DEAR JOAN: We put sunflower and other smaller seeds out on our back patio every day in feeders for our myriad bird visitors, and on our back table and around the patio for the birds and several squirrels that visit from the nearby trees.

At times we have five or six squirrels on the table or patio at the same time, usually with a lot of mourning doves, jays, tits and other small birds.

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Is it one or two snakes shedding skin in my backyard? We notice the squirrels frequently wag their tails vigorously in the tree or on the backyard fence, and are curious what they are signaling. Is this territorial, sexual, or some other way of expressing themselves to the other squirrels?

We find it fascinating to watch them and want to learn more about their way of communicating. The tail wagging does not seem directed at any of the birds.

We notice that the squirrels and birds get along fine. They often eat seeds together on our backyard table with no indication of dispute or antagonism. Most of the squirrels also seem to get along fine and two or three of them will share space as they are eating.

We would appreciate any help you can give us in understanding what the squirrels’ tail wagging means.

Jim Paton, El Sobrante

DEAR JIM: A squirrel’s tail is a spectacularly useful thing. It allows them to balance in precarious positions and to race across high wires. It’s also used to communicate.

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The primary message a squirrel sends with its wagging tail is a warning. If they see something dangerous or suspicious, they wag their tails to alert other squirrels. They also use it to let predators know they’ve seen the danger, taking away the element of surprise.

If the tail is trembling or shivering, that’s another story. Squirrels do that when approaching members of the opposite sex to draw attention to themselves.

DEAR JOAN: It was with great interest and appreciation that I read your column describing how the river otter coped with a blocked waterway, and the letter from Karen Davis regarding animal intelligence.

The animals with whom we share our planet have all the intelligence and skills they need to survive in the world in which they evolved. However, humans have introduced hazards and challenges with which these creatures were never designed by nature to cope.

Despite that, not only do the wild birds and animals around us survive, they reproduce and raise their families in an environment that has become increasingly inhospitable. When I am hungry, I open my refrigerator or head for the supermarket. When an animal is hungry it must forage in its shrinking habitat for enough calories to make it through each and every day while avoiding the many human-made obstacles.

All of this requires a level of intelligence and skill that deserves our utmost respect and willingness to take into account their needs as we seek to further our own interests.

We humans consider ourselves to be the smartest life form on the planet while knowingly continue to foul our own nest with countless manufactured threats to our own survival. How intelligent is that?

Patricia Howitt, Bay Area

DEAR PATRICIA: Thanks for your thoughtful comments. I am in total agreement with you.