Weddell’s Saddle-Back Tamarin, Leontocebus weddelli
WEDDELL'S SADDLE-BACK TAMARIN
Leontocebus weddelli
Geographic Distribution and Habitat
Weddell’s saddle-back tamarin (Leontocebus weddelli) is endemic to Bolivia, Brazil, and Peru, and lives in the lowland Amazonian forests. They live at elevations between 328 feet (100 m) and 3280 feet (1000 m).
This region’s wet season runs from October to April, with an average rainfall of 70.8 inches (180 cm) each month. October is typically the hottest month of the year, with temperatures up to 84 °F. In the dry months, between May and September, the average monthly rainfall is 11 inches (28 cm). It is also coldest at that time of year, with temperatures in June as low as 68 °F (20 °C).
Weddell’s saddle-back tamarin can live in forests where the canopy is open, but the understory is dense. They live in both primary and secondary forests–those that have not been disturbed by human development and those that are in the process of recovering from disturbance, respectively.
Weddell’s saddle-back tamarin was once considered to be a subspecies of the brown-mantled tamarin (Saguinus fuscicollis), but its unusual white color pattern led some to argue it should be a unique species. In 2016, Weddell’s saddle-back tamarin was reclassified from the Saguinus genus and placed in the Leontocebus genus. This new group included not only Weddell’s saddle-back tamarin, but all species in the “white-mouthed tamarin” group.
Size, Weight, and Lifespan
Weddell’s saddle-back tamarins are small and show only slight sexual dimorphism, or physical difference between the sexes. Females are slightly heavier, at an average weight of 0.81 pounds (366 g) compared to the male average weight of .71 pounds (324 g).
Measured from the top of their head to the rump, females are typically 7.7 inches (196 mm) long, while males come in just a bit shorter at an average length of 7.5 inches (190 mm). Both sexes have tails that, in comparison to their body length, are impressively long. Females’ and males’ tails are typically 10.1-14.9 inches (257-380 mm) long.
Weddell’s saddle-back tamarin can live up to 10.5 years in the wild.
Appearance
Weddell’s saddle-back tamarin has thick black fur all across the arms and upper torso. Their titular “saddle” a marbled patch of orange-yellow with black hair, creating a marbled patch on their back. Towards their rump, the coloring becomes predominantly orange as it spreads over their upper thighs.
Their long tails are mostly black, with a little bit of orange just underneath the base. Combined with their long, narrow hands, Weddell’s saddle-back tamarin is well adapted for a life of leaping in the trees and reaching into small crevices to find food.
They belong to a group of tamarin species known as the “white-mouthed tamarin” group. Take a look at their face, and you’ll understand why. Although their crown, tiny ears, and neck are black, their nostrils and mouth are adorned with light gray hairs. The look is complete with a bright white band of fur that traverses the brow ridge over their eyes, creating a very distinct set of “eyebrows.”
Their long, non-prehensile tails are characteristic of the Callitrichidae family that they belong to. This group, which also includes marmosets, is also known for having two molars on each side of the jaw, rather than three as found in other Latin American monkeys. Additionally, they have non-opposable thumbs and claws on every finger and toe—save the big toe, which has a flat nail.
Diet
Weddell’s saddle-back tamarins primarily eat fruit and insects, but will supplement their diet with some gums, nectar, and small amphibians or reptiles.
Some of the most important plants in their diet include Leonia glycycarpa (a tree that produces a peach-sized fruit called achocon), trees in the Pourouma genus, Symphonia globulifera (commonly known as the boarwood tree), and trees in the Combretum genus.
They also eat a lot of orthopterans—an insect group that includes grasshoppers, locusts, and crickets. The insects offer important macronutrients such as protein and fat, as well as micronutrients like iron, zinc, and manganese.
When they’re looking for insects to eat, they spend 62% of their time on tree trunks and broad branches. They will also forage in tree holes and bark crevices in the lower canopy. Occasionally, they’ll descend to the ground to look for insects in the leaf litter.
They typically forage about 37 feet (11.2 m) off the ground when seeking fruit and 20 feet (6.1 m) off the ground when looking for animal prey.
Individual feeding bouts are short—lasting between 5 and 8 minutes. In a single day, a group of Weddell’s saddle-back tamarins visits between 10 and 20 different trees to eat fruit, nectar, gums, and saps. They spend the same amount of time at each tree, regardless of whether it has high or low productivity. Scientists have two hypotheses for why this may be: it could be that their body sizes are so small that they can eat a satisfactory meal even when there’s a limited amount of fruits and flowers. Another possibility is that the less productive trees produce higher quality, more nutritious food.
Behavior and Lifestyle
As a diurnal species, Weddell’s saddle-back tamarin is active during the day and asleep at night. Their home ranges, the area a group claims as their territory, are typically between 62 and 247 acres (25 and 100 hectares).
Their movements within their home range, between feeding and sleeping sites, are not random. In fact, they navigate their habitat using a series of route segments, many of which are frequently reused.
An arboreal species, they spend most of their time in the trees. They use all four legs to move about and are adept at leaping and climbing. Weddell’s saddle-back tamarins jump more frequently from tree trunk to tree trunk than other tamarin species. In fact, these big leaps make up 20% of all their jumps.
Although they can tolerate some human disturbance, they spend most of their time in undisturbed forests.
10% of the prey animals that Weddell’s saddle-back tamarin eats are lizards.
