This fascinating talk by Jeff Reed, Ph.D. was part of Yellowstone Forever's 2024 Summer Speaker Series. The event took place on 6/20/2024 at YF's Gardiner headquarters. For the full Speaker Series schedule, go to https://www.yellowstone.org/summer-speaker-series/. Description: Join us as we delve into new techniques that help unravel the mysteries of animal communication, with a focus on wolf vocalizations. We'll highlight the Cry Wolf project, a collaboration of Yellowstone's renowned Wolf Project. The session includes insights into bioacoustics (i.e. the study of the sounds made by living things), autonomous recording technologies (that you can use to record your own backyard), and most importantly, an immersive experience of listening to and discussing the possible meanings of actual wolf communication in Yellowstone National Park. Bio: Jeff Reed is a software engineer for Yellowstone National Park’s Cry Wolf bioacoustics project, a long-term study of wolf communication. Jeff was born and raised in the Greater Yellowstone Ecosystem in southwest Montana, where he grew up exploring the Absaroka mountains. With a PhD in computational linguistics and 30 years in the technology industry, Jeff now develops camera and acoustic recorders to assist our understanding of animal behavior (https://www.grizcam.com). An advocate for hands-on, measurable conservation, he works to preserve the Greater Yellowstone through business alliances (https://www.wildlivelihoods.com) and inspirational auditory projects (https://www.thelanguagesoflife.com, https://www.fivetoedwolf.com). Cover Image: Tom Murphy

Dr. Jeff Reed is a computational linguist who is based just beyond the northern border of Yellowstone National Park. Working in tandem with the Yellowstone Wolf Project, the Cry Wolf Project records wolf sounds 24 hours a day from up to 60 recorders. One of the many goals is to explore wolf communication, what it may mean, and how we can better understand what they are relaying to one another. Dr. Reed went into great detail about how he is able to decipher wolf sounds from other species, how to read those harmonics and frequencies on a spectrogram, the many types of sounds they've found thus far, and how the data collected could help research and coexistence in the future. Languages of Life (Cry Wolf Project) (https://www.thelanguagesoflife.com/crywolf) @thelanguagesoflife (https://www.instagram.com/thelanguagesoflife/) AI Powered Devices Track Howls to Save Wolves (https://developer.nvidia.com/blog/ai-powered-devices-track-howls-to-save-wolves) A New Way to Help Save Yellowstone's Wolves (https://www.washingtonpost.com/climate-solutions/2024/10/12/yellowstone-wolves-howls-bioacoustics/) A Bioacoustics Study in Greater Yellowstone (Yellowstone Forever) (https://www.youtube.com/watch?v=hx5tWHxv8e4) @thewolfconnectionpod (https://www.instagram.com/thewolfconnectionpod/)

A 3D Spectrogram of various wolf vocalizations taken during a one month period in 2023 in Yellowstone National Park.

This video contains 49 variations of wolf howls, and one human, who were recorded in Yellowstone National Park. As you can see and hear, wolves have a variety of howls, and these are just a representative sampling. Can you find the pups? The human? 907F - the matriarch of the Junction Butte pack? Or the now deceased alpha male of the Rescue Creek pack? The spectral analyzer at the bottom of the video shows the frequency at which the current audio is playing. To the far bottom-left are sounds with a pitch of 200 hertz, and the bottom-right at 1,400 hertz (or 1.4 kilohertz). A common wolf howl is 340 hertz (or Middle F on your piano keyboard) on the low end, but they will frequently howl up towards 500 hertz, and sometimes higher. Larger body sized wolves can likely achieve lower pitches. Pups typically howl at around 1,000 hertz, but within 3-5 months of leaving the den, their voices will lower in to their adult range. The parallel lines you see running horizontally in the each of the square images are harmonics, and your ears focus on the lowest line, or fundamental frequency of the howl; but as you can see on the spectral analyzer, the harmonics show up as multiple bumps, each an octave apart. The lower that line is on the y-axis of each square, the lower the pitch of that wolf. Wolves sometimes combine other sounds, such as growls or barks, with a howl to indicate a threat. When they do this, they often modulate their howl in what shows up as a wavy line in the spectrogram. This is a very basic form of syntax (what is called a two-slot syntax). The second to last vocalization is actually a human, pronouncing the word "woof" and using the "oo" (as in "hoot") vowel to best emulate a wolf. Our vowels have harmonics too. And even though it is easy for you to understand your own language, wolves are also likely able to distinguish the various nuances in timing, emphasis, and pitch for deciphering other wolves. The Cry Wolf bioacoustics project is studying how wolves can identify each other through their howls as well as how different types of howls may mean different things.

