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The niche hypothesis

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  • Wild Sanctuary, Inc.
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The Niche Hypothesis: A virtual symphony of animal sounds, the
origins of musical expression and the health of habitats
Author: Bernard L. Krause, Ph.D
Source: The Soundscape Newsletter 06., June, 1993
Native Americans have long been aware that there is a symphony of natural sounds where
each creature voice performs as an integral part of an animal orchestra . They are not alone.
Indigenous cultures throughout the world are keenly aware of the power and influence of
natural sound in each of their musical creations. As an artist and naturalist, l have long been
fascinated by the ways in which hunters from non-industrial societies determine types,
numbers, and conditions of game and other creatures hundreds of meters distant through
dark forest undergrowth by sound where nothing appears to the Western eye or our untrained
ear to be especially distinct. As we are primarily a visual culture, no longer connected to what
environments can tell us through sound, we've lost aural acuity once central to the dynamic
of our lives.
While working with the Nez Perce in Idaho and central Washington in the late 60s and early
70s, a tribal elder by the name of Angus Wilson suddenly became very silent when I told him
I was a musician. "You white folks know nothing about music," he said, teasing me. "But I'll
teach you something about it if you want." Early the next morning we headed out from
Lewiston to Lake Wallowa into northeastern Oregon... to one of the many ancient campsites
of Chief Joseph and his small band prior to 1877. Wilson led me to the bank of a small
stream coming out of a valley just south of the lake and motioned for me to sit on the
ground. I immediately began to shiver in the cold October air but continued to sit for the
better part of an hour, every now and then watching Angus, who was sitting quietly about 50
feet away upstream. For a long while, except for a few jays and ravens, nothing happened.
Suddenly, a slight breeze coming from up the valley began to stir some of the branches and
the forest burst into the sound of a large pipe-organ chord appearing to come from
everywhere at once. Angus, seeing the startled look on my face, walked slowly to where I
was sitting and said, "Do you know what makes the sound, yet?" "No," I said. "l have no
idea." He then walked over to the bank of the stream and, kneeling low to the water's edge,
pointed to the different length reeds that had been broken by the wind and weight of the
newly formed ice. He took out his knife and cut one at the base, whittled some holes, brought
the instrument to his lips and began to play a melody. When he stopped, he said, "This is
how we learned our music." It wasn't until ten years later,while recording the forests of
eastern Kenya that that morning at Lake Wallowa came to mind again. It was there that I
began to wonder about the importance of natural sound to the entire context of our survival
and our cultural success.
Since the end of the 19th Century, biologists and zoologists have been focussing their
research in large part on the study of singular creatures in an effort to understand an
organism's connection to the whole environment. Isolated studies were always easier to grasp
and measure within the canons of pure and carefully considered academic terms. Study
controls were easier to impose.And quantified results have been the proverbial means to
heaven's gate... at no little cost to comprehensive knowledge. Indeed, even in the relatively
new field of bio-acoustics (bio = life, acoustics = sound) where feasible recording technology
first emerged in the late 60s, field researchers have earnestly sampled single creature sounds
and have tried to isolate individual animal vocalizations only to find that significant parts of
the messages have eluded them altogether.
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In a recent essay on this subject, Stephen Jay Gould spoke of "... the invisibility of larger
contexts caused by too much focus upon single items, otherwise known as missing the forest
through the trees." ("Abolish the Recent," Natural History, May, 1991, pages 16-21.) Later in
the article Gould suggested that we have a great deal of difficulty grasping the larger, more
complex concepts -even when they may hold the key to simpler truths. Bearing this in mind,
we are just now beginning to realize the important role ambient sound plays in our
environment. Abstracting the voice of a single creature from a habitat and trying to
understand it out of context is a little like trying to play Samuel Barber's "Adagio for Strings"
absent a violin section as part of the orchestra.
From what we have just begun to see, it appears that ancient human beings had learned well
the lessons imparted by natural sounds. Their lives depended as much (if not more) on their
ability to hear and understand the audio information imparted by their surroundings as those
given by visual cues. Small enclaves like the Jivaro and other tribes of the Amazon Basin
survive using this information today. Not only can these extraordinary folks distinguish one
creature sound from another but they recognize the subtle differences in sound between the
various mini -habitats (as small as 20 sq. meters) in a forest, even when these localities
appear to have visually identical biological and geological components. More likely than not,
even when travelling in total darkness these remarkable groups appear to determine their
exact location simply by listening. Furthermore, when we closely observe the effects of
chimpanzees, Mountain Gorillas and Orang-Utans pounding out complex rhythms on the
buttresses of rainforest trees, one cannot help but be struck by the articulation of the
message, its effect on other groups of primates in the vicinity of the sounds, and the natural
origins of the human art of drumming and making music.
