This website was completed by John Doehring in partial fulfillment of the requirements for Biology 323, Animal Behavior, at Davidson College in the Spring Semester 2007.

Golden Lion Tamarin

(Leontopithecus rosalia)

Social Relationships

Food Sharing (Provisioning)

Golden lion tamarins differ from most primates in that they engage in food sharing rather than compete for food resources.  Food sharing occurs between siblings as well as between adults and offspring.  Several hypotheses have been proposed for this behavior as it contrasts with predicted evolutionary tendencies.  The most likely is the nutritional-benefits hypothesis which states that provisioning is needed to allow young to obtain an adequate protein/lipid content in their diet.  The assistance is needed because offspring are occupied, devoting their time and energy to mastering complex foraging techniques and learning to identify appropriate food items (Rapaport, 2005).  Research has shown that insects are more readily shared than common foods such as fruit.  Furthermore, adults and juveniles are more willing to share food resources with and initiate food calls to younger offspring than with older individuals (Jolly, 1985).  These trends indicate that the younger offspring are not yet adept at procuring the protein-rich foods such as insects and selection pressures favored adults who shared.  Common and frequent food sharing has been observed in only a few species, however, it is observed in most Callitrichines; Leontopithecus exhibits the most generous provisioning of all Callitrichines.  By far the most common food resource transfers among most primates occurs when dominant individuals force subordinate, elderly, younger, or weaker individuals to relinquish what food resources they have obtained (Smuts, et. al., 1987).

Allogrooming

Allogrooming is commonly observed between all group members.  This behavior simply consists of one individual running his or her fingers through the fur of the “groomee”  Allogrooming is asymmetrical, however, in that females receive grooming more often than males and breeding, dominant females are favored as breeding partners.  Additionally, research has shown that young individuals within the group are often the initiators rather than the receivers (Hoage, 1982). 

While the group functions as a cooperative unit, there are two established dominance hierarchies for both males and females.  An individual’s position in the dominance hierarchy directly correlates with how often that individual will have reproductive opportunities (Mason, 1993).  The hierarchy between males is much more stable if the males are related.  Additionally, breeding males are more inclined to share reproductive responsibility with unrelated subordinates than with related subordinates (Bales, et. al., 2006). 

Female-Female Relationships

The primary concern of the female golden lion tamarin is obtaining food resources.  Securing food results in earlier maturation, which allows for better lactating abilities, which contributes to bigger babies, and thus offspring that are more likely to survive (Jolly, 1985).  When attempting to procure food resources females within groups can become extremely aggressive towards one another.  The breeding female is also the dominant female.  Subordinate breeders and other subordinate females will constantly supply the breeding female with food so that her reproductive fitness is ensured.  Reproductive suppression of subordinate females is routinely carried out by the dominant female.  This suppression is aggressive and physical attacks by dominant females on subordinate individuals have been regularly witnessed.  Often the more dominant females will facilitate the extrication of subordinate females from the group, regardless of relatedness (Jolly, 1985).  Females constitute a threat to one another because of competition for obtaining food and attaining a higher status.  Female-female relations in golden lion tamarins are much more aggressive than is observed in males.  Captive lion tamarin mothers have even been observed killing their daughters (Jolly, 1985).  Though aggression between females is high, subordinate females do not show increased stress levels.  Research has shown that cortisol and other glucocorticoid levels remain constant among all female group members, regardless of breeding or social status.  This is most likely due to the high level of social support within the group and outlet options available for subordinates (Bales, et. al., 2005).

Photo courtesy of Lisa G. Rapaport

Infant-Carrying

Golden lion tamarins are infant-carriers, meaning that the adults serve as transporters for the young who have yet to develop sufficient climbing abilities.  The offspring, usually twins, cling to the back of the adult as he or she moves around.  The continued exposure of this behavior to the juveniles is believed to function as a teaching method.  If the juveniles are not exposed to this behavior they will neglect or even kill their own offspring once they become of reproductive age (Jolly, 1985).  Therefore it is of increased importance that the juveniles linger with their natal group, as the practice must be learned and is not instinctual.  Both males and females carry infants and one study has even demonstrated that males carry infants more often than females.  This is most probably observed because females are forced out of the group earlier due to reproductive suppression - thus males on the whole are exposed more often to the behavior (Jolly, 1985).  Research also indicates that males are more likely to carry related infants while females exhibit no preference.  It would seem that kin altruism (inclusive fitness) would not be the basis for this alloparenting behavior because there would be no explanation for why females show less preference.  It has been suggested, however, that because females are extricated from the group earlier than males they tend more often to be in groups of a higher degree of unrelatedness.  Although emigration by males does occur, this may serve as an explanation for why males are more willing to carry infants (Solomon, 1997).

Any questions regarding the content or design of this website should be sent to John Doehring or to Dr. Verna Case, Chair of the Biology Department at Davidson College.