Shopping with Spectators: Our new experiment to see how social factors influence the food storing decisions of western grey squirrels

The beautiful western grey squirrel is a California native tree squirrel species that is very active at my favorite research site, the UC James Reserve in the San Bernardino National Forest in Southern California 🐿🌲. You can learn more about this illusive species in our previous posts on their habitat use and in our squirrel profiles! 

One of many super interesting facts about these fluffy tailed cuties is that they do not hibernate over the winter when the mountain is snowy 🏔 During that time there is very little food available in the environment, so in order to survive they have to bury enough food to make it through the season. 
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But how do they decide when to eat an item and when to store it?

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​When a squirrel finds a food item it can choose to eat it right away or store it by burying it underground to eat  later. The burying of items by squirrels for future use is typically called 'caching' by Squirrel Gazers 🐿👀

The decision to eat or cache something is a complex one that is influenced by many different factors including the food item's quality, size, and condition. Check out our post from 2019 to see a little more on some of the assessment behaviors squirrels perform to "quality check" their nuts! 🥜🔍🐿

In this new experiment we are intersted in learning more about how having an audience of other squirrels or birds  would impact the decision to eat or store a food item. After all, squirrels are known thieves and burying something while others are around may increase the chance that nut is stolen. 

To explore more about how the presence of other animals might influence a squirrels preference for eating or storing food, we set out an automated feeding station 🥜🤖

The black and red rectangle you see there is actually a microchip scanner! The squirrels at our field site have been implanted with Passive integrated transponders or "PIT-tags". This is just a science term for saying microchip!

These are the same type of microchips we put in our cats and dogs. These tags allow us keep track of the squirrels in our area and identify them when they appear at the feeder. 

​And yes, all our squirrels have names! That is Han Solo there in the photo! 🐿💕

Surrounding the microchip scanner are several cameras that record what the squirrels are doing while at the feeding station. 
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The squirrels are given an important choice at the feeder.
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In the center of the feeder they have two food options to choose from. The squirrel can select hazelnuts that are still in the shell and hazelnuts that have been minced. 
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Hazelnuts in the shell are storable items that squirrels can bury for future use. Their tough shells make them great for storage! 🌰

Minced hazelnuts are super easy for the squirrels to eat quickly but they can not be carried away and buried for later!

Then we wait for the squirrels to arrive!

Once the squirrels show up and the cameras start rolling, the data collection begins! 🎥🐿📈

In this video you can see that Spring Roll the ground squirrel is enjoying a snack until Rain the grey squirrel shows up to chase her away. Notice how Rain can't quite decide what to do and opts for the minced nuts until she is sure Spring Roll has left the area.

Next, we wanted to test out how squirrels would react to a model squirrel standing in a territorial posture. Turns out our model squirrel Professor Peanut Sauce, who can be seen on the front right of the screen, did not have such a good day! 

And of course because squirrels will always find a way to out smart any experimental set-up you provide them with, here is a short video of the ground squirrel C3PO digging her own personal VIP entrance to feeding station- pay close attention to the lower left corner of the screen!

What are the results of this experiment?

That is a great question! You will have to subscribe to find out! This was a pilot test meaning it was a practice run to make sure our methods would work because as CP3O demonstrated in the video above, not everything we plan for the squirrels always works out. 
 
Based on the microchip scans and hours of footage from the past two weeks, the future of this experiment  looks bright!