Squirrel Stone Caching, Dust-bathing & Sitting High

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Stone caching

Many mammals cache surplus food -- hiding it when plentiful for retrieval when conditions are hard -- and squirrels are among the most proficient cachers known to science, even organising their larders to help them remember what is stored where. The word itself comes from the French cacher, "to hide", and is pronounced "cashing". There are, however, a handful of intriguing reports of squirrels caching something altogether different: inedible objects, mostly stones.

The first account I stumbled across dates from New Year's Day 2005, when Maria Salmon wrote to veteran squirrel biologist John Gurnell about unusual behaviour she'd observed in a grey squirrel visiting her garden. The squirrel had been stealing pebbles, each roughly the size of a walnut (approximately 5 x 3.5 cm / 2 x 1.5 in.), every day for weeks, to the point where she had to replenish her supply. The behaviour continued until at least the end of February. The squirrel, one of several visiting the property, would enter the garden and go straight for the pebbles, ignoring any food that had been put out, then carry one away. Where the stones were taken was never established -- though her observation that the squirrel did not always depart in the same direction perhaps suggests they were scattered around -- nor what became of them.

In August 2010, a user posted to the RSPB Community forum describing similar behaviour: a squirrel was taking gravel and pebbles from their garden, "usually after licking it all over". When larger pebbles were added, the squirrel shifted its attention to these, typically picking up four or five before settling on one to carry away; suggesting it was selecting for some specific quality. Not all the stones were cached in the conventional sense, however, and some were left on fence posts, on the roof of a summer house, or underneath it.

Since then, I have come across further reports of similar behaviour online and now have examples from Britain, the United States (Maine and California), and Canada (Peterborough in Ontario and Manitoba). In some cases the stones were licked before being taken; in all cases they were removed and either buried or presumed to have been buried.

In April 2011, a lady contacted me describing how:

"A cheeky grey squirrel runs up to the house from the bottom of the garden, sniffs the ground for a few seconds then carefully selects a rather large piece of gravel (c. 2 cm in length, smooth, more of a small pebble), puts it in his mouth, finds another the same size and puts that in his mouth too, then runs off down to the conifers at the bottom of the garden!!"

The squirrel was doing this most of the day and had removed quite a few stones.

In December 2018, Vicky Harrison wrote to tell me about grey squirrels that "consistently take small stones from my garden and bury them, usually next door". She had first noticed the behaviour in the winter of 2017, apparently involving just a single individual who was "very particular about the size (acorn) and shape (smooth) of the selected stones". By the following autumn, four of the five or six squirrels visiting the garden were doing it, and in some cases jagged stones were being taken. The stones were removed throughout the day and mostly buried next door, though Vicky also found several in her flower pots.

Between August and November 2020, I received eleven reports of stone-stealing; seven from the UK (among them Sussex, Oxfordshire, County Durham, and Edinburgh) and four from North America (Minnesota and two locations in Canada). The descriptions share the same core elements: one or two squirrels carefully select a stone, rotate it in their forepaws -- often while licking it -- and carry it away. In several videos I have been sent, the squirrel can be seen burying the stone before returning for another; in others it simply disappears from view. Even in cases where the stone's fate goes unobserved, the speed with which the squirrel returns suggests caching is taking place. Stones range from acorn-sized to walnut-sized or a little larger – one observer described the upper end as "a boiled egg cut in half". Only one case has so far shown any evidence of colour preference. Jane Hankinson told me:

"The stones are about the size of an acorn and interestingly always a dark brown colour, even though I have a mixed colour pebble area in the garden."

The most recent account came from Evelyn Bernacki's property in Manitoba, Canada, in February 2026. The squirrel (or squirrels) involved had begun removing "mainly smooth white stones" from a gravel strip between a path and a building the previous spring, shortly after Evelyn had started applying a homemade weed suppressant of salt, vinegar, and detergent to the area. A substantial number of stones were subsequently recovered from open larder caches in the lawn, amounting to just over a litre in total volume.

