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)

Mating System

Golden lion tamarins have been described as monogamous, polygynandrous, polyandrous, and polygynous.  However, the most compelling evidence supports polyandry as their mating system.  There are usually more reproductive males present in the group due to aggressive relations between females and their tendency to disperse earlier.  A sex ratio favoring males and the absence of sexual dimorphism also contributes to polyandrous mating (Frantom, 1999).  Additionally, the relative abundance of food resources precludes the potentiality of monogamy in most cases.  There is usually a single breeding, dominant female who gives birth to all the offspring.  The gestation period is 130 days and like many other Callitrichines golden lion tamarins often give birth to twins.  An interesting difference between golden lion tamarins and other tamarin species are the reproductive hormone levels found in female subordinates.  One would expect to find lower estrogen levels in subordinates; however, in golden lion tamarins subordinate breeders tend to have higher levels of estrogen than the dominant breeding female.  Therefore, the reproductive suppression of these individuals is exclusively behavioral and there is no physiological or endocrinal suppression observed as in most other tamarin species (Solomon, 1997).  This is consistent with stress level studies (Social Spacing). 

Golden lion tamarins are cooperative breeders as they have the three classical diagnostic features of cooperative breeding species:  (1) delayed dispersal of offspring, as many remain to assume a helping role, (2) alloparental care of offspring, and (3) delayed breeding by subordinate individuals (Solomon, 1997).  Cooperative breeding behaviors of the entire group are examples of kin altruism.  Because members in the group tend to be related (though emigration between groups slightly dilutes this influence) both helpers and “helpees” (the young and the breeding female) have similar genes.  Therefore, a helper who contributes to the reproductive fitness of the breeding female increases his or her own inclusive fitness, as the sacrifice in perpetuating his or her genes is compensated for and exceeded by the reproductive fitness gained by the helpee (Solomon, 1997).

Golden lion tamarin males are also behaviorally exceptional in that the alpha males exhibit a surprising amount of tolerance toward the breeding female who mates with multiple males.  This behavior contrasts with that of most primate species.  The alpha male, while monopolizing the majority of copulations with the breeding female, does not act antagonistically towards either the female or the other males.  This behavior is further perplexing in light of the linear dominance hierarchy among males in the group.  One possible reason for this tolerance is that subordinate males are more likely to engage in helping behaviors (caring for young) that benefit the alpha male and the group if he has a better chance to mate with the female.  The subordinate male, in turn, may prefer this behavior to facing the associated risks with leaving the group (Strier, 2007).  As a result, there are usually two breeding males in one group (Mason, 1993).  Additional support for polyandry as the mating system among golden lion tamarins is their larger testis size compared to similar Callitrichids; research has shown that multi-male groups consistently exhibit larger testis size relative to their body weight (Harcourt, et. al., 1997).

Research has also shown that breeding females employ an energy-reducing strategy during times of pregnancy and lactation.  Breeding females are much more active during non-reproductive times as they will obtain more of their own food and sleep less.  However, during reproductive periods, the cooperative group works harder to ensure that her needs are taken care of and thus she will sleep more often and assume a sedentary lifestyle.  This decreases her energy expenditure and contributes to her reproductive success (Miller, et. al., 2006).

Photo courtesy of Roy Fontaine

Infanticide

Although the practice is not as readily observed as in other primate species, golden lion tamarin males at time commit infanticide.  One theory about this practice may explain in part the polyandrous mating system in golden lion tamarins.  The theory argues that females “employ” polyandry as a counter-strategy to occasional infanticide performed by males (Kappeler, et. al., 2004).  A male will kill an offspring if he suspects he is not the father of the offspring.  Thus, infanticidal behavior is dependent on paternity certainty.  The female will mate with multiple males so as to dilute the paternity certainty of each male.  The males involved will then be rendered less likely to commit infanticide.  Infanticide among golden lion tamarins is observed more often than in other tamarin species.

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.