rainforests. Behaviour Diet The western pygmy marmoset is an exudativore-insectivore, thus its diet comes mainly from the exudates (fluids) from trees, such as tree sap, gum, and latex from lianas and trees. Through evolution of feeding on gum and sap from trees, the western pygmy marmoset developed dental adaptations that its ancestors did not have. These dental adaptations allow it to actively stimulate the fluids from the trees, as it gouges holes in the bark. It can also be found, on occasion, eating arthropods and fruits. Breeding The pygmy marmosets frequently have fraternal twins. When born, their infants are smaller than expected compared to their gestation length. This is probably due to their slow growth rate when in utero. Studies have shown that Cebuella pygmaea is potentially able to prevent reproduction in their population through hormonal suppression. If a single dominant female marmoset does not wish for her subordinate group members to reproduce, she can produce pheromonal signals which suppress hormones (LH secretion) which leads to ovulatory failure. However, this does not always work. If a subordinate female group member succeeds at breeding, the dominant female might resort to killing the offspring. Vocalizations Due to the natural habitat in the dense Amazonian River basin, the western pygmy marmoset must rely on vocal communication. This marmoset uses trills when it is at close distance, up to , from one another and they use J calls when they are more than apart. The western pygmy marmoset’s “habitat acoustics have shaped the physical structure of the signals used for short and long-range communication”. Long-range calls are the only ones that are distinctively heard compared to the trills and J calls, as they produce a lower frequency call at long distances. By using these different calling methods, the pygmy marmoset has developed a way of communicating distances to determine individual locations. Interestingly, the western pygmy marmoset has been observed to change “the structure of their trill vocalizations in response to pairing with a new mate”. Prior to mating, marmosets would display unique trill vocalizations, and after six weeks of pairing, their trills become more homogenous. These same studies also show that these vocal structure changes remained stable three years after pairing. Threats and conservation As of 2015, the western pygmy marmoset (Cebuella pygmaea) has been listed by the IUCN as vulnerable based on the A4cd criteria. Based on their assessments, the population has declined