During our spring field season (Sept-Nov) in Bunbury, Western Australia, we were on the water for over 130 hours and encountered 64 groups of dolphins. Spring is an exciting time to conduct fieldwork because humpback whales pass on their southern migration. During this time, mother and calves pass closer to shore than on their northern migration. This spring we came across 12 humpback whale mum and calf pairs on our coastline transects. On two of these occasions the dolphins were associating with the whales. We also saw three mum and calf pairs of southern right whales, which is interesting, as we did not see any last year. Our whale images have been passed on to the SouWest whale research group for addition to their database.
Spring is also an exciting season because the flying fish come back into our study area. When driving along our transect lines searching for dolphins the boat scares the flying fish and they fly out of the water. We have also witnessed dolphins chasing after flying fish and last month we saw a dolphin leap out of the water and caught a flying fish in the air!
As spring began, the cuttlefish spawning period was ending. The cuttlefish appear to aggregate around Bunbury during the winter and some dolphins take advantage of