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The niche hypothesis

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03/02/2007 12:20 PMThe Niche Hypothesis: <I>A virtual symphony of animal sounds, the origins of musical expression and the health of habitats</I>
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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.
... This means that the physical environment can filter animal calls, prompting the evolution of calls to best propagate in the habitat in which species naturally occur (Couldridge and Van Staaden 2004). A second hypothesis, put forward by Krause (1993), is that of the acoustic niche, stating that the frequency spectrum is divided into bands, or acoustic niches, which can only be occupied by one species in one place at one time (Krause 1993;Mullet et al. 2017). ...
... This means that the physical environment can filter animal calls, prompting the evolution of calls to best propagate in the habitat in which species naturally occur (Couldridge and Van Staaden 2004). A second hypothesis, put forward by Krause (1993), is that of the acoustic niche, stating that the frequency spectrum is divided into bands, or acoustic niches, which can only be occupied by one species in one place at one time (Krause 1993;Mullet et al. 2017). ...
... Interestingly, the 11-13 kHz band was occupied by only two species, Plangia sp. 1 and Conocephalus sp. 1, which were often highly sympatric. Since they fall in the same frequency band, acoustic interference of the one species should eventually lead to acoustic niche partitioning (Krause 1993). However, these two species often call together. ...
Soundscape comprises of a mix of species-specific calls, where individuals compete for acoustic space, yet a different vegetation structure allows for differential call filtration. We focus on an assemblage of bush cricket species in a human-transformed landscape, with a special focus on the seemingly endangered Thoracistus thyraeus. Landscape transformation produces both novel ecological and acoustic spaces in which species must maintain effective communication. Using acoustic activity and species' total call times to characterise their response to the different biotopes in the landscape , we determine how species are distributed across the landscape to optimise ecological and acoustic space. We further investigate the distribution of occupied frequency bands to determine whether species are exposed to potential acoustic interference from other sympatric species. We identified 11 bush cricket species and hypothesised that where acoustic interference between species is likely; the different species will be found in different biotopes. We found that acoustic interference between species is low as species co-exist by having distinct ecological resource requirements and inhabit different biotopes, thus preventing acoustic interference from other species. Acoustic and environmental factors play interactive roles in enabling sympatric species to co-exist across complex landscapes, illustrating that these insects can co-exist without acoustic interference.
... Gymnogryllus and Nisitrus, see Tan et al. 2018. Furthermore, based on the prediction of the Acoustic Niche Hypothesis (ANH), selection will favour differences in signalling behaviour of syntopic species to help reduce errors in recognition and avoid acoustic interference (Krause 1993;Farina 2014). Consequently, parts of Singapore and brought back to the laboratory for recording by MKT. ...
The scaly crickets, Mogoplistinae, form a monophyletic group of crickets and are characterised by scales covering the integument. In many species, males have modified forewings for producing highly tonal calling songs. Despite being a highly speciose and abundant group of orthopterans in tropical forests, data on their calling songs and studies on their bioacoustics remain scanty. In this study, we recorded and described the calling songs of seven sympatric scaly cricket species belonging to three genera-Cycloptiloides, Ectatoderus and Ornebius-from Singapore. We compared call structure and call parameters of syntopic species occurring together in the same locality within Singapore and found that syntopic congeners exhibit acoustic partitioning to avoid inter-specific competition for the acoustic space. We also found that calling songs can be highly varied among congeners and species from the same species groups. Finally, we also observed that syllable duration and peak frequency exhibit vastly different allometric relationships with body size. Larger scaly cricket species bear disproportionately longer syllable duration, but not differences in peak frequency. ARTICLE HISTORY
... The most developed theories in this field are the Acoustic Niche Hypothesis and the Acoustic Adaptation Hypothesis 169 . The Acoustic Niche Hypothesis 170 suggests that species that have evolved together will also have evolved their own niche in time and frequency space, in which they can communicate clearly to conspecifics without interference from other species. For example, birds may call at frequencies lower than more dominant cricket species, whilst other species may avoid vocalising when the avian dawn chorus is at its peak. ...
Technical Report
Full-text available
Passive acoustic monitoring has great potential as a cost-effective method for long-term biodiversity monitoring. However, to maximise its efficacy, standardisation of survey protocols is necessary to ensure data are comparable and permit reliable inferences. The aim of these guidelines is to outline a basic long-term acoustic monitoring protocol that can be adapted to suit a range of projects according to specific objectives and size. Here we summarise some basic recommendations for audible-range terrestrial ecosystem monitoring - more detail can be found in the following chapters. A ‘Quick start guide’ giving further rationale for these recommendations can be found in Appendix 1.
