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Humpback whale research – Acoustic and Photographic

In 2016, Ilka Beith from Germany joined the Sea Search team in Cape Town for a 2 month internship. During her time here she helped us get going with the data processing on on some of the acoustic and photographic data we’d collected from supergroups of humpback whales in 2015.  Her words below:

 The goal of the study was to collect sounds of animals known to be feeding in the large aggregations of whales, which occur off the west coast in late winter and early summer. This data will then be used to help us identify sounds made on moored hydrophones as part of the E3C project. The data was collected around Hout Bay in November 2015 over 6 days in collaboration with Steve Benjamin of Animal Ocean who took us out to sea when we didn’t have our own boat.

Photo-Identification (photo ID):

Photo-identification is the practice of identifying animals from their natural marks (fin shapes, scars, injuries, colouration etc) from photographs of them. Important for photo-ID of whales and dolphins are shots of the dorsal fin from both left and right sides and for humpback whales, the underside of tail fluke, which has individually distinctive black and white patterning.

My task was identifying all the individuals photographed over the 6 days by pulling out all the left dorsal fins (LD), the right dorsal fins (RD) and the tail flukes (TF). I identified every single individual and gave everyone a number and identified the ‘best’ image each side (and tail) of each whale for each day, essentially making three catalogues a LD, RD and TF catalogue. I drew the different dorsal fins and tail flukes of the whales on paper and I also named a few of them to remember them better, which is pretty helpful during the identifying process. On the basis of the best pictures I matched the left and right dorsal fin together to one whale where possible. Matching the tail fluke to the right and left dorsal fin was the hardest part. The main identifying feature used is the under-side but by using the many different angles photographed it is often possible to match a ‘side shot’ to both a dorsal fin and a good underside from scarring on the edges or trailing edge shape.

There are now over 120 individuals in the photo-ID catalogue. I found 33 matches between days of the right and left dorsal fin, 17 matches all (LD, RD & TF) and 37 matches of the dorsal and tail fluke.  Once complete, this catalogue will be compared to those from other research groups to contribute to a national level project.

I also did field work and it was pretty cool that I identified one whale which I saw on my first research trip, as a member of the catalogue. This whale was also seen in November and it has been hanging around the Hout Bay area for several months.

Acoustics:

Humpback whales are known as the best singers in the ocean, but only the male whales sing. Most of the time they sing during mating season to attract female whales. But there are also social vocalizations produced by both male and female humpback whales which are heard on the feeding and breeding grounds and even surface-generated percussive sounds as breaches, pectoral flipper slaps and tail slaps (Dunlop R. A. et al., 2007). [ this work has been taken further in 2017 as part of the MSc thesis of Mariana Silva – updates to follow ]

During my internship, I did the first part of the acoustic analysis Adobe Audition. I converted the spectrograms to the right settings for viewing, noted the start and end time of ea ch noise and quantified, classified and categorized the noises (mostly following the categories defined by Rebecca Dunlop and colleagues in Australia – Dunlop et al. 2007). Most of the sounds are between 100 Hz and 4 kHz and can be divided into low-, mid- and high-frequency sounds. Low frequency sounds are the most common, especially the “wop”, “grumbles” and “barks”. The most common mid-frequency sound is the “modulated cry”.

 

Occurrence and distribution of cetaceans in Namibian waters

Occurrence and distribution of cetaceans in Namibian waters

A summary of Pauline Glotin’s MSc thesis, 2016

 

The Benguela upwelling, situated in the west coast of Angola, Namibia and South Africa, is a region highly productive and biologically diverse. Namibia was one of the world’s largest whaling areas in the 20th century and with at least 25 species known to occur here, hosts more than 60% of the world’s whale and dolphin species (Best, 2007). Despite this – knowledge about cetacean fauna is remarkably poor.

Figure 1: Map of the Benguela current upwelling system (Kirkman et al., 2015)

Figure 1: Map of the Benguela current upwelling system (Kirkman et al., 2015)


The main aims of my study were to provide an updated description of cetacean diversity within Namibian waters, especially within and adjacent to the Namibian Islands Marine Protected Area (NIMPA), and to predict the spatial and seasonal distribution patterns of the cetaceans in coastal and offshore Namibia.

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Acoustic and photo-ID research on humpback whales (Megaptera novaeangliae)

Internship @ Sea Search Africa

IMG_0317b2

Ilka Beith, German intern from the 01.02.2016 to 01.04.2016. She did her Bachelor degree in Geography at the Ruhr-University of Bochum in Germany and is going to do her Masters in Marine Science in Scotland.

During my internship with Sea Search Africa I worked on a set of photographic and acoustic data on humpback whales (Megaptera novaeangliae) collected late last year. The goal of the study was to collect sounds of animals known to be feeding in the large aggregations of whales, which occur off the west coast in late winter and early summer. This data will then be used to help us identify sounds made on moored hydrophones as part of the E3C project. The data was collected around Hout Bay in November 2015 over 6 days in collaboration with Steve Benjamin of Animal Ocean who took us out to sea when we didn’t have our own boat.

