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Sneeze to leave: African wild dogs (Lycaon pictus) use variable quorum thresholds facilitated by sneezes in collective decisions - PubMed

  • ️Sun Jan 01 2017

Sneeze to leave: African wild dogs (Lycaon pictus) use variable quorum thresholds facilitated by sneezes in collective decisions

Reena H Walker et al. Proc Biol Sci. 2017.

Abstract

In despotically driven animal societies, one or a few individuals tend to have a disproportionate influence on group decision-making and actions. However, global communication allows each group member to assess the relative strength of preferences for different options among their group-mates. Here, we investigate collective decisions by free-ranging African wild dog packs in Botswana. African wild dogs exhibit dominant-directed group living and take part in stereotyped social rallies: high energy greeting ceremonies that occur before collective movements. Not all rallies result in collective movements, for reasons that are not well understood. We show that the probability of rally success (i.e. group departure) is predicted by a minimum number of audible rapid nasal exhalations (sneezes), within the rally. Moreover, the number of sneezes needed for the group to depart (i.e. the quorum) was reduced whenever dominant individuals initiated rallies, suggesting that dominant participation increases the likelihood of a rally's success, but is not a prerequisite. As such, the 'will of the group' may override dominant preferences when the consensus of subordinates is sufficiently great. Our findings illustrate how specific behavioural mechanisms (here, sneezing) allow for negotiation (in effect, voting) that shapes decision-making in a wild, socially complex animal society.

Keywords: African wild dog (Lycaon pictus); consensus decision-making; signal; social communication.

© 2017 The Author(s).

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Conflict of interest statement

We have no competing interests to report that may influence the objective presentation of our manuscript.

Figures

Figure 1.
Figure 1.

Spectrogram of dominant male African wild dog ‘sneeze’ recorded prior to a group departure event. This example spectrogram was prepared in CoolEdit Pro 2002 (v. 2.0, Syntrillium Software Corporation, Phoenix, AZ), with 44 100 sampling rate visualized in Hamming window, resolution 1024 bands, and linear energy plot at 20% scaling. The spectrogram shows linear bars (likely an intake of breath), followed by atonal high-frequency bandwidth rapid exhalation, or ‘sneeze’. Energy is shown from light (low) to dark (high).

Figure 2.
Figure 2.

Effects of attempt number, initiator demographic, and sneeze frequency on rally success. Panel (a) shows that the proportion of successful rallies (those that resulted in collective movements) increased with every failed rally in an observation period. Bars indicate the standard error of the mean. Panel (b) shows the frequency of successful (n = 28) and unsuccessful (n = 40) rallies initiated by individuals from each demographic category of priority of access to carcasses (POA): POA1, dominants and pups (less than 1 year old); POA2 yearlings (1–2 years old); and POA3, subdominant adults (more than 2 years old) with bars indicating standard error. Panel (c) shows the mean frequency of sneezes per minute before and after the end of successful and unsuccessful rallies. Hatched lines represent standard error. Data were gathered by critical incident sampling of sneezes from all packs' (N = 5) successful (n = 28) and unsuccessful (n = 40) rallies. The presented data are limited to the sneezes 4 min before the end of the rally and 4 min after the first individual departed or individuals returned to rest, which includes 80% (209/260) of total observed sneezes in rallies. Panel (d) contains the plot of the interaction total number of sneezes in a rally and initiator POA effect on rally success. Solid lines show the estimated effects from the GLMM model (table 1) across a range of sneeze counts (increasing along the x-axis and scaled to the range of the actual data 0–25). These lines are colour-coded to initiator POA. Raw data are represented by the dashed lines, the lengths of which indicate the four bins into which raw data were directed on the basis of frequency of sneezes observed in the rally (0, 1–2, 2–9, more than 10).

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