This event occurred over twenty years ago when my hearing was considerably better than it is today. The winds were calm and I was positive that I had heard no sounds in the direction the young bobcat was going until I heard the distress cries. How did the youngster know that its mother or littermate was about to catch the fawn? While this was my first experience with bobcats and ultrasonic sound, it was not my first with coyotes. On many occasions, while observing pairs of coyotes hunting in open country, I have seen one stop and get the other’s attention though they might be 100 yards apart. The coyotes would stare at each other, tilting their heads from side to side, as your pet would do when listening intently to something. After the silent conversation, at least to me, they would change directions or hunting tactics.
When I first started calling critters, I didn’t know there was anything that you could use other than hand calls. It wasn’t until 1967 that my cousin introduced me to recordings on cassette tapes as an alternative to blowing through a call. My first thought when I heard about using recordings of rabbits or birds in distress was that I would never have to experience another dry stand. Unfortunately, while I have had success with animal recordings, I have found that they are not always effective.
Without a doubt, the most common question I have heard over the last 30 years is “I can call coyotes with my hand calls but can’t get anything to respond to an electronic caller, so what am I doing wrong?” Most of you are thinking, “Now how can that be? Most sounds on electronic callers are recordings of live animals, what can be more realistic than that?” The answer to this question is simple; you can produce a wider frequency range with a mouth call than you can with the electronic callers and speakers currently on the market. The higher frequency range generated by hand calls or diaphragms is much more realistic to the predator’s ear, therefore the response to these call will be greater.
Before we go any further into sounds and why one might be more appealing to a critter than another, let’s look at the very basic terms used when describing a sound, volume and tone. Volume is simple, you see the adjustment on the radio in your truck or on the TV remote. Volume is measured in decibels, the unit in which sound is measured. As an example, a whisper is about 15 decibels (db) while a jet engine may reach 150 decibels. Volume is obviously very important when trying to lure a critter with sound, if he cannot hear the sound, he is not coming to it. It is for this reason that most of the electronic callers on the market today will generate 120-125 decibels.
While volume is extremely important to calling success, so is sound quality. Sound quality or tone is measured in Hertz (Hz). Hertz is defined as a unit of frequency equal to one cycle per second or a unit used for measuring the frequency of sound waves. For example, the human can hear sounds from 64-23,000 Hz, anything above that sound level cannot be heard and the term for the sound that we cannot hear is ultrasonic. Since we are using sounds to attract predators, it is more important to find that dogs or canines can hear 67-45,000 Hz and cats or felines, 45-64,000 Hz. On the extreme range are mice that can hear 1,000 to 91,000 Hz, bats, 2,000-110,000 Hz and Beluga whales, 1,000-123,000 Hz. I was surprised to find that most birds can hear from only 250-8,000 Hz with the owl having the keenest from 200-12,000 Hz.
Now that you have an idea how sophisticated a critter’s hearing is compared to ours, it is just as important to know what the frequencies of some of the common distress sounds used for calling predators are. Until now, I did not have the ability to record and produce sounds ultrasonically so testing was almost impossible. Recently, I purchased an ultrasonic recorder that will record up to 96,000 Hz and recorded several popular distress sounds. In order to accurately test the frequency of these recordings we employed an oscilloscope, a device that measures sound waves, (frequency). The results that we got from these tests was shocking and gave greater proof why electronic calls are rarely successful in areas where there is calling pressure.
The first sound that we recorded was a simple lip squeak, a sound that I make by sucking on the palm of my hand. To my surprise, the oscilloscope waves peaked over 65,000 Hz. It was then I knew that we were on to something that would change calling with electronics forever. A few days later, we recorded a baby cottontail and found that the frequency of its distress cries exceeded the 90,000 Hz that I was capable of recording. Since we have been testing sounds with this new ultrasonic equipment, most every distress sound that we have recorded and tested has exceeded 50,000 Hz.
After testing most of the electronic callers currently on the market, we have found that most speakers are good at the low end but can replicate and produce only 15,000 to 18,000 Hz on the high end. Since the human ear can hear up to 23,000 Hz, we can hear all of the sound generated by the call and it may sound pretty good to us but what about the coyote that can hear to 45,000 Hz or the bobcat who can hear 64,000 Hz? This makes it much easier to understand why so many critters would not respond to the electronic calls, especially in areas where there is calling pressure.
Our next challenge was to find a speaker or speakers that would produce tones or frequencies from the lows of less than 1,000 Hz to near 50,000 Hz. After testing everything that we could get our hands on, we found that we would need two speakers, one to handle to low frequencies and another to handle the higher frequencies.
Like many of you, I have difficulty understanding things that I cannot see, feel, smell or hear. While the oscilloscope proved to me that there were sounds generated that I could not hear, I wanted to see how animals would react to these ultrasonic recordings. I was familiar with silent dog whistles and had seen dogs respond to them though I never heard anything other than wind passing through the call.
For the last 25 years, Deb and I have had Dachshund females as pets. They have always been indoor dogs and go to the office with us every day. These dogs have heard most every predator call and animal recording in our sound library and are totally immune to them. I can blow a series on the Mini Blaster or play a recording of a coyote howling without getting them to so much as lift their heads from the bed. If there was ever a dog that was broke to distress sounds, I would have to say that Dash was as close as it gets. I could not wait to see how she would react to ultrasonic recordings.
The sound that I chose for the test was one of the baby cottontail distress recordings that reached frequencies above the 96,000 Hz that I was able to record. While the speaker I was using was limited to reproducing 40,000 Hz, this was much higher frequency than she was accustomed to hearing in the office.
When I turned the recorder/player on at low volume, Dash was sleeping in her bed. As soon as she heard the distress cries, it was if a spring had launched her from her bed and she was jumping at the desk and whining where the recorder was playing. It was then I knew that the calling game would be forever changed and could not wait to try it in a hunting situation.
Though I am still field testing BURNHAM BROTHERS ultrasonic caller, there is no doubt that I am getting more, and more aggressive responses to my calling than ever before when using electronic calls. I feel that the ability to record and reproduce ultrasonic sounds is the greatest innovation in predator calling in over 50 years!