WEDDELL'S SADDLE-BACK TAMARIN

Leontocebus weddelli

Geographic Distribution and Habitat
The Weddell’s saddle-back tamarin (Leontecebus weddelli) is a species of New World monkey whose range overlaps the South American countries of Peru, Bolivia, and Brazil. These highly adaptable tamarins live in the Amazon’s southwestern basin, exploiting the lowland, primary, and secondary rainforests growing there.

During the last century, the taxonomy of saddle-back tamarins was a bit simpler than the most recent genetic research has revealed. Since its analysis, the Weddell’s saddle-back tamarin was removed from the Sanguinus genus and put into a brand new category, Leontocebus, which includes the ten saddleback tamarin species now recognized by science. 

The Weddell’s saddle-back tamarin has three subspecies, with L. w. weddelli considered as the nominate subspecies. The other two, the white saddleback tamarin (L. w. melanoleucus) and Crandall’s saddleback tamarin (L. w. crandalli), are genetically very similar to it, despite looking quite different in terms of pelage.

As an aside, we have no idea as to why the Weddell’s saddle-back tamarin is spelled as it is, i.e., “saddle-back,” while all other saddleback species are presented as “saddleback.” We’re just as baffled by it as you may be. It’s a mystery.

Weddell's saddle-back tamarin range, IUCN 2020

Size, Weight, and Lifespan
Tamarins are small monkeys, similar in size to squirrels. The average male Weddell’s saddle-back tamarin measures only seven inches (19.0 cm) from his head to the start of his tail. Females are slightly bigger but only by about half an inch (19.6 cm).

Both sexes sport extensive tails, measuring approximately 11 inches (29.6 cm) on average.

Altogether, males and females weigh less than a pound (approximately 12 ounces, or 358 grams).

In the wild, this species may live up to 10 years.

Appearance
The three Weddell’s tamarin subspecies have distinct pelages, with the Cradall’s (L. w. crandalli) and the white saddleback tamarins (L. w. melanoleucus) looking more similar to each other than they do to Wendell’s, L. w. weddelli.

The Weddell’s saddle-back tamarin (L. weddelli wedelli), the nominate subspecies, sports dark fur. Their fronts are completely black, and their hind legs are brown. The saddles of lighter fur on their backs look like hunks of sleek gray marble. The fur covering their claws and running down their tails is also black. Their faces are smeared with crescents of white fur that curve around their mouth, nose, and eyes, and up into their brows, forming what looks like a mask.

In contrast, the white saddleback tamarin (L. w. melanoleucus) and Crandall’s saddleback tamarin (L. w. crandalli) both sport much lighter fur. The former has a very simple patterning: completely white fur with black-tipped ears and no distinguishable saddle.

Crandall’s saddleback tamarins (L. w. crandalli) also have black-tipped ears, as well as black fur around their eyes—but their torsos are only white at the front and darken slightly nearer their tails. The fur on their hind legs is a tan hue with black streaks. Their tails are stark black. Members of this subspecies do sport saddles, but their patterning is somewhat less marbled than those of the nominate subspecies. The fur around all four of their claws is the same tan color found on their hind legs.

Photo credit: ©Edson Guilherme/iNaturalist/Creative Commons

Diet
The diverse diet of Weddell’s saddle-back tamarins make them an exceptionally adaptable species. Though half of their meals consist of fruit, they also eat a large number and variety of insects and arthropods. They get at these by digging past a tree’s bark with their sharp claws, which are longer and more nimble than other tamarin species’. Saddle-back tamarins are also known to descend to the ground to harvest bugs from the leaf litter. This is a behavior rarely seen in tamarins, who have a tendency to prefer the protection of the canopy.

Gums, seeds, and nectars make up the final significant portion of their menus.

This species has also been observed to eat small vertebrates, like amphibians and reptiles. However, how frequently they do so is not entirely clear at this time.

Behavior and Lifestyle
Tamarins are arboreal. As such, they are phenomenal climbers, with sharp claws that allow them to cling to the sides of trees. They scramble up with ease and speed. Adventuring out onto a branch, tamarins scurry on all-fours, their tails giving them exceptional poise as they do. Reaching the end of the branch, their muscular hind legs contract, tense, and release—launching them through the air to land gracefully on another one.

A few behaviors make the Weddell’s saddle-back tamarin an exceptional species. For one, they are known to travel frequently to the ground in order to forage for insects and other small fauna in the dead foliage. They are also a less territorial species than many of their close tamarin relatives. In fact, researchers have noted them to be especially egalitarian for tamarins. For instance, they very willingly share food with members of their group no matter their rank in the hierarchy. In contrast, emperor tamarins, a sympatric species with which Weddell’s saddle-back tamarins frequently associate, share food significantly less often. This ability to get along with other tamarin species is another behavior that makes Weddell’s saddle-back tamarins quite unique among tamarins.

