The golden-headed lion tamarin (Leontopithecus chrysomelas), also known as the golden-headed tamarin, is a lion tamarin species endemic to Brazil. It is found exclusively in the lowland and premontane tropical forest fragments of Bahia, making it an endangered species. This article delves into the dietary habits of this fascinating primate, its foraging behavior, and the critical role it plays in its ecosystem.
Habitat and Social Structure
Golden-headed lion tamarins inhabit mature humid lowland and secondary forests, typically residing at heights of 3-10 metres (9.8-32.8 ft). The species prefers mature forests, but due to habitat destruction, they are not always found in optimal conditions. Their home range can span 52-180 acres (21-73 ha). They navigate the closed canopy of the forest, moving bipedally and using their long fingers for support.
These animals live in groups ranging from 2-11 individuals, most often with more than one adult of each sex. A group often consists of a breeding pair, offspring of 1 or 2 litters and possibly other relatives. Golden lion tamarins breed within their group, which includes a single breeding (dominant) female which may mate with a single male (monogamy) or 2 or more males (polyandry); also, there may be breeding by multiple females, usually daughters of primary breeding female. Gestation is 125-130 days, with births peaking in the 2-3 months in early to mid-wet season, during high fruit availability-due the high cost of lactation and carrying the infant. These animals give birth to dizygotic twins, with an average weight of 60g (the twins weight being 20% of the mother’s body weight. In the wild they usually give birth once/year. Infants are carried by an adult, most often the father, but infant carrying can be shared by the mother or other adult males in the group.
Golden-headed lion tamarins are territorial, defending their area through scent markings and vocalized threats. They use a variety of vocalizations to communicate with group members. High-pitched calls and squeaks are used to warn intruders and alert group members to predators. Different calls are used for predators in the air (like hawks) and predators on the ground or in the trees.
Dietary Diversity
The golden-headed lion tamarin is an omnivore with a very wide diet, consuming plants, fruits, flowers, nectar, insects, and small invertebrates. This includes insect larvae, spiders, snails, frogs, lizards, bird eggs, and small snakes. Typically, fruits are eaten shortly after awaking, as the fruit sugars provide quick energy for hunting later on.
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Raboy and Dietz observed that the golden-headed lion tamarin tends to defend a large home range relative to its small body size, ranging from 40-320 hectares. It searches for animal prey within epiphytic bromeliads; if its home range does not contain many bromeliads, then it will also forage in crevices, holes in trees, between palm fronds and in leaf litter. It occasionally eats gum, but this behavior is rare in this species of tamarin.
Foraging Behavior
The golden-headed lion tamarin spends much of its time foraging and traveling within its home range to the next foraging site. A study showed that in the wild the golden-headed lion tamarin spends about 50% of its time in only 11% of its home range. Its ranging patterns appear to be strongly influenced by resource acquisition and much less by territorial defense.
The groups showed very few encounters with neighboring groups, but when it did occur, the encounters were always aggressive, and included intensive bouts of long-calling, chases, and fights between the different groups. The home ranges defended by these tamarins average around 123 hectares.
The Role of Food Transfers
Food sharing is more important in the lion tamarins than in other marmosets and tamarins, and helps maintain social structure. Food transfers are often accompanied by food-associated calls. In captivity, infants are more likely to obtain food from an adult, when adults produced food calls (golden lion tamarins: Brown and Mack 1978; Ruiz-Miranda et al. 1999; cotton-top tamarins: Joyce and Snowdon 2007; Roush and Snowdon 2001). Those vocalizations may play an important role in directing the juveniles’ attention towards food, and may be a form of information donation about what food to include in the diet, on which substrate to focus, or how to communicate about food (Rapaport, 2011; Rapaport and Ruiz-Miranda 2002; Roush and Snowdon 2001; Troisi et al.
