Wednesday, February 13, 2019

The Sociable Gray Squirrel

squirrels On winter mornings when I look out my window, I often see a gray squirrel clinging upside down to the post supporting my bird feeder, with his front paws in the tray, munching sunflower seeds. Sometimes, a much smaller red squirrel is perched on the opposite side of the feeder.

This brings to mind my studies of squirrels years ago and the differences between the two species. For my thesis in biology at Williams College, I conducted a field study of social behavior and organization in the eastern gray squirrel in a suburban area in Williamstown, Massachusetts. My first step was to live-trap and mark squirrels so I could identify individuals.

Using peanut butter as bait, I captured 34 gray squirrels, weighed them (inside the trap), and checked underneath for their sex. To mark them, I attached the live-trap to a wire cone. Once the squirrel was in the cone, I dabbed a spot of black hair dye in a different location on each squirrel and assigned a number to it. After this quick procedure, I released them.

That fall and winter, I spent many hours wandering around my study area with binoculars, a notebook, and a chart of squirrel markings, looking for “my squirrels,” often eliciting odd looks from other students. I observed 500 social interactions between gray squirrels. The majority of these interactions were not aggressive – feeding or resting in close proximity, social grooming, and play.

Aggressive behavior like chasing was observed mostly between resident squirrels and transient squirrels, between males competing for females during the winter breeding period, or during contests for food at a bird feeder. There was a high degree of tolerance and association among gray squirrels, a finding confirmed by other researchers.

I often observed several squirrels feeding peacefully on maple seeds or apples in the same tree. Five squirrels (probably a mother, her two spring-born young, and her two summer-born young) shared a den cavity in a big silver maple. Once, I saw three of them gathering leaves and following each other up the tree to line their den hole. This tree was conveniently located outside the house I lived in, so I could observe the squirrels from my window when they emerged at daybreak while I sat in a comfortable chair sipping tea.

Some researchers have observed a dominance hierarchy among gray squirrels based on sex and age, though these studies were conducted at artificial feeders – a concentrated food source. I did not discover clear evidence of a pecking order and concluded that it may only function in times of food scarcity.

I plotted my sightings of each squirrel on a map and discovered that the home ranges overlapped considerably, a finding consistent with other studies. Gray squirrels are not territorial; they do not exclude others from their home ranges, though nursing females will defend den trees.

I also recorded interactions between gray squirrels and red squirrels. Half of these encounters were aggressive, and in most of these, the smaller red squirrel initiated the conflict. Red squirrels also chattered a warning when a gray squirrel entered the vicinity. In contrast to the sociable gray squirrel, red squirrels are territorial in their preferred habitat – pure coniferous forest – and vigorously defend forest patches from other squirrels.

The difference in social behavior between the two species likely stems from a difference in feeding habits. The buds, leaves, fruit, and seeds of deciduous trees, all favorite foods of the gray squirrel, are normally abundant from spring through fall, though they change as tree species flower and fruit at different times. The amount of mast fluctuates from year to year, and it’s an advantage for gray squirrels to be able to travel around their home ranges to forage without interference from other squirrels. During winter, gray squirrels usually rely on cached nuts, which they hide from other squirrels by burying them individually in scattered locations.

Red squirrels prefer the small seeds of conifers like spruce and fir, which they remove by turning the cones in their front paws and chewing off the scales, much like we eat corn on the cob. They store large piles of cones so the seeds will be available year-round, and so they must defend this larder and the trees they harvest the cones from.

Of course feeding habits and social behavior can change when humans tip the scales, which brings us back to the gray and red squirrels feeding within a foot of each other at my feeder, something not usually seen in nature.

Susan Shea is a naturalist, writer, and conservationist who lives in Brookfield, Vermont. The illustration for this column was drawn by Adelaide Tyrol. The Outside Story is assigned and edited by Northern Woodlands magazine and sponsored by the Wellborn Ecology Fund of the New Hampshire Charitable Foundation.

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7 Responses

  1. Jim S. says:

    When they fight they are called “squarrels”.

  2. Sherry says:

    This must have been a fun thesis! There is a society of grey squirrels all over Central Park, NYC who are so friendly, they run up to people for peanuts, or pose for photos even without peanuts as a reward.They do chase each other when it comes to food. What amazes me is when they bury the extras, how do they know which ones are theirs? And do other squirrels respect this? Thanks for posting your article!

  3. A study some time ago showed that gray squirrels have excellent spatial memory for recovering their own food caches and use smell only when right next to the cache’s location. In response to Sherry, I’ll add that spatial memory is how they find their own – but they’ll take any they see, smell, or find. By the way, the student of mine who did this study now teaches at Skidmore.

    • Sherry says:

      Ernest, thank you for this information. Another question: I often fed squirrels peanuts, and they seem to be blind…can’t see or smell the peanut even 6″ away. Have studies been done on squirrels who might be blind? I’ve seen several who act this way, while others almost catch the peanut. Thanks in advance.

  4. Sherry – Sorry; I don’t know anything to add about blind squirrels, although we know that odor is a less important cue than one might expect. I’ll add that squirrels are unusual rodents. Most rodents live in a two-dimensional world – e.g., mice running around on the ground – but corresponding to the three-dimensional world in which they live, squirrels have surprising memory and sensory abilities.

  5. Harv Sibley says:

    We have a large feeder viewable from our kitchen. Gray squirrels keep us amused daily….like acrobats on the high wire..

  6. Charlie S says:

    As in all animals I find squirrels interesting. I have noted ‘individuality’ in gray squirrels over the years in that while some are wary of cars before crossing a road (will hesitate or go back when a car approaches) others run right out and often become victims of Henry Ford’s patent. I have seen squirrels race like bat’s out of hell over busy three or four lane roads and make it by a hairs breadth, while others take their time and even sit up on twos while cars approach. I have found that slowing down will usually save them as they will run off, but if you don’t slow down they obviously get confused and sit tight or run back and forth in a frantic until they at once meet their Goodyear fates.

    One time I saw a squirrel run so fast so as to beat the heavy traffic in both directions on a busy road that by the time it got to the other curb it bounced right over it then rolled a bit over a sidewalk before it caught its balance and ran into a thicket. That was years ago and still I see that image. How it made it across is beyond me as I watched it come within inches of not a few tires as it ran. Totally amazing! And there have been times I’ve seen them run over….all too often this! It don’t take much effort to slow down yet…..

    I have been witness to two recent squirrel events, one of which I wont share because I wish not to depress anybody. The other is not pleasant but is less troublesome. That is: I was standing across the road from where I live one early morning talking to a friend when at once there was a loud explosion nearby. My immediate thoughts were a gunshot, and right afterwards we both looked over across the street and saw a squirrel fall from the sky and hit the road with a loud smack. It was up on the wire and evidently went where it shouldn’t have went and that was the end of this squirrel is was dead way before it hit the ground. I went over and picked it up. It’s fur was browned and stiff and there were short,elongated lacerations where its blood-red innards could be seen. As I say…I was relieved in that it never knew what hit it.

    Of course power was knocked out in some parts of the neighborhood to which one of the neighbors (the one nearest the electric pole) griped, and bi#*!ed and moaned, “This is the third time!” as though a squirrel had knocked her power out twice before. It was early in the morning and I gathered that she was in her bathroom making up her face getting ready for work and I suppose I could see where she had a legitimate grievance. Me! I was feeling sorry for the squirrel The utility people finally came out and I learned from them that this is a very common problem…squirrels getting zapped and knocking out power in the neighborhoods. This was my first experience with this and from it I learned something, as noted above.

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