Hermanus is a seaside resort in Walker Bay, 122 km east of Cape Town. Between June and November, the winter in the southern hemisphere, it becomes one of the world’s most famous places to watch whales. Elsewhere in the world, ocean giants stay far out to sea to meet them, a boat trip is required, but in Hermanus the whales come straight to shore and can be observed up close and in person from beautiful points. Sometimes there can be up to 70 whales in the bay. The local council even runs a “call-whale” that blows a horn made of local kelp, warning people of an approaching whale.
The species that so easily manifests itself off the African coast is the “southern right whale.” The whalers thought it was the “right” whale to catch, because it could be easily approached and harnessed to the manual and trusting. The carcass floated, reached easily and gave a lot of oil.
The North Atlantic whale, which is very rare in Irish waters, is a close relative. In contrast to this northern species, which is in “critical danger,” the southern has recovered from the mass killings of industrial whaling and is now of “least concern” to IUCN.
Whales are strange-looking creatures; black on all but white spots on the abdomen. The head is one-third the length of the body, and the maximum circumference of the torso is 60% of the length of the animal. Like baleen whales in general, females are larger than males. Southern right females can be up to 15 m in length.
But why does the southern whale dare so close to shore?
Calves need warmth; cold-water currents that take from Antarctica along the South African coast are not suitable for them, while the coastal waters of the bay are relatively warm. As such, Walker Bay is the perfect maternity ward for whales.
The bay also provides protection from the sworn enemy of the right whale, the killer whale; mothers and their calves are there safe from these “killer whales”. This may seem somewhat unbelievable, as killer whales are capable of hunting in relatively shallow water, and the location of whale kennels should definitely be well known to them. But researchers from Syracuse University have found additional evidence to support the idea of calf safety. They measured acoustics and sound propagation in places on three continents that are often visited by whale mothers and calves.
Whale songs are extremely loud and move long distances, but they are not the only vocalizations of whales. The Danish team installed acoustic tape recorders on nine female whales. When the animals sank into the water, they let out soft cries that could be heard near them, but were masked by background noise even at a distance of 200 meters. Whales use these calls to “whisper” to their calves. Killer whales would find it difficult to overhear such conversations.
But in shallow water the sounds propagate less well than in the open sea; the seabed and rocky shoreline block the transmission, and the sound of waves crashing against the beach mask the sounds of whales. By moving to Walker Bay, mothers and babies reduce the risk of being detected by eavesdropping killer whales.
Researchers believe that mothers of other whale species may also use such “acoustic crypsis‘.
