Aotus nancymaae Hershkovitz, 1983

Voss, Robert S. & Fleck, David W., 2011, Mammalian Diversity And Matses Ethnomammalogy In Amazonian Peru Part 1: Primates, Bulletin of the American Museum of Natural History 2011 (351), pp. 1-81 : 25-28

Aotus nancymaae Hershkovitz, 1983

VOUCHER MATERIAL (TOTAL 5 11): Marupa (AMNH 98330, 98331), Nuevo San Juan (AMNH 268238; MUSM 11111–11113), Orosa (AMNH 73701, 73702, 74035), Quebrada Esperanza (FMNH 88868, 88869).

UNVOUCHERED RECORDS: Actiamë ( Amanzo, 2006), Choncó ( Amanzo, 2006), Divisor ( Jorge and Velazco, 2006), Jenaro Herrera ( Aquino, 1978), Reserva Comunal Tamshiyacu-Tahuayo ( Puertas and Bodmer, 1993; Heymann and Aquino, 1994), Río Cochiquinas ( Aquino and Encarnación, 1988), Río Orosa ( Aquino and Encarnación, 1988), Río Tahuayo ( Aquino and Encarnación, 1988), Río Tapiche ( Bennett et al., 2001), Río Yavarí (left bank below Angamos; Salovaara et al., 2003), Río Yavarí-Mirím ( Salovaara et al., 2003), Tapiche ( Jorge and Velazco, 2006). (Note that some early reports of night monkeys from the Yavarí-Ucayali interfluve identified the local species as Aotus trivirgatus ; see below.)

IDENTIFICATION: Night monkeys exhibit a limited range of phenotypic variation, mostly in pelage traits, and all of the named forms in this genus were once considered to belong to a single geographically variable species, Aotus trivirgatus (see Hershkovitz, 1949; Cabrera, 1958). However, subsequent karyotypic research by R.A. Brumback and N.S.F. Ma (reviewed by Hershkovitz, 1983) revealed unexpected geographic variation in diploid numbers (2 n) and fundamental numbers (FN) that they interpreted as evidence for multiple species. The hypothesis that at least some night monkey karyomorphs represent valid taxa is supported by a variety of data, including correlated pelage traits, comparative serology, and clinical responses to experimental infection with malaria parasites ( Hershkovitz, 1983); evidence of sympatry without apparent hybridization in the wild ( Pieczarka et al., 1992); substantial mtDNA sequence divergence ( Ashley and Vaughn, 1995; Plautz et al., 2009; Menezes et al., 2010); and reduced fertility in at least some hybrid pairings ( Kumamoto and Houck, 2001). Together, these and other results ( Ford, 1994; Defler and Bueno, 2007) effectively refute earlier notions that Aotus is monotypic, but many taxonomic issues remain unresolved.

The most frequently cited phenotypic character in the recent literature on Aotus concerns the coloration of the fur of the neck. The so-called ‘‘red-necked’’ and ‘‘graynecked’’ phenotypes are defined by the presence or absence, respectively, of a lateral extension of the reddish ventral coloration along the neck below and behind the ear ( Hershkovitz, 1983: fig. 1 ). Allegedly, the gray-necked forms of Aotus (for which the oldest available name is trivirgatus Humboldt, 1811 ) occur north of the Amazon, and red-necked forms (for which the oldest available name is azarae Humboldt, 1811 ) occur south of the Amazon, but Hershkovitz (1983) discussed some exceptions to this geographic pattern and others are indicated by specimens that we examined (see below). Although neck coloration is commonly used as the basis for recognizing species groups of Aotus (e.g., by Hershkovitz, 1983; Ford, 1994; Groves, 2001), recent sequencing studies do not support the reciprocal monophyly of gray-necked and red-necked night monkeys ( Plautz et al., 2009; Menezes et al., 2010).