Daily Life and Group Dynamics 
Weddell’s saddle-back tamarin groups can take on a few structures. Some are composed of multiple males and females while others may have multiple females but only one male. Even male and female pairs have been observed in the wild. Groups can have anywhere from two to nine members.

While their groups do function according to an established hierarchy, this species is known for being exceptionally egalitarian. They willingly sharing food with their peers and keep relations peaceful without constant aggressive signaling. A group tends to have a male and female that act as the highest-ranking members. Everyone else falls into a sort of class system of what some researchers have described as “producers,” “scroungers,” and “opportunists.” Age and social finesse also influence a tamarin’s place in the hierarchy.

Their peaceful attitudes make them one of the few species of tamarins that associates with other monkeys, including emperor tamarins, white-lipped tamarins (also known as red-chested mustached tamarins), and Goeldi’s marmosets. They tend to be especially close to emperor tamarins, who have been observed to take note of Weddell’s tamarins’ foraging behaviors when in their midst in order to improve their own search for food. In fact, researchers have noticed that emperor tamarins find food with greater efficiency when associating with Weddell’s saddle-back tamarins, while the latter are typically more efficient when foraging amongst their own species.

Weddell’s saddle-back tamarins wake early in the morning to begin foraging. Depending where they are, they may travel to find a certain type of food.

Once their bellies are full, they rest in the general safety of the canopy. This is also the time when they socialize. Taking turns grooming one another helps to nurture and cement their bonds.

Eventually, with their stomachs grumbling once more, they seek out more food. This species is known to re-use routes through the forest, routinely checking the same spots for food.

As the light in the rainforest fades, they settle down to sleep for the night.

What Does It Mean?

Alloparent: 
An individual other than the biological parent of an offspring that performs the functions of a parent (as by temporarily caring for an infant).

Arboreal:
Physically adapted to living primarily or exclusively in trees.

Arthropod:
An invertebrate animal (one with no spine) having an external skeleton, a segmented body, and jointed appendages. Includes insects, spiders, crustaceans, and myriapods.

Forest floor:
The fourth and bottom layer of the forest. It’s very dark and almost no plants grow in this area as a result.

Gestation Period:
The time of pregnancy from conception until birth. 

Hierarchy:
A system of organization in members of a group who are ranked one above the other according to status or authority.

IUCN: 
​International Union for Conservation of Nature.

Lowland forest:
An equatorial evergreen rainforest, commonly known as a tropical rainforest, which receives high rainfall (80 in; 2 m) throughout the year.

Monogamy:
A mating system in which a male and female mate exclusively with each other.

Multi-male multi-female group/unit (MMU): 
A social group consisting of multiple adult males and multiple adult females.

New World monkey:
Monkeys native to Central and South America.

Nominate subspecies:
In zoological nomenclature, when a species is split into subspecies, the originally described population is retained as the “nominotypical subspecies,” which repeats the same name as the species.

One-male group/unit (OMU): 
A social group consisting of one adult male and multiple adult females.

Pelage: 
The fur, hair, or wool of a mammal.

Polyandry:
A pattern of mating in which a female animal has more than one male mate.

Polygynandry:
A mating system in which both males and females have multiple mating partners during a breeding season.

Polygyny:
A pattern of mating in which a male animal has more than one female mate.

Subadult: 
An animal who is not fully adult.

​Subspecies:
A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.

Sympatric: 
Occurring or living in the same area; overlapping in distribution.   

Taxonomy: 
A branch of science that encompasses the description, identification, nomenclature, and classification of organisms.​

Vertebrates:
Animals with a backbone, including mammals, birds, reptiles, amphibians, and fish.

Visit the Glossary for more definitions

Communication
Tamarins are avid communicators and use an extensive variety of vocalizations, body postures, facial and hands gestures, as well as olfactory signals to share information about their inner and outer worlds.

The communication methods used by Weddell’s saddle-back tamarins are not well-studied at this time, but their surprisingly egalitarian social structure should suggest that this species communicates in particularly complex ways compared to other tamarin species.

Members of another tamarin species, known as red-handed tamarins, have been found to mimic the accents of pied tamarins. These two species find themselves more and more at odds with each other as their already dwindling habitats shrink smaller and smaller. By adopting the pied tamarins’ accents, red-handed tamarins seem to be able to more effectively avoid conflict with there nemeses. Might Weddell’s saddle-back tamarins manage their own relationships with emperor tamarins in a similar fashion? Hopefully researchers will one day find out!

