Go on a guided marine walk at De Hoop Nature Reserve

5/3/2014

By Roxanne Reid
It was February and as hot as Hades. Yet the guided marine walk at De Hoop Nature Reserve that would see us poking about in rock pools was scheduled to start at 11am – because that was low tide – and continue under the noonday heat. We nearly chickened out.

We needn’t have worried. The breeze off the sea kept us cool while our jovial guide Pinkey Ngewu pumped us full of information from the encyclopaedia of intertidal creatures and their habits that she keeps in her head.

We learnt that there are two distinct intertidal zones. Closer to shore is the dry area, where you’ll find only creatures that can adapt to being dry for six to eight hours a day, such as limpets, barnacles and tongue weed. Nearer to the sea is the wetter zone, where you’ll find mussels, abalone and other creatures that have to attach very strongly to the rocks so the movement of the sea doesn’t knock them loose.

A breeze off the ocean kept us cool as we walked the white sands and explored rocky pools

Our journey began with a walk to the top of the highest dune, glaring white in the sunlight. From there we could look out to sea, where in the months of June to November we would have been able to watch whales. Around 40% of the world’s southern right whales come here to breed during those months, making De Hoop one of the best land-based whale watching spots in South Africa.

Guide Pinkey Ngewu is in her element among sea creatures in De Hoop's rocky pools

But the lack of whales in February didn’t bother Pinkey at all. She had lots of other interesting things to show us. Like limpets clamped to the rock.

‘There are 23 limpet species in South Africa and at De Hoop we have 18 of them,’ she said. ‘We’re No. 1 in the whole world for limpets. The next is the Mediterranean, which has only 10 species.’

It's not an aerial view of a desert, but the tracks left by limpets as they moved about to feed

Each limpet occupies a scar on the rock surface into which its shell fits to form a watertight seal. It may move around to feed during high tide and you can trace the trails they make. But when the tide recedes it always returns to its own scar, where it fits exactly. ‘You can’t open a neighbour’s door with your key,’ Pinkey quipped.

A keyhole limpet hiding under a rock - note the big body and small shell

She stepped into a pool, the water rippling around her calves, and started upending rocks until she found what she wanted – a keyhole limpet hiding under the rocks.

‘I call these the popes of the limpet world because they have a small hat and a large body,’ she said. Usually when a limpet attaches itself to the rocks, its shell totally covers it and makes a good seal. But the keyhole limpet’s body is fleshy and you can clearly see it bulging out under the small shell. ‘That’s why they have to live under rocks, so they don’t dry out in the sun – because you don’t want to see biltong limpets.’

She told us that the blood of keyhole limpets is being used in California to create medicine to treat leukaemia. Luckily, the blood is harvested without killing the limpet.

Sea fern

A couple of dark-green, almost blackish sea cucumbers with sausage-like bodies and soft rubbery skin were also hiding under the rocks. They’re members of the starfish family, and will turn themselves inside out to avoid predation.

‘Their poop is important to coral,’ Pinkey explained. ‘It’s 50% calcium carbonate which the coral uses to create its exoskeleton.’

Toothed and volcano barnacles attach to the rocks with a really strong 'glue' that means they're stuck there for life

We saw lots of barnacles – those lazy-looking things that attach themselves to a rock, a ship’s hull or even a whale. Toothed barnacles, giant toothed barnacles and volcano barnacles, all of them with a life span of up to 35 years. Although they’re hermaphrodites, they prefer to cross-fertilise and the runty-looking little barnacle in fact has the longest penis for its size of any animal. It can’t unstick itself from the rock so a long penis is the only way it can mate with its neighbours.

Sea urchin

We saw pretty purple sea urchins, noticing that their mouths are on the underside while their anus is on top. Covered in shortish pointed spines that weren’t all that prickly to the touch, they’re grazers that help to keep kelp in check.

Red bait expelling water

And we saw red bait in action. A rash of them were attached to the side of a rocky pool. They’re part of a family called sea squirts, and they feed by sucking in water and filtering out the yummies before squirting the water out again. Pinkey extended one finger and pressed a few to make them squirt on cue – a good six inches or so.

No prizes for guessing why the giant chiton is also called the armadillo

There were giant chitons with eight greenish-grey plates that look like armour plating. This and the fact that they’ll curl up into a ball when they’re in danger give them their alternative name of armadillo. Like the land-based armadillo too, they’re nocturnal and Pinkey had to brush away a good bit of sand off the top of them so we could see them as they snoozed in the heat of the day.

Giant periwinkle, De Hoop Nature Reserve

A giant periwinkle, or alikreukel

There were a few bits of jellyfish, one of them floating in a pool where it looked just like a plastic bag. There were abalone and bright orangey-red anemones. Tiny black periwinkles and a giant periwinkle (alikreukel) in its spiral shell. Pinkey prised it from the rock and we watched as the muscular orange and grey body retreated into the shell and ‘closed the door’ behind it with a tough shell-like seal.

Thanks to the protection offered by the reserve, thousands of mussels cluster on the rocks

Closest to where the waves were breaking, huddled cheek by jowl on the rocks, were more mussels than we have ever seen in one place – a feast for the African black oystercatchers.

‘I’ve never seen an oystercatcher eat an oyster even though that’s its name,’ said Pinkey. They eat mostly mussels and limpets, as well as whelks, periwinkles and crustaceans. The males can’t open the mussels themselves, but will eat them if they’re open. The females have a cutting plate in their beak that can open the mussels, which they need for protein to make eggs.

Territory for a pair of oystercatchers can be 800 to 1000 square metres. ‘And they don’t go to court for divorce papers,’ said Pinkey. ‘They mate for life and only take another mate if one of them dies.’ Some have been known to remain together for 20 years.

A pair of near-threatened African black oystercatchers with thousands of mussels that make up most of their diet

To us that seems like an admirable quality, but in nature such conservatism – together with their specialised diet and vulnerability to interference by man – threatens their survival. Here at De Hoop that was hard to believe while four pairs piped shrilly around us; because it’s a protected area, the oystercatchers and the mussels that they feed on are protected too.

It’s just one of many reasons why the De Hoop Nature Reserve is so special.

Need to know
The interpretive marine walk lasts about 3 hours.

You may also enjoy
15 things to do at De Hoop Nature Reserve in the Overberg
Cape Nature reserves: from Cederberg to Kogelberg and more

Like it? Pin this image!