Squirrel
Anatomy
Here are eleven interesting facts that I have learned about squirrels since I have been following them...
1. Whiskers
Did you know that squirrels have extra sensors (vibrissae) all over their body?
They might look like one big collection of whiskers, but they actually have a bunch of long and thick, specialised hairs for sensing their surroundings. As well as on their nose, squirrels also have whiskers above their eyes, under the chin, on their neck, multiple places on their legs and arms, their chest, belly and tail. In the case of Scandinavian squirrels, the whiskers on their face seem to be dark, whereas the ones on their arms and chest are lighter, to match the surrounding fur. This might seem obvious, but this is not always true of the Fuscoater subspecies in Central Europe, which have bright whiskers on their face.
These sensors help them with things that they cannot see (or see well). Their vision has a large radius for spotting predators, but they have a blind spot behind and underneath their skull. If a squirrel turns their back on you, they are trusting you to look out for predators in the other direction.
2. Thumbs
Did you know that squirrels have adorable little thumbs?
They sometimes have little nails on them, but not claws. Set quite far back on their arm, they're less likely to touch messy surfaces when climbing or running around, and thus they stay cleaner for holding and manipulating food. After eating, they will vigorously lick their hands, making especially sure to have clean thumbs. This is common in all rodents.
3. Ankles
Did you know that squirrels can rotate their back feet 180 degrees due to having double joined ankles.
They are one of a few animals that can do this, which enables them to run down trees quickly and better escape from predators. In addition to this, their tail allows them to shift their centre of balance quickly, enabling them to balance, jump and cling to tree trunks much better.
4. Tail
Did you know that the cross-section of a red squirrel's tail can show multiple tones & colours.
This often doesn't show up as you only see the outer colour. These colours also change a lot between the summer / winter coats, but also the individuals vary quite a bit too. Although they're not all this bold and varied, plus they do change in the summer, they all end with the squirrel's main colour and have darker colours just underneath. Thus, you will never see a red squirrel with a bright halo like the Eastern Greys. Since red squirrels can be quite grey in the winter, this can be a reliable way to identify grey squirrels in locations that have both (like the UK & Italy) if you're struggling to identify them. Of course, red squirrels will also have tufted ears in the winter, so this shouldn't be a problem.
5. Fur
Did you know that red squirrel's coat changes colour in the winter?
It can be quite difficult to recognize your squirrels between the winter and summer, due to how much their coat changes. Their colours go from a thick grey in the spring to a shorter deep-red in the summer, and their tufts will disappear around a month later. The thickness of the tail fur will also change. The Winter fur will start to grow back during September. These changes are mostly triggered by daylight hours rather than temperature (due to reliability). The thicker Winter fur is not only brighter, but it also scatters light more, making it more adaptable to various surrounding colours (infrequent & patchy snow) and changeable lighting for camouflage. The squirrel's base colour comes from their food and dwellings. Pine trees here are bright red at the top, and forest floors are often a saturated ochre (from pine needles and dead leaves). Higher altitudes tend to be exclusively darker pine trees, so follows the squirrel's coat colour.
6. Body Fat
Did you know that the Eurasian Red, or Sciurus Vulgaris (meaning "Common Shadow-Tail") cannot get fat?
Unlike other tree squirrels, they cannot store body fat for winter. This is why they grow a thick winter coat instead. If you see a rather round adult red squirrel, it will likely be a pregnant female (like the one above).
7. Young
Did you know that squirrels are pretty much independent at only 8 weeks old?
These ridiculously adorable creatures are out of the nest and highly capable ath this point. Sadly their mortality rate is around 70% for their first year. They might look rather clueless, but the ones that remain will be stealthy little ninja survivors. No matter what time of the year they are born (can be any time), they will be complete with a winter coat, just in case. They will have their tufted ears and extra fluff, even if the adults have lost all of theirs already. Although they will also lose it pretty quick too.
Mammal's normal litter size range is between half and the total number of nipples they have. Thus, 3-6 and 4 perhaps being the most common number of kits (babies) for squirrels. They can have two, or in rare cases even three litters per year (if there is an abundance of food). They will stay in the drey (nest) for about 8 weeks. Red squirrels are so territorial that the male and females won't nest together unless it's extremely cold. Only the mother will bring up the young, and when they are out of the nest they will soon be on their own and treated as competition for food sources by the adults.
8. Bite
Did you know that squirrels have one of the strongest bites?
If you're wondering how a squirrel can break open a walnut or hazelnut so quickly, their jaw muscles are able to concentrate about 48 megapascals (7000 psi) of pressure on to their front teeth. Although localized, that's a harder bite pressure than a Great White Shark or a Crocodile. Needless to say, they can cause a lot of damage if they're scared, so treat them a healthy amount of respect if getting close. They have four back teeth on each side, top and bottom, totalling twenty including their four front ones. Like Beavers, the front teeth have an orange tint due to being infused with iron for extra strength. These never stop growing, so they need to gnaw things often in order to keep them in check.
9. Food
Did you know squirrel's have a surprisingly varied diet?
As well as nuts, squirrels like to eat mushrooms, flowers, insects, tree sap, seeds, fruit and vegetables. They can eat birds eggs, although that is not very common. They like to wedge some food in trees to dry it out for later. This is quite typical with mushrooms. To see more specifics of what to and not to feed them, see the section on food here.
10. Leucism
Did you know that squirrels can have patches of white fur?
One interesting colour characteristic in squirrels is where patches of their skin and fur lose their colour. This seems to affect squirrels with darker coats more, although not exclusively. One image I saw showed a dark squirrel with white hands and feet. This condition should not to be confused with Albinism, which affects the whole body and also turns the eyes red.
11. Autumn Face
If you're wondering why squirrels look like they've been sniffing glue in the Autumn...
If they have black crusty bits around the corner of their mouth, or a rather stained face even when it's not that wet (during the late summer, early autumn), this is probably because they have found some fresh pine cones. They find these sap infused, green pine-cone seeds irresistible, and the sap gets stuck to their face.
12. Autumn Fur
Another thing that's common to see in squirrels during the autumn is patches of missing fur...
Although you can often see squirrels scratching throughout the year, it's mostly when their coat is transitioning between its summer and winter modes that the overzealous scratching from their back claws tends to remove chunks of fur. Small patches of missing fur is not much to worry about and isn't necessarily caused by mange (microscopic mites).
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More Squirrel facts coming soon...