Squirrels are among the quirkiest of wild creatures. They seem to live their lives on the edge: they pull off dramatic long-distance leaps from high rises to tree branches without a hitch, run headfirst into oncoming traffic, and stroll along telephone wires with the ease and grace of tightrope walkers. But one of their weirder (and more adorable) behaviors is their propensity to rub their faces on things—tree branches, acorns, just about anything really. Where does this inclination come from?
Squirrels rub their faces on things to mark their territory and leave their scent, helping them find mates, orient themselves, and claim ownership. Squirrels have well-developed olfactory senses, and this makes it easy for them to detect the scent of other squirrels on various objects.
This article discusses why squirrels rub their faces on things and the important role that scent plays in the squirrel’s world.
Why do Squirrels Rub Their Faces on things?
All mammals have apocrine glands, which are responsible for secreting sweat and pheromones. Male and female squirrels, in particular, have a high concentration of these oral scent glands in their faces around their mouths, and it is commonly held that their face rubbing serves the purpose of scent-marking.
Squirrels have a powerful sense of smell, and their olfactory senses dictate many of their instinctual behaviors. Their sense of smell plays a large part in how they communicate with one another, their ability to orient themselves, and dictates how they choose to mark their territory.
A good deal of biological information is thought to be left in the pheromonal secretions from cheek rubbing, including details like the age, gender, and reproductive status of the squirrel who left them. Some squirrel species can even tell if another squirrel is related to them just from a few whiffs of the other squirrel’s pheromonal secretions.
There are three main ways for squirrels to mark their territory—cheek rubbing, urination, and chewing:
- Cheek rubbing: Cheek rubbing has purposes other than mating and is sometimes more focused on orientation and learning about habitat areas. All squirrels do it unilaterally, regardless of their age and gender.
- Urination: Marking via urination is typically more male behavior and is more deliberate. It seems to have a more defensive, aggressive intent—sending a message to other squirrels in the area that they are trespassing.
- Chewing: Squirrels’ front teeth are always growing during their lifetime and will grow into their teeth and skull if they don’t find a chewing outlet. Strips and stripes chewed in bark serve as a visual territorial marker to other squirrels passing through the area.
What’s Smell Got to Do With It?: The Role of the Apocrine Glands in a Squirrel’s Life
The Social Importance of Pheromones
Getting to Know Each Other
Unacquainted squirrels greet each other by sniffing the apocrine glands when first getting to know one another, oftentimes putting their hands on each other shoulders during the salutary exchange and forming a sort of embrace. To many onlookers, this may have the appearance of a hug, making real all of our Disney fantasies of cuddlesome woodland creatures.
Upon first meeting, California ground squirrels will investigate the other male’s apocrine and anal glands to both identify potential relations and determine levels of aggression.
To Determine the Relationship
As mentioned above, a considerable amount of biological information is available, left from the pheromones during cheek rubbing. Many squirrels can tell by smell whether another squirrel is a blood relative, creating a veritable mental family tree in seconds.
This can be a factor of life or death in some cases. Female Belding squirrels, for example, will give preferential treatment to closer female relatives—i.e., their mothers, daughters, and sisters—while showing less of a predilection for nieces and nephews.
While a female Belding ground squirrel may stick her neck out to save a closer relative from a predator—for example, when putting out an alarm call—she may not be quite so inclined to offer the same courtesy to more distant kin. “Saving the sister’s life is similar to saving its own genotype while saving an unrelated squirrel doesn’t make evolutionary sense,” observes Ph.D. Psychologist Jill M. Mateo who spent time researching the relationships of ground squirrels.
This ability to detect kin is also important for procreation purposes: determining whether another squirrel is too closely related helps squirrels avoid mating with another squirrel that is too genetically similar.
Flirting & Sexual Potency
Cheek rubbing behavior peaks from January to May during the breeding season, when female squirrels are inclined to leave their scent all over the place—rubbing their faces and bottoms all over tree branches, occasionally even leaving traces of urine. The Columbian ground squirrel experiences swelling of both the oral and dorsal glands during the reproductive season, useful for scent marking while in heat. Based on the pheromones emitted through cheek rubs, male squirrels can gauge a female’s reproductive capacity and detect when females are fertile and ready to mate.
It is thought that squirrels use their pheromone markings as a secondary form of communication in different scenarios, including:
- To communicate danger, warning conspecific squirrels of a nearby threat.
- To indicate the marker’s social status and how dominant or submissive he is.
- To show possession, warning strangers that the area is occupied or off-limits.
The Role Scent Marking Plays in Food
In anticipation of colder months when food is more scarce, squirrels hide stores of berries, nuts, and seeds for later use. Most squirrels are “scatter hoarders,” dispensing their various bounties over a distance of up to seven acres wide—a distance larger than five football fields! (YouTube)
They’re fairly organized in categorizing their hidden stockpiles, delineating by type of nut, etc.
UC Davis post-doctoral fellow Mikel Maria Delgado asserts that they spread out their hoards as a survival instinct, to avoid going hungry should another creature happen upon their hidden inventory.
Their sense of smell serves two purposes here:
- Determining eligibility: Squirrels use their sense of smell to determine if nuts have holes or have already been infiltrated by insects. A cracked shell means that the nut will rot in the ground. They’ll eat flawed specimens at the moment they find them but won’t include them in a haul for future consumption.
- Locating past food stores: squirrels use their visual and spatial memory to remember where they hid their food supply, but also strongly rely on their sense of smell. This is why you may see a squirrel rubbing its face on an acorn or pine cone—it’s marking its food to make it easier to locate down the road.
Squirrels surprisingly have a 90% success rate of relocating previous caches, a pretty amazing feat. But you win some, you lose some: occasionally they lose track of their caches, another animal got to it first, or the seeds already began to germinate. Squirrels could be called Nature’s Johnny Appleseed, as we have them and their buried treasure to thank for a majority of our forests’ propagation.
Among the most interesting creatures in the animal kingdom, squirrels partake in various behaviors that to the casual human observer seem strange and unorthodox.
Among these is the phenomenon of rubbing their faces on things—the purpose being to deposit pheromones, which alternatively can give biological information and mating cues to other squirrels, as well as establishing relationships. In turn, it also helps the squirrels orient themselves in their environment.
- American Psychological Association: Squirrels recognize degree of kinship by scent, psychologist finds
- Cornell Chronicle: Kissing cousin or close kin? One sniff is all some animals need to tell difference, Cornell behavior researcher discovers
- University of Nebraska Digital Commons: PHEROMONES: THEIR POTENTIAL FOR GROUND SQUIRREL CONTROL
- Wildlife Online: Squirrel Behaviour – Scent Marking
- YouTube: How Do Squirrels Find Their Nuts? | How Do Animals Do That?
- Skedaddle Wildlife: How Squirrels Mark Their Territory
- Live Science: How Do Squirrels Find Buried Nuts?