This month’s flora and fauna update

No creature can survive without a supportive habitat that will provide both food and shelter. Park Island and the Cape Flats are the perfect habitat for the Cape Dune Mole-rat so I guess we should not be surprised that its most ardent predator is the Mole Snake [Pseudaspis cana]

The Mole Snake is a misunderstood snake, often confused with the venomous Black Mamba or the Cape Cobra. In fact, it is not a danger to humans at all, although it could bite if provoked. It varies tremendously in colour from nearly black to light brown, so look for its small head and pointed snout. It also enjoys sunbathing. Sadly, this useful snake is often mistakenly identified and killed on sight.

marina-da-gama-mole-snake

Its preferred habitat is sandy scrubland/dunes. It is a powerful constrictor with a pointed head that is well adapted for its burrowing existence. It spends most of its time underground in search of food, typically moles and other rodents. It has been known to take birds, eggs and nestlings. Juveniles feed largely on lizards. Its prey is seized by the head and constricted.

Adult males are known to engage in combat during the mating season, but otherwise they are generally solitary and viviparous, giving birth to an average 25-50 young in late summer. The newborn snakes measure 20-30cm in length.

The Mole Snake pictured here was discovered idling over the Park Island road bridge a few weeks ago. Despite some efforts to relocate it into the nearby bush, it was determined to continue unhurried under the gate and into suburbia!

Cape Mole-rat (Georychus capensis) I have featured these animals, the largest of all moles, before. But after having the opportunity to photograph the Mole Snake, last week I came across this Cape Mole-rat above ground, displaying this interesting behaviour. I’m not sure whether it was lining a nursery burrow or storing fodder for the winter. While they destroy many a gardener’s joy, I can’t help being curious about them.

They have soft fur, cinnamon to pale fawn underparts, short tails, rounded heads, well developed prominent incisors and tiny ears and eyes. This species is distinguished from the others by black and white head markings.

They display fossorial or burrowing behaviour, digging extensive underground burrow systems marked on the surface by mounds of sand. They dig using their well developed incisors, then use their feet to shovel loosened earth out of the way. Most digging follows rain. Within burrow systems, there are usually chambers that serve for food storage. Activity patterns do not seem to be tied to day or night but active and resting periods are spread through 24 hours. They are vegetarian, eating mostly roots, bulbs and tubers. They are considered a pest by gardeners, farmers and in urban areas damaging roads, runways and golf courses to mention just a few.

While the majority of Mole-rats live in colonies, the Cape Mole-rats are solitary burrow dwellers, only coming together to mate. They are seasonal breeders, producing 4-10 pups per litter after approximately 55 days of gestation. On average, they live for around three years, during which time they typically grow to a weight of 650-890g but can grow as big as 2kg. The larger the animal and larger its mounds.

Judging by the very large population residing on Park Island, we need more Mole Snakes!

Photos: Cherry Giljam

Calling all twitchers: join us for the next CWAC

It was a rather cool and overcast day on 23 January in the Zandvlei Estuary Nature Reserve (ZENR), with only a light wind. In other words: perfect conditions for the quarterly Co-ordinated Waterbird Count (CWAC), organised by Gavin Lawson and the Cape Bird Club. This is a national census for counting water birds, which takes place across most of the wetlands in South Africa. A small group of Marina residents and ZENR staff joined in the fun.

The Zandvlei is divided into two areas for the bird count, Upper and Lower, with the  Park Island bridge as the boundary.

Here is a breakdown of the findings:

Upper – Total number of birds 1121
Total number of species 29

Lower – Total number of birds 685
Total number of species 25

Bird nameUpperLower
Greater Crested Grebe3
White Breasted Cormorant14
Cape Cormorant27
Reed Cormorant5231
African Darter131
Grey Heron31
Little Egret379
African Sacred Ibis2117
Hadeda Ibis29
African Spoonbill4
Greater Flamingo2
Spurwinged Goose8
Egyptian Goose5060
Cape Shoveler4
Yellowbilled duck11016
Cape Teal84
Common Moorhen10
Red-knobbed Koot521248
Threebanded Plover2
Blacksmith Lapwing3726
Common Greenshank1
Pied Avocet169
Blackwinged Stilt5410
Water Thick-Knee3
Kelp Gull39146
Greyheaded Gull11
Hartlaubs Gull7956
Caspian Tern3
Common Tern1
Sandwich Tern7
Pied Kingfisher129
Malachite Kingfisher1
Cape Wagtail6
Mallard4
Mallard Hybrid115

Marina residents are welcomed and encouraged to help count birds at the quarterly CWAC count. Please contact Gavin Lawson on glawson@axxess.co.za
Counters on foot and in canoes are welcome.

