MATLAB Code from Adaptation of sperm whales to open-boat whalers: rapid social learning on a large scale?

Animals can mitigate human threats, but how do they do this, and how fast can they adapt? Hunting sperm whales was a major nineteenth century industry. Analysis of data from digitized logbooks of American whalers in the North Pacific found that the rate at which whalers succeeded in harpooning (‘striking’) sighted whales fell by about 58% over the first few years of exploitation in a region. This decline cannot be explained by the earliest whalers being more competent, as their strike rates outside the North Pacific, where whaling had a longer history, were not elevated. The initial killing of particularly vulnerable individuals would not have produced the observed rapid decline in strike rate. It appears that whales swiftly learned effective defensive behaviour. Sperm whales live in kin-based social units. Our models show that social learning, in which naive social units, when confronted by whalers, learned defensive measures from grouped social units with experience, could lead to the documented rapid decline in strike rate. This rapid, large-scale adoption of new behaviour enlarges our concept of the spatio-temporal dynamics of non-human culture.动物能够减轻人类带来的威胁，但它们具体如何实现这一点，又能以多快的速度完成适应？19世纪时期，捕猎抹香鲸（sperm whales）曾是一项重要的产业。对北太平洋海域美国捕鲸船队的数字化航海日志数据进行分析后发现，在某一区域的捕鲸活动最初数年内，捕鲸者成功叉击（striking）所发现鲸鱼的概率下降了约58%。这一下降趋势无法用早期捕鲸者能力更强来解释——因为在捕鲸历史更为悠久的北太平洋以外海域，捕鲸者的叉击成功率并未更高。最初仅捕杀特别脆弱的个体，也不会造成观测到的叉击成功率快速下降。种种迹象表明，抹香鲸能够迅速习得有效的防御行为。抹香鲸以亲缘社群为单位生活。我们的模型显示，社会学习（social learning）过程可带来文献中记载的叉击成功率快速下降：当缺乏经验的社会单元遭遇捕鲸者时，会从具备捕猎经验的群居社会单元处习得防御策略。这种快速、大规模的新行为习得现象，拓展了我们对非人类文化（non-human culture）时空动态的认知边界。