Revealing the consequences of social structure in animal societies is largely determined by our ability to accurately estimate functionally relevant patterns of social contact among individuals. Of particular relevance are social contacts that drive and maintain the cohesion of moving animal groups. Prior studies have predominantly built up social structure from dyadic connections, which while effective in open societies, where groups are ephemeral and thus less cohesive, may not be sufficient to characterize the fine-grained structure within more cohesive animal groups. This is because associations or interactions can involve more than two individuals participating together, which current approaches cannot distinguish from independent sets of dyadic connections. Here we applied higher-order temporal network approaches to high-resolution GPS data from every group member in two cohesive groups of vulturine guineafowl, Acryllium vulturinum. By quantifying moment-by-moment association dynamics, we revealed clear sex-biased contributions to the group cohesion. Specifically, males form the cohesive core of the group as they participated in temporally consistent subgroups and tended to occupy forward positions in moving subgroups. Females instead remained peripheral and were more likely to leave subgroups, while also occupying rear positions in moving subgroups. These results reveal a likely pathway to leadership that is independent of dominance rank, whereby the cohesion among males, which were previously found to be more likely to lead group movements, results in subgroups that allow them to more often form a majority. Our study thus demonstrates that subgroup association dynamics derived from high-resolution GPS data can provide insights into the fine-scale spatial and social organization of cohesive groups that may shape processes such as collective movement and leadership.
Predation risk affects the behaviour of prey species, which often reduce their activity when predator cues are sensed. The sensory environment influences how prey assess this risk. In aquatic species, medium colour largely depends on dissolved organic carbon, which stains water and impairs vision. In darker media, the lower light level may influence the way individuals express antipredator behaviours throughout the day. However, predictions about how prey should respond are ambiguous. We tested the influence of predation risk (fish olfactory cue) and water colour on the diel activity pattern of the newt Lissotriton vulgaris. Predation risk strongly attenuated activity. The effect of water colour was more complex. Newts reduced their activity in the presence of fish cues. This response occurred earlier in the dark water group than in the control group. Therefore, the interaction between predation risk and water colour was time dependent. Newts may anticipate the shift in the activity of the predator, whose peak activity is expected to occur earlier in darker water too. Our finding highlights the importance of considering the prey's capacity to finely assess variation in predation risk and tune their diel activity to the visual environment. It also emphasizes the need to address this issue not only from the predator's perspective but also from the prey's perspective, to assess the consequences of current changes in sensory environments such as water browning in boreal freshwaters.
Individuals commonly compete with others that share their ecological niche, both within and among species. To avoid physical confrontations, individuals can use various types of signals to demonstrate their dominance, including vocalizations. Kerivoula hardwickii is a solitary bat species that roosts in plant structures that are highly ephemeral, making them a limited resource. So far, it is unknown whether individuals of K. hardwickii use vocalizations during competitive encounters for roosts or whether these vocalizations convey information about the roost defender to potential rivals. We hypothesized that the calls produced during roost competition contain information that influences the ability of an individual to defend its roost. We conducted roost competition experiments in a flight cage, where one individual was allowed to take possession of a roost (‘owner’) and a second individual released into the cage (‘intruder’) attempted to evict the owner. All vocalizations produced by the roost owner during these encounters were recorded and analysed to determine which acoustic parameters, if any, influenced the probability that the owner would successfully defend the roost. We found that males that produced calls with higher entropy were more likely to retain their roosts against a male intruder, while there was no such effect in female–female experimental pairs. High entropy suggests that encounters between males of K. hardwickii escalate to high levels of aggressiveness. We suggest that the vocalizations of K. hardwickii contain important information about individual characteristics, which in turn helps bats to make decisions during resource competition.
Wild animals often socialize in microhabitats where direct observations are difficult or impossible, limiting the reconstruction of complete social networks and the understanding of variation in social structure. We designed and tested a novel proximity-logging radiocollar (MamTag) in semifossorial Columbian ground squirrels, Urocitellus columbianus, assessing collar effects, comparing collar- and observation-based social networks, and examining association data gathered in otherwise unobservable contexts. We did not detect a significant effect of collars on body mass or reproduction. Observation- and collar-based networks correlated moderately but consistently. Continuous collar data revealed diel shifts in social behaviour and coherent above- and belowground social organization, with individual centrality largely conserved and spatial proximity shaping network structure. Overall, MamTag collars provided reliable, biologically meaningful measures of social associations and a powerful tool for studying social organization in natural environments.
