The benefits of hoarding

It seems like you can’t walk through Edmonton’s river valley without being yelled at by a red squirrel. It’s pretty obvious that the squirrel is unimpressed by your presence but what exactly is it freaking out about? Chances are, the squirrel is worried you are going to raid its larder and its telling you to keep your paws out of its cookie jar.

There are two types of hoarders out there. Scatter hoarders have many small caches of food spread throughout their territory. Larder hoarders, on the other hand, have one large cache of food. Both have squirreled away (pun intended) some food when they had extra and stored it someplace to use later when food is scarce. Its a brilliant and necessary plan but it depends on keeping those caches hidden from anyone whether a fellow species mate or a devious invader intent on stealing an easy meal like those dastardly hikers in the river valley (apparently, in my head, the squirrels are quite melodramatic).

Larder hoarders have a single cache to defend and to remember, but a higher potential for loss if their one cache is robbed. Scatter hoarders have the opposite with many caches to defend and remember but lower potential for loss because each cache is only a part of their food stores.

While the animals are storing food to get them through times of scarcity, the caches have a side effect that helps the plants they animals are eating. The seeds from the plants end up being spread out by the animals. This helps the plant because seeds tend to survive better when they are away from the parent plant. In addition, the seeds often end up in appropriate habitat when dispersed by animals. But is there a difference for the plants when they are being spread by scatter hoarders versus larder hoarders?

Goheen and Swihart (2003) examined how forest regeneration is impacted by a change in the squirrel population. Gray squirrel populations were declining in hardwood forest areas that had been converted to intensive agriculture. Gray squirrels are scatter hoarders. Red squirrels, a larder hoarder, moved into the area as the gray squirrels declined. Goheen and Swihart created a model to examine how the two hoarding approaches might impact forest regeneration. They found that the red squirrels, with their single caches, do not help forest regeneration as much as the grey squirrels would.

Outside of this research specifically, I think it has important implications for climate change. There are so many interconnections between species and habitats that it is incredibly difficult to predict all of the changes that might occur.