Cape Verde 2006: "They must be somewhere"

10th Mar 2006 When my little man back home in West Clare is asked where have his slippers gone, he often answers “they must be somewhere”. The same could be said for humpback whales off Cape Verde. In 2003, we literally sailed into a group of at least six and maybe up to a dozen whales on first arriving at Boavista and as soon as we put the hydrophone (underwater microphone) in the water, could hear their beautiful, evocative song. In 2006, things appear to be different.

Over the last 13 days we have sailed 500 nmls (760km) from Sao Vicente to Boavista, from Boavista to Maio, from Maio to Sao Nicolau and from Sao Nicolau to Sal and have had four encounters with humpback whales, one possible mother and calf pair off Boavista and a group of three off Maio. The following encounters of two off Maio might have been from the group of three the day before. More surprisingly we have heard no singing. We had a false alarm off Boavista, where Tony Whelan tried to convince us that the motion of the hull through the water was in fact the simple, monosyllabic rumblings of a hormonal male humpback. Despite these few encounters we have managed to obtain two good fluke images and two not so good fluke images, which is an impressive return on scarce opportunities.

During our 15 hour passage today from Sao Nicolau to Boavista we heard the definite singing of humpbacks as we sailed off the continental shelf around Sao Nicolau, into waters over 4000m deep. Humpbacks are thought to be restricted to waters shallower than 100m, so how and where were we picking up these vocalisations from ?

No singing humpbacks were heard as we approached Boavista as darkness fell. This does not mean that there are no humpbacks around but it would have been reassuring to hear them. We are now half way through our month long expedition in Cape Verde. We have followed our intended plan with time spent searching for humpbacks around Maio in the Sotavento or leeward islands, and also for sperm whales, in an attempt to help Ricardo record sperm whale codas. We have seen five species of dolphin (rough-toothed, bottlenose, spotted, short-snouted spinner dolphins and short-finned pilot whales) as well as humpbacks, and also heard sperm whales. Today we also saw and photographed two whales or dolphins that we cannot identify (possibly pygmy killer whales). This is already over twice as many species as we saw in 2003.

Over the next two weeks we will concentrate on locating humpback whales. Hopefully we will find some around Boavista but if they are not there we will have to travel to Sal, Sao Nicolau and Maio in an attempt to find them. Although numbers around Cape Verde are small, according to the old whaling records from the 17th century this is the peak of the breeding season, so “they must be somewhere”.

Simon Berrow