By Kevin Hong, Wild Oakland intern
Intern Kevin here!
On Saturday, July 13th, we met in a shady grove in front of the entrance to Children’s Fairyland for our squirrel walk with Lila Talcott-Travis, founder of Yggdrasil Urban Wildlife Rehab. She’s got about twenty years of squirrel experience under her belt- how many people can claim that?
Lila kicked off our walk by telling us about the species of squirrels we could see in the Bay Area: Eastern fox squirrels (Sciurus niger), Western grays (Sciurus griseus), Eastern grays (Sciurus carolinensis), and California ground squirrels (Otospermophilus beecheyi). Around the East Bay, the Eastern fox squirrels are going to be the type you see around, while the Eastern grey is the predominant squirrel in San Francisco.
The Eastern fox and Eastern gray squirrels are considered “non-indigenous natives” because they’ve lived in the area for more than a hundred years. They were brought to California about a hundred years ago supposedly because people missed seeing tree squirrels- California’s native Western gray squirrel is very elusive and has no interest in mingling with humans in the urban environment. However, transposal of species often happens without deliberate human intervention – for example, the brown-headed cowbird (Molothrus ater) and the Virginia opossum (Didelphis virginiana) are also non-indigenous natives to California. Opossums have simply migrated westward across the continent, and the brown-headed cowbird followed the by bison herds as they were pushed westward.
Lila also talked about black squirrels, which are a melanistic variant of the Eastern gray; a kind of a mutation related to hair and skin pigments. This means that wherever there is a population of Eastern grays, there will likely be some percentage of it that is melanistic. Interestingly, melanism is becoming more commonly seen in Eastern gray squirrels. Perhaps it could be adaptive; camouflage could be less important in an urban environment, and the darker coat allows for better heat absorption. In addition, melanistic genes in other species are thought to increase animals’ resistance to diseases.
Squirrels have a very important ecological niche as the world’s gardeners- it’s thought that well over half the world’s forests today were originally planted by squirrels or squirrel-like animals. Lila said that she often hears complaints about squirrels that get into fruit trees and ruin the fruit by taking only a couple bites, dropping it, and repeating until a mess of partially eaten fruit litters the ground. However, by doing this they’re triggering germination; the fruit they drop, if left alone, will sprout a new fruit tree on the spot!
As we walked, we spotted several squirrel nests (dreys) in the trees. These are nests constructed by squirrels that in the branches trees that look very much like a crow’s nest from the bottom. They’ll certainly nest in tree hollows if they’re available and not already occupied, and in attics if they have babies to keep safe. There are two types of dreys – baby pads and bachelor pads (noticeably smaller and messier!), and squirrels construct them by weaving branches and two layers of lining (one rough, one softer) made of leaves and whatever they can find that’s soft and comfortable. Dreys have a wide overhang along the edge of the nest, creating a hollow similar to the shape of a tire. This overhang protects babies from predators and the weather, and is lined with especially soft material to keep the young squirrels cozy.
Squirrels have a long “K factor”, meaning they spend a relatively long amount of time as young with their mothers. They are blind until they are five weeks old and can’t fully see until six weeks; consequently, they don’t leave the nest until then. They live in the same nest with their mother until they’re five to six months of age, at which point the mother will kick them out, forcing them to build their own. They do play at nest-building before then, so they’re not completely unprepared!
Lila walked us through the daily life of a squirrel. About an hour after dawn they get up and forage. Around 3 to 4 PM they have a siesta and then continue the search for food and maintain their nests. Their activity becomes more frantic as dusk approaches; and then at dusk, they go home. They build a new nest a couple times a week, except for mother squirrels, which will stay in the same nest with her babies for months while maintaining multiple back-up nests.
Squirrels have a ridiculously good sense of smell! They can find nuts buried 12 inches underground, and they can detect other things as well. Squirrels have distinguished enough noses to be able to smell THROUGH the shell and determine whether or not a nut is rotten.
Lila talked a little about their caching behavior. We’ve probably all seen them collecting nuts and burying them- they also store food in caches. They don’t do this as much when food is plentiful, and they cache more as winter approaches. In winter, they go into torpor (which is like a mild form of hibernation)- they’ll live off their fat stores for the most part, but they’ll also go out occasionally to forage.
Lila also talked about feeding them. Their natural diet consists of nuts, grains, lichens, and bark. People often feed them peanuts (remember: it’s a legume, not a nut!), sunflower seeds, and bread, which is fine, but it’s not the healthiest thing for them, and they need a varied diet. If you want to feed them, Lila recommends walnuts and almonds because they’re far more for the little guys. And feeding them is a big deal; it’s a small act that helps us maintain a connection to wildlife.
Their incisors at the front of their mouths grow their entire lives, so they need to gnaw to grind down the teeth- another reason nuts in hard shells are good for them. The front of their teeth are orange, and it’s often thought that it’s because they’re dirty. Actually, the orange is hard enamel that wears down slower than the tooth material behind it, creating a sharp, chisel-like end on the tooth. Orange teeth are a sign of a healthy squirrel!
It’s also a common misconception that tree squirrels are rabies vectors, when in fact, they are not. Tree squirrels have dry mouths, which means they can’t transmit it as rabies vector animals do – with saliva.
Cool facts Lila told us about squirrels
- A long history of having the short end of the stick when interacting with other species of animals has created some defense-mechanism-behaviors. They tend to keep their tails between themselves and what they consider a threat, so if something tries to get ’em, it’s more likely that they’ll get away (even if they lose their tail in the process)
- Squirrels are among the animals that have learned new ways to get food as a result of humans being almost everywhere. For example, both crows and squirrels have been seen stealing from vending machines.
- They are one of very few non-primate mammals with full color vision (they can see it at least as well as we can). This is especially helpful for helping them track down fruit to eat.
- Fox squirrels are likely at a figurative evolutionary dead end, and there are several pieces of evidence indicating this. For one thing, they’ve looked the same for a very long time in our fossil record. For another, there’s a cranium width to pelvic size ratio. If a mother squirrel has even the smallest amount of scar tissue in her pelvic region, it makes birthing impossible because the birth canal becomes too small for the skull of newborn squirrels. This implies that their craniums can’t get any larger than they are now (unless they go through some highly unlikely radical changes to their anatomy)
At this point Lila pulled a baby squirrel out of her shirt. She introduced us to Petunia, the 3 month old Western gray she was rehabbing and feeding every four hours (and therefore carried everywhere). Petunia has a congenital pelvis and nerve problem and can’t use her back legs, so she is not releasable into the wild. Instead she will stay with Yggdrasil as an education animal for the purpose of educating people about wildlife.
Lila talked about her experience rehabilitating and carrying squirrels. Animals certainly feel emotions and experience emotional and physical pain. We’re not even all that different from them; most animals, including us, go through very similar developmental stages. “These baby squirrels that come in are usually orphaned by some terrible misfortune – an automobile accident or a toppled nest – and they’ve lost their only comfort in this world,” Lila said. “My first reaction when I started doing this 15 years ago was to just put the baby squirrel up against my chest so it could stay warm and hear a heartbeat, and know that it’s safe.” She encouraged all who were willing and able to volunteer to help rehabilitate wildlife.