In golden lion tamarins, a species of Callitrichidae, adult-juvenile food transfers seem particularly important for the development and survival of the young as juveniles are dependent on others to receive their first solid foods, and initially receive most of their solid food from food transfers. Golden lion tamarins are an ideal species in which to study teaching, as they are cooperative breeders, meaning that the relatedness between putative teachers and pupils is high, and that the cost of putative teaching is shared amongst several individuals. They also hunt individually for relatively large prey, suggesting low opportunities for inadvertent social learning (Rapaport 1999). They have a broad diet, with ephemeral and patchily distributed food sources, creating a need during ontogeny to rapidly learn what food are good to eat (Dietz et al. 1997). Given their high reproductive turnover, and short maturation period, teaching could be a strategy to speed up the learning of essential foraging information, and reducing the burden of provisioning young by hastening the transition to independent foraging (Troisi et al. 2018). Moreover, there is already some evidence supporting teaching in golden lion tamarins in another foraging-related context. Rapaport (2011) and Rapaport and Ruiz-Miranda (2002) suggest that adults may use food-offering calls, a vocalization often emitted prior to food transfers, to indicate a substrate where the juveniles can find prey. Furthermore, although the evidence was rather weak and based on small sample sizes, Troisi et al.
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In the wild, food items that are voluntarily transferred to juvenile golden lion tamarins are more likely to be vertebrate and invertebrate prey (Ruiz-Miranda et al. 1999) than fruits. In a captive study with lion tamarins, Price and Feistner (1993) found that when food items are more difficult to acquire for juveniles (out of reach), and when items are presented singly (rare) rather than all at once, food transfers from adults to young increase and so did the adult’s response to juvenile begging. The results from this captive study suggest that food transfers in lion tamarins allow juveniles to receive adequate amounts of food. In the wild, reintroduced animals were also found to transfer a high number of provisioned bananas, an easily obtained food, further supporting the nutritional hypothesis (Ruiz-Miranda et al. 1999). However, another study on captive golden lion tamarins by Rapaport (1999) found that novel foods (be they novel to all individuals or novel to the young but familiar to the adult) are transferred to juveniles more than familiar ones. This would support the informational hypothesis, since experience of novel food items will provide more valuable information to juveniles about which foods to eat. However, Price and Feistner (1993) found that although juveniles ate less of the novel food, this pattern was not compensated by an increased transfer of those foods from adults to juveniles. This second result suggests that food transfers are not used to transmit information to juveniles about what to include in their diets. The seemingly contradictory results between Rapaport (1999) and Price and Feistner (1993) could highlight the dual role of food transfers in golden lion tamarins depending on the juveniles’ age. In Price and Feistner’s (1993) study, the juveniles were younger (7-21 weeks) than in Rapaport’s (1999) study (13-37 weeks). Plausibly, young juveniles, who sustain a high growth rate, might primarily receive food that they would not be able to acquire otherwise (nutritional hypothesis), while older immature individuals might mainly receive food that they have not sampled yet (informational hypothesis). By changing their behavior (first criterion), adult golden lion tamarins might teach the young what to incorporate in their diet.
An experiment was conducted to examine whether golden lion tamarins teach their young what to eat using food transfers. The researchers first wanted to see if Rapaport’s (1999) findings hold in the wild, i.e., whether adults modify their food transfer behavior in the presence of juveniles (first criterion of the teaching definition). If food transfers were mainly for nutritional purposes, we would expect that the food novelty has no impact on the pattern of transfers: either all food items are transferred equally, or the most nutritious food are preferentially transferred. If transfers serve mainly for an informational objective, then we would expect the probability of success of an attempted food transfer (i.e., proportion of attempts in which the recipient receives food) involving a food that is novel to the receiver to be higher than the probability of success for familiar food, thereupon giving the juvenile the opportunity to learn. The researchers also further investigated the role of the donor and receiver in food-transfer patterns by examining the decision of juveniles to attempt a food transfer and the decision of adults to resist those food transfers. They then wanted to examine whether juveniles learn from the food transfers (the third criterion of the teaching definition). If juveniles learn from food transfers, then we would expect that their experience with food through food transfers is more important in predicting their future food choice than other experience with food (such as eating food independently).
Different food types were introduced to groups of wild golden lion tamarins in their natural environment over two time periods (thereupon “phases”) to evaluate which factors would affect the transfer of food between individuals, particularly between adults and subadults (thereupon adults) and juveniles, and understand the role of transfers in future food choices. At the time of first exposure (January-February 2014), this provided the opportunity for adults to transfer food to juveniles and for juveniles to learn about the different food types, both independently, and from social interactions (first phase). This first phase was conducted during the second half of the wet season (Dietz et al. 1994). Seven months later (August-September 2014), just before the start of the wet season (Dietz et al. 1994), the researchers assessed how previous experience with the different food types influenced juveniles’ food choice once they were independent foragers (second phase).
