WILDLIFE WATCHING
In his series of great places to watch wildlife in the UK, the star of BBC One’s The One Show this month picks his way across rocky shores, revealing the wildlife that thrives where land and sea meet.
Rocky shores are among a select group of habitats remaining in the British Isles that can still be considered largely free from the impacts of human (mis)management. Constantly transitioning between terrestrial, marine and ‘somewhere in between’, according to the state of the tide, the raw and wild nature of the rocky ribbon encircling large parts of our coast ensures this is not a habitat for wildlife best described as faint of heart.
Substantial sections of Britain’s northern and western coasts are primarily rocky by nature. These hard shores are not just directly impacted by the tide, since the levels of inundation and duration of exposure will also greatly influence temperature, moisture and salinity levels. In terms of topography, the gradient of any rocky coastline will depend on its geological genesis and can range from sheer cliffs to large expanses of gently sloping rock. Each location also contains its own unique combination of boulders, pools, channels, gullies and crevices, so no two stretches of rocky coast are exactly the same. However, despite an infinite number of differences in appearance, all rocky shores do tend to be variations on a theme.
Tidal heights divide all rocky shores into upper, middle and lower sections.
The middle section is generally the only part covered and uncovered by the tide twice daily. By contrast, the other two sections typically become fully immersed or open to the elements during spring tide events – when the high tides are higher, and the low tides lower, than average.
If you explore a rocky shore, starting at the splash zone (which is just beyond the highest tides), and then move towards the furthest reaches only exposed at low tide, it becomes obvious that overlaying these physical sections are ‘colour coded’ biological zones. These horizontal bands can easily be made out even on a cold February day.
Once you leave behind the thin green line of salt-tolerant vascular plants, the first zone you usually encounter is
Clockwise from top left: the rocky nature of Dorset’s Kimmeridge Bay is revealed at low tide; coastal otters can be spotted in Scotland; Mellon Udrigle on the Highland’s west coast; a turnstone coming in to land on the tideline; common seals are less numerous in the UK than grey seals; rock pipits forage on our shores. the upper orange zone, so called due to its domination by orange and yellow lichens of the genera Caloplaca and Xanthoria respectively. Just below this is the black zone, where the black tar lichens of the genus Verrucaria quickly gain the upper hand.
Descending still further, these lichens then give way to a grey zone, where barnacles and limpets invariably monopolise the rock surface, before you finally pass into the brown zone, home to plentiful large brown seaweeds.
The perfect spot
More mobile animals, such as otters and various wading birds, travel seamlessly between these biological zones. Other species tend to be sessile (rooted to the
spot), and stay put in one zone. A case in point are the weird and wonderful anthozoans, or ‘flower animals’, such as sea anemones and their relatives, which are frequently found towards the low water mark.
Indeed, many rocky-shore creatures, from snails and crabs to prawns and fish, carve out their own particular niche at some point along the shore’s transect. A degree of rockpool gazing or seaweedlifting is needed before their hiding places are revealed.
Naturalists visiting rocky shores can probably be split into two groups: those keen to explore rockpools; and the vertebrate spotters. As rockpools have featured in these pages already (August 2018), this month’s list of target species is biased towards feathers and fur.
Rock-loving waders, such as purple sandpipers and turnstones, are best looked for on a rising tide, when there is much less rock left to scan, with the birds additionally forced closer to dry land. Sea-faring otters also prefer to hunt as the tide is incoming. Common seals, by contrast, generally carry out their very passable impersonations of huge bananas on rocks when the tide is out.
Common seals carry out their very passable impersonations of huge bananas on rocks when the tide is out.