136
tocetes have considered the acoustical emissions separately, examining only click
trains (Verfub et al. 2007, 2013; Roch et al., 2011), or whistle sequences (Oswald
et al. 2007). Lu et al. (2013) integrated features from both whistles and clicks for
classification of bottlenose dolphin, spinner dolphin, melon-headed whale, shortbeaked common dolphin and long-beaked common dolphin.
Proposing an integrative bioacoustics approach – combining whistles and clicks we classified eight delphinid species: spinner (Stenella longirostris), Atlantic spotted (Stenella frontalis), rough-toothed (Steno bredanensis), Risso’s (Grampus
griseus), bottlenose (Tursiops truncatus), short-beaked common (Delphinus delphis) dolphins, killer (Orcinus orca) and long-finned pilot (Globicephala melas)
whales from the Southwest Atlantic Ocean, at the Brazilian shelf break (Amorim
et al. submitted). For that, we extract whistles acoustic parameters: maximum
frequency, minimum frequency, frequency range, peak frequency, center frequency,
beginning frequency, ending frequency and duration; and clicks parameters: interclick interval, sound pressure level peak-to-peak (SPL), rms (root mean square)
amplitude, 3 dB bandwidth and 10 dB bandwidth. The sequential classification
analysis consisted of two methodological techniques, Discriminant Function
Analysis (DFA) and Classification Tree Analysis.
The discriminant function showed that the overall whistle classification had the
highest number of false classifications (40.7%, N = 475, Wilks’ λ = 0.18), these
numbers decrease when only clicks were analyzed (25.0%, N = 158, Wilks’ λ =
0.14). The discrimination result improved with the combined analysis of whis-tles
and clicks, given that the misclassification percentage was only of 5.8% (N = 30,
Wilks’ λ = 0.01). In classification tree analysis, the optimal classification whistle
tree consisted of 28 splits and misclassification rates of 0.606. Click opti-mal tree
consisted of 60 splits and misclassification of 0.260. When whistles and clicks were
combined, optimal tree consisted of 90 splits and a false classification of 0.188.
In summary, the eight delphinid species showed species-specific qualities in their
whistles and clicks. When taken individually, echolocation clicks presented greater
efficiency in distinguishing species; this might be related to the behavioural context
encoded in whistles and the relationship between echolocation signals features and
animals’ head morphology, which makes feasible to accurately determine a species
from their clicks. Otherwise, analysing both signals in combination enhanced the
correct classification scores. An integrati ve bioacoustics approach potentially presents a higher contribution in the classification process, once it considers the different signals produced by the species as part of a whole communication system
employed in different ecological contexts.
5.5.2 Sperm Whale Social Structure
Sperm whales (Physeter macrocephalus) are the largest and long-lived odontocete,
reaching between 8.3 and 20.5 m long and with lifespan of over 50 years old
(Chivers 2009; Whitehead 2009). There is a marked sexual dimorphism in body
A. Andriolo et al.
tocetes have considered the acoustical emissions separately, examining only click
trains (Verfub et al. 2007, 2013; Roch et al., 2011), or whistle sequences (Oswald
et al. 2007). Lu et al. (2013) integrated features from both whistles and clicks for
classification of bottlenose dolphin, spinner dolphin, melon-headed whale, shortbeaked common dolphin and long-beaked common dolphin.
Proposing an integrative bioacoustics approach – combining whistles and clicks we classified eight delphinid species: spinner (Stenella longirostris), Atlantic spotted (Stenella frontalis), rough-toothed (Steno bredanensis), Risso’s (Grampus
griseus), bottlenose (Tursiops truncatus), short-beaked common (Delphinus delphis) dolphins, killer (Orcinus orca) and long-finned pilot (Globicephala melas)
whales from the Southwest Atlantic Ocean, at the Brazilian shelf break (Amorim
et al. submitted). For that, we extract whistles acoustic parameters: maximum
frequency, minimum frequency, frequency range, peak frequency, center frequency,
beginning frequency, ending frequency and duration; and clicks parameters: interclick interval, sound pressure level peak-to-peak (SPL), rms (root mean square)
amplitude, 3 dB bandwidth and 10 dB bandwidth. The sequential classification
analysis consisted of two methodological techniques, Discriminant Function
Analysis (DFA) and Classification Tree Analysis.
The discriminant function showed that the overall whistle classification had the
highest number of false classifications (40.7%, N = 475, Wilks’ λ = 0.18), these
numbers decrease when only clicks were analyzed (25.0%, N = 158, Wilks’ λ =
0.14). The discrimination result improved with the combined analysis of whis-tles
and clicks, given that the misclassification percentage was only of 5.8% (N = 30,
Wilks’ λ = 0.01). In classification tree analysis, the optimal classification whistle
tree consisted of 28 splits and misclassification rates of 0.606. Click opti-mal tree
consisted of 60 splits and misclassification of 0.260. When whistles and clicks were
combined, optimal tree consisted of 90 splits and a false classification of 0.188.
In summary, the eight delphinid species showed species-specific qualities in their
whistles and clicks. When taken individually, echolocation clicks presented greater
efficiency in distinguishing species; this might be related to the behavioural context
encoded in whistles and the relationship between echolocation signals features and
animals’ head morphology, which makes feasible to accurately determine a species
from their clicks. Otherwise, analysing both signals in combination enhanced the
correct classification scores. An integrati ve bioacoustics approach potentially presents a higher contribution in the classification process, once it considers the different signals produced by the species as part of a whole communication system
employed in different ecological contexts.
5.5.2 Sperm Whale Social Structure
Sperm whales (Physeter macrocephalus) are the largest and long-lived odontocete,
reaching between 8.3 and 20.5 m long and with lifespan of over 50 years old
(Chivers 2009; Whitehead 2009). There is a marked sexual dimorphism in body
A. Andriolo et al.