The superior colliculus

encountering each other on the migration south. But the new research reports results from six sea-floor acoustic recorders placed in the western George’s Bank off Cape Cod deployed in two triangular arrays each of three devices. The recorders were placed around 3 kilometres apart in the triangular array and the centre of two sets were 18.4 kms apart. Based upon the detection of song from one whale 29 kilometres from the devices, the researchers calculated that they were able to monitor sounds over an area of 2,600 square kilometres. The results reported by the researchers are the first effort to continuously monitor humpback whale vocalisations in a feeding ground over an extended period. They believe their results show that, far from being sporadic, singing occurs throughout the day in the study area until late spring. Given the links with singing and mating, the authors believe such vocal activity may be associated with aseasonal conceptions, perhaps with females who failed to conceive during in the main breeding season during the winter in the tropics. And there are some historical whaling records of fetus size in captured female whales that suggest some whales became pregnant outside of the winter breeding period. But the researchers found that singing tailed off dramatically towards the end of their recording period in late June when testosterone levels, associated with singing, become depressed. “The results underscore the flexibility of mammalian mating systems, and we suggest that singing by male humpback whales in spring and summer represents low-cost opportunistic advertising by males to court females who failed to conceive the previous winter,” they write. The male humpback’s song may therefore have a little more currency than presently thought. Primer