Golden-Backed Uakari, Cacajao melanocephalus
GOLDEN-BACKED UAKARI
Cacajao melanocephalus
Geographic Distribution and Habitat
The golden-backed uakari, also known as the black-headed uakari, golden-backed black uakari, and Humboldt’s black-headed uakari, is a platyrrhine monkey, meaning it is among the species of monkeys that evolved in Central and South America. Its primary distribution occurs in south Venezuela, northwest Brazil, and southeast Columbia. These regions experience a wet season and dry season, and these monkeys live in primarily fluvial wetlands, which are swamp-like forests. Because of this habitat, the monkeys are highly arboreal (tree-dwelling), spending much of their time in the understory and high canopy. Due to their unique habitat and adaptation to living atop wetlands instead of dry, they have not experienced any significant habitat loss.
The golden-backed uakari lives in close proximity to the neblina uakari (Cacajao hosom), making identification and taxonomy difficult to ascertain at some points. It is largely accepted that the Rio Negro River, in northern Brazil, separates the two species—with the golden-backed uakari living northeast of the river. The delineation of the two neighboring species was contested by many scientists, however, after chromosomal testing was done it was shown to be a separate species.
Size, Weight, and Lifespan
The golden-backed uakari is a moderately sexually dimorphic species, meaning there is a difference in body size and attributes based on their sex. In this case, males are larger and have more pronounced canines. On average, males are around 16 inches (41.5 cm) in length, and females are 15 inches (39 cm). Golden-backed uakaris weigh 5.5 to 8.15 pounds (2.5 to 3.7 kg). Their tail is one-third of their body length, making it shorter than other arboreal primate species in comparison. Their life span in nature is approximately 20 years.
Appearance
Golden-backed uakaris, as their name may suggest, have golden-colored pelage down their backs. This coloration starts at their neck and is more cream, and gradually progresses to a gold or burnt orange color down their backside. Their face, arms, and legs are black, and their bellies are black or a deep brown. Their tails can vary in color, either appearing as a deep orange or black. Their tails are not prehensile, meaning they do not use them to wrap around tree limbs or grasp things. Rather, their tails are used for balance when they are in the canopy.
Diet
Golden-backed uakaris have a unique diet compared to other large-bodied Central and South American monkeys. They eat seeds, leaves, unripe fruit, and even insects. Their physical adaptations—powerful jaws, large canines, and specialized incisors—allow them to break through the hard exterior of various seeds and eat fruit from many different tree species. This makes them specialized feeders. They often eat seeds from unripe fruit, which further allows them to flourish within their dietary niche. This provides flexibility in their environment and results in less competition with other animals. Generally, leaves and insects are consumed more readily when fruit is sparse in the region, making it a fallback food. Fallback foods are vital for many primate species. Their diet seems to have influenced some of their social behaviors. Research has shown that seed distribution in wetland forests lends itself to foraging in small groups, which is exactly what the golden-backed uakari does for daily eating.
Behavior and Lifestyle
Golden-backed uakaris move quadrupedally through the trees, carefully balancing and expertly choosing their next move. As mentioned before, they do not use their tail to grasp branches, but rather for balance when moving from branch to branch. One means of locomotion the golden-backed uakari uses is called “bridging.” This is when they lay across small branches, evenly distributing their body weight across the area. They then pull new branches toward them, shimmying along the upper canopy.
Allogrooming behaviors, that is mutual social grooming between and among monkeys, are rarely seen among wild golden-backed uakaris, as their troops tend to spread out over several trees when large groups reunite (see their fission-fusion social system below). However, it is a common occurrence among captive uakaris. Allogrooming is often crucial for establishing and reinforcing bonds among primates that live in large groups, such as the golden-backed uakari. This highlights how little we know about this magnificent monkey.
The golden-backed uakari has been known by many different names, accurately or not! For many years it shared a common name with another species, Cacajao hosomi, now known as the neblina uakari. The multiple names and mistaken identities made education difficult, which is why many sources are still in the process of rectifying their common name.
