NO. 80/ 2009
19 FEBRUARY 2009
The Rondevlei hippo, now fondly named Zoro, is happy and relaxed in his current home at the Cape Flats Waste Water Treatment Works (CFWWTW). He has been so named due to the zigzag scar on his back, caused by his father’s tusks during fighting. He is approximately 4 years old and weighs an estimated 800kg. The Waste Water Treatment Works adjacent to Zeekoevlei and Rondevlei is part of the False Bay Coastal Park, a core area in the City’s Biodiversity Network. The City of Cape Town is an international hotspot for biodiversity, housing many critically rare and threatened plants and animals. The hippos at Rondevlei are a keystone species in Rondevlei, one of the City’s 24 nature reserves.
“After intensively monitoring the hippo for the last week and half, we have established he has a favoured night time stroll between three of the retention pans. He has proven elusive at times but we believe this is all part of his hide and seek game – trying to keep us busy” states Manager of Rondevlei Nature Reserve, Penny Glanville.
Since Saturday 7th February 2009, the City has successfully installed a one way funnel at the point where he had originally exited the Rondevlei Nature Reserve. This was done in the hope that he would attempt to rejoin the herd. A funnel with a mouth of five meters and an end of 1.8 meters was constructed, with a backing fence which allows the animal to re-enter the reserve but makes it impossible for him to turn around and get out again. “Unfortunately, he has not taken up this opportunity, and we speculate that this is due to his fear of further attacks from Brutus, his father” states Penny Glanville.
The City’s Biodiversity Management Branch staff from Zeekoevlei, Strandfontein and Blaauwberg Nature Reserves are installing a 2.4meter high fence line along the northern section of the CFWWTW to prevent Zorro from entering Zeekeovlei, as was the case with Houdini, the Hippo who escaped in 2004. The City has also constructed a gate to prevent the animal from accessing any public areas.
Simultaneously, preparations have been made to install a mobile electric fence which can be set up around the pan, in which he resides. This will allow Conservation staff to contain the animal in a smaller area, allowing time for the detailed passive capture operation.
The City will continue to monitor Zorro’s movements and keep the public updated on his movements.
BACKGROUND ON RONDEVLEI’S HIPPO POPULATION
The population of hippopotami at Rondevlei is important, as hippopotami populations across Africa are threatened due to a reduction in habitat, loss of access to fresh water and illegal poaching. In addition to these threats, the genetic diversity of hippos needs to be preserved to ensure the safety of the species. According to the 2006 IUCN Red List, hippos are considered vulnerable. It is estimated that 125 000 to 150 000 occur at present, which shows a decline of between 7 and 20 percent since the 1996 IUCN study. In addition, Rondevlei is the only hippo population in the City of Cape Town, an area where they were once numerous.
Despite their physical resemblance to pigs and other even toed ungulates, their closest living relatives are cetaceans, namely whales. The common ancestor of whales and hippos split from the even toed ungulates around 60 million years ago.
Hippopotami are recognizable by their great size, short barrel shaped body, smooth naked skin and stout legs. The head is massive with an enormous broad muzzle of up to 50 cm wide. The upper and lower tusk-like canines work against each other, keeping the tips sharp. The tail is short and flattened, with sparse bristles at the tip. The lips, neck and tips of ears are slightly covered with bristly hair.
Adult hippos are not typically buoyant; rather they propel themselves in leaps, pushing off the bottom in deeper water. They walk on the bottom very lightly, their feet leaving and touching the floor similar to an astronaut on the moon. While in the water they may reach speeds of approximately eight kilometres per hour and on land up to 30 km/h. On land they proceed at a trot, looking clumsy and ungraceful. They cannot jump or climb. When they lie down, they sit on their haunches before reclining and rise up on their front legs first.
Before submerging they fill their lungs with air, and as they submerge, sphincter muscles close the nostrils and hearing ducts to prevent water from entering. When they return to the surface they empty their lungs with a loud blast. The skin protects the mammal from the sun through its thickness and secretes a natural sunscreen substance, which is red in colour; therefore it has been referred to as “blood sweat”.
The hippo’s diet consists mainly of land grasses. They spend most of their time in the water, even for defecation. These deposits sink to the bed or wash up along river or lakeshores. It is generally accepted that the nutrients released from the dung into the water are necessary for continued high fish production.
Hippos do have a significant impact on the land they walk across, as they use the same paths to feeding grounds, therefore they help to keep land clear of vegetation by causing depressions in the ground. Hippos have an effect on the geomorphology of large wetland systems, maintaining pathways and developing new channels that lead to the expansion of the wetland. At Rondevlei Nature Reserve, it has been observed that over a prolonged period of time, many footpaths result in water canals or connect two smaller bodies of water.
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