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An Unlikely Intervention: The Importance of Human Involvement in Saving Brazil’s Golden Lion Tamarin

The Golden Lion Tamarin’s Plight

The golden lion tamarin (GLT), scientifically referred to as Leontopithecus rosalia, is quite a striking species. This animal’s majestic golden coat and flowing mane have probably caught your attention at your local zoo; a large population of GLT’s today have been raised in captivity because their population in the wild has dropped significantly over the last century due to predation and deforestation by humans. However, there is still time to reverse the damage done. Humans, although the cause of the GLT’s struggle, are now the last hope in ensuring this small, highly vulnerable primate’s survival for years to come.

Over the last few decades, much of the golden lion tamarin’s home has been cleared. Its total area was once 1,315,460 km² and dropped to only 275,800 km² in 2015, the remaining area spread in patches throughout 17 different states . This makes survival difficult for the golden lion tamarin since it is dependent on this rare habitat for its survival. The tamarin was listed as critically endangered in 1982. At this time there were only approximately 200 left in the wild . 

Habitat fragmentation has resulted in no forest fragment being large enough to maintain viable populations of GLTs . A solution to this would be to connect these forest fragments in order to ensure appropriate patch size and shape, water levels, dispersion, amount of vegetative cover, and diversity. Creating habitat corridors is one way of doing this, but such a project needs to be carefully planned and monitored because fire, invasive species, disease, and predators could also use these passages . The golden lion tamarin association in Brazil, AMLD, has established such areas already and is working to create more. In 2013, AMLD planted native trees across 504 acres of fragmented forest to connect these areas and expand future GLT habitat .

GLT Habitat and Conservation

The GLT has become a national symbol for the conservation of Brazil’s Atlantic Rainforest and many conservationists are devoting their lives to its wellbeing. The biological reserve Poco das Antas has played a huge role in recent successes. This 5,052-hectare reserve is located in Rio de Janeiro, Brazil, and was established as a haven for these animals . The work of those involved has resulted in a GLT ‘insurance population’ — a population of individuals that are not only healthy enough but supported and trained enough to be successfully released into the wild and survive after being cared for in captivity. The GLT insurance population numbers some 500 individuals across 150 zoos worldwide; these animals are valuable in helping AMLD reach its goal of having at least 2,000 GLTs living in 25,000 hectares of connected and protected forest habitats by 2025. 

Having 2,000 GLTs spread across this amount of land will result in fewer genetic and reproductive problems for the species and a lower risk of disease and mass losses due to predation . This is because there will be more space for GLTs to inhabit. They can therefore spread out, making it less likely that there will be inbreeding depression – a situation that arises when a population’s genetic diversity decreases to the point that the majority of animals wind up with unfavorable genes that can result in a loss of vigour, fertility, and ultimately physiological efficiency . Additionally, there will be a lower risk of disease and mass losses from predation because having more space between these groups decreases the likelihood that a catastrophe hitting one group of GLT’s will hit neighboring groups as well.

It is valuable to focus on how GLTs use their habitat since the space they have is now so limited. GLTs are arboreal and live in the subcanopy of the rainforest, where they use their long tails for balance when climbing and sleep in tree cavities . These primates prefer to use swamp forest as opposed to areas consisting of more hillside forest and pasture, likely because of the availability of foraging habitats rich with palm leaves, vines tangles, tree bark, and tropical flowering plants known as bromeliads . GLTs use their elongated hands and fingers to reach prey hidden in these crevices. These microhabitats are critical to GLT survival because they differ from their surrounding habitat and contain prey species–such as frogs, lizards, snakes, nestling birds, and snails–that are not found in the larger area. These swamp areas also have more tree cavities available to tamarins as sleeping sites than hillside forests do .

Density of golden lion tamarin populations is regulated by the prevalence and distribution of keystone plant species, which are species that are heavily depended on by a variety of other species in their ecosystem and without which that area would change drastically. These particular species are vital in providing temporal stability, meaning that they help to stabilize local temperature and humidity . One example is the bromeliad, which provides temporal stability and is also used for foraging and as a water source for GLTs and other species in the area. Unfortunately, though, bromeliads are costly to establish in restoration areas due to limited seed dispersal and a lack of suitable transplant sites. One solution is to transplant bromeliads from much older forests into these new restoration sites because these mature bromeliads are larger and therefore more established and effective in performing their role as a keystone species.

Tamarin home range is correlated with biomass rather than group size, meaning that the amount of living matter in an area is the primary factor in determining home range. Findings show that these primates require a larger home range than other New World monkeys. This is likely due to a greater availability of cryptic prey—prey, often small invertebrates, that is well camouflaged . With this in mind, groups in higher quality habitat with increased foraging opportunity will generally have smaller home ranges than groups in poor quality habitat . As golden lion tamarin group size increases, groups will travel further and occupy larger home ranges. This is based on their survival and reproductive needs. Small populations are more vulnerable than larger populations because they are more likely to face detrimental losses from threats such as environmental catastrophes and loss of genetic variation .

An additional threat for all GLTs is predation, usually by snakes and wild cats. Increased predation generally means decreased home range size. Since the 1990s, the rate of predation on GLTs has risen. It is increasingly common for predators to wipe out entire groups rather than single individuals, as was more common in the past . It is believed that this is due to habitat loss and therefore less available hunting ground for predators. However, it is still unclear which species is responsible for the increased carnage as no cameras have been able to capture these events in action.

