNM 337632, 338859. Panama: AMNH 147772, ANSP 17911 (holotype of pauli), 18850, 18851, 18852, 18893, 18894, BMNH 3.12.6.3, 5.5.4.5, KU 165554, MCZ 38506, TCWC 12941, USNM 316230, 324293, 324294, 516945, 516946.