Thus far, all but one report involves a grey squirrel, and I have yet to come across an example of the behaviour in European reds – though this may simply reflect the grey's wider distribution and greater tendency to visit gardens. Stone caching is not, however, exclusive to greys. In August 2020, Keith Guise described to me repeated stone-caching by an American red squirrel (Tamiasciurus hudsonicus) visiting his isolated mountain garden in New Brunswick, on Canada's east coast. Keith described how the squirrel selected smooth, rounded grey stones roughly 2.5-3.5 cm (1-1.5 in.) in diameter, then either disappeared into the forest with them or left them around the garden in plant pots. This continued throughout the summer, and Keith told me:

"... we see it about four or five times per day but there could be more; it goes to great trouble to choose the one it wants, picking them up putting them in its mouth, turning the stone around until it has the "best" one; always heads off on the same route down our mountain ..."

Stone caching is intriguing behaviour, and sufficiently uncommon that I have never managed to observe it personally, despite having left a dish of suitably sized stones in my garden for two years. The same appears to be true of squirrel biologists: I have been unable to find any reference to it in the literature. Max Planck squirrel biologist Pizza Ka Yee told me that, despite her curiosity about it, she has never witnessed the behaviour. Similarly, Lucia Jacobs -- a neuropsychology professor at the University of California, Berkeley, who has devoted much of her academic career to studying caching behaviour in grey squirrels -- has observed the caching of non-food items only very rarely. In one instance, a squirrel stole an experimental cue shaped like an ear of corn and cached it. Regardless, all accounts describe the same patient deliberation in selecting stones, and the regularity with which the behaviour occurs suggests the squirrel has some purpose it is committed to.

There remains much we do not know about this behaviour. Whether it is sex- or age-specific is unclear, though several reports have suggested yearlings are involved. We do not know whether the stones are ever retrieved or relocated, as food caches are. What we can say is that squirrels are highly proficient at selecting seeds for caching and have a keen sense of smell, making it unlikely they are simply mistaking pebbles for food. Alan Walker in Shropshire provided a telling illustration: the squirrel taking stones from his garden immediately dropped the one it was carrying when he offered it a walnut instead. Vicky Harrison's account is similarly instructive: squirrels visiting across multiple years exhibited the behaviour, implying they were feeding themselves normally between bouts of pebble caching. Several other observers who feed squirrels in their gardens have watched them cache both stones and nuts within the same session.

Three theories have so far been proposed. The first, based on the discovery of stones in the lining of a squirrel's drey, suggests they may serve as ballast or even as a form of heat retention ('radiators'). This strikes me as unlikely; the stones were probably incidental inclusions.

The second hypothesis, put forward by Natural Heritage Information Centre zoologist Don Sutherland, is that stone caching may be an attempt to reduce pilfering by rival squirrels. There are two plausible mechanisms: stones could 'dilute' a cache so that any thief is as likely to unearth a pebble as a nut; or a stone placed on top of a food item might deter or deceive a would-be pilferer. I have not come across direct evidence for either in the reports I have received, though when Fiona Turner dug up one of the caches in her Oxfordshire garden, she found only a stone, and where larder caches were reported there was no food amongst the stones.

The third hypothesis, and in many ways a logical extension of the second, was raised by Professor Jacobs, who pointed to research from the Konrad Lorenz Forschungsstelle (part of the University of Vienna's Faculty of Life Sciences) showing that ravens will openly cache low-value objects such as small toys in the presence of competitors, while concealing food far more carefully. The researchers suggest the ravens may be practising being pilfered from; it is possible squirrels do something similar with stones, though most squirrels seem disinterested in stones.

Taking these ideas further, it is tempting to speculate that stones might serve several overlapping purposes: evaluating a new storage site, keeping a competitor occupied, or actively discouraging one. We know that some squirrel species organise their caches spatially to aid retrieval, with memory and eyesight playing the most significant role. If grey squirrels use a similar strategy, stones could allow them to "test" a location at low cost – losing a stone rather than a food item. A cache of stones that remains undisturbed might indicate a good hiding spot; one that is dug up or scattered might be best avoided. There is also a social dimension worth considering: a squirrel that has watched a rival cache in a particular area may invest time searching that spot, finding only stones, while the real food is hidden elsewhere. If a pilferer consistently finds nothing of value in another squirrel's caches, it may eventually give up targeting that individual altogether.

