Page 18 - Special Issue
P. 18

bioacoustic Monitoring Contributes
to an Understanding of Climate Change
methods for tracking habitat modification and species dis- otrciebauntiboencbauy saecolougsitsitcicms ohnaviteoprirnegv,eannteddbsycqieunatnisttisfyfirnogmanacimidai-l fsyoiunngdtshaenladrbgehvaovluiomraelsroesfpsoeanwseastetor ntheecseessaoruyntdosoabssaenrviendex- corfesapsecsiiens ahbesaoltrhp.tion.
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danisdruRpitcihnagrdthse, i1r9a7b8i)l.itThy toroduegthecotuatnedvololuctaiolinzearsyoutinmdes, osouurcnedss.
used for long distance communication between members of
fthreesasmhewspaetciesrhsavpeebceeiensmolded by the environment so
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cieeisveirs, wmiothremdiinffiimcualti.nThterefesrieznecoefamndandyegfraedshatwioante(r“ascyostuesmtics
iasdbapeltoawtiotnh”ehryepsoltuhteiosins;oMf oGrltobna,l1C9l7im5)a. teThMeoidmeplsli(cGatCioMnso)f,
wthheiscehencvoinrsotnraminesnttahl ecoancscturarianctys onf tchliemaactoeusptricojsetcrtuioctnusreforf
tchoemsemeunnviicraotniomnesnotus n(dHsoibsdthayata, nasdtLheouegnhvi,r2o0n1m1)e.nAt cdhdaitnigoens-,
athlley,souunnlidkse ththeemrselavteisvemlyayhnoemedogteoncohuasngoec,etaonos., freshwater
ized to detect (that is, are maximally tuned to) important
frequencies in their species’ mating and advertisement calls
(Gerhardt and Huber, 2002). In the Puerto Rican coqui frog
Eleutherodactylus coqui, the two notes in the male’s adver-
tisement call are at frequencies of about 1000 Hz and 2000
Hz. The second, higher qui note is important for attracting
a female to the calling male, and the female’s auditory nerve
responds best to this note. In this way, the male sender and
systems are enclosed and habitat specific. Because climate Vegetation is a particularly significant environmental con-
Some researchers are now beginning to address the effects particular temperature. These results have particular impli-
of the changing climate on the acoustic structure of vocal- cations for how fishes may respond to climate change. First,
izations. Snell-Rood (2012) analyzed acoustic features of temperature will not affect the hearing sensitivity of all spe-
songs from 50 species of North American wood warblers cies to the same degree, and second, if animals can acclimate
and of echolocation sounds from 11 species of Southwestern to temperature variations, then the negative consequences
bats, and correlated these features with levels of atmospheric of increased temperature on hearing sensitivity may be less-
absorption at various locations in the geographic ranges of ened (Wysocki et al., 2009).
these species. She found small but significant correlations between some acoustic features and atmospheric absorp-
models predict droughts in some regions and heavier rainfall straint on the structure of animal vocalizations. It provides
in others, we cannot create a unifying prediction as to how perches from which animals can call, but it can also affect
effect on Aerially
climate change will impact freshwater species (Hobday and the acoustic parameters of the call. As one example, song-
tion. In wood warblers, the frequency bandwidth of song
Lough, 2011). For example, streams associated with melt- birds living in forests tend to produce long tonal, whistle-
Communicating Animals
ing glaciers may increase in flow and volume as the planet like songs with low modulations while songbirds living in
was narrower in habitats with greater sound absorption. Climate change impacts terrestrial species as well as aquatic
Differences in absorption were on the order of 0.03 dB/m species. Changes in temperature (Figure 1- see page 9), pre-
warms, whereas lakes and ponds in other regions may desic- more open habitats tend to produce songs with rapid modu-
to 0.1 dB/m, which translate into differences in the inten-
cate as those environments experience droughts. Increased lations (Morton, 1975). The presence and type of vegetation
cipitation, and CO levels, combined with the increased
temperatures can result in a decrease in aquatic mixing and interacts with atmospheric conditions such as temperature
sity of the song by as much as 10 dB over a 100 m propaga- climatic variability caused by global warming, can initi-
tion distance, a typical communication range for these birds. ate or exacerbate habitat loss and thus affect biodiversity
Mean frequency of the echolocation calls in the 11 bat spe- by altering species distribution, behaviors, and viability.
