The Goeldi's marmoset or Goeldi's monkey (Callimico goeldii) is a small, South American New World monkey that lives in the upper Amazon basin region of Bolivia, Brazil, Colombia, and Peru. It is the only species classified in the genus Callimico, and the monkeys are sometimes referred to as "callimicos".[5] The species takes its name from its discoverer, Swiss-Brazilian naturalist Emil August Goeldi.[6]
Goeldi's marmosets are blackish or blackish-brown in color and the hair on their head and tail sometimes has red, white, or silverly brown highlights.[7] Their bodies are about 8–9 inches (20–23 cm) long, and their tails are about 10–12 inches (25–30 cm) long. They weigh about 0.4835 kg in captivity and 0.500 kg in the wild. Their digits have claw like nails except for the hallux, which serve for clinging, scansorial travel, and to extract food from trees.[8][5][9]
Goeldi's marmoset was first described in 1904, making Callimico one of the more recent monkey genera to be described.[1] In older classification schemes it was sometimes placed in its own family Callimiconidae[10] and sometimes, along with the marmosets and tamarins, in the subfamily Callitrichinae in the family Cebidae.[1] More recently, Callitrichinae has been (re-)elevated to family status as Callitrichidae.[3][2]
Molecular phylogenetics shows that C. goeldii evolved from an ancestral callitrichine and shares this origin with marmosets making them sister taxa. One evolutionary argument to account for their differences, states that C. goeldii conserves primitive traits such as single births and a third molar lost in many marmosets. Alternatively, another evolutionary argument indicates that Callimicos came from a two-molar marmoset and reintroduced the remote traits, which in either case selectively give them the ability to access to different resources and occupy different niches.[11][5][12] Similarities in delayed embryonic development and secondary limb-bone ossification between C. goeldii and marmosets are evidence of their close evolutionary relationship.[13]
Females reach sexual maturity at 8.5 months, males at 16.5 months. The gestation period lasts from 144 to 159 days. Callimicos studied in captivity in North America and Europe for near 40 years have shown to produce on average 3.5 offspring during their lifetime. However, 30% of the females and 45% of the males observed in these settings never reproduced.[14]
Unlike other New World monkeys, they have the capacity to give birth twice a year.[14] Biannual births occur regularly in captivity and less consistently in the wild and are attributed to postpartum estrus that allows the female to be ready to reproduce soon after parturition. The availability of fungus -an important food source for C. goeldii- throughout the year also contributes to these multiple births.[15][13]