Four different wolf packs in Yellowstone National Park were recorded at different locations in the northern range during the same month in 2024. These four spectrograms and the associated audio are chorus howls from those different packs. Pack size differences as well as the social, age and sex makeup of each pack result in a "sound signature" whereby individual packs can likely identify each other and themselves from distances up to at least 7 kilometers. The first recording from the Shrimp Lake pack has a melancholic feel to it because of the echoes created in the location they were recorded - namely, the mountainous bowl of Round Prairie.

Are you new to spectrograms (aka sonograms)? This is an introduction on how to understand spectrograms, which is a relatively simple but important tool used in the study of animal communication.

On January 4th 2024 at about 8am in Yellowstone National Park, two separate wolf packs called the Junction Butte pack and the Mollie's pack came together in a tense reunion which ended amicably. In addition, a dispersing black wolf (1407M) from the Willow Creek pack is seen attentively trying to figure out the players surrounding him. Howling and other wolf communication can be heard throughout this video. Acoustic recorders also captured the two packs chorus howling towards one another the night before. Wolves have many variations of howls with which to communicate, though little is known as to whether different types have different functions. There is reasonable evidence, however, that larger bodied wolves have lower pitched howls, which can serve as an honest signal to other wolves about their size. In addition, barks (which you'll hear in one segment of this video) definitely have a different function than howls. Barks come in different forms such as woofs, disturbance barks (which are shorter in duration and lower in pitch) and agonistic barks (which are longer in duration and have more harmonics). Agonistic barks are often emitted by the dominant individual and often show dominance displays (e.g. tail held high). Disturbance barks are only emitted in conflict scenarios…for example towards other packs, humans, cougars or bears. There are several types of different howls in this video, many of which we are still trying to decipher as to possible functions. In addition, at 4:28 in to the video you'll hear a "woa" vocalization from several wolves off camera when a group of the wolves first reunited, and towards whom a different black wolf is running. The "woa" call is done in contexts of social bonding where wolves are often muzzling one another. The Cry Wolf project (grizcam.com/crywolf) is studying the frequency at which wolves vocalize to better model their population and occupancy, as well as the different functions of their sounds.

Typically, when a wolf howls, the fundamental frequency (or first harmonic) is the loudest and the one your brain "hears" the most. Less frequently, wolves howl where the second harmonic is louder than the first, and it slightly changes the overall quality of the howl. This video by Taylor Rabe of 1048M of the Mollie's pack in April 2025 is an example. We don't know if the signal carries any meaning, or if it is used in IDing a wolf (we just don't have enough samples), but it is an interesting phenomenon. Note: 1048M weighted 119lbs when collared in 2019. Assuming a similar weight, that might explain the lower than average fundamental frequency (325hz) of this howl. The second harmonic can be louder than the fundamental frequency due to the interplay of vocal tract resonance, vocal fold dynamics, and non-linearities in the vocal system. Resonance in the vocal tract can amplify harmonics that match formant frequencies, particularly the second harmonic. The shape and tension of the vocal folds also influence harmonic content, and a sharper glottal pulse can enhance higher harmonics. The glottal pulse is the waveform produced by the opening and closing of the vocal folds during phonation, generating the fundamental frequency and its harmonics. Non-linear wave propagation further contributes to the amplification of certain harmonics. This phenomenon is used by singers, such as those practicing overtone singing, to manipulate vocal harmonics effectively. In other words, the complex dynamics of the vocal folds and the vocal tract can introduce non-linearities that amplify certain harmonics, such as the second harmonic, making them more prominent than the fundamental frequency.