August 2008
This is been a busy field year for me and the volunteers with regard to koala research and – surprisingly this is the first time I have had the peace of mind to update the science diary. Even now I am writing this entry four days before setting out on a 15 day expedition to central and north - western Queensland to get some sense of koala habitat at the edge of the species range in tropical Australia. I’ll talk about that trip after I get back in mid-September.

St Bees Island
The wet season
There have been two Earthwatch supported field trips to St Bees Island this year – in May and July. The May trip is in autumn and just after our wet season. The wet season had been intense and about 1.5 metres of rain fell in February. It was fortunate that we had decided, in 2007, not to run wet season trips as any work would have been impossible. Peter Berck has water running through his house. All the rainforest streams and gullies carried large volumes of water and the ground was saturated. In May we found many small land slips and fallen trees. Our field equipment was covered in mould. Despite the intense rain there was no indication of adverse impacts on the koalas. The island vegetation has responded to the rain and in May it was difficult to find koalas in the thickened foliage.

This wet season is ecologically important being a decadal event. The flood flows scoured the valleys and carried large volumes of litter and debris to the bay and reorganising the beach dunes and tidal sand banks. There has been a widespread seedling response and we can expect to see a pulse of young trees, shrubs and vines growing into the rainforests and eucalypt forests over the next decade.

Despite that there is still no evidence of regeneration of the koala’s food species Eucalyptus tereticornis (Blue Gum) and Eucalyptus platyphylla (Poplar Gum).

The goats
Queensland Parks and Wildlife (formally Queensland Parks and Wildlife Service) commenced managing the island goats last year after it became evident that the vegetation was being severely graded. Goat browsing was also considered as one possible factor limiting regeneration of the koala food tree species. About 2,500 goats have been removed so far. Despite that in the May and July trips we found small groups of goats wherever we went on the island. So it is possible that the remnant browsing pressure is still sufficient to suppress Eucalyptus regeneration. Goat control teams are continuing to visit the island with the intent of removing all goats eventually. There has been an exponential decline in goat numbers and the project is now in a long tail of low detection numbers for effort. It will be some years before goat eradication is achieved.

We can detect changes on the island, however. Firstly, the island is much quieter. The constant background bleating of nanny and kid is gone. It is no longer possible to glance at a hillside and see 40 or so goats. Also the degradation of the vegetation seems to have stopped. No evidence of recovery yet, but it seems that this will be evident soon.

The field trips
Five Earthwatch volunteers (an all USA group) joined the team in May. We spent the time relocating the koalas last tracked in October last year, servicing the weather stations and data loggers and assisting Bill and Sean to catch koalas and recover GPS data loggers. The trip went well although the sand flies were frustrating in the evening.

The July trip was at capacity with 10 volunteers (five Australians, 5 from USA). The work focused on tracking the 13 radio collared koalas to follow their response to the severe weather experienced during this trip. The weather was cold and windy at times. At the end of the first week a three day gale blew across the island. We confined ourselves to the houses for a day and a half when flying branches, falling tree limbs and coconuts as well as buffeting wind gusts and heavy rain made field activity dangerous. By day the koala’s reaction to the adverse weather was not what we expected. As the gale and rain intensified the koalas moved to exposed trees and limbs – some leaving their usual habitat in sheltered rainforest communities. Once the rain and wind had passed and the sun reappeared they returned to their use of sheltered trees and gullies. Why would these animals place themselves at greatest exposure to the elements rather than retreating to the most sheltered aspects of their habitat available to them? Can we presume that they are seeking sun for warmth - although there was no sun, only strong winds and rain? Interestingly we observed a change of behaviour at the start of the gale and another as the gale declined. When we collect the weather data (in October) we’ll look for a potential environmental trigger. These sorts of observations are rare and, in turn, rarely replicated in the field. However, they help us develop our understanding of the increaslingly complex behavioural world of the koala.

In the last few days of the July trip a team from Queensland Parks and Wildlife arrived to monitor the vegetation recovery after goat removal.

The upcoming October trip will, hopefully, be assisting in catching koalas and changing radio collars and observing the private lives of some of the island’s male koalas in the breeding season as well as tracking the movement and tree use of the collared group in this season.

Later in September I’ll give an account of the expedition to the north western edge of the koala’s range.

Thanks to everyone who assisted in the field trips so far. It is making a difference!

Alistair.

Figure 4: Trina and the spider. Orb-web spiders are particularly common in summer.

This entry was posted on Sunday, August 24th, 2008 at 3:55 pm and is filed under Alistair Melzer. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.