If you ever visit the dense jungles of South and Central America, you may be lucky enough to encounter an elusive titi monkey (Callicebus spp.). Titi monkeys are small-bodied, monogamous New World primates that mate for life¹. There are over thirty species of titi monkeys, but all share some unique characteristics. For instance, they have a very specific social structure. Titis live in small family groups of a pair-bonded male and female and their offspring². Male and female titis pair up when they are about two years of age and disperse from their respective natal groups. This marks a crucial time in a titi monkey’s life when their social attachments shift from their parents to their mate, whom they will likely remain with for their entire life.

While asleep or when resting side-by-side, titi monkeys wrap their long, partially prehensile tails together in a behavior called “tail twining”². Tail twining is a behavior displayed in times of stress or times of contentment: it’s a comfort mechanism similar to a human hug. Titi monkeys often wake up with a spiral bed head on their tails from twining all night!

One of the most distinctive features of the titi monkey social behavior is the considerable amount of time titi monkey fathers invest in raising their offspring. For the first six months of life, titi monkey infants spend almost all of their time riding around on their father’s back². Titi monkey mothers only carry the infant while actively nursing. This heavy paternal investment is rare in the primate order and in mammals in general². Typically, males take the first opportunity they can to leave a female and seek out other mates; during gestation and lactation, females typically require no investment from their male companions³. However, in some species of mammals, monogamy and heavy paternal investment have co-evolved. By investing heavily in their offspring, male titi monkeys increase the chances of their young surviving, while also monopolizing access to their pair-mated female. As titi monkey offspring mature, they become more mobile and wander around close to their parents. Once they are old enough to sleep next to their parents, as opposed to on a parent’s back, they join the nightly group tail twine.

While weighing in at less than four pounds, these tiny creatures can actually be quite mighty. The easiest way to find a titi monkey in the jungle is by sound. Titi monkeys are territorial, and do not share their home range with other groups. The leading hypothesis explaining the function of titi monkey bioacoustic symphonies is that they use loud duet vocalizations to enforce territorial boundaries each morning⁴. These songs can be heard up to half a mile away. The adult male and female alternate notes back and forth as they sing, and the duet can last anywhere from a minute to an hour. As titi monkey offspring reach adulthood, they begin to sing along with their parents as they learn how to duet.

Check out black-fronted titi monkeys duetting in response to a group encounter here.

[By: Allison Lau]

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References:

¹Díaz‐Muñoz, S. L., & Bales, K. L. (2016). “Monogamy” in Primates: Variability, Trends, and Synthesis: Introduction to special issue on Primate Monogamy. American journal of primatology, 78(3), 283-287.

²Hoffman, K. A., Mendoza, S. P., Hennessy, M. B., & Mason, W. A. (1995). Responses of infant titi monkeys, Callicebus moloch, to removal of one or both parents: evidence for paternal attachment. Developmental psychobiology, 28(7), 399-407.

³Gubernick, D. J., & Teferi, T. (2000). Adaptive significance of male parental care in a monogamous mammal. Proceedings of the Royal Society of London B: Biological Sciences, 267(1439), 147-150.

⁴Robinson, J. G. (1981). Vocal regulation of inter-and intragroup spacing during boundary encounters in the titi monkey, Callicebus moloch. Primates, 22(2), 161-172.

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