Olalla Brothers’ titi (Callicebus olallae)

Also known as: Beni titi monkey, Olalla’s titi, Olalla’s titi monkey
GenusCallicebus (1)

Classified as Endangered (EN) on the IUCN Red List (1) and listed on Appendix II of CITES (2).

One of the rarest titi monkeys, the Olalla Brothers’ titi is restricted to a tiny tract of lowland Bolivian gallery forest (1). An attractive, small-bodied primate, the Olalla Brothers’ titi has an elongated tail, a dense pelage of long, soft hairs, and a small, rounded head with a flattened face (3). A blackish facial fringe, an orange coloured back and limbs, and small, inconspicuous white ear tufts distinguish the Olalla Brothers’ titi from closely-related species (4) (5). The tail is a contrasting black with alternating bands of reddish-brown (4) (5). 

The Olalla Brothers’ titi is endemic to the southwest of the Beni Department, Bolivia, where it is found near the Yacuma and Manique Rivers (1). This monkey is believed to have one of the highest levels of primate endemism in the world, with a total range of only 50 to 400 square kilometres (6). The species’ range is confined in the west by the vast Rio Beni River and to the east by a road. The Olalla Brothers’ titi has become extirpated from much of its former range, and a population that was once found around La Laguna is now considered extinct (5).

The Olalla Brothers’ titi is found in humid, evergreen forests bordering rivers and wetland habitat, and in forests on river islands (1).

Rarely descending to the ground, titi monkeys traverse the canopy with a distinctive gait, skilfully climbing through the branches on all four limbs. While resting, titi monkeys hunch the body, hanging the tail vertically over a branch. From this position they can use the powerful rear limbs to jump spectacular distances, grasping onto branches with leading forehands. Titi monkeys forage during the day for fruits, leaves and insects, resting during midday, and sleep on carefully selected trees that offer safety from predators at night (3). The male leads the group whilst foraging, communicating to the rest of the group with a wide array of vocalisations and visual signals (3). 

Titi monkeys are monogamous, with groups consisting of strongly-bonded parents and their offspring. Partners often reinforce the pair bond by perching side-by-side and entwining tails. Females give birth annually during the wet season to just one infant, after a gestation period of five to six months (7). Juveniles grow rapidly to reach adult size within ten months (3). 

Already restricted in range, the Olalla Brothers’ titi is threatened by further habitat loss and hunting (1). Many groups are found in isolated, relict forest patches surrounded by cattle ranches and agricultural grasslands, limiting the species’ natural dispersal. Hunting pressure also exists throughout its range, as some indigenous groups of people still rely on subsistence hunting of primates, and its skin and fur may be used to make rope and thread. Hunting is particularly intense during the annual Brazil nut harvest when workers obtain most of their food from hunting (6). The Olalla Brothers’ titi may also be captured for use as bait in fishing and cat hunting, or as pets (1).

Although not found in any protected areas, the Olalla Brothers’ titi has received some protection from landowners that prohibit hunting on their land. However, this endangered monkey is still highly vulnerable to encroaching agriculture and urbanisation and it is imperative that its habitat receives some form of legal protection (1). Thankfully, the Wildlife Conservation Society is helping indigenous people to develop sustainable livelihoods and reduce deforestation (8). Other organisations, such as Asociación Armonía and Asociación Boliviana para la Conservación, are also working to highlight the plight of some of the most vulnerable species in the region (9) (10). Further research into the ecology and distribution of the Olalla Brothers’ titi is urgently required if this species is to escape extinction (5).

For more information on conservation in Bolivia, see:

Authenticated (20/05/10) by Matthew Richardson, primatologist and author.

  1. IUCN Red List (March, 2010)
  2. CITES (March, 2010)
  3. Nowak, R.M. (1999) Mammals of the World. The John Hopkins University Press, Baltimore.
  4. van Roosmalen, M.G.M., van Roosmalen, R. and Mittermeiser, R.A. (2002) A taxonomic review of the titi monkeys, genus Callicebus Thomas, 1903, with the description of two new species, Callicebus bernhardi and Callicebus stephennashi, from Brazilian Amazonia. Neotropical Primates, 10: 1-52.
  5. Felton, A., Felton, A.M., Wallace, R.B. and Gomez, H. (2006) Identification, behavioural observations, and notes on the distribution of the titi monkeys Callicebus modestus Lonnberg, 1939 and Callicebus olallae, Lonnberg 1939. Primate Conservation, 20: 41-46.
  6. Martinez, J. and Wallace, R.B. (2007) Further notes on the distribution of endemic Bolivian titi monkeys Callicebus modestus and Callicebus olallae, Neotropical Primates, 14: 47-54.
  7. Macdonald, D.W. (2009) The Encyclopedia of Mammals. Oxford University Press, Oxford.
  8. Wildlife Conservation Society Bolivia (March, 2010) 
  9. Asociación Armonía (March, 2010)
  10. Asociación Boliviana para la Conservación (March, 2010)