Photo-Identification (photo ID):

Photo-identification is the practice of identifying animals from their natural marks (fin shapes, scars, injuries, colouration etc) from photographs of them. Important for photo-ID of whales and dolphins are shots of the dorsal fin from both left and right sides and for humpback whales, the underside of tail fluke, which has individually distinctive black and white patterning.

My task was identifying all the individuals photographed over the 6 days by pulling out all the left dorsal fins (LD), the right dorsal fins (RD) and the tail flukes (TF). I identified every single individual and gave everyone a number and identified the ‘best’ image each side (and tail) of each whale for each day, essentially making three catalogues a LD (e.g. FIG. 2), RD (e.g. FIG. 1) and TF catalogue. I drew the different dorsal fins and tail flukes of the whales on paper and I also named a few of them to remember them better, which is pretty helpful during the identifying process. On the basis of the best pictures I matched the left and right dorsal fin together to one whale where possible.

Some of the pictures I turned into black and white, because it is easier to see marks and it also highlights the shape.

20151104_6D_HB-IMG_1975 (SSA - Simon Elwen)

FIG. 1: 20151104_RD_001 (date, right dorsal fin, number)  WSAMN_001 (first whale of the catalogue)

20151104_6D_HB-IMG_2035 (SSA - Simon Elwen)

FIG. 2: 20151104_LD_001 (date, left dorsal fin, number)  WSAMN_001 (first whale of the catalogue)

 

Matching the tail fluke to the right and left dorsal fin was the hardest part. The main identifying feature used is the under-side but by using the many different angles photographed it is often possible to match a ‘side shot’ as below to both a dorsal fin and a good underside (FIG. 3).

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FIG. 3: pictures of the left dorsal fin, the right dorsal fin, the tail fluke in different perspectives and a “side-shot” of the whale WSAMN_006

 

 There are now over 120 individuals in the photo-ID catalogue. I found over 30 matches of the right and left dorsal fin, nearly 20 matches all together (LD, RD, TF) and nearly 40 matches of the dorsal and tail fluke. Once complete, this catalogue will be compared to those from other research groups to contribute to a national level project.

I also did field work and it was pretty cool that I identified one whale which I saw on my first research trip, as a member of the catalogue. This whale was also seen in November and it has been hanging around the Hout Bay area for several months.

Acoustics

Humpback whales are known as the best singers in the ocean, but only the male whales sing. Most of the time they sing during mating season to attract female whales. But there are also social vocalizations produced by both male and female humpback whales which are heard on the feeding and breeding grounds and even surface-generated percussive sounds as breaches, pectoral flipper slaps and tail slaps (Dunlop R. A. et al., 2007).

During my internship, I did the first part of the acoustic analysis Adobe Audition. I converted the spectrograms to the right settings for viewing, noted the start and end time of each noise and quantified, classified and categorized the noises (mostly following the categories defined by Rebecca Dunlop and colleagues in Australia – Dunlop et al. 2007). All in all I found over 1500 sounds in the acoustic data of the first three days of research. Most of the sounds are between 100 Hz and 4 kHz and can be divided into low-, mid- and high-frequency sounds. Low frequency sounds are the most common, especially the “wop” (FIG. 4), “grumbles” (FIG. 5) and “barks” (FIG. 6). The most common mid-frequency sound is the “modulated cry” (FIG. 7) and the common high-frequency sound is the “shriek” (FIG. 8). For those who are interested in listening to some social sounds of humpback whales, here are some sound clips you can listen to (above is an example of the associated soundwave).

example_wop_logo

FIG. 4: most common low-frequency sound – wop

example_grumble_logo

FIG. 5: low-frequency sound – grumble

example_bark_logo

FIG. 6: low-frequency sound – bark

example_modulated_cry_logo

FIG. 7: most common mid-frequency sound – modulated cry

example_ascending_shriek_logo

FIG. 8: most common high-frequency sound – shriek

Playlist shuffle: The daily acoustic repertoire of bottlenose dolphins

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Anja Badenas, MSc Student on Marine Biodiversity and Conservation

 

Playlist shuffle: the daily acoustic repertoire of bottlenose dolphins

 

As mentioned on the previous post , bottlenose dolphins rely on sound production for orientation, feeding and communication with con-specifics. It is therefore of great importance to study their vocalization repertoire as it can provide important information on their habitat use and responses to human induced stress. Acoustic monitoring using hydrophones (underwater microphones) to record the different vocalizations naturally produced by dolphins is particularly important in coastal habitats, where dolphins may be affected by boat traffic noise and coastal construction.

spectogram

Spectogram showing different bottlenose dolphin vocalizations.BP = burst pulse, W=whistle, LFN=Low frequency narrowband sounds. (from Gridley et al. 2015).

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