Experienced composers know that in order to achieve an unimpeded resonance the sound of
each instrument must have its own unique voice and place in the spectrum of events being
orchestrated. All too little attention has been paid to the fact that insects, birds and mammals
in any given environment have been finding their aural niche since the beginning of time and
much more successfully than we might have imagined. Indeed, combining an audition with a
graphic print-out of the diversity and structure of natural sounds from a rainforest forcefully
demonstrates very special relationships of many insects, birds, mammals, and amphibians to
each other. A complex vital beauty emerges that the best of sonic artists in Western culture
have yet to achieve. Like the recent acknowledgment that medicine owes much to rainforest
flora, it is my hunch that the development of our sound arts owes at least as much to the
"noise" of our natural environments.
Based on R. Murray Schafer's exceptional vision of sound, the premise that soundscape
ecology or the study of sound in any environment provides important clues as to "the effects
of the acoustic environment... or the physical responses or behaviourial characteristics of
those living within it" (Handbook for Acoustic Ecology, B.Truax, Ed., ARC Publications, 1978),
we are just beginning to listen more symbiotically to sound in our varied environments. What
our ancestors knew and what successfully guides many forest inhabitants today is the
knowledge that every zone in any given environment, where the natural habitat is still
completely intact, has its own unique voice. Sometimes, if one moves just 10 or 20 meters in
one direction or another in any old-growth habitat, the sound will be quite different even
where there is similar vegetation and climate.
From the early bio-acoustic studies we have done, I believe we have recently discovered
some evidence of the roots of ancient musical composition... something which has evolved
over time and from which ancient human beings learned some pretty complex formulae. First
of all, these folks seem to have been aware that each creature appears to have its own sonic
niche (channel, or space) in the frequency spectrum and/or time slot occupied by no other at
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that particular moment.
Taking a giant leap when considering the habitat as a whole, the sounds of each of these
zones are so unique and important to creature life in a given location, if one creature stops
vocalizing, another immediately joins the chorus to keep that audio bio-spectrum intact. An
audio bio-spectrum is an acoustical spectrographic mapping of any particular habitat by
frequency (pitch, sometimes tone) and amplitude (loudness) over short periods of time.
Territory is now defined in dimensions well beyond the 3-D topographical. In younger habitats
birds and mammals will occupy only one niche at a time. However, in older environments,
some tropical rainforest animal vocalizations, like the Asian paradise flycatcher (Terpsiphone
paradisi), are so highly specialized that their voices occupy several niches of the audio bio-
spectrum at the same time thus laying territorial claim to several audio channels. From our
observations of the Asian paradise flycatcher, we suspect that we will soon be able to utilize
this acoustical methodology to help determine the age of certain habitats. Not a few migrating
eastern American warblers, able to learn only one song and call in their lives, find themselves
unable to adjust to the changes in ambient sound when they fly to their disappearing Latin
American winter nesting grounds. Where these environments have been deforested, and when
birds try to move to nearby and ostensibly similar or secondary growth habitats, they
discover that they are unable to be heard. Our studies are beginning to show a strong
likelihood that survival might be impaired because territorial and/or gender related
communications are masked.
(Figure 1: 10kHz-10 second audio bio-spectrum of Pic Paradis, St. Maarten.) (Not available)
(Figure 2: 20kHz-10 second audio bio-spectrum of Kalimantan, Borneo.) (Not available)
Figures 1 and 2 show simple and complex habitat ambient niches where consistent dark lines
running horizontally across the page represent a unique mixture of insect voices shown
occupying several "bands" of a 20-10,000 Hertz frequency spectrum in Figure 1 and a 20-
20kHz spectrum in Figure 2. The darker the line, the greater the amplitude in that particular
range. The short lines toward the bottom of the page in Figure 1 represent the low voice of a
Zenaida dove, a species of bird living in the Virgin Islands of St. Maarten. This sample was
taken on Pic Paradis, a 400m mountain on the French side. The Figure 2 sample was recorded
recently in Borneo. Again, the consistent horizontal lines running across the middle of the
page represent insect voices. However, notice the Asian paradise flycatcher (Terpsiphone
paradisi) vocalizations at both the left and right sides of the page. Its voice is made up of
three harmonic components called formants. And they fit uniquely and exactly into several
niches where there is little or no vocal energy represented by the light or white spaces. It
turns out that in every unaltered habitat we have recorded, many birds, mammals and
amphibians find and learn to vocalize in acoustical niches unimpeded by the voices of less
mobile creatures such as near-ranging insects.
