Red-Naped Tamarin (Saguinus geoffroyi)
by Katharine Milton, Ph.D.
Tamarin species occur throughout the Neotropics in both Central and South America. They are often found in secondary forest or areas of forest in which there are many vine clusters and tangles. On Barro Colorado Island, most of the forest is mature, ranging from around 85 to more than 500 years old. Thus BCI is not an ideal habitat for tamarins which tend to be far more common in the surrounding mainland areas where most growth is secondary. In spite of this fact, it is estimated that 40 or more tamarins live in the BCI forest, organized in small groups of 4 to 7 members. Tamarin groups consist of one or more adult females and males with their immature offspring.
Tamarins can be found in various areas of BCI, but they occur in highest density in the Zetek-Armour area, particularly between Zetek-0 and Zetek-10. Not only are tamarins uncommon on BCI, they are also very small monkeys, weighing only about 500 grams as adults and they tend to travel high in the canopy. Thus the best way to find them is to listen carefully for their bird- like chirps and calls, which they will give loudly as soon as they see a human being.
The tamarin species on BCI is a beautiful little monkey with a very striking coat composed of a pure white chest, deep red-brown on the back of the neck and tortoise mottling down the back. Tamarins often travel single file through the forest, leaping quietly from limb to limb. They are very active little monkeys and most of their day is spent travelling through the canopy in search of food. Their diet is made up of ripe fruits and animal matter, primarily insects such as katydids and soft-bodied jungle cockroaches. They are remarkably agile and rapid, skills useful in catching fast-moving forest insects.
Generally only one female in a tamarin group, the dominant or alpha female, has infants. Reproduction in other adult females in the group is somehow suppressed. Tamarins give birth to twins which the mother passes to the father or other troop members soon after they are born. These "helpers" carry the babies through the forest, passing them to the mother when it is time to nurse. Apparently, it would be too much of an energetic burden for a tamarin mother both to carry and nurse two rapidly growing infants. Thus others help with the task of carrying the infants as the group travels and feeds. By the age of three months, tamarin infants are largely independent of the mother and are able to travel and feed on their own.
Because they are small monkeys, tamarins are vulnerable to many predators that do not pose a threat to the considerably larger howler and spider monkeys. Large snakes can easily consume an animal the size of a tamarin as can many forest hawks as well as small jungle cats such as margays. The shrill, piercing calls of tamarins serve as alarm signals, alerting group members to possible dangers. Tamarins tend to retire earlier than the other monkey species on BCI, moving into leaf clusters, vine tangles, or other dense cover at around 5 pm and remaining quiet there until daybreak. This may be an adaptation that helps them avoid the many predators that tend to become active around twilight, such as owls, snakes and small cats. Katharine Milton, 1998