Epsilon Archive for Student Projects

Abstract

The pine marten (Martes martes) and Eurasian red squirrel (Sciurus vulgaris) are old forest specialists in Sweden, experiencing historic and current population declines, possibly due to climate change and habitat loss. However, studies have shown mixed results regarding pine marten predation on red squirrels. Earlier theories suggest that the marten is thought to have evolved specifically to hunt red squirrels, even though its current main food source is other small rodents.
Camera trap data was utilised from two areas in boreal Sweden, collected over seven months from September to March. Cameras were baited with peanut butter to identify individual martens in another project. There were a total of 1290 pine marten, 687 small rodent and 29 red squirrel observations. A time until the first event was recorded for each camera, along with the average tree height, standard deviation of tree height, and the proportion of trees under 6 m, in a 50 m radius around the camera, were included as variables. Intraspecies spatiotemporal interactions between marten and red squirrel, as well as between small rodents and marten, were analysed. Tree height significantly shortened the time until first detection for rodents and pine martens, but not for red squirrels, while the other factors had no significant effect. Earlier literature suggests that both rodents and martens favour older forests, possibly due to better shelter and thermal protection provided by these habitats. A higher chance of detecting rodents after marten observation was found, but no significant effect for squirrels. Martens were more likely to be observed shortly after squirrels and rodents. Martens likely follow the other species due to predation. The few squirrel observations could be because of strong avoidance of martens, obscuring the true response, as martens were observed at 45 out of 53 cameras. The apparent disregard of rodents towards their predator may stem from their exposure to many different predators, making it impossible to evade all threats, or possibly an attraction to the bait, which might also affect the squirrels. The conclusions, therefore, are that clearcuts in forestry create worse conditions for the pine marten and rodents, while more pine marten might be worse for the red squirrel, which might make it necessary to adapt forestry practices in the future.