We first noticed this phenomenon while working in Africa in the early 80s. Many habitats have
been recorded since. To obtain these recordings we would typically spend 500 hours on site to
get 15 minutes of usable material ... a ratio of 2,000:1. The long wait is due primarily to the
introduction of human-induced mechanical noise(s) like chain saws (from 20 miles away),
aircraft, motorized riverboats, etc. To date, our library consists of approximately 2,500 hours
of material ... 15% of it from now-extinct habitats.
While recording species-specific creatures, we would often wait for up to 30 hours in one
location for a desired event to take place. Out of boredom and because there was nothing
else to do at the time, we began to record pure ambient sounds. When a bird sang or a
mammal or amphibian vocalized, the voices appeared to fit in relation to all of the natural
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sounds of the immediate environment in terms of frequency and prosody (rhythm). Over a
number of years we would return to the same sites only to find, when the recordings were
analyzed, that each place showed incredible bioacoustic consistency, much like we would
expect to find from fingerprint matching. The bird, mammal and frog vocalizations we
recorded all seemed to fit neatly into their respective niches. And the bio-acoustic niches from
the same locations all remained the same (given time of year, day, and weather patterns).
Having just begun to work in Indonesian rainforests, early analysis indicates similar results
from each of the biomes we have visited and recorded.
While the audio bio-spectra of each location remain essentially constant, large habitats of the
same region will show local variability and regional similarities, all at the same time. However,
each area generates its own unique voiceprint and can be identified by sonogram. We find this
to be particularly true where the density of living organisms is greater such as tropical
rainforest habitats. As more creatures vie for acoustical space, the ability to clearly articulate
a voice within that space is more critical to each species' survival. As would be expected,
acoustical definition changes as we move away from the equator north or south to more
temperate zones. In these habitats, creature voices and well-defined acoustical spaces are
determined by more loosely tangible criteria.
If, as we are suggesting, the ambient sound of primary growth habitats functions much as a
modern day orchestra with each creature voice occupying its own place on the environmental
music staff relative to frequency, amplitude, timbre, and duration of sound, then there is a
clear acoustical message being sent as to the biological health of these locations. Some
people, believing that fragile environments can be continuously and endlessly developed, must
begin to listen, as well as observe what changes are taking place. Developmental advocates
suggest that if just small biological islands are preserved, that will be enough, especially for
the development of eco-tourism. 'Life is too short not to get as much as we can out of it.'
However, it has been shown in our own country from work done in North American national
parks that species are becoming extinct and that they are doing so in an inverse relationship
to the size and age of the parks and at an increasing rate. The smaller the park, the faster
the decay. When we have tried to record in new stands of trees planted in the Olympic
peninsula by Georgia-Pacific and other lumber companies, we have found a profound lack of
bio-diversity evidenced first by the obvious monoculture of corn-rowed stands of fast-growing
pines and very little supporting vegetation growing on the forest floor, but more so by the
overwhelming silence. Compare these recordings with those of nearby healthy old-growth
forests and the measurable differences are astounding.
Research continues on the issues suggested by this hypothesis. The study of acoustic ecology
began in the late 70s and has just recently begun to be considered as a valuable tool for
defining the health of both marine and terrestrial habitats around the world. Adding this
information to the body of knowledge is important for many reasons not the least of which is
rediscovery of a direct cultural link to our natural surroundings before they all disappear. For
the past two centuries Western academics, writers, and artists have laboured at some length
to keep ourselves separated from the notion of "nature." The use of the very word, itself, sets
us apart. It is interesting to note that no Native American word for "nature" exists in any
language of the 500 nations. My wife, Katherine, and I have chosen not to use it to describe
any of our work.
Natural orchestrations, the sounds of our unaltered temperate, tropical, arctic, desert and
marine habitats, are becoming exceedingly rare and difficult to find. The keys to our musical
past and the origins of complex intra-species connection can be learned from the acoustic
output of these wonderful places. We are learning that the isolated voice of a song bird
cannot give us very much useful information. It is the acoustical fabric into which that song is
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woven that offers up an elixir of formidable intelligence that enlightens us about ourselves,
our past, and the very creatures we have longed so earnestly to know.
(April 2, 1993) Bernard L. Krause, Wild Sanctuary Communications, 124 Ninth Ave., San
Francisco, CA, 94118 USA.
... Species markers may be inherent to the frequencies in which the calls are made, or the modulation over a frequency range over the duration of the call. Krause [82] suggested that each species has their own sonic niche, also described as their acoustic channel, defined by the range of frequencies that their repertoire covers. This is the acoustic niche hypothesis (ANH). ...
