Behavioural Responses In Seed-hoarding Of Sympatric Rodents To Catastrophic Pilferage

In some animal species, food-hoarding is an important adaptation to the variations in, and the unpredictable nature of food supply. This adaptation assists in survival and facilitates an increase in reproduction for hoarders. There are two food-hoarding patterns: larder-hoarding and scatter-hoarding. It is the sign of successful food-hoarding and the main evolutionary cause of food-hoarding behaviour that hoarded food items are successfully protected for use when resources are scarce. Food pilferage by other animals(conspecific and/or heterogeneous) is a significant factor in loss of stored food. Hoarder tactics have evolved to minimize food loss by pilferage. These tactics can be placed into three categories:pilferage avoidance, pilferage prevention, and pilferage tolerance.In the pilferage avoidance strategy, hoarders try to store food in locations that are difficult for pilfers to find and access. These tactics including modifying consumption and caching rates, recovering and moving caches repeatedly, aggressively preventing access to cached items, shifting from scatter-hoarding to larder-hoarding, avoiding and delaying caching when in the presence of potential thieves, and spacing caches further apart or out of sight. Pilferage prevention involves hoarders aggressively defending their caches, preventing pilfers from gaining access to the cache sites or entering into the cache area. When it comes to pilferage tolerance strategy, hoarders do not avoid or prevent pilferage but instead, steal food items from other hoarders to compensate for their own losses. Pilferage is reciprocal, and as such, tolerated. Social animals and solitary rodents with overlapping home ranges appear to tolerate pilferage.However, very few studies have focused on the behavioural response to pilferage among sympatric hoarders at the community level, or the behavioural response of hoarders to catastrophic food loss(complete food loos). Furthermore, very few studies have been conducted under natural conditions.In this study, we examined the behavioural responses to catastrophic pilferage in five species that scatter-hoard and/or larder-hoard. Under natural conditions and within outdoor enclosures, we simulated complete pilferage events by removing wild apricot (Prunus armeniaca) seeds hoarded by Pere David's rock squirrels(Sciurotamias davidianus), Korean field mice(Apodemus peninsulae), striped field mice(Apodemus agrarius), Chinese white-bellied rats(Niviventer confucianus) and rat-like hamsters (Tscheskia triton). Following pilferage, all five species increased seed removal from the source and total hoarding intensified, especially the scatter-hoarding, in both natural and captive conditions. There was no effect of sex in conspecific on seed-hoarding behaviours of the focal animals. In addition, our pilferage manipulations in the field also increased the distance that seeds were buried from the source. These findings suggest that increased intensity of seed-hoarding may be the common behavioural reaction of food-hoarding animals to catastrophic pilferage. It was also found that scatter-hoarding might be better than larder-hoarding for avoiding complete pilferage, for rodents that already perform a combination of larder- and scatter-hoarding behaviours.We found that sympatric hoarders have a convergence in behavioural response to complete pilferage. This is the first study to focus on the behavioural response of sympatric rodents to catastrophic pilferage at the community level.