The original description of Aotus nancymaae was largely justified on the basis of karyotypic data, but no morphological voucher material of known geographic origin is apparently available for any chromosomal preparation attributed to this species, and existing vouchers of karyotyped laboratory animals do not consistently exhibit diagnostic pelage traits. 7 Instead, only indirect evidence is available to correlate chromosomes with phenotypes. According to Hershkovitz (1983), unvouchered night monkey karyotypes prepared by N.S.F. Ma from blood samples obtained at Peruvian localities on the south (right) bank of the Amazon (including the Yavarí-Ucayali interfluve) all have 54 chromosomes and 72 autosomal arms (2 n 5 54, FN 5 72), whereas most karyotypes from the north (left) bank of the Peruvian Amazon have 2 n 5 46 and FN 5 60. Hershkovitz (1983) attributed divergent pelage traits to these karyotypes by examining skins from north-bank and south-bank Peruvian localities. He identified the north-bank 2 n 5 46 karyotype as belonging to the gray-necked species Aotus vociferans (Spix, 1823) , and he described a new species of red-necked night monkey, A. nancymaae (originally misspelled nancymai ; see Groves, 2001) for the southbank 2 n 5 54 karyotype. However, an allegedly unique enclave of red-necked night monkeys with 2 n 5 54 chromosomes (also referred to A. nancymaae ) occurs along the lower Río Tigre, a north-bank tributary of the Amazon ( Hershkovitz, 1983: fig. 9).

Although Aquino and Encarnación (1988) believed that Aotus nancymaae and A. vociferans are allopatrically distributed, recent reports of sympatry from several localities near Leticia ( Pieczarka et al., 1992) and a few specimens of nancymaae from northbank localities where only vociferans should occur (e.g., AMNH 74382, from Apayacu) suggest otherwise. Future fieldworkers should be alert to the possibility that both species could be present along either bank, where they might occupy adjacent but distinct habitats.

All of the night monkey specimens that we examined from the Ucayali-Yavarí interfluve match the pelage characters attributed to Aotus nancymaae by Hershkovitz (1983). In particular, the reddish ventral coloration extends up the side of the neck below and behind the ear (conforming to the red-necked phenotype of other south-bank Amazonian forms), the interscapular whorl ( Hershkovitz, 1983: fig. 1 ) is absent, the flanks are predominantly grizzled-grayish, and the distal half of the tail is blackish above and below. A distinct middorsal blackish stripe is present on the proximal half of the tail in some specimens (e.g., AMNH 73701, 73702), but not in others (e.g., AMNH 74035, 268238). Craniodental measurements of these specimens ( table 5) compare closely with homologous dimensions of topotypic material ( Hershkovitz, 1983: table V). Most specimens from the Yavarí-Ucayali interfluve are unaccompanied by external measurements and weights, but an adult male (MUSM 11111) from Nuevo San Juan measured 307 X 343 X 89 X 32 mm and weighed 820 g; an adult female (AMNH 268238) from the same locality measured 308 X 390 X 96 X 32 mm and weighed 804 g.

Pending a critical revision of Aotus , we follow the currently accepted taxonomy ( Groves, 2005) in referring our material to A. nancymaae , but it is not clear that this taxon is really diagnosable from A. miconax Thomas, 1927 , a geographically adjacent species from the foothills of the eastern Andes. Hershkovitz (1983) admitted that nancymaae and miconax might be conspecific, and subsequent morphological analyses ( Ford, 1994) have failed to discover any phenotypic trait that distinguishes them, but the karyotype of miconax is unknown. Although it would be reasonable to conclude on the basis of morphology that miconax is a senior synonym that should replace nancymaae as the oldest available name for the night monkeys of the Yavarí-Ucayali interfluve, we prefer to maintain existing usage and await karyotypic data from Andean foothill populations to support or refute this hypothesis.

Puertas and Bodmer (1993) suggested that Aotus nigriceps (another allegedly distinct red-necked species) might occur in the Reserva Comunal Tamshiyacu-Tahuayo— from which they also reported A. nancymaae —but noted that the species had only been recorded from vocalizations. In the absence of corroborating details, their identification is difficult to evaluate, but sympatry between congeneric species of night monkeys is not implausible (as noted above). Future primatological fieldworkers in the area should take care to record unusual vocalizations and (ideally) collect voucher specimens of locally co-occurring taxa.