Read more on https://www.capebirdclub.org.za/zandvlei-cwac-counts/

Our popular flora and fauna focus returns

By Cherry Giljam

Love it or hate it, healthy water bodies should exhibit a range of different algae as well as various floating/rooted aquatic plants. All estuarine wildlife is dependent on such plants for food (direct and indirectly) and nesting material for its survival.

The Great Crested Grebe and its favourite delicacy, the endangered Pipefish, are great examples. To a greater or lesser extent, they are both residents of Zandvlei, depending on the abundance of aquatic plants.

Photo credit: Wilbert Mcllmoyle

The Great Crested Grebe is termed an uncommon resident. It is unmistakable, with long crests when breeding and long, flattened cheek feathers. They are tailless waterbirds, feeding beneath the surface by diving, remaining submerged for 20-50 seconds. They are seldom seen on land but fly long distances at night to new waters. Breeding and non-breeding plumages differ. Small chicks are striped on the upperparts, the head stripes remaining until the bird is nearly fully grown. Chicks ride on their parents’ backs. Normally silent, pairs occur on large inland waters or estuaries bordered by low, emergent vegetation. On water, when preening, they habitually expose their white underparts. Their courtship dance is something very special to witness.

Some years ago, when the Kingfisher weed eater was out of action for the whole winter, the Marina da Gama scored the highest number of Great Crested Grebe breeding pairs in the entire country!

Way back in 2001, Clifford Dorse, the first manager of the Zandvlei Estuary Nature Reserve (ZENR), discovered the extremely rare Pipefish [Syngnathinae] in Zandvlei. They are a sub-family of small fishes, which form the family Syngnathidae together with the Seahorses (Phycodurus) and Seadragons (Phyllopteryx).

They are marine dwellers in tropical and temperate zones, their usual habitat being sheltered coral reefs or sea grass beds. Their discovery living in the pondweed (potamogeton) in our estuary was quite a revelation. Usually only 35-40cms in length, they lack strong swimming ability and are easily disturbed by human recreation and pollution. Parenting duties are the responsibility of the male. They are in high demand for pseudo-scientifc medical cures and the aquarium trade. Due to their narrow distribution they are less likely to adapt to new habitats. In 2018 when the estuary mouth was opened seasonably for the winter, creating a drop in water levels, there was suddenly a bird feeding frenzy in the pondweed. To our amazement, it was Pipefish they were feeding on.

Thanks to our visiting photographer, Wilbert Mcllmoyle, Grebes, Cormorants, Hartlaub Gulls and even Herons were photographed in evidence enjoying the feast, while cut pondweed transferred to the land also contained ‘pickings’ for Egrets and other birds.

Since then, we have occasionally witnessed Pipefish being devoured by our water birds. But following the crash of our pondweed growth in 2000, we have feared for their existence. ExCom member, Lise Carswell, captured a picture of a Grebe eating its favourite delicacy a couple of weeks ago. So, we can only hope this remarkable creature is still alive and thriving in our estuary.

Please keep us posted!

Below the surface on Fisherman’s Quay…

It has been marvelous to see the herons and coots return to the Zandvlei over the past few weeks. The lowered oxygen levels in the canals, while not ideal for the fish or crabs, have resulted in buffet feasts for the birds.

The birds are easy for us to spot, but what happens below the surface? Many thanks to Marina da Gama resident, Gordon Hiles, who took this wonderful underwater footage from his pier in Fisherman’s Quay.

Estuaries are extremely important when it comes to essential ecosystem services such as providing fish with nursery and breeding areas, flowing fresh water into the marine environment, and replenishing nutrients. The Zandvlei Estuary is rated among the top most important 25% of all the estuaries along the South African coast. It is also the only functioning estuary in the city of Cape Town.