cies was lower in habitats with higher absorption. For two As discussed above for aquatic species, studying these im-
representative species of bats, absorption ranged from 1.53 pacts in terrestrial species is also not trivial, because these
to 1.73 dB/m, which translate into a change of about 4 dB in impacts vary between different habitats (tropical and tem-
intensity for a prey 5 m away (10 m travel time, from the bat perate zones, high and low elevations; Navas, 1996; Deutsch
to the prey and back), a distance over which these small bats et al., 2008), and between different species (longer-lived
can detect prey.
species such as birds may be affected in a different manner
than shorter-lived species such as insects; Şekercioğlu et al.,
turnover, resulting in stratified regions with hypoxic condi- gradients, absorption, scattering, refraction and reflection
tions and low pH. Acidification of freshwater systems is pre- to influence call propagation and degradation (Bradbury
dicted, but it is not known if significant changes in sound ab- and Vehrencamp, 1998). As patterns of vegetation become
sorption will occur due to the small size of most freshwater modified by climate change, will communication sounds
systems. Clearly more data are needed.
still propagate efficiently in these changing habitats?
An additional factor to consider in predicting the impact The physical environment also impacts the receiver of the
on climate change in freshwater environments is the effect vocalization. The receiver must detect the call at various
of ambient temperature on the auditory system. Fishes are distances from the source (the sender) and against envi-
ectotherms that regulate their body temperature by refer- ronmental noise that can mask it; otherwise, communica-
ence to external temperature, rather than by internal physi- tion will fail. One strategy to make the receiver’s job easier
2012). Because of the complexity and variability of different
ological setpoints. The water temperature at which animals has been identified in some orthopteran insects (crickets,
Changes in patterns of precipitation produced by climate habitats and the different life histories of species living in
change can impact animal sounds both by varying humid- these habitats, we still do not know which species will ac-
ity and thus sound absorption by the atmosphere, and also climate and adapt to a changed habitat, which will disperse
by altering the times at which animals will vocalize. Snell- to other habitats, and which may go extinct. This is where
Rood (2012) observed that in the same bat species, acoustic animal bioacoustics can play a major role, both by providing
| 11
were housed affects the hearing sensitivities of two species grasshoppers, katydids) and anuran amphibians (frogs and
of catfish, the channel catfish (Ictalurus punctatus) and the toads). These animals have evolved an auditory system (ear,
tropical catfish (Pimelodus pictus). Thresholds of neural re- auditory nerve, and auditory brain areas) that are special-
the female receiver are coupled, suggesting that the vocal
Figure 3: Effect of carbon dioxide concentration on auditory be- production system and the acoustic processing sy2stem have
havior of juvenile clownfish. Fish reared in ambient CO conditions
co-evolved (Narins and Capranica, 1976). But, will climate
avoided simulated predator noise, whereas fish reared in elevated cahrabnogneddioixsirduepetnvthiriosnbmaelnatnscdeidbneotwtaeveonidtthenseonisde.eFrigaunrdeatdhaeprted-
from Simpson et al. (2011).
ceiver? Will the receiver’s hearing change quickly enough so that any communication sounds that have been modified by
the environment can still be detected and discriminated? If sponses from auditory nuclei in the brain varied with hous-
not, then acoustic communication essential for reproductive ing temperature (Wysocki et al., 2009); at high temperatures,
behaviors and species viability will be disrupted.
thresholds increased and hearing sensitivity decreased. The
magnitude of these changes varied between the two species,
sound Absorption
and was further affected by how long the fishes were kept at a
 18 | Acoustics Today | Spring 2020, Special Issue 10 | Acoustics Today | Summer 2014
Reprinted from volume 10, issue 3
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