Phylogeny of Balaenoptera species, indicating placement of Madagascar B. omurai samples among known available B. omurai sequences from the western Pacific and eastern Indian Oceans. Topology is a maximum-likelihood tree inferred from partial mitochondrial control region sequences. Symbols near nodes refer to bootstrap support (BS) scores and posterior probabilities (PP), for maximum-likelihood, maximum-parsimony and Bayesian analyses, respectively (BS/BS/PP). A double asterisk indicates nodes with greater than 90% BS and greater than 0.95 PP. Other scores are represented as BS/BS/PP. Scale bar shows estimated changes per site.
Images of Madagascar Balaenoptera omurai displaying details of pigmentation and external appearance. Five different individuals are pictured: underwater video frame captures of an adult female with calf sighted on 9 November 2013 that had just completed a feeding lunge (first row), and a lone adult on 22 October 2014 (second row), and above surface photographs from three adults sighted on 13 November 2014 (third row), 9 November 2013 (fourth row) and 12 December 2012 (fifth row). Visible features: (A) asymmetrical coloration of the lower jaw, with lightly pigmented right jaw and darkly pigmented left jaw; (B) asymmetrical coloration of the gape (inferred by inner lower lip), with lightly pigmented left gape and darkly pigmented right gape; (C) leading edge of pectoral fin white from tip to shoulder; (D) the apparent absence of lateral rostral ridges, with only faint indications detectable at some angles; (E) lightly pigmented blaze originating anterior to the eye, present only on the right side, with dark eye and ear stripe, two additional dark stripes and a light inter-stripe wash; (F) lightly pigmented chevron anterior to dorsal fin, present on both sides but asymmetrical and most prominent on right where it displays a double banded pattern; (G) highly falcate dorsal fin with gradual sloping insertion into dorsum.
Distribution of sightings of Balaenoptera omurai within the northwest Madagascar study site. Tracks during the two different phases of the project, based off Nosy Be and Nosy Iranja, respectively, are shown by colour.
Spatial and temporal distribution of Balaenoptera omurai sightings in 2014, showing clustered tendency of loose aggregations of individuals interspersed with periods without sightings despite consistent survey effort throughout the field season.
Spectrograms of recordings with calls attributed to Balaenoptera omurai showing (a) a stereotyped, amplitude-modulated pulsative call at 15–50 Hz, recorded on two separate days assumed to be from different individuals, (b) 10 min clip of a rhythmic series of calls with consistent 170–180 s repetition rate, interpreted as uttered by a single individual, and (c) 10 min clip of what appears to be a chorus of four individuals inferred from overlapping rhythmic series with different apparent received levels, including two animals in the foreground (labelled ‘1’, red and ‘2’, blue) and two animals in the background (labelled ‘3’, green and ‘4’, magenta); stereotyped, rhythmically repetitive vocalizations uttered in choruses of different individuals suggest song-like characteristics and function.
Pairwise sequence differences between and within species. (Between species number of sequence differences and net nucleotide substitutions per site (DA) are shown above and below the diagonal, respectively. Number of samples of each species shown in the left column.)