154
For these purposes, two autonomous acoustic recording devices were deployed but
unfortunately no sounds were recorded. Some challenges they have found in developing this project were bad weather conditions and difficult access to the study area,
lack of human resources specialized in cetacean acoustics as well as counting on the
proper equipment. However, they will explore the possibility of recording porpoises
using a hydrophone made by the Laboratorio de Hidroacústica (INIDEP), which is
more adequate to record the type of signals they aim to study.
Currently, the LAMAMA together with the Laboratorio de Hidroacústica, use
active acoustic devices with eco-integrators to study presence, abundance and distribution of prey in presence of dolphins.
To summarize, historically in Argentina there have been many attempts to study
wild cetaceans acoustically, but faced several difficulties which comprises mostly
lack of trained researchers and difficulties to obtain the proper passive acoustic
recording devices. Additionally, adverse weather conditions and accessibility to the
area with existing resources may challenge the research even more. However, more
recently several governmental and non-governmental institutions are turning the
tide and began to explore and develop new research lines using acoustics, slowly
learning to overcome some of the aforementioned obstacles.
6.2 Learning the Acoustic Repertoire of Cetaceans
Sound is a very efficient way for energy to propagate through water. This feature of
aquatic environments together with a rapid attenuation of light along distance have
been probably the main driving factors of the development of a complex sound
production and reception systems that play a crucial role in marine organisms (Tyack
and Clark 2000; Au and Hastings 2008).
Studying cetaceans in the wild is challenging because they spend most of the
time submerged, out of the human vision range, and often inhabit remote areas with
difficult access. Passive acoustics can overcome some limitations of the traditional
visual methods to study cetaceans in the wild. For example, the time an animal
spends underwater turns into an advantage using passive acoustics, since it improves
the likelihood of recording its vocalizations. This is one of the reasons why some
researchers are interested in learning the acoustic repertoire of different species of
cetaceans, and even of different populations of cetaceans around the world. The
acoustic repertoire comprises the different types of sounds that can be produced by
animals within a species and/or population. Once the sounds produced by different
species have been characterized, a combination of spectral and/or temporal features
can generally be used to identify and discriminate among species.
Learning the acoustic repertoire of cetaceans consists of a dynamic process since
the emitted sounds can change over spatio and/or temporal scales. These variations
occur due to several factors: (1) Natural variations within the environmental features,
e.g. coastal vs. oceanic habitats, or seasonalities. (2) Anthropogenic pressures (e.g.
increase in ocean noise) can also lead animals to change sound types, patterns or
M.L. Melcón et al.
For these purposes, two autonomous acoustic recording devices were deployed but
unfortunately no sounds were recorded. Some challenges they have found in developing this project were bad weather conditions and difficult access to the study area,
lack of human resources specialized in cetacean acoustics as well as counting on the
proper equipment. However, they will explore the possibility of recording porpoises
using a hydrophone made by the Laboratorio de Hidroacústica (INIDEP), which is
more adequate to record the type of signals they aim to study.
Currently, the LAMAMA together with the Laboratorio de Hidroacústica, use
active acoustic devices with eco-integrators to study presence, abundance and distribution of prey in presence of dolphins.
To summarize, historically in Argentina there have been many attempts to study
wild cetaceans acoustically, but faced several difficulties which comprises mostly
lack of trained researchers and difficulties to obtain the proper passive acoustic
recording devices. Additionally, adverse weather conditions and accessibility to the
area with existing resources may challenge the research even more. However, more
recently several governmental and non-governmental institutions are turning the
tide and began to explore and develop new research lines using acoustics, slowly
learning to overcome some of the aforementioned obstacles.
6.2 Learning the Acoustic Repertoire of Cetaceans
Sound is a very efficient way for energy to propagate through water. This feature of
aquatic environments together with a rapid attenuation of light along distance have
been probably the main driving factors of the development of a complex sound
production and reception systems that play a crucial role in marine organisms (Tyack
and Clark 2000; Au and Hastings 2008).
Studying cetaceans in the wild is challenging because they spend most of the
time submerged, out of the human vision range, and often inhabit remote areas with
difficult access. Passive acoustics can overcome some limitations of the traditional
visual methods to study cetaceans in the wild. For example, the time an animal
spends underwater turns into an advantage using passive acoustics, since it improves
the likelihood of recording its vocalizations. This is one of the reasons why some
researchers are interested in learning the acoustic repertoire of different species of
cetaceans, and even of different populations of cetaceans around the world. The
acoustic repertoire comprises the different types of sounds that can be produced by
animals within a species and/or population. Once the sounds produced by different
species have been characterized, a combination of spectral and/or temporal features
can generally be used to identify and discriminate among species.
Learning the acoustic repertoire of cetaceans consists of a dynamic process since
the emitted sounds can change over spatio and/or temporal scales. These variations
occur due to several factors: (1) Natural variations within the environmental features,
e.g. coastal vs. oceanic habitats, or seasonalities. (2) Anthropogenic pressures (e.g.
increase in ocean noise) can also lead animals to change sound types, patterns or
M.L. Melcón et al.