Fun Facts

The genus Leontocebus is known informally as the “white-mouthed group” of tamarins, in reference to the white fur found on their faces.

Some researchers have hypothesized that Leontocebus weddelli crandalli could be a hybrid of other two Weddell’s saddle-back tamarin subspecies, but so far this is inconclusive.

Though there are currently no major threats to Weddell’s saddle-back tamarins, researchers do not know in which direction their populations are trending at this time.

Reproduction and Family
Much like their group dynamics, Weddell’s saddle-back tamarins have no consistent mating system. While most groups are either polyandrous or monogamous, polygyny and polygynandry have also been observed. Typically, though, only a single female produces offspring per group, her vital role lasting up to three years.

No specific mating or birthing season has been noted. But new mothers generally have their first birth between 24 and 60 months of age and continue to have new offspring—frequently twins—every six months or so.

After mating, the gestation period lasts approximately 150 days. Her twins are already weaned at three days old. Their juvenile stage lasts between three and twelve months, and they are considered subadults between 12 and 15 months. Both males and females are sexually mature by 15 months of age.

While examples of alloparenting are regularly observed in several other tamarin species, it is unclear at this time how frequently it occurs in Weddell’s saddle-back tamarin groups. However, given their more egalitarian group dynamics, one might hypothesize that this is common practice.

Photo credit: ©Zach Baranowski/iNaturalist/Creative Commons

Ecological Role
Weddell’s saddle-back tamarins are adaptable, exploiting multiple niches in order to nourish themselves. Therefore, though such research remains scant for this species, these monkeys may play several potential roles in their eco-systems.

As frequent fruit eaters, they may ingest seeds that are then spread via their feces as they travel through the forest. Small monkeys that feed on the nectar of plants, like tamarins, are sometimes responsible for flower pollination. Additionally, this species’ hunting of small critters may or may not have an impact on those populations.

Conservation Status and Threats
The Weddell’s saddle-back tamarin is classified as Least Concern by the International Union for Conservation of Nature (IUCN, April 2020), appearing on the IUCN Red List of Threatened Species. The white saddleback tamarin subspecies is also listed as Least Concern (IUCN, 2020). The Crandall’s saddleback tamarin is listed as Data Deficient (IUCN, 2015) as no information is available on the population status or threats of this subspecies.

Overall, the Weddell’s saddle-back tamarin is highly adaptable and faces no major threats. As such, these tamarins continue to thrive throughout its natural range.

Tamarin species are often traded as pets indiscriminately, a practice detrimental to them as individuals and species. Though there is no indication that Weddell’s saddle-back tamarins are of unique concern in this regard, it should be noted that tamarins—and primates in general—do not make good pets.

Primates who end up as pets, either as a result of poaching or captive breeding, are doomed to suffer a miserable life lacking proper upbringing, socialization, and nutritional needs. This often causes irreparable damage to them emotionally, mentally, and physically.

Primates raised as pets cannot return to the wild without proper rehabilitation. Even then, mortality rates are high. Depending on the species and the individual, it can take years before they are ready to be released—if they are ever ready at all.

Conservation Efforts
The Weddell’s saddle-back tamarin is one of the few primate species in the world whose situation is far from dire. This species is already found in multiple areas of various protection status throughout their range in Peru, Bolivia, and Brazil, where it continues to thrive.

Since its taxonomy has recently changed, the IUCN does note that the Convention on International Trade in Endangered Species (CITES) Appendix II should be updated to list the Weddell’s saddle-back tamarin.

Regardless of its current status, it is important to keep in mind how tenuous these situations are, even when they look perfectly fine. While Weddell’s saddle-back tamarins find themselves in a uniquely favorable situation for primates thanks to their exceptional adaptability, their status always has the potential to change. Keeping tabs on this species through regular surveys—and learning about what makes this species unique through research—is necessary to ensure that its future remains bright.

References:

  • https://www.iucnredlist.org/species/160939221/192315781
  • https://www.iucnredlist.org/species/160885500/192315580
  • https://www.alltheworldsprimates.org
  • https://www.semanticscholar.org/paper/Taxonomic-review-of-the-New-World-tamarins-Rylands-Heymann/f36c98d3ce5134fa6263417be9c5e2d22901c8a1
  • https://www.zootierliste.de/en/index.php?klasse=1&ordnung=108&familie=10813&art=1070417
  • https://www.proquest.com/openview/e3572071bf6de140f123caebd5f3e789/1?pq-origsite=gscholar&cbl=54193

Written by Zachary Lussier, September 2021