Impact of human presence and activity on urban Eurasian red squirrels' innovative problem-solving

Humans impact wildlife positively and negatively, and increasing evidence shows that humans potentially play a major role in shaping urban wildlife cognition. However, it remains unclear which, and how specific anthropogenic factors, shape animal cognitive performance. Here, across 15 urban areas in Oulu, Finland, we investigated how varied levels of human presence nearby, types of human activity (walking, dog-walking, cycling, and playground activities), and distance to the nearest footpaths influenced 64 squirrels' innovative problem-solving ability-measured as the proportion of solving success at the site level, solving outcome at the individual level as well as individuals' first-success latency. Higher mean human presence nearby and all measured human activities significantly decreased the proportion of success at the site level. Playground activity showed the highest negative impact on both the first- and subsequent-visit success rate at the site level. Increased mean human presence and walking decreased the likelihood of a squirrel successfully solving the novel food-extraction problem. When examining the problem-solving latency of individual squirrels, increased human presence also decreased squirrels' first-success latency, and dog-walking was the outstanding factor affecting first-success latency. These results show the negative effects of specific human-related factors on an important cognitive trait, problem-solving ability. These factors may also potentially exert selective pressure on shaping urban wildlife cognition.