For group-living animals to remain cohesive they must agree on where to travel. Theoretical models predict shared group decisions should be favoured, and a number of empirical examples support this. However, the behavioural mechanisms that underpin shared decision-making are not fully understood. Groups may achieve consensus of direction by active communication of individual preferences (i.e. voting), or by responding to each other’s orientation and movement (i.e. copying). For example, African buffalo (Syncerus caffer) are reported to use body orientation to vote and indicate their preferred direction to achieve a consensus on travel direction, whilst golden shiners (Notemigonus crysoleucas) achieve consensus of direction by responding to the movement cues of their neighbours. Here, we present a conceptual model (supported by agent-based simulations) that allows us to distinguish patterns of motion that represent voting or copying. We test our model predictions using high-resolution GPS and magnetometer data collected from a herd of free-ranging goats (Capra aegagrus hircus) in the Namib Desert, Namibia. We find that decisions concerning travel direction were more consistent with individuals copying one another’s motion and find no evidence to support the use of voting with body orientation. Our findings highlight the role of simple behavioural rules for collective decision making by animal groups.

Heading_data.RData provides animal orientation for each individual and event across the study. Data were collected using magnetometers and accelerometers attached to goats. Full methods for transforming these data into animal orientation can be found in the Supplemental Material for the manuscript. 

Loc_data.RData provides GPS fixes for each individual at each timestep (1 second) for the events of interest across the study. 

Heading data contains the following column names: "event"   "id"      "time"    "heading"

"event" refers to the identified collective decision

"id" to the individual goat

"time" is the number of seconds since January 1st 1970 (standard notation)

"heading" refers to the animal orientation with respect to north

Loc data contains the additional column names:"lat"  "lon" 

Which refer to the latitude and longitude of the individual goat as read from their GPS collar.