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Aotus
| Aotus azarae |
Azara's owl monkey
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| Aotus brumbacki |
Brumback's owl monkey |
| Aotus hershkovitzi |
Hershkovitz's owl
monkey |
| Aotus infulatus |
Feline owl monkey |
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Aotus lemurinus griseimembra |
Lemurine owl monkey |
| Aotus miconax |
Andean owl monkey |
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Aotus nancymai |
Ma's owl monkey
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| Aotus nigriceps |
Black-headed owl
monkey |
| Aotus trivirgatus |
Northern owl monkey
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| Aotus vociferans |
Noisy owl monkey |
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Primate Information Clearing House Taxonomy |
The northern owl monkey is found in Southern
Venezuela and North-central Brazil (Nowak, 1999). This species lives in
forests where the trees are evenly dispersed. The southern owl monkey is
found in the countries of Bolivia, Paraguay, and Northeastern Argentina
(Nowak, 1999). This species lives in low vine forest and the tall forest,
and is predominately found in the middle stratum of the forest (Wallace
et al., 1998). In Argentina this species is found in both low and
tall forests that have dense canopies (Rathbun and Gache, 1980).
The owl monkey is a frugivorous species that also eats leaves insects and
small ripe fruit (Kinzey, 1997). An advantage of foraging at night is decreased
competition from diurnal frugivores and the presence of larger nocturnal insects
(Wright, 1989).This species spends all of its life up in the trees (Kinzey,
1997). The owl monkey becomes more active when the moon is bright (Wright,
1984), and they travel the same route during the night, so they may memorize
routes when they travel when the moon is brighter (Wright, 1989). Southern
species are known to eat the seeds of the species Brosimum alicastrum,
which differs from other members of the genus Aotus (Wright, 1985). In
the cold season in Paraguay this species eats more leaves than other members of
the genus Aotus, because during this time of the year in Paraguay
fruits are very scarce (Wright, 1989). In Argentina the predominate food for
this species was found to be fruits and flowers (Rathbun and Gache, 1980).
This species feeds more frequently during the first hours of activity (Garcia
and Braza, 1987). The southern owl monkey sleeps in groups in trees which are
located in the middle stratum of the forest, and the trees have a mean height of
12.8 meters (Garcia and Braza, 1993). The sleeping sites have a mean height of
10.8 meters (Garcia and Braza, 1993). In the trees the sleeping locations are
either thickets, dense foliage, or lianas (Garcia and Braza, 1993). Garcia and
Braza (1993) found the use and distribution of the trees used as sleeping sites
is related to food availability and structural characteristics of the habitat.
The mean group size for the southern owl monkey is 3 individuals with a range
from 2 to 5 (Wallace et al., 1998). In Argentina this species has been
shown to be active during the day (Rathbun and Gache, 1980). This species can
also be active during the day in Paraguay, where they were seen to forage for a
couple of hours during the day (Wright, 1989). The mean group size for this
species for populations found in Argentina is 2.9 individuals (Rathbun and Gache,
1980).
The basic group of owl monkeys is composed of a
breeding pair and their offspring. This species has a monogamous mating
system (Kinzey, 1997). The monogamous mating system is correlated with
having males present to help raise offspring and having food resources in
predictable, uniform patches (Wright, 1986). Both males and females
disperse in this species (Kinzey, 1997). The young stay with their birth
group until between 2.5 and 3.5 years old, then they disperse (Kinzey,
1997). Social grooming is not common for members of this genus (Fleagle,
1988). In this species the father becomes the main carrier of the infant
and only gives the infant to the mother to suckle (Jantschke et al.,
1998). If the father dies when the infant is still young, other siblings
will assume the caregiver role, but not the mother, and the infant does
become independent sooner than if the father cared for it (Jantschke
et al., 1998). Jantschke et al. (1998) found that in an
infant reared without a father the infant became independent at 12 weeks
verus 33 weeks for an infant with a father.
Aotus is usually reported as a highly monogamous primate. Groups are often
composed of an adult male and female and up to three infants and juveniles.
However, reliable observations of up to five multi-adult groups moving through
the canopy together have been reported (L. T. Rosengreen, pers. comm.) and
multiple-adult groups nesting together (Hernandez-Camacho and Cooper, 1976).
Other reports of larger groups of up to 30 individuals found in fruiting trees
are probably aggregations of smaller groups, a point supported by a high degree
of agonistic behavior between individuals in the larger groupings (Wright,
1981).
Owl monkeys have a relatively short interbirth interval of about one year
which is possible due to high levels of paternal care which alleviates much of
the energetic costs to the mother (Garber and Leigh, 1997). Male owl monkeys
carry the young, defend them from predators, play and instruct them (Wright,
1985). The social system benefits the male, usually limited by access to
females, by providing high parental certainty (Garber and Leigh, 1997), low
infanticide rates and short interbirth intervals. Owl monkeys are unique in that
females will actively refuse to carry the young if the male is unavailable,
going so far as to violently pull the infant off of its back (Eduardo ???, pers.
comm.) Two birth peaks occur, one at the end of the dry season and the other in
the middle of the wet season (Wright, 1985). Gestation is about 133 days (Hunter
et al., 1979). Young disperse at two to three years (Wright, 1985) and probably
pass into a nomadic, "vagabond" stage before pair-bonding with a female
(Charles-Dominique, 1977).
Male-male aggression is common and is a factor in keeping groups apart
(Moynihan, 1964). Agonistic encounters involve back arching, stiff-legged
jumping, pilo-erection, urination and defecation, as well as giving
clicking/grunting alarm calls. Identical agonistic displays occur between
conspecifics and other species (Wright, 1978).
Aotus is highly territorial. Territories are extremely small for a primate of
its size, usually no greater than 10 ha (Wright, 1985). Although little work has
been done on the dynamics of territory size and location over time, it has been
suggested, based on the behaviors of nocturnal prosimians, that Aotus
is relatively sedentary (Charles-Dominique, 1977). This is supported by Isbell's
(1994) conclusion that use of unfamiliar areas by primates may increase the
rates of predation. Relatively mobile, daily path lengths are reported to be
approximately three-quarters of a kilometer. Territories between neighboring
groups overlap extensively (Wright, 1978). Aotus has been reported to
come out of trees and cross open savanna to move between forest patches (Rathbun
and Gache, 1977). Population densities in Peru are reported to be around 25 to
50 individuals per km2 (Moynihan, 1976).
Aotus is a relatively noisy monkey, uttering loud contact and locomotory
notes (Moynihan, 1976). Olfaction is an important component of communication and
Aotus marks substrates by rubbing a gland at the base of its tail and
exuding a brown, oily substance (Wright, 1981).
The northern owl monkey most often gives birth to a single offspring,
although twins have been recorded. The interbirth interval for this species is
one year. Copulation attempts tend to be brief and rapid, with the male and
female first quietly approaching each other (Moynihan, 1964). Then the male
performs social sniffing, and the female may social sniff
while the male is doing the same to her (Moynihan, 1964). Mating is done dorso-
ventrally, with the male inserting his penis under the female's tail, with
female moving the tail slightly (Moynihan, 1964). The male usually makes 3 to 4
pelvic thrusts, with ejaculation occurring on the last thrust (Moynihan, 1964).
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