As I sit down to write this note, the image that comes to
my mind is that of my first night in the forest two years
ago. That night, I laid down on my back, stared at the full
moon, a listened to the forest. I took a deep breath and felt
that every creature, every leaf, every sound was welcoming
me. I was about to start an ambitious and challenging project:
a long-term study of nocturnal owl-monkeys (Aotus azarae)
of Formosa, Argentina.
Owl monkeys, or Mirikinas, as they are called in Argentina,
are small neotropical primates found from Panama in the north,
to Argentina in the south.
Two characteristics of owl monkeys make them unique. First,
owl monkeys are the only nocturnal primates that live in the
neotropics. Although there are other nocturnal primates, (
e.g. the aye-ayes from Madagascar described in the summer
issue of Positively Primates), they all live in Africa or
Asia. Secondly, Mirikinas are one of the few primate species
that live in small monogamous groups (2-5 individuals), usually
composed of an adult pair, one infant, and sometimes a juvenile.
Traditionally considered monogamous, owl monkey males and
females believe to pair for life and remain sexually faithful
to one another.
In 1996, I began “Proyecto Mirikina,” a long-term
research program aimed at studying the behavior, ecology,
and conservation of owl monkeys. After establishing camp at
a cattle ranch in the Province of Formosa, Argentina, we began
to work in collaboration with Argentinean students and Earthwatch
volunteers. We established more than fifteen kilometers of
trails through 70 hectares of forest. The trails had to be
marked with fluorescent plastic tape to facilitate walking
through the forest at night. After four months, we had identified
10 groups regularly using this area. Over a period of three
months, we collected more than 300 hours of observation from
five different groups. We observed them foraging, traveling,
vocalizing, and mating during the day as well as at night.
Their territories ranged between four and eight hectares.
Group size ranged between three and six individuals. Between
April and October of 1997, we never observed a newborn or
dependent infant in any of the groups. However, with the support
of the DuMond Conservancy, three Argentinean students returned
to the forest this past January to check for the presence
of newborns, and found a new infant in five of the ten groups,
confirming that births occur seasonally.
In the next few months, we will continue monitoring the
groups and habituating them to our presence. In July, we will
begin a 12-month study to examine in detail some of the ecological
and environmental factors that may contribute to the very
unusual pattern of activity characteristic of owl monkeys.
We will also try to collect blood samples to examine the genetic
structure of the population.
Studying the behavior of nocturnal monkeys poses some extra
challenges to the already difficult task of finding and following
monkeys as they jump and run through the forest. To improve
the quality of the work and to make it more efficient, we
need to use sophisticated night vision equipment. We also
would like to capture at least one individual per group, and
fit them with a radio-collar to facilitate locating and following
the groups. The night vision binoculars and the radio collars
are relatively expensive pieces of equipment, which we are
currently seeking support for.
Dr. Fernandez – Duque wrote this article for Positively
Primates several years ago.