... Fish, for example, use a form of acoustic orientation, relying on sonic information received from biotic or abiotic sources [4]. Water turbulence, wind-driven waves and surf noise, geothermal noise, the diversity of marine life present, bathymetry, and the seafloor and shoreline composition create unique, location-based sound fields [82]. Wladichuk et al. [225] suggest, for example, that gray whales utilize these sound additions for navigational cues during migration, with a similar suggestion also made for humpback whales [226]. ...
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... A key challenge in biodiversity monitoring stems from the difficulty in assessing the 122 dynamics of ecological systems in a standardized way. The acoustic signature, or soundscape, 123 of an ecosystem is rich in both ecological 25,27 and functional 28,29 information but the 124 complexity of sound presents significant interpretive challenges. Acoustic indices were 125 developed as metrics to simplify this complexity 30 . ...
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... Next, from PMN, we derived the index soundscape saturation, which reflects the proportion of frequency bins per minute that are acoustically active (at a threshold of 1.5 dB), as defined in Buřivalová et al. (2018). Soundscape saturation, calculated for each minute, operates under the assumption of the acoustic niche hypothesis that species have evolved to minimize how their vocalizations overlap to decrease signal interference (Krause, 1993). As such, it is assumed to provide an intuitive proxy for vocalizing species richness. ...
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... Next, from PMN, we derived the index soundscape saturation, which 262 reflects the proportion of frequency bins per minute that are acoustically active (at a threshold of 263 1.5 dB), as defined in Buřivalová et al. (2018). Soundscape saturation, calculated for each 264 minute, operates under the assumption of the acoustic niche hypothesis that species have evolved 265 to minimize how their vocalizations overlap, to decrease signal interference (Krause, 1993). As 266 such, it is assumed to provide a proxy for vocalizing species richness. ...
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Thesis
O som emitido pelos organismos é um componente biológico e físico. Nos “insetos cantores” a bioacústica é uma questão ainda pouco explorada, apesar da relevância destes sinais para sua ecologia e evolução. O registro e identificação dos sons em insetos é insipiente, principalmente no contexto do monitoramento acústico. Assim, o objetivo desta Tese é identificar, descrever e relacionar os parâmetros espectrais e temporais dos sons de chamado das espécies de grilos, esperanças, gafanhotos (Orthoptera) e cigarras (Hemiptera) no Sul do Brasil. Para isso, são apresentados quatro capítulos, sendo o primeiro um guia acústico-visual com as espécies da Savana Uruguaia (Brasil e Uruguai); o segundo avaliou a partição de nicho acústico entre insetos cantores em áreas de vegetação nativa aberta e fechada no bioma Pampa; o terceiro analisou a distribuição espaço temporal em duas cigarras simpátricas da tribo Carinetini; o quarto capítulo descreve uma assembleia acústica de grilos cantores de copa em Floresta Atlântica com Araucaria. Para as gravações dos insetos foi utilizado o gravador digital portátil Tascam DR-100 MKIII, com taxa de amostragem entre 48 kHz e 96 kHz. Para o monitoramento acústico foram utilizados os gravadores SongMeter 2 ou Audiomoth 1.2.0, configurados sob taxa de amostragem 44 kHz, registrando 1 minuto a cada 5 minutos, ao longo de 15 dias. No primeiro capítulo apresentamos o repetório de mais de 65 espécies de insetos cantores distribuídas entre 13 espécies de cigarras, 18 espécies de esperanças, 4 espécies de gafanhotos e 30 espécies de grilos. No segundo capítulo observamos que areas de vegeção aberta apresentam um número maior de espécies, mas ambientes de vegetação fechada apresentam o dobro de registros acústicos destas espécies. Embora o NMDS tenha formado dois agrupamentos distintos, a composição de espécies não diferiu entre a área aberta e de floresta fechada. No terceiro capítulo apresentamos o repertório acústico e o comportamento de acasalamento de duas cigarras simpátricas, mas não sintópicas, Carineta diardi (Guérin-Méneville, 1829) e Guaranisaria llanoi Torres, 1964. A primeira apresenta repertório com som de voo e chamado, enquanto a segunda apresenta o som de voo, chamado, corte e wing-flick, este último emitido pelas fêmeas. Destaque para o som de voo, registro inédito para a região Neotropical. No quarto capítulo apresentamos uma assembleia acústica composta por quatro espécies de grilos. Com estes capítulos apresentamos, disponibilizamos e demonstramos o repertório de espécies da ecorregião Savana Uruguaia e sul da Floresta Atlântica, que podem servir de base para estudos de monitoramento acústico, comportamento e evolução de insetos.
ResearchGate has not been able to resolve any references for this publication.