On a typical day, Weddell’s saddle-back tamarin travels between 0.5 and 1.1 miles (800 and 1700 meters). They spend about half the day resting and the rest of their time divided fairly evenly between looking for food and travelling.
Weddell’s saddle-back tamarin lives in groups of 2-9 individuals with a mix of kin and non-kin. Aggression is uncommon among group members. Though there may be high-ranking members, the groups are quite egalitarian, with open sharing of resources.
They share part of their range and 43% of their fruit diet with the black-chinned emperor tamarin (Saguinus imperator). Although they sleep separately and don’t interact closely, the two tamarin species will travel and forage together, a practice that offers greater safety in numbers against predators. The slightly smaller and more agile Weddell’s saddle-back tamarin often reaches the food more quickly than the emperor tamarins. Upon arrival, however, the larger emperor tamarin may intimidate the smaller tamarin into giving up the best spot on the fruit tree. Despite these dynamics, the relationship is generally peaceful, with both species tolerating the presence of the other.
Weddell’s saddle-back tamarins have three distinct scent glands on their chest, right above their pubic bone, and around their anus. They can rub these glands on trees and other surfaces in their environment to leave their scent behind. This is known as olfactory communication and is the primary way that Weddell’s saddle-back tamarins communicate.
Olfactory communication plays an important role in helping them find mates. A scent-mark by a breeding female gets a lot of attention—other Weddell’s saddle-back tamarins may respond by sniffing or licking it to take in more chemical cues and investigate it further. A breeding male may “overmark” the breeding female’s mark by adding his own scent on top, likely a message to other interested parties to back off. Females scent-mark more than males do.
Occasionally, Weddell’s saddle-back tamarin may directly mark another tamarin, but this is less common and may serve a social role that scientists don’t understand yet. Other potential purposes of olfactory communication include marking their territory, advertising their social status, and marking the location of resources.
When they’re hanging out with individuals from other species, Weddell’s saddle-back tamarins keep the group together by sharing long calls composed of 2 to 7 high-pitched notes. It doesn’t seem like they’re terribly picky about who they associate with, given that they don’t distinguish between long calls from neighboring groups and strangers.
Weddell’s saddle-back tamarins don’t seem to follow any rulebook when it comes to mating. For the most part, they are polyandrous or monogamous–meaning that either one female mates with several males, or one female and one male mate exclusively. This is not a hard and fast rule, though, as one male may also have several female mates, or both males and females may each have several mates.
This species reaches sexual maturity around 13 months. When they come of age, both males and females may leave the group they were born in to join another troop.
It’s most common for a group to have just one breeding female at a time, though sometimes there can be two. Her breeding tenure lasts an average of 3 years, while males typically spend around 4.26 years breeding.
The breeding female typically gives birth every 6 months. Her pregnancies last an average of 150 days and frequently result in the birth of twins. When a mother is nursing a child, her reproductive cycles temporarily halt, making her temporarily infertile. This is a strategic adaptation that ensures she doesn’t have to care for too many babies at once, making it more likely that her young will survive.
In a group of Weddell’s saddle-back tamarins, several females may care for the child in a practice known as “allomothering.” The biological mother benefits greatly from this relationship, as it means she often provides just 16% of the infant transporting and 30% of the infant feeding in the 15 months after giving birth. Despite all this additional help, the biological mother still spends less time resting than the allomothers do. It truly does take a village!
As the babies grow older and become more independent, they rely on adults for assistance finding and—in the case of insects—catching their food. Sometimes they may still try to beg for food, but they are not often successful.
As fruit eaters, Weddell’s saddle-back tamarin plays an important role in maintaining the growth and biodiversity of plants in their ecosystem. The plant matter that they eat is later defecated in a different part of the forest, allowing the seeds to disperse while offering a little boost of fertilizer in the process. By eating insects, Weddell’s saddle-back tamarin also provides pest control, which helps keep the ecosystem balanced.
Because they are specially adapted to digest the gums and sugars that are secreted by trees, they also play the important ecological role of cycling these nutrients back into the ecosystem.
Weddell’s saddle-back tamarins keep the lowland Amazonian forests healthy and balanced in many ways. Without them, the ecosystem would have one less species to disperse plant matter, and the insect population might grow out of control.
The International Union for Conservation of Nature lists Weddell’s saddle-back tamarin as Least Concern (IUCN, 2015), appearing on the IUCN Red List of Threatened Species. This is because the species is widespread and common in its range and faces no major threats that could cause significant population decline.
Occasionally, Weddell’s saddle-back tamarin is traded as a pet. This practice often involves nabbing individuals from the wild with no regard for how many are being taken and from where. If left unchecked, this practice could pose significant problems down the road.
Weddell’s saddle-back tamarin is listed in Appendix II 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.
This species is found in many protected areas. In Peru, Weddell’s saddle-back tamarin can be found in Manu National Park, Bahuaja-Sonene National Park, and the Tambopata National Reserve. In Bolivia, they are found in the Madidi National Park and Natural Area of Integrated Management, the Manuripi National Reserve for Amazonian Wildlife, and the Pilon Lajas Biosphere Reserve and Indigenous Territory. In Brazil, they are present in the Serra da Cutia National Park, state parks (such as Guajará-Mirim and Serra dos Três Irmãos), Biological Reserves (such as Abufarí and Guaporé), and National and State Forests (such as Humaitá).
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Written by Jiayu Liang, July 2026