Zanzibar Humpback Whale Research Project 2012

Blog 10: Hydro Buoy, 04/08/2012

Although the lighthouse pilot study is completed we are still very busy especially now that Jake Levenson from our funding agency the International Fund for Animal Welfare (IFAW) has arrived. The team is excited, not only to enjoy Jake’s company, but also because he brought with him an additional tool for the humpback whale research – a recording hydrophone buoy (underwater microphone). The hydrophone will be used for nearly continuous acoustic recordings of all underwater sounds including dolphins, whales, vessel activities and any other sounds occurring in the waters in our study area off southern Zanzibar.

 Jake Levenson preparing the hydrophone buoy for deployment.

The hydrophone buoy will remain deployed for the rest of the 2012 season and, once retrieved, will provide the project with additional data on the day-and-night acoustic presence of humpback whales and other underwater sounds. It was an interesting process deploying the hydrophone buoy; we had to decide on a location, to minimise noise from reefs (reefs are noisy places!) and the coastline, where waves crash onto shore. In the end, the hydrophone buoy was deployed in an area commonly used by Indo-Pacific bottlenose dolphins (Tursiops aduncus) and Indo-Pacific humpback dolphins (Sousa chinensis) and also where we previously have recorded humpback whale song. Humpback whales sing on the breeding and mating grounds and it is believed the males do this either to attract females or to express their breeding fitness to other males. With these recordings, in addition to data we collect during boat-based hydrophone recordings, the project will be able to compare humpback whale songs throughout the season and between seasons.

Captain Foum on our survey vessel on the way to deploy the hydrophone bouy.

The buoy was anchored to the seafloor at a depth of 13 m and will remain there for approximately 6 weeks until the end of the season. Prior to deployment a sampling rate (times throughout the day it will record acoustic data) was chosen to ensure battery life across the full extent of the deployment period – you would not want to discover that the batteries died halfway through the deployment.

Foum preparing the ‘anchor’ which will be used to hold the hydrophone buoy in place.

Abas, a local friend & divemaster, who dove with Jake to deploy the hydrophone

Khamis, our local captain, with the hydrophone buoy.

Abas post-dive: texting while diving?

Many thanks to Jake for bringing the exciting new piece of equipment to the Zanzibar Humpback Whale Project; the data collected from the hydrophone buoy will help us assess the occurrence and singing behaviour of the whales and other noise including vessel traffic, offshore oil and gas activities, dynamite fishing and other human or natural sounds off southern Zanzibar.

Pictures © Zanzibar Humpback Whale Project

Zanzibar Humpback Whale Research Project 2012

Blog 9: A Friendly New Face, 03/08/2012

On the 29^th of July the team was very happy to welcome a new local student to the Zanzibar Humpback Whale Project. Khamis Khamis is a second year undergraduate student at the University of Dar Es Salaam where he is studying for a Bachelor of Science in Aquatic Environmental Science and Conservation. Khamis is happy to join the Project this year and hopes that this experience will give him further knowledge about the whales around Zanzibar. Karibu Zanzibar Humpback Whale Project, Khamis!

Nat, Yussuf, Khamis & Lynne

After an incredibly busy ten days of conducting both lighthouse and boat-based surveys we finished the lighthouse pilot study on Friday the 3^rd of August. Overall, the addition of the lighthouse surveys resulted in more logistics for the team; every day we were busy working in sub-teams for boat and lighthouse surveys so had to organize food for both teams, coordinate timing of boat departures and travel by car to Makunduchi, and established new data collection protocols and their related databases. Despite the additional effort the team was very pleased with the data we collected from the Makunduchi lighthouse!

Makunduchi, on the southeast end of Zanzibar (Unguja) Island, appears to be one of the most popular areas for the whales in our survey area; almost every morning we receive fisher’s reports of whales and we often observe them there while conducting boat-based surveys. It takes about one hour to travel by survey boat from Kizimkazi-Dimbani to Makunduchi and, being more exposed to the open sea of the Indian Ocean, we are often unable to survey in the area due to the less protected, rougher seas that often occur here. The opportunity to conduct land-based surveys at Makunduchi allowed us to collect previously inaccessible data.

View from Makunduchi lighthouse looking up the east coast of Zanzibar

View looking down from the Makunduchi lighthouse

Over the course of the lighthouse pilot study, whales were seen almost every day and their behaviour and respiration rates could be easily recorded…whale blows are easy to spot when you are viewing an expanse of sea from 44 m above sea level! We collected data on their behaviours and respiration rates and were able to do so in a way similar to our boat behaviour surveys. We could time the surface intervals (times the whales were at the surface breathing between dives) and a variety of behaviours including traveling, resting and socializing. It was spectacular watching huge breaches, often multiple ones, from the lighthouse! One day we had a wonderful observation of one animal doing nine pectoral-fin slaps in just over a minute, just off the shelf edge below the lighthouse! In addition to tracking the whales’ movement we performed boat scans at regular intervals with the intention to collect data on interactions between vessels and whales.

Kristin keeping out of the sun while scanning from the lighthouse

By conducting land-based surveys from the lighthouse we could easily track animals in the area and had so much success viewing animals that we had to establish a protocol for tracking multiple groups of whales. We had to decide which, of often many, groups of whales we would track and for how long we would focus on an single group. By the end of the ten day study we had figured out what to do when we had multiple sightings at a time…which was the case most days!

Yussuf scanning from the lighthouse

Due to the success of the land based surveys we intend to collect more of this data next year and for the extent of the research season. It will result in a busy season for the team in 2013 but we will surely get some great data to assess the presence of whales, their behaviours, and their interactions with vessels around southern Zanzibar.

Finally, we would like to extend thanks to the community of Makunduchi for allowing us to work at the lighthouse in their village. Without their willingness to support this research, data collection from the lighthouse would not be possible!

Photographs © Zanzibar Humpback whale Project

Zanzibar Humpback Whale Research Project 2012

Distinct and beautiful songs of the male humpback whales have been making waves in Zanzibar and our research team has been able to take full advantage with some lengthy recordings using a specialised hydrophone to allow for the low frequency sounds to be picked up.

The preliminary results have been very encouraging with the majority of the songs being visible in the analysis.

When the team analyse the songs we use a specialised bioacoustics program. This allows for the song to be viewed on a graph, a spectrogram. Humpback whale songs are relatively complex but they have distinctive patterns that may be used for analysis. Each song is about 20-30 minutes long but may be repeated for several hours. The song is divided into different sections, the largest being themes. These themes can then be further broken down to smaller fragments called phrases and units.

The organisation and structure of the songs is of particular interest to Nat Stephenson (research assistant and Newcastle undergraduate student) who will be analysing the recordings for his dissertation project. Nat will be comparing the songs from this year to recordings from previous years to look for changes within season and also changes over a greater temporal span.

The songs are seen as a crucial ingredient in the mating behaviour of humpback whales and we hope that the song analysis in combination with all other data we are collecting will give us further understanding about the humpback whales off east Africa.

Nat and Kristin deploying the hydrophone to record humpback whale song.

Example of humpback whale song (dark wiggles) as shown in a spectrogram.

Photographs © Zanzibar Humpback whale Project