In addition to vocal sounds, gray squirrels use the position of their ears to communicate with each other.
By Scott Roller, Pittsburgh Parks Conservancy
The “Let’s Talk About Parks” series is designed to encourage exploration and discovery of Pittsburgh’s urban parks.
Step outside into the nearest patch of grass — or, even better, venture out to one of our city’s five regional parks — and stand still for a second. If you are in Highland Park, you will eventually hear geese honking as they fly overhead, or a swoosh as a duck slides into Carnegie Lake. If it’s early morning and you are deep into lower Frick Park, you may hear deer kicking up leaves as they high-tail it across Firelane Trail. On a warm spring afternoon along Schenley Park’s Hollow Run Trail, you’ll hear spring peepers in vernal pools joining in a chorus that proclaims winter — you hope — is over. Take a Saturday hike on Wissahickon Trail in Riverview Park and you will hear pileated and red-headed woodpeckers knock-knock-knocking on trees as they look for food and shelter, or communicate with other members of their species. We hear animals all around us when we are quiet in our favorite greenspaces. But can they hear us?
Indeed, many animals in our part of the country have finely tuned hearing and complex — and sometimes funny-looking — ears. Bats are found throughout our city parks, and as the weather warms you will begin to hear them squeak and flutter in the trees when night begins to fall. The squeaks they make help them have one of the most astute hearing senses in the animal kingdom. These bat squeak sounds bounce off of nearby surfaces, allowing them to instantly measure the distance from surrounding objects in a process called echolocation. Bats’ pointy ears can change shape to help them hear better, altering in about 100 milliseconds to quickly adapt to different acoustic sensing tasks.
Squirrel ears have many variations, with some being small and rounded, while others are pointed and have long tufts of gray or reddish hairs that protrude a half-inch or more from each ear. Squirrels have excellent hearing, tree squirrels hear lower frequencies better, while ground squirrels are more adept with higher frequencies. Squirrels also use their ears in communications with each other. Ear position may play a role in their body language communication, and they have vocal communications that fall into several main categories, including nesting, mating, aggressive and warning calls. Yes, squirrels that chatter above your head as you get out of your car, with their ears twitching back and forth as they look toward you, are probably talking with each other about you.
It makes sense that rabbits have astute senses of hearing. Their long convex-shaped ears gather sounds, and when under alert, the ears move forward or backward as they attempt to sense where the danger is located. Rabbits can move each ear independently of the other, allowing them to scan for sounds from different directions at once. Rabbits have been known to hear sounds from up to two miles away, including nearly all sounds that humans can hear, plus many higher-pitched sounds — such as those from bugs, rodents and some electronics — that we cannot hear.
Deer are especially visible this time of year, and while they can hear most sounds that humans can hear, their large pointed half-conical shaped ears allow them to pick up sounds much quicker than Homo sapiens. This size, shape and, in particular, the maneuverability of deer ears allows them to make slight tweaks to the position of their ears that enables them to pin-point and identify sounds extremely quickly. Human voice frequency is within their hearing range, so if you want to observe deer in the woods, it is best to keep quiet.
Not all animal ears are immediately visible. While there is little more than a thin membrane visible on of each side of a frog’s head to show us where their ear holes are located, don’t let this fool you: They can hear. This outer ear drum acts as a shield and protector for the inner ear and is made of skin that has no glands — so it doesn’t sweat — and can be a telltale sign of the sex of a frog. Many types of male frogs have larger visible ear holes that allow them to hear the more subtle chirps of potential female mates. In these males, the membrane-covered ear hole may be larger than their eyes, while those of females are usually smaller than their eyes.
The award for the most effective ears on an animal found in our city parks does not go to the long-lobed rabbit, the membrane-covered eardrums of the frog, or the hair-covered ears of the squirrel or deer. As spring approaches and bugs begin flitting overhead, keep an eye out for the brownish-gray wax moth, recently found to have the most astute hearing of all known creatures. The wax moth — and other moths, too — can hear frequencies beyond even those that bats can identify. Unlike butterflies that have well-developed hearing sensors on their wings, wax moths ears are hidden among the fine hairs that cover their thorax near the point their wings meet their body. Like most animals with finely tuned audio skills, the wax moth’s ears and hearing have adapted over time to help it survive. Bats and other animals love to eat moths, and as a result, the wax moths’ ears and hearing have evolved to give them a better chance of outsmarting their predators.
For upcoming Pittsburgh Parks Conservancy nature hikes where you can spot animal ears, visit www.pittsburghparks.org/events.
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