Six readily accessible groups of wild golden lion tamarins that were habituated to regular human contact and consistently monitored, in Silva Jardim municipality, Rio de Janeiro, Brazil were studied. Three groups were at the Poço das Antas Biological Reserve, and three groups were in a fragment of Atlantic forest at the Fazenda Afetiva-Jorge, Imbaú region. At the start of the experiment, 42 individuals from those six different groups participated in the experiment, including ten juveniles between 4 and 5 months old. Each study group had one or two juveniles (golden lion tamarins often give birth to twins). This age range was chosen because juveniles are still dependent on adults for provisioning, and is in line with previous captive studies (Price and Feistner 1993; Rapaport 1999). Group AF2 lost both juveniles during the first phase of the experiment (after four valid trials), and before the start of the second phase of the experiment group Alone lost one juvenile. Thus, all…
Conservation Status and Threats
The IUCN Red List categorized the golden-headed lion tamarin as endangered in 1982. The forest of Bahia, Brazil has been reduced to 2% due to farming, ranching, mining and urbanization. The Atlantic Forest is highly fragmented, and the disappearance of this habitat is the main reason for the golden-headed lion tamarin's decline. The majority of the forest was once dominated by cocoa plants through a method known as cabruca. This is a system of shade cropping in which the middle and understory trees are removed and replaced with cocoa trees. Although the tamarin's habitat is reduced, it still leaves old growth trees which give the tamarins a place to forage and to sleep. In 1989 farmers abandoned their cocoa plants due to a fungus that attacked their harvest.
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The greatest threats to these tamarins are deforestation and habitat loss. Only one to five percent of Brazil’s original Atlantic forest remains. The population size of this species in the Una Biological Reserve (Bahia, Brazil) is around 400-450 individuals.
Conservation Efforts
In 1980 the Brazilian government created the Una Biological Reserve for the protection of the golden-headed lion tamarin and its habitat. Over the years the park has been growing slowly as the government acquires more land. The population at Una is the largest population in the most intact forest. There is also a captive breeding colony of 25 golden-headed lion tamarins at the Rio de Janeiro Primate Center.
In the early 1990s, the Landowner's Environmental Protection Plan was created to educate the community about the importance of protecting the forest and the tamarin. The protection plan included conservation activities on over 70% of the neighboring farms, educating farmers on how to use sustainable agriculture in order to preserve the tamarin's habitat. The plan also educates school children, hunters and forest guards on conservation, property rights and land use.
Between 1985 and 1991 IBAMA established four International Recovery and Management Committees (IRMCs). Public concerns of the tamarin species occurred in the 1960s when Adelmar Coimbra-Filho brought to the attention the rapid declines of the golden lion tamarin due to exportation and habitat destruction. His input helped with the establishment of the biological reserves to protect lion tamarins. He founded the Rio de Janeiro Primate Center and he was the first person to breed the golden-headed lion tamarin.
From 1983-1994 large numbers of golden headed lion tamarins were exported to Japan and Belgium as part of the exotic pet trade. IBAMA asked Jeremy Mallinson to form and become chair of an IRMC for the golden-headed lion tamarin. The initial objective of the committee was to have all of the tamarins returned to Brazil, and some of them were returned.
The IRMC is divided into several tasks which include the captive management and research program, conservation and education program in Bahia, a Landowner's Environmental Education Program, and a field study of ecology and behavior in the Federal Una Biological Reserve.
Ecological Role
Golden-headed lion tamarins play a very important role in seed dispersal. They eat many different fruits which have seeds. Recent research has demonstrated that marmosets and tamarins play a significant role in seed dispersal. Many of the fruits they eat have seeds that pass through the monkey's digestive tract unharmed and end up deposited well away from the parent plant. The seeds may also help to dislodge intestinal parasites in the monkey's digestive tract.
This species may form mixed species groups with Wied's black-tufted-ear marmoset. They do not compete with each other because they forage in separate areas and occupy different niches in the environment. Golden-headed lion tamarins forage in the upper levels of the forest, while Wied's black-tufted-ear marmosets forage in the middle and lower levels of the forest.