CONSERVATION ISSUES - AUGUST 2006

During his Galapagos stopover, Darwin’s attention was captured by the marine iguanas, a strange beast even by island standards. It is the only lizard on Earth that dives in the ocean to feed. He found them abundant throughout the archipelago, always near the water along rocky coastlines, and never much more than ten yards inland. He wrote “It is a hideous-looking creature, of a dirty black colour, stupid and sluggish in its movements” But he admitted that it was graceful when it swims. He cut open the stomachs of several marine iguanas and found nothing but ‘minced sea-weed’ He wrote “I do not recollect having observed this sea-weed in any quantity on the tidal rocks, and I have reason to believe it grows at the bottom of the sea. If such is the case, the object of these animals occasionally going out to sea is explained” Ever the astute naturalist, he was right, the marine iguanas live on a diet of algae.

Evolutionary biology, is not generally an experimental science, but there are historic exceptions. He cornered an animal, grabbed it, and threw it into a large tide pool left by the ebbing sea, and the hapless iguana swam right back to where Darwin stood. Darwin threw it in again. Again it returned. “I several times caught this same lizard, by driving it down to a point, and though possessed of such perfect powers of diving and swimming, nothing would induce it to enter the water, and as often as I threw it in, it returned in the manner above described” So what did Darwin learn from this little experiment? “Perhaps this singular piece of apparent stupidity” he concluded, “may be accounted for by the circumstance, that this reptile had no enemy whatever on shore, whereas at sea it must often fall prey to the numerous sharks. Hence, probably urged by a fixed and hereditary instinct that the shore is the place of safety, whatever the emergency may be, it there takes refuge” Evolution had provided that single defensive instinct: when threatened or attacked, head for shore. But evolution hadn’t provided the wit to adjust to altered circumstances. Darwin did not seem to realise that another reason for getting out of the water quickly was to keep its temperature up, for they can only stay in the water for a short period due to loss of heat, and the longer it spent in the tidal pool meant that it would have a shorter time to feed later. They seem to be abundant still, judging by Liz Hall’s photograph, taken earlier this year.    

There were 136 reported sightings of Basking Sharks during July, all around the coast from Bude to Plymouth Breakwater. Numbers ranged from single sharks to 68 counted from Pendeen Watch on the 25th. Ocean Sunfish were reported 21 times, one sighting of 3 fish, 2 of 2 fish the other 18 were of single fish. There were 7 reports of Common Dolphins, pod sizes ranging from 2 to 100. Bottlenose Dolphins were reported 15 times, all along the north coast from Cape Cornwall to Port Isaac. The 6 Harbour Porpoise reports were all from around west Cornwall again, from St Ives to Helford. These reports were all of one or two animals except for one report of 20 off Pendeen. 7 whales were seen, 2 were Minke Whales 1 Sperm Whale, 1 Pilot Whale and one thought to be an Orca, the rest were unidentified. Other sharks seen were one Blue, one Porbeagle and a Thresher.

Grey Seals were reported 12 times, 2 of which were of a pup with a hat on St. Clements Island. Cyanea lamarckii and Moon Jellyfish were seen and a Triggerfish was seen just below the surface at Treen Cove, lifted out and found to be alive, it had bruised sides and tattered fins, but when put back into the water, swam off strongly.  Strandings on Cornish beaches were quite low during July, one dolphins carcass was found near Porthleven, and Harbour Porpoise carcasses were found near Bude and Portholland. A dead Basking Shark turned up at Trenow Cove near Perranuthnoe,  4 Grey Seal carcases were found, 3 on the north coast, one on the south.    

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