Research ArticleORGANISMAL BIOLOGY

Titi monkeys combine alarm calls to create probabilistic meaning

See allHide authors and affiliations

Science Advances  15 May 2019:
Vol. 5, no. 5, eaav3991
DOI: 10.1126/sciadv.aav3991
  • Fig. 1 Results of the multimodel inference analyses.

    Circle colors in (A) to (C) refer to the Akaike’s weight, i.e., the probability that a given model supports the hypothesis (white: w = 0, weak support; red: w = 1, strong support; n.c.: the model did not converge). (A) Information encoded in titi monkey alarm sequences: Metrics are presented row-wise, and information hypotheses are presented column-wise. For simplicity, the null and urgency models were combined as “control,” and their weights were added. For the metric “probability that first call is A,” models that addressed the possibility that predator type and location were encoded are not relevant because the first call can only be one of two possibilities and, thus, can only provide information about predatory type or location. (B) Gaze reaction of titi monkeys to the information contained within the playback stimuli sequences, i.e., the original condition during which broadcasted sequences were recorded. For a graphic representation of the best model (interaction between predator type and location), see Fig. 2. (C) Gaze reaction of the titi monkey to the metrics extracted from the playback stimuli sequences. For a graphic representation of the best model (proportion of BB-grams), see Fig. 4. (D) Illustration of sequence metrics that support each hypothesis. Letters refer to the corresponding model weights in (A). (E) Illustration of experimental design of the predator presentations.

  • Fig. 2 Proportion of time the listener spent looking upward across original recording conditions of the playback stimuli.

    The figure shows raw data (one line per individual), as well as estimates per condition (black circles) and bootstrapped estimates (colored circles, 1000 bootstraps) of the model testing how gaze reaction depends on both predator type and location (main effects). Subjects looked more upward when they were presented with sequences elicited by an aerial predator (compared to a terrestrial predator) or elicited by a predator in the canopy (as opposed to a predator on the ground). For simplicity, we displayed the most salient reaction, i.e., looking upward. Results for other looking directions can be found in fig. S2.

  • Fig. 3 Proportion of BB-grams in the alarm call response depending on the eliciting stimulus.

    The figure shows estimates (black circles) and bootstrapped estimates per condition (colored circles, 1000 bootstraps) of the model testing how the proportion of BB-grams encodes both predator type and location (main effects). The proportion of BB-grams is higher in vocal responses to terrestrial predator than to aerial predators and higher when the predator is on the ground than when it is in the canopy.

  • Fig. 4 Listener’s gaze reaction, depending on the proportion of BB-grams of the alarm sequence.

    Proportion of time listeners spent looking downward (A), toward the speaker (B), and upward (C), depending on the proportion of BB-grams of the playback stimuli. The figure shows raw data (circles), as well as estimates (black lines) and bootstrapped estimates (colored lines, 1000 bootstraps) of the model testing how gaze reaction depends on the proportion of BB-grams. Listeners spent more time looking toward the speaker (B) and less time looking upward (C) when there were more BB-grams in the sequence. The time looking downward (A) was not affected.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/5/eaav3991/DC1

    Fig. S1. Soft alarm calls of titi monkeys.

    Fig. S2. Listener’s gaze reaction depending on the eliciting stimulus of the sequence.

    Fig. S3. Location of the speaker during the playback experiments.

    Table S1. Design of the set of models for each metric.

    Table S2. Composition of the six titi monkey groups during our study and that of Cäsar et al. (4).

    Table S3. Description of the final dataset of predator presentations.

    Table S4. Playback stimuli.

    Table S5. Playback experiments schedule.

    Table S6. Models formulas.

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Soft alarm calls of titi monkeys.
    • Fig. S2. Listener’s gaze reaction depending on the eliciting stimulus of the sequence.
    • Fig. S3. Location of the speaker during the playback experiments.
    • Table S1. Design of the set of models for each metric.
    • Table S2. Composition of the six titi monkey groups during our study and that of Cäsar et al. (4).
    • Table S3. Description of the final dataset of predator presentations.
    • Table S4. Playback stimuli.
    • Table S5. Playback experiments schedule.
    • Table S6. Models formulas.

    Download PDF

    Files in this Data Supplement:

Stay Connected to Science Advances

Navigate This Article