Bridges, A. D. | Search bioRxiv

bioRxiv2023

Social learning of a challenging two-step action sequence fulfils key criteria of cumulative culture in an insect

Culture in non-human animals refers to behaviour that is socially learned and persists within a population over time. Human culture is notable in that it is cumulative: new innovations have built on previous ones over thousands of years. As a result, what is acquired via social learning often goes far beyond the capacity of any individual to independently discover it during their lifetime1-3. To date, no previous study has convincingly demonstrated this phenomenon in a non-human animal. Here, we show that bumblebees can learn from a trained demonstrator to open a novel, 3D-printed two-step puzzle box to obtain food rewards, even though they fail to do so independently. Experimenters were unable to train demonstrators to perform the unrewarded first step of the behaviour without providing a temporary reward linked to this action: the reward then being removed during later stages of training. However, a third of naive observers learned to open the two-step box from these demonstrators, without ever having been rewarded after the first step. This suggested that social learning might permit the acquisition of behaviours too complex to "re-innovate" via individual learning. Furthermore, naive bees failed to open the box despite extended exposure over the course of 12 days. The temporal and spatial distance of the unrewarded first step from the reward appeared to inhibit acquisition of two-step box-opening via individual associative learning, but this limitation was overcome by the presence of a trained conspecific. To our knowledge, these results make bumblebees the first animal to demonstrate the ability to socially learn a behaviour that is beyond their ability to innovate individually. This finding challenges the prevailing opinion of the field, which generally considers cumulative culture, which is built on this capacity, to be unique to humans.

animal behavior and cognition↗

bioRxiv2022

The establishment and transmission of novel foraging techniques indicates a capacity for culture in bumblebees (Bombus terrestris).

The astonishing behavioural repertoires of social insects have been thought largely innate, but these insects have repeatedly demonstrated remarkable capacities for both individual and social learning. Using the bumblebee Bombus terrestris as a model, we developed a two-option puzzle box task and used open diffusion paradigms to observe the transmission of novel, non-natural foraging behaviours through populations. Box-opening behaviour spread through colonies seeded with a demonstrator trained to perform one of the two possible behavioural variants, and the observers acquired the demonstrated variant. This preference persisted among observers even when the alternative technique was discovered. In control diffusion experiments that lacked a demonstrator, some bees spontaneously opened the puzzle boxes but were significantly less proficient than those that learned in the presence of a demonstrator. This suggested that social learning was crucial to proper acquisition of box-opening. Additional open diffusion experiments where two behavioural variants were initially present in similar proportions ended with a single variant becoming dominant, due to stochastic processes. This could lead to the emergence and maintenance of local cultural variation. These results suggest that bumblebees, like mammals and birds, may have the capacity for culture and to sustain cultural variation.

animal behavior and cognition↗