Early-Life Stress Triggers Juvenile Zebra Finches to Switch Social Learning Strategies.

This is the final version of the article. Available from Elsevier (Cell Press) via the DOI in this record.Stress during early life can cause disease and cognitive impairment in humans and non-humans alike. However, stress and other environmental factors can also program developmental pathways. We investigate whether differential exposure to developmental stress can drive divergent social learning strategies between siblings. In many species, juveniles acquire essential foraging skills by copying others: they can copy peers (horizontal social learning), learn from their parents (vertical social learning), or learn from other adults (oblique social learning). However, whether juveniles' learning strategies are condition dependent largely remains a mystery. We found that juvenile zebra finches living in flocks socially learned novel foraging skills exclusively from adults. By experimentally manipulating developmental stress, we further show that social learning targets are phenotypically plastic. While control juveniles learned foraging skills from their parents, their siblings, exposed as nestlings to experimentally elevated stress hormone levels, learned exclusively from unrelated adults. Thus, early-life conditions triggered individuals to switch strategies from vertical to oblique social learning. This switch could arise from stress-induced differences in developmental rate, cognitive and physical state, or the use of stress as an environmental cue. Acquisition of alternative social learning strategies may impact juveniles' fit to their environment and ultimately change their developmental trajectories.We thank Ben Sheldon, Kevin Laland, Will Hoppitt, Lucy Aplin, Bram Kuijper, and Willem Frankenhuis for their constructive feedback, James Sturdy for his help scoring the videos, and Roland Stump for his help setting up the PIT/RFID system. D.R.F. was funded by grants from the NSF (NSF-IOS1250895) to Margaret Crofoot and BBSRC (BB/L006081/1) to Ben Sheldon, K.A.S. was funded by a BBSRC David Phillips Research Fellowship, and N.J.B. was funded by a Netherlands Organization for Scientific Research (NWO) Rubicon grant