... Many factors can influence the circadian rhythm of acoustic signalling, such as changes in light and temperature (Clink et al., 2021;Feng & Bass, 2016), endogenous time-keeping mechanisms (Fergus & Shaw, 2013), social cues from conspecifics (Favreau et al., 2009;Fuchikawa et al., 2016), the presence of other acoustically signalling species (Hart et al., 2021), or a combination of these factors. When co-occurring species have similar circadian rhythms, the Acoustic Niche Hypothesis (ANH) predicts that selection will favour differences in signalling behaviour to help reduce errors in recognition and avoid acoustic interference (Krause, 1993;Farina, 2014). These differences may include producing sounds at different frequencies (Krishnan, 2019;Allen-Ankins & Schwarzkopf, 2022) or avoiding temporal overlap on short time scales (Hart et al., 2021). ...
Full-text available
Background Many factors can influence circadian rhythms in animals. For acoustically communicating species, both abiotic cues (such as light and temperature) and biotic cues (such as the activity of other animals), can influence the timing of signalling activity. Here we compare the 24-h singing activity of the cricket Lebinthus luae in the laboratory and field to assess whether the presence of other singing insects influences circadian rhythm. Methods Acoustic monitors were placed in four localities in Singapore and the number of L. luae calls were counted for 10 min of each hour. Individuals from the same localities were captured and recorded in the laboratory in silence but with similar abiotic conditions (temperature and light cycle) as they experience in the field, and the number of calls over 24 h was quantified. Results The 24-h pattern of L. luae singing was not significantly different between laboratory and field recordings. Singing activity peaked in the morning, with a secondary peak in the afternoon and a smaller peak at night. In the field, L. luae sang in the same locations and at the same time as diurnally singing cicadas, suggesting that the sympatric cicada chorus did not affect the circadian rhythm of communication in this species. Acoustic niche partitioning could potentially explain the ability of this cricket to call alongside cicadas: L. luae sings at higher frequencies than sympatric cicadas, unlike nocturnally singing cricket species that overlap with cicadas in frequency.
... Επιπλέον μέσω των μελετών έχουν προκύψει βασικές υποθέσεις για την ακουστική προσαρμογή των ειδών. Για παράδειγμα σε περιοχές με αυξημένη βιοποικιλότητα, όπου ο διαειδικός ανταγωνισμός για την μετάδοση των φωνητικών σημάτων αυξάνεται, σύμφωνα με την υπόθεση του ακουστικού θώκου (Krause, 1993) τα είδη προσαρμόζουν το εύρος συχνοτήτων των φωνητικών λειτουργιών, ώστε να αποφευχθεί η αλληλοεπικάλυψη, δημιουργώντας διαφορετικές επικράτειες συχνοτήτων. Επιπλέον, καθώς τα γεωγραφικά χαρακτηριστικά μιας περιοχής επηρεάζουν την μετάδοση του ήχου, τα είδη προσαρμόζουν τις ακουστικές λειτουργίες ανάλογα με την ιδιαιτερότητα του οικοσυστήματος που κατοικούν, σύμφωνα με την υπόθεση της ακουστικής προσαρμογής (Morton,1975). ...
