In 2007, following a successful two month whale watching trip the previous year, we packed up a mountain of supplies and headed up back up the Kimberley coast on the houseboat to Camden Sound, to spend three months observing, filming and photographing the Breeding Stock D population of Humbpack whales. In preparation for the trip, and in competition with waves of newly arrived caravaners heading up the Gibb River Road, I scoured the supermarkets for supplies of surprise peas and anything else that would last for three months and provide some culinary variety. With no road access to Camden Sound and no towns the only chance of resupply was from sympathetic charter boats. We left town with cabbages and pumpkins crammed into every crevice on the houseboat as both last well without refrigeration.
Camden Sound, on the mid north Kimberley coast, is a vast body of water bounded by Deception Bay to the east, Byam Martin, Champagny and the Heyward Islands to the north and Montgomery Reef to the south. The area is rich in fringing reefs, and has been proven to be an area of remarkable biodiversity and great primary productivity; in layman’s terms, the waters of Camden Sound are a rich and nutritious soup.
Camden Sound is also one of the world’s most important humpback whale breeding grounds: a cetacean maternity ward abundant in fringing reefs which shelter the female humbpacks from testosterone charged bulls. The females calve in the Kimberley’s warm, tropical waters, spending several months fattening their calves and strengthening them for the long journey back to their summer feeding grounds in the Antarctic. Calves weigh approximately 2.3 tonnes at birth and require up to 600 litres of milk per day, rapidly gainly weight and developing a thick layer of blubber by the time they are weaned at 11-12 months.
The Kimberley coast is an area of huge tidal movement with differences of up to 14.1m between high and low tide over a six hour cycle in Collier Bay to the south of Camden Sound. From a marvellous vantage point on top of Hall Point at the edge of Deception Bay, we watched the whales using tides and currents to travel from northern Camden Sound out to Montgomery Reef and down to Collier Bay, teaching calves important lessons in conserving energy and working the tides. The whales also used Hall Point to herd small fish, pushing the shoals against the headland. Sitting off Hall Point in a dinghy, we dropped a hydrophone to listen to a nearby group of whales diving steeply in a small area. Through the hydrophone came excited chatter with a distinct echo off the underwater walls of Hall Point. Humpback whales communicate largely by sound with up to 640 identified vocalisations, including whalesong and social sounds. The Kimberley’s water are turbid with limited visibility so this vocal ability is vital in passing information between individuals. Although males are thought to be responsible for the haunting and complex songs, females and calves also communicate with social sounds. A 2001 Hawaiian studyfound that mother/calf pods had the highest rate of communication with 10.91 sounds per whale per hour.
By midway through the trip we’d run out of wine and beer and had exhausted our capacity for innovation with cabbages. Fortunately Camden Sound is a midway point for yachts sailing from Darwin to Broome, desperate for vegies. Gasping by this point, I scoured the horizon for charter boats and passing yachts , trading cabbages for wine, and exchanging well read paperbacks and news. A message in a bottle retrieved from a remote beach showed that we weren’t alone – just 3 words: “Please send grog” and co-ordinates.
As the tides cycle changed from neap tides to spring tides we relocated the houseboat a little further up the coast to the western side of Augustus Island, which boasts an extensive sandcovered reef system at the northern end. Whale numbers were sparser than further down the coast, and mostly isolated cow/calf pairs sheltering behind the reefs. Humbpack whales form loose bonds for short periods; indeed the cow’s relationship with her calf lasts barely past weaning.
The October spring tides are some of the lowest of the year, exposing shingly sandbanks in Deception Bay that are up to 10m underwater on a high tide. As the tides rise quickly there was only a short window of opportunity to explore these sandbanks covered in rarely seen marine life. We left the houseboat before dawn as the tide receded, exposing, amongst other things, Melibe viridus, a large sea slug with ten paddle like appendages and a pronounced oral hood used to hoover up small crustaceans, flapping on the sand. We photographed it quickly and returned it to a shallow pool as the tide rose around us, all the while eyed off by a crocodile in the middle of the bay. Also of interest was the fine layer of carbon sedimentation that had settled onto the sandbank through the water column after extensive and prolonged dry season bushfires. The same type of carbon deposits were noted on the sandbank in March 2012, again on some of the lowest tides of the year.
Towards the end of the trip we found a dead humpback washed up on the rocks just to the south of Hall Point. The whale had washed up at the end of a spring tide cycle, left high and dry and decomposing at a great rate during the neap tides. The carcass deflated like a badly punctured tyre and exposure to the sun swiftly rendered the blubber into a silky sheen of whale oil spreading over the sea surface as far out as Montgomery Reef and down to Doubtful Bay, accompanied by an indescribable stench. The oil seeped into the dinghy’s ropes and for months afterwards we were trailed by the smell of stale whale.
Six large crocodiles lay in a torpor on the rocks around the whale, gorged on whale meat, whilst six tiger sharks, as wide and as long as the 6m dinghy milled just off the rocks, snatching stray chunks of meat as they floated past with each wave. A succession of smaller crocs lay fanned in wait down the coast with the outgoing tide, grabbing smaller morsels drifting past.
Toward the end of the trip, anchored in Doubtful Bay, we noticed a thin, mint green line painted around the rocks of the bay. On closer inspection it proved to be solidified whale oil which had settled like butter as the tide receded. The rapid spread of whale oil around Camden Sound was a stark reminder of the power of the Kimberley tides in the event of an industrial disaster.