A final possibility, one I confess seems less convincing than the above, is that squirrels may be using stones as a mineral source. Most reports describe licking before the stone is taken, and while some of this almost certainly represents the squirrel rotating a stone in its mouth to find a secure grip, several accounts give a strong impression of genuine licking. Richard Stallard, who observed this behaviour in squirrels visiting stones beneath his bird feeder in Sussex, noted when I raised the mineral theory that he had been distributing salt in his garden to deter slugs, and that living on the coast meant salt was routinely deposited on the house and garden by sea spray. Nikki Wyrill from Dorset, who watched a squirrel very selectively removing stones from her garden, made a similar connection: "I also live on the coast in a very windy area - so perhaps the theory of salt deposits on the stones may be true." Similarly, Evelyn Bernacki only noticed the caching behaviour after applying salt-based weedkiller to the area and told me salt was her theory, too.

We know squirrels will use mineral licks, and that mineral deficiencies (particularly low calcium) have been linked to bark-stripping behaviour. In the early 1980s, Lawrie Tee attempted, without success, to curb bark-stripping by providing a mineral lick. Alexander Panichev and colleagues later recorded red squirrels visiting mineral-rich soil outcrops known as kudurs in Russia's Sikhote-Alin Biosphere Reserve. More recently, Jon Southwood observed and photographed a grey squirrel licking at a stone column at Fountains Abbey in Yorkshire, seemingly undeterred by Jon's presence. And Fiona Turner, whose account is particularly striking, noticed the stone-taking behaviour began only after she replaced the gravel in her garden with Douglas Muir quartz. Descriptions and photographs from other readers suggest quartz or quartz-like stones are frequently chosen. If mineral deficiency is driving this behaviour, it might also explain why squirrels are so selective: smooth stones may offer easier access to surface salts or minerals, or may themselves have a more favourable mineral composition. One aspect I find harder to account for, if minerals are the answer, is the apparent absence of reports describing squirrels returning to retrieve stones from their caches. It's possible that enough stones are available that individuals don't need to revisit specific sites within a season – but the energetic cost of caching, particularly for those squirrels that spend considerable time storing stones one by one, seems disproportionate if the stones are never used again.

We cannot yet say with any certainty why squirrels take and bury stones. The dummy or test-cache hypothesis seems to me the most coherent, but it is not without its difficulties. The squirrels do not appear to be performing for an audience, and they make no attempt to fake-cache the stones in the way they are known to do with food when they suspect they are being watched. The scale of the behaviour is also striking: a single squirrel may bury dozens, perhaps hundreds, of stones over a season, which would presumably come at some cost to its food-caching efforts ahead of winter. It's possible, on reflection, that we are looking at an aberrant behaviour. No stone caches have yet been methodically examined, so we do not know whether they typically contain food as well -- though several anecdotal reports suggest they don't -- or whether the owner ever returns to them. I would be very interested to hear from anyone who has observed this behaviour or has theories as to its purpose.

Dust bathing

Animals, particularly birds, rolling around in dirt or sand is not an uncommon sight. This is a phenomenon we refer to as a maintenance behaviour, because we think it helps rid the bather of parasites, while also probably helping soak up excess oils in fur and feathers to keep them and the skin in good condition. For mammals, this is largely speculative, but in the case of some birds, chickens in particular, we know that they develop skin conditions if denied access to a dust bath, suggesting it is essential for their wellbeing.

Interestingly, despite this being a behaviour often recorded in ground squirrels, dust bathing appears less commonly witnessed among tree squirrels and I have yet to find a reference to it in the literature. I have, nonetheless, come across a handful of reports online, and had some readers readers contact me, describing Greys rubbing themselves on the ground, in wood fragments of decomposing logs, and even in flower pots. In other words, engaging in what appears to be dust bathing. Additionally, Edythe Butler recently contacted me to describe six American Red squirrels (T. hudsonicus) dust bathing in rotting tree stumps in Quebec, Canada, during the spring of 2024. (I would be interested to hear from anyone who has observed similar behaviour in Eurasian Reds.) These accounts have a couple of elements in common: they occur in dry dirt or dry crumbling wood -- I'm not aware of any examples of mud wallowing behaviour in squirrels -- and are typically punctuated by bouts of grooming and scratching.

