Islas Murcielago, Guanacaste, Costa Rica

Today we awoke to yet another morning sailing along the spectacular coastlines of the northwesternmost province of Costa Rica: Guanacaste. Within this province, now largely deforested and dedicated to the raising of cattle, we explored the last remnants of a unique ecosystem: the tropical, semi-deciduous dry forest, much of which is now protected within a UNESCO world heritage site. Much of this is found within the Santa Rosa National Park, but our morning’s destination was dedicated to exploring the latest addition to this park: the Murcielago (or bat) Islands.

This small, remote island group is situated just southeast of the fishing port of Cuajiniquil, on the Santa Elena peninsula, and is rarely visited. It is a rugged, impressive area of rocky peaks and valleys that is largely deforested but is a centre of ecological restoration efforts. Our arrival to the area was heralded by the discovery of a female humpback whale and her calf that were actively feeding on the large schools of tiny fish below, and they were surrounded by schools of spotted dolphin.

Our visit here concentrated on the rich and wonderfully warm waters that bathe the island group. Just after breakfast, we had a snorkelling briefing and picked out equipment to use during the week. Some of us chose to hike to the top of the island for some great scenic views, whilst others kayaked around the enclosed bay. Most of us, though, dedicated large amounts of time to exploring the underwater world. Although pretty much devoid of large coral reefs, the waters of the Tropical Eastern Pacific are extremely rich with life, including many large and colourful reef fish. These flit amongst the odd clump of branching coral or rocky outcrop, and include species of wrasse, puffer fish, grunt, angelfish and butterflyfish.

I took the ship’s video camera in its underwater housing, and got some great footage to share with all at recap that night. The species that I got most carried away with was the one pictured here: the juvenile stage of the Cortez angelfish. Whilst the other angelfish, the king angelfish, ranges throughout the Eastern Tropical Pacific including the Galápagos, the Cortez angelfish is only found as far south as central Costa Rica. Though relatively dull-coloured as an adult, the juvenile fish are brilliantly coloured and patterned, as though they were clamouring for attention! While this might seem illogical as it renders them more susceptible to predation, there actually is an explanation: they want to be seen! There is an incredibly important ecological niche on a reef, that of small cleaner fish – these inhabit cleaner stations and are never eaten by would-be predators, as they are needed to clean these of parasites and dead skin. As a protective measure, the juveniles of several reef fish adopt this behaviour as a protective measure, as well as a source of food – thus they need the advertising!

It truly is a rich and complicated world out there…