GLT Behavior and Conservation

Golden lion tamarins typically do not get along well with neighboring groups of their own species. In fact, resident tamarins act aggressively towards potential immigrants, making immigration into established groups of golden lion tamarins rare; this usually only occurs for breeding purposes. The hostility between separate groups prevents the movement of outsiders into already established groups, limiting their size further . Due to these factors, the average group size for golden lion tamarins is about six individuals . These individuals live in family groups with a female and a male, their most recent offspring, and sometimes the prior offspring, who help to take care of the younger siblings . Unlike in many other species, golden lion tamarin males and females play an equivalent role in raising their young: Both parents carry infants, provide food, and act as sentinels for predators. This care will typically continue well into the first year of their offspring’s life .

Golden lion tamarins often use scent-marking as a way to communicate territory ownership. To scent-mark an area, golden lion tamarins use sweat glands located on their chests and bottoms . It is mainly the alpha females who will mark areas to advertise their presence and deter potential immigrants who could steal their mates, because neighboring females are seen as a threat to their own social positions . In fact, most golden lion tamarin groups contain only one reproductive female. If ever there are two in a group, they would likely be sisters or mother and daughter . Males, on the other hand, tend to only use scent-marking as a way to facilitate relocation of food resources within their own groups .

Implications and Challenges of Captive GLT Breeding

Saving golden lion tamarins is heavily dependent on being able to breed them in captivity and then reintroduce them to the wild. These New World primates are able to breed about twice a year in the wild and three times a year in captivity with a gestation period of about four months. The increased frequency in breeding provided by captivity is one of the reasons captive breeding programs are so important for GLTs. Increased breeding means faster population growth.

It is important to consider the behavioural ecology of GLTs when raising them in captivity. For example, hand-raising GLTs is problematic because, in most cases, hand-raised offspring will become psychotic once reintroduced to the wild; they are doomed to lead solitary lives because they are unlikely to be accepted into another group and GLT parents will not typically surrogate or foster. The loneliness will then cause them to engage in self-mutilating behaviors, such as chewing off their own tails . This is why it is so important to reintroduce captive-raised golden lion tamarins to the wild in groups as opposed to as individuals. By doing this, the individual is guaranteed a family and is unlikely to engage in these negative behaviors.

In order to breed and effectively reintroduce captive GLTs back into their natural habitat, there needs to be an understanding of the behavioral competency of these captive-born animals– that is, their ability and the skill-set required to survive in their environment. Thus far, upon initial reintroduction, they have been shown to be deficient in locomotor and foraging skills when compared with wild-born tamarins . A life in captivity is not fully able to prepare them for the challenges of surviving in their dwindling natural habitat and leaves them ill-prepared for interacting with wild-born neighboring groups, who are likely to act with hostility. A study conducted on a reintroduction effort in 1991 found that only 29 of 85, or 34%, of reintroduced golden lion tamarins survived . At the time of this study, exotic pet trade was very popular. Therefore, many of these losses could be attributed to human theft because reintroduced GLTs are more acclimated to humans and, as a result, they are less fearful and consequently more vulnerable to capture. Fortunately, AMLD has been working tirelessly for the last 3 decades to educate the public and create a conservation ethic in this area, greatly slowing the capture of GLTs for pet trade. 

Additionally, captive-born golden lion tamarins are more susceptible to predation by animals since a life in captivity has left them lacking in survival skills and with little to no awareness of their natural predators . This is why reintroduced populations are closely monitored by conservationists via tagging, cameras, and regular supervision and support. These first few months are the most difficult and require the most human intervention. However, once the reintroduced tamarins survive this period, most are able to adapt to these new challenges throughout their first and second years back in the wild, and their offspring show no signs of lacking survival instincts. In other words, captivity does not have a permanent effect on their behavior or attentiveness to predators . They are capable of fully acclimating to their natural environment over time.

Humans: The Final Hope for GLTs

In light of these initial struggles, it is important that reintroduction programs work on creating more complex, naturalistic environments that simulate natural patterns of behavior, or at least can provide adequate post-release support for captive-born golden lion tamarins. This post-release support would include ensuring that there is a dependable food source/foraging habitat for the species, that they have the medical care they need as they adapt to their new, wilder, and unpredictable surroundings, and that they have nest boxes to provide them with shelter and safety.

Extensive, prolonged pre-release training and conditioning has been found to be ineffective if GLTs spent the majority of their pre-release years in relatively small cages or enclosures. However, living in a large, protected, wooded area such as that of a zoo has proved to be advantageous . This is why 150 zoos worldwide have a partnership with AMLD and are working to breed GLTs and prepare them for reintroduction into the wild.

As mentioned above, the offspring of reintroduced golden lion tamarins do not appear to have any disadvantage when compared to those born to wild parents . What this means is that the success of reintroduction as the means of sustaining this population is heavily dependent on exposure to a realistic, free-range environment and extensive post-release support and training. In this way, the reintroduced parents have a better chance at survival and therefore at reproducing in their natural environment. They can then, bit by bit, rebuild a lasting population. 

*Donate to SGLT, the American partner of AMLD Save the Golden Lion Tamarin is a public charity focused on providing technical and financial support to help Associação Mico-Leão Dourado (AMLD or Golden Lion Tamarin Association) If you would like to support this cause, please donate at https://www.savetheliontamarin.org/donate