Golden-backed uakaris live in multi-male, multi-female groups. The size of these groups can range from 35 to 100 monkeys! This large group number can present challenges in some situations, such as feeding. If all of the group members foraged in the same place at once, they would soon deplete an area. Lower-ranking individuals would suffer as a result. As a solution to this, golden-backed uakaris, along with many other primate species, use a fission-fusion system. This is when large group-living primates split into smaller groups during the day for foraging and socializing. At the end of the day, or sometimes several days, these smaller troops unite into large groups to sleep in greater numbers. It has been observed that these smaller groups will retain the same members for days or weeks at a time. This maintenance of specific individuals in the group may give us further insight into their social systems and preferences, such as hierarchy and dominance.
The golden-backed uakari is considered highly social, as evidenced by their large group numbers. Aggression is rarely seen in this species, which is unusual for primates living in a multi-male, multi-female society.
Golden-backed uakaris communicate through auditory signals, primarily. Most communication occurs within foraging groups. Through various clicking sounds, the group can warn each other of predators or anything irregular in their environment. Juveniles make many different vocalizations, which enhance play and are vital for development.
For adults, especially males, tail wagging is an important communication tool. This behavior communicates aggression and dominance displays. While males may compete among themselves, they are not considered particularly territorial. While tail wagging is considered an indicator of aggression, some researchers argue that it is simply a behavior induced by anxiety or unease.
While there is much about the golden-backed uakari that we do not know, we know that social hierarchy plays an important role in their mating behaviors. In their large, multi-male multi-female groups, there is ample competition for partners. However, some researchers believe that, due to the lack of exaggerated sexual dimorphism, the species may have a more monogamous mating system. It is thought that reproduction is seasonal, as many infants have been recorded in March and April, which just so happens to be when fruit is abundant in the wetland forests.
Females reach sexual maturity at around 3.5 years old and have their first pregnancy soon after. Infants are weaned at approximately one-year-old. Uakaris have never successfully reproduced in captivity, limiting some knowledge of their reproductive behaviors and cycles, nor have they been studied in the wild long term.
Golden-backed uakaris are both seed dispersers and seed predators. When fruit is abundant, their fruit-eating results in the swallowing of seeds, which are later dispersed through fecal matter. When fruit is not as abundant, however, the monkey will husk open the shells of fruit and eat the seeds for extra nutrients.
The International Union for Conservation of Nature lists the golden-backed uakari as Least Concern (IUCN, 2020), appearing on the IUCN Red List of Threatened Species.
The golden-backed uakari has not been severely impacted by deforestation or habitat loss, making it one of the only primates to boast this advantage. Because of the wet, swamp-like forest these monkeys inhabit, the area is not seen as valuable for deforestation. There has not been a significant reduction of habitat in the last 20 years, and this is not expected to change anytime soon.
Hunting and poaching do not seem to be a significant threat to these monkeys, either. Some local indigenous peoples sometimes keep or feed young golden-backed uakaris, however, there is no evidence of long-term captivity or restriction.
The golden-backed uakari is listed in Appendix I of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.
Much of the habitat the golden-backed uakari lives in is protected. The Nukak and Puinawai Natural National Reserves in Columbia are well protected, however, further water and land management are needed. In Brazil, they occur in Jaú National Park and Amanã State Sustainable Development Reserve.
While the golden-backed uakari is currently in a good place regarding population and habitat, more research and monitoring are needed in order to best assess further conservation needs.
- https://www.iucnredlist.org/species/160875418/191697842
- https://animaldiversity.org/accounts/Cacajao_melanocephalus/
- https://www.inaturalist.org/taxa/43653-Cacajao-melanocephalus
- https://www.britannica.com/animal/black-headed-uakari
- https://www.bioexplorer.net/animals/mammals/monkeys/black-uakari/
- https://karger.com/fpr/article/83/2/126/143651/Terrestrial-Foraging-by-Cacajao-melanocephalus
- https://pubmed.ncbi.nlm.nih.gov/20635117/
- https://pubmed.ncbi.nlm.nih.gov/7200049/
- https://www.researchgate.net/publication/237049474_Ecology_of_the_black_uakari_monkey_Cacajao_melanocephalus_melanocephalus_in_Pico_da_Neblina_National_Park_Brasil
- https://primate.wisc.edu/primate-info-net/pin-factsheets/pin-factsheet-uakari/#behavior-sociality
Written by Robyn Scott, February 2024