It is also worth noting that some of the same body and chin rubbing that is associated with scent marking is often observed during dust bathing; this may be coincidental, or it may imply that dust baths have a role in territorial maintenance as well as pelage maintenance. Certainly, this seems to be the case in some rodents and in his Ph.D. on Belding's ground squirrel (Urocitellus beldingi) ecology, issued in 1972, University of Arizona biologist Larry Turner described how these rodents dust bathed as part of their grooming regime as well as during aggressive encounters with intruders. Turner noted that squirrels often rubbed their upper backs while bathing, apparently depositing scent from the dorsal skin glands that lie in the shoulder region:

"Secretions from this gland leave an odor in dust bathing areas, and at the same time, the dust absorbs excessive secretions which might mat the fur. Thus dust baths may serve the dual function of scent marking an area and personal cleanliness."

Interestingly, five of the Tamiasciurus squirrels Edythe watched dust bathing were suffering from mange. Skin infections or parasites might make squirrels more disposed to such behaviour, although one of Edythe's squirrels, as well as all Greys I have had described to me, dust bathed despite not suffering from any apparent skin disorder. Edythe noted that all the squirrels seemed to enjoy dust bathing and told me: "I think it is very likely that wildlife uses the clean dried out wood fibres in stumps of trees to keep their fur coat clean, and also to help get rid of mites and fleas etc.". As far as I know, no studies have thus far been conducted on dust bathing sites of grey squirrels to know whether there are particular criteria that the squirrels seek out, or whether any detectable scent remains after bathing. We also don't know how frequently bathing occurs, or whether squirrels use the sites as both a kind of "community noticeboard" as well as a "spa". It nonetheless appears to be an uncommon behaviour among tree squirrels and is therefore presumably not an essential aspect of fur/skin management as it is in, for example, some bird species.

Sitting up high

Over the spring of 2020, I received four accounts of squirrels apparently taking prolonged refuge up high, and in December 2021 a similar observation was posted to a Facebook group. Two cases involved squirrels sitting right at the top of a tree, one atop a telegraph pole, the fourth on the side of a person's house, up by the apex, and the most recent one an adult Grey remained 'frozen' in the same location in a tree in the observer's front garden in Shropshire. In all these cases, the animal remained there for several hours and in a couple of instances for more than 24 hours. In the example given to me by Claire Moylan in April 2020, for example, the squirrel sat motionless in the top of a tree at the bottom of her garden for just over 24 hours, ignoring food she left at the bottom for it, before it simply climbed down and ran off. During this time, the squirrel sat upright (not obviously sunbathing) and didn't vocalise while Claire was watching. The following month, Bob Cole described a similar, but slightly different, behaviour in a Grey outside his house:

"We have a grey squirrel which for the past 4 days has been sitting on top of a telegraph pole in the garden for several hours each day. The first day there was lots of 'barking' and alarm calls, but not so much since."

In only one case was this aerial freezing behaviour seen to follow a traumatic encounter. Surrey-based writer and designer Siobhan O'Neill described an incident in which one of the squirrel frequenting her garden was caught by a neighbour's cat:

"... but let her go as I went charging out after them. She sat terrified in a tree at the end of our garden for hours. We kept checking and put water and nuts on the roof of our nearby shed for her but eventually she recovered and left."

I have found no references to this behaviour in the scientific literature, and only one popular account, in chapter 9 of Paul Thomas' captivating book The Year of the Tawny Owl, published in 1984:

"There had been a great buzz of excitement in the main street of Ston Gurney. The small boys especially were interested. All day they had pointed and thrown discreet stones, even tried climbing the telegraph pole, but to no avail – an adult had always come along just in time to protect the grey squirrel snoozing on the hot metal capping. Earlier in the day an excited dog had chased it there and so it had stayed in the full light of the sun, hunched up, head hidden by its two front paws, only occasionally changing its precarious position. The Cloud Hill buzzards had either not seen it or discounted the creature as pretty because it was so close to houses and people. Six o’clock chimed from the chapel dedicated to St Stephen and the squirrel sat low on his haunches and began to groom himself. ... With a final brush of his face, the squirrel turned, jerked forward, tested his grip on the downward vertical, and spiralled down in a slow, coarse, scratching corkscrew."

Taken together, these accounts tentatively suggest that a squirrel may seek safety up high following a distressing event. At first appraisal, these locations may seem rather exposed, but that may be of benefit to the squirrel if its main concern is ground predators. The squirrel presumably remains in the location until either it feels safe again, or is driven down by hunger/thirst.