Ae fond kiss, and then we sever! *

Animals tend to breed seasonally, giving birth at that time of year when their young will have the greatest chance of survival. That means, of course, that they must have some means of knowing when the correct season has arrived. Many use changes in day-length which are totally predictable. Some though, use much more obscure environmental cues to determine when to get themselves into a sexual frenzy.

Consider, for example, the Palalo worm, a marine polychaete worm living among the reefs of the South Pacific. During the breeding season the worms break in half and the tail section (the “epitoke”), bearing reproductive cells, swims to the surface, where it releases eggs and sperm. Tens of thousands of epitokes swarm and release gametes simultaneously. The front section of the worm (the “atoke”) remains below in the substrate and eventually regenerates another tail section. The worm seems to time its reproduction using the phases of the moon; the free-swimming sections always makes their appearance in the early morning for two days during the last quarter of the Moon in October. Twenty-eight days later, they appear in even greater numbers in the final quarter of the November Moon.

Much nearer home the tank traps on our beach appear to use the New Year high spring tides as the cue to commence their courtship. Now over 70 years old they still enjoy a bit of slap and tickle. Over the last few days they have started their elaborate and sensuous courtship display in which they rise out of the sand and lean over to touch each other in a most tender fashion.

The round creature on the sand quietly observing this wildlife spectacle is a coil of second world war barbed wire. Carefully rolled up at the end of hostilities the coils were left abandoned on the beach and were soon covered in sand and only appear after gales or at spring tides. Their courtship behaviour has never, to the best of my knowledge, been observed.

* Robert Burns. 1791.