Pygmy Marmosets at Sacha Lodge

Report of Stella de la Torre
University San Francisco de Quito
Ph.D.  Zoology, University of Wisconsin, Madison, USA

The third field research season at Sacha Lodge!

Thanks to the support of Sacha Lodge of the primatological research carried out by faculty and students of Universidad San Francisco de Quito, in this new field season we will focus on the ecology and behavior of pygmy marmosets. We will continue to gather data about cooperative and foraging behaviors in this species to understand the factors that influence group formation and to assess the intra and intergroup variability in the use of hunting techniques, respectively. We will also collect fecal samples of the marmosets to carry out laboratory studies of fecal cortisol, to know more about the stress level of these primates.

Two new baby pygmy marmosets

In our first week of fieldwork, we observed the family group living in the Torre Baja trail and we have good news. There are two new-born infants in this group and they seem to be in good condition! With these two infants, this family now has 10 individuals, one of the largest group sizes we have recorded in more than 20 years of research. We expect the group will split in the near future and hope the dispersing individuals will settle in a nearby area so we could still study them. We have not been able to observe the family of marmosets that lived close to the kapok tower. Some guides told us that two marmosets visit the area sporadically. We are actively searching the surroundings and hope we will eventually find them. In our next reports, we will present our findings about these fascinating species.

Infant pygmy marmoset. Credits: P. Yépez

Adult pygmy marmoset with infants on back. Credits: R. Burton

Marmoset family matters

The family living in the torre baja trail is quite large for pygmy marmoset standards. It has 10 members, two of them are infants 2-3 months old. Infants are getting increasingly vocal and playful. They babble almost all day but play more in the afternoons. Pygmy marmoset babbling is a unique behavior of the infants of this species and is analogous to babbling in human infants since the young practice the vocalizations they will use as adults.  Both parents and the older brothers and daughters take care of the infants, carrying them and attending all their needs. When the infants play, there is always someone else, usually the father, that stays close to them, ready to protect them if needed.

We were able to observe the two individuals that remain from the group that lived in the area of the metal tower. One of them is an adult and the other is a juvenile. They are still using the area but they are not easy to spot.

They are very shy and use more the upper strata of the forest. Considering the unusual composition of this group, with only one adult, the only possibility they have to become a family is if a migrant adult of the opposite sex arrives to the area. We are periodically monitoring this group to record the dynamics of the group and the behavior of the marmosets.

Pygmy marmosets playing. Credits: R.Peters

Adult pygmy marmoset. Credits: R.Peters

What do Pygmy Marmosets eat?

In our third week of field work, the family group living in the torre baja trail thoroughly took care of the infants. They are more active and begin to participate in most of the activities of the group. Pygmy marmosets in this family feed on exudates of guaba trees (Inga spp.). Guaba trees are one of the plant species from where pygmy marmosets obtain exudates. In our study in 15 different populations of pygmy marmosets in Ecuadorian Amazonia, we have reported a total 21 different exudate species. This number is low, considering the high plant diversity of this region, and points to the high specialization of pygmy marmosets. Each marmoset’s population has a few preferred species. In the Sacha Lodge reserve, these species are the guabas and the cedars (Cedrella odorata). Pygmy marmosets complement their diet with animal prey, mainly insects, which they hunt using different techniques. Infants follow their parents during insect hunting. When a parent catches a prey, it is always willing to share it with the infants. This is how infants learn to hunt!

Pygmy marmoset feeding on a grasshopper 1. Credits: R.Peters

Pygmy marmoset feeding on a grasshopper 2. Credits: R.Peters


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