REMARKS: One of our voucher specimens (AMNH 268238) was shot at 1500 h on the afternoon of 31 May 1996 as it followed a troop of Saimiri sciureus at a height of 15 m above the ground in secondary upland forest. Two other night monkeys were part of this mixed-species troop, an unusual association not reported by the Matses (see below) nor, apparently, one previously reported in the literature.

ETHNOBIOLOGY: The Matses call the night monkey dide, but another Matses name for the night monkey is diku. The term dide is the one usually overheard in everyday conversation, and diku is used mostly in myths. There is some controversy among the Matses as to whether diku is a synonym of dide or a less-commonly encountered subtype (different from dide).

The Matses eat night monkeys, but because the Matses traditionally did not hunt at night, and night monkeys are rarely encountered in the day, they were infrequently killed. Now that the Matses hunt at night with flashlights and shotguns (mainly for pacas, deer, tapirs, and caimans), they could kill night monkey more easily, but since night monkeys are small, the Matses are seldom willing to expend a shotgun shell to kill one. The Matses kill night monkeys opportunistically when the animals are detected at dawn entering tree holes, or when a monkey sticks its head out of its hole as a hunter passes by during the day. In the latter case, the hunter will shake vines and saplings to see if the animal exits the hole; if it does, the hunter will shoot from the ground. If the monkey stays inside its hole, the hunter may climb up a neighboring tree, make a bit of noise, and then shoot it when it sticks its head out again. If not, the hunter might climb the tree, plug the hole, and later return later with an axe to fell the tree or enlarge the hole to get the monkey(s) out.

The Matses believe that night monkeys ‘‘inform’’ people with their calls by revealing that large terrestrial game (especially whitelipped peccaries) or a jaguar is approaching or in the vicinity. The Matses consider night monkeys good and helpful because they provide this information.

MATSES NATURAL HISTORY: Night monkeys have big eyes, flat snouts, and striped foreheads. They have a gray body with a red chest, and a black tail-tip. They are the size of a squirrel monkey.

They live in small troops of about four individuals. They call saying ‘‘ ii ii ii ii ’’ [the vocalization attributed to night monkeys in traditional Matses ceremonial chants, not a phonetically accurate rendition of actual calls]. They are active at night and sleep in the day. They can see in the dark and forage for fruits in the dark. They sleep in holes in dicot trees and palm trees. They do not always sleep in the same hole. When they see that the day is dawning, they go inside their hole. Then at dusk they come out again.

They eat mostly dicot tree fruits, including diden këku [ Parahancornia peruviana (Apocynaceae) ; this term means ‘‘night monkey’s këku fruit’’; këku is another fruit in the family Apocynaceae ]. They surely eat other sweet dicot fruits that other monkeys eat, but it is hard to be certain which ones because they are seldom seen feeding.

Figures

Fig. 1. The Yavarí-Ucayali interfluve (shaded) in relation to surrounding geographical features of western Amazonia.

Tables

TABLE 5 Craniodental Measurements (mm) of Aotus nancymaae from the Yavarí-Ucayali Interfluve

	Males a	Females b
CIL	50.7 (50.3–51.0) 3	49.6 (49.4–49.8) 3
OB	43.6 (42.7–44.1) 3	42.9 (42.3–43.3) 3
POC	33.2 (32.6–34.0) 3	30.4 (28.3–31.6) 3
ZB	40.2 (38.1–41.8) 3	38.0 (37.4–39.1) 3
BB	34.7 (34.2–35.5) 3	32.8 (31.9–33.8) 3
PPL	26.0 (25.9–26.2) 2	25.0 (24.2–26.0) 3
LMT	18.1 (17.6–18.7) 3	17.8 (17.5–18.2) 3
BM1	4.0 (3.9–4.0) 3	4.2 (4.1–4.2) 3
M1–M1	20.6 (20.3–20.9) 3	20.0 (19.8–20.3) 3
I2–I2	11.2 (11.0–11.4) 3	11.6 (11.5–11.8) 2

a Summary statistics (mean, observed range in parentheses, and sample size) for measurements of AMNH 73701, 98330; FMNH 88868.

b Summary statistics (mean, observed range in paren-

theses, and sample size) for measurements of AMNH 73702, 74035, 268238.