Full-text available
Several human activities in the urban environment pose as a source of pollution including environmental noise. The increasing human population movement towards urban areas has brought a series of environmental pressures that affect the quality of life and the quality of the overall environment. A response towards the problems caused by noise is the creation of quiet areas in agglomerations. The quiet areas of an urban complex, as defined in the Directive 2002/49 / EC, are a societal response in order to deal with environmental noise. However, the concepts of noise and quietness are multidimensional and vague. So far, two approaches have been applied in order to find quiet areas. The first recognizes noise as a sound of increased intensity and the rational that "less" is better than "more", urges the creation of noise maps in order to highlight areas with lower levels of intensity. An important remark about this particular tactic is the homogenization of all sounds in the light of their intensity. However, the emergence of noise as an urban disease and the promotion of quietness as a panacea, offers short-term and one-dimensional benefits. The second way concerns the general conclusion that the quality of the acoustic environment is responsible for declaring an area as quiet and not the intensity of the sounds it contains. This soundscape approach inevitably leads to the search for the concept of the aforementioned quality and its connection with the concept of quietness. The potential risk of using this tactic, which has now been applied in several European countries, is left to the human instrumental rationality towards the environment, the grouping of opinions in order to highlight the preferred one and the practical application of the dominant opinion in a public space without investing in ecological co-benefits. The goals of this dissertation was to create a flexible protocol for urban quiet areas identification, the efforts of ecological connection of quiet areas, the redefining of the concept of urban quietness and the creation of the new Composite Urban Quietness Index (CUQI) that quantifies the state of urban quiet areas, so that possible changes in the quality of the urban environment are observed in a timely manner. The main research tools were noise level measurements and sound recordings. The collected data were used in such a way as to extract noise maps and sound maps that strengthened the efforts of quiet area identification, with the study area being the city of Mytilene. At the same time, altered fixed tactics of evaluating soundscapes such as the soundwalk were used in order to highlight the perception of the acoustic environment. Then, using a special sampling protocol, the Composite Urban Quietness Index was formed. In conclusion, noise emerged as an immaterial barrier to ecological connectivity in an urban environment. Finally, the dysfunctionality of the so far evaluation metrics which concern exclusively to intensity or preference emerged. The introduction of additional aspects of sound in the analysis of urban acoustic environments regarding frequency and acoustic complexity is considered necessary.
... When acoustic signals sent from individuals overlap in frequency and time, acoustic interference and signal masking occurs, which may reduce the receiver's ability to discriminate information from the signal (Klump, 1996;Brumm and Slabbekoorn, 2005). Under the acoustic niche hypothesis (ANH; Krause, 1987Krause, , 1993, signaling behavior has evolved to minimize overlap with heterospecific calling individuals through selection on signal structure and the sender's ability to adjust the timing of signals. This hypothesis may be viewed as an extension of the niche theory of Hutchinson (1957) whereby acoustic space is a resource that organisms may compete for and that can be partitioned both spectrally (frequency range of the signal) and temporally. ...
Full-text available
When acoustic signals sent from individuals overlap in frequency and time, acoustic interference and signal masking may occur. Under the acoustic niche hypothesis (ANH), signaling behavior has evolved to partition acoustic space and minimize overlap with other calling individuals through selection on signal structure and/or the sender’s ability to adjust the timing of signals. Alternately, under the acoustic clustering hypothesis, there is potential benefit to convergence and synchronization of the structural or temporal characteristics of signals in the avian community, and organisms produce signals that overlap more than would be expected by chance. Interactive communication networks may also occur, where species living together are more likely to have songs with convergent spectral and or temporal characteristics. In this study, we examine the fine-scale use of acoustic space in montane tropical wet forest bird communities in Costa Rica and Hawai‘i. At multiple recording stations in each community, we identified the species associated with each recorded signal, measured observed signal overlap, and used null models to generate random distributions of expected signal overlap. We then compared observed vs. expected signal overlap to test predictions of the acoustic niche and acoustic clustering hypotheses. We found a high degree of overlap in the signal characteristics (frequency range) of species in both Costa Rica and Hawai‘i, however, as predicted under ANH, species significantly reduced observed overlap relative to the random distribution through temporal partitioning. There was little support for acoustic clustering or the prediction of the network hypothesis that species segregate across the landscape based on the frequency range of their vocalizations. These findings constitute strong support that there is competition for acoustic space in these signaling communities, and this has resulted primarily in temporal partitioning of the soundscape.
... The acoustic competition represents a particular case of competition that might occur between species vocalizing at the same place and at the same time, constituting acoustic communities (Farina & James 2016;Gasc et al. 2013). Each species within the acoustic community would compete for the acoustic space and would occupy an acoustic niche (Krause 1993). Acoustic niches could lead to acoustic partitioning as has been observed at community level (Aide et al. 2017) and species level, mainly in anurans and insects more rarely in birds (Malavasi & Farina 2013;Popp, Ficken & Reinartz 1985) particularly in the tropics (Brumm 2006;Ficken & Hailma 1974;Luther 2009;Planqué & Slabbekoorn 2008). ...
Full-text available
The structure of ecological communities is thought to be mainly driven by competition processes between species. One special case of resource shaping community dynamics is the acoustic space. However, the acoustic communities have been rarely described for tropical birds. Here, we aimed at estimating acoustic competition between the iconic species Pharomachrus mocinno and the other bird species occupying the same habitat. An acoustic survey was conducted in a cloud forest in Guatemala for 17 days in six simultaneous recording sites. All species occurring in the same frequency bandwidth were identified, and the acoustic overlapping between P. mocinno and these species was estimated. Eighteen species were identified as acoustic competitors. Ecological traits and phylogenetic distance were defined for all species. The rate of acoustic competition between P. mocinno and other species was related to different ecological traits and competition for resources. The acoustic overlap was high with species competing for similar food resources and phylogenetically close species and low with predator species and phylogenetically distant species. These unique observations provide new behavioural and ecological information that might be useful for the knowledge of this species and the cloud forest.
... While a few studies have been undertaken in old-growth forests (Luther, 2009;Pilcher et al., 2009;Burivalova et al., 2017;Burivalova et al., 2019;Monacchi and Farina, 2019), the majority of theories (Krause, 1993(Krause, , 2012 and empirical ecoacoustic studies have been inspired by or come from secondary succession forests (de Camargo et al., 2019), or rural (Matsinos et al., 2008) and urban landscapes (Dein and Rüdisser, 2020). Rural and urban landscapes offer little to our understanding natural acoustic conditions or their natural patterns in the absence of human-generated disturbances (Pavan, 2017). ...
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The Sasso Fratino Integral Natural Reserve (Central Italy), a rare example of climax Mediterranean forest, provides an extraordinary opportunity to create an important soundscape reference of old-growth forest. In this study, we describe the soundscape of three localities (Lama, Sasso 950, Sasso 1400) representative of a gradient of variety and complexity of habitats, recorded during the period 10 May to 9 June 2017. Our results reveal temporal partitioning into acoustically homogeneous periods across 24 h suggesting that soniferous species (mainly birds) adopt ecological routines in which their acoustic activity is organized according to specific transient physiological needs. We processed multi-temporal aggregates of 1, 5, 10, and 15 s recordings and calculated the Acoustic Signature (AS) with four new indices: Ecoacoustic Events (EE), Acoustic Signature Dissimilarity (ASD), and their fractal dimensions (D EE and D ASD), derived from the Acoustic Complexity Index (ACI). The use of the EE and ASD greatly improved the AS interpretation, adding further details such as the emergence of a clear sequence of patterns consistent with the daily evolution of the overall soundscape. D EE and D ASD confirm the patterns observed using the AS, but provide more clarity and detail about the great acoustic complexity that exists across temporal scales in this old-growth forest. The temporal turnover of different acoustic communities occurs as a result of a gradual shift of different homogenous acoustic properties. We conclude that soniferous species use distinct, species-specific temporal resolutions according to their physiological and ecological needs and that the fractal approach used here provides a novel tool to overcome the difficulties associated with describing multi-temporal acoustic patterns.
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Natural sound contains data about the ecology of animal populations, communities, and the full ecosystem, resulting from a complex evolution and varying according to the environment. Amongst the processes that are hypothesized to explain sound assemblages, or soundscapes, one is the acoustic niche hypothesis: sounds produced by species calling at the same time seek avoid overlapping, leading to an acoustic differentiation of signals. Soundscapes are more complex in the most pristine environments and show responses to habitat degradation and physical perturbations; hence here, we focus on La Gomera, in the Canary Islands (Spain). This island is the only location in Europe where primary cloud forests are well preserved and thrive on an island with varied orography, microclimates, disturbances, and vegetation types. In this article, we adapted a method to quantify the importance of acoustic niche partitioning and also the opposite process: acoustic aggregation. To do so, we explored soundscapes at different temporal scales in forests with variable degrees of perturbation and maturity. A secondary goal of this report is to compare how soundscapes could differ in an area affected by a wildfire, and undisturbed equivalents, in summer in winter, seasons with contrasting temperatures and wind regimes. We conclude that tracking faunal activity and behavior through soundscape monitoring could be a piece of useful complementary information to guide conservation decisions and future restoration efforts in the Garajonay National Park (La Gomera).
Environmental fundamentals like time, senses, and signs originate as many ecoscapes (timing-scapes, sensory-scapes, semio-scapes) species specific. Timing-scape is represented by a mosaic of patches shaped by phenomena that occur at a geological, biological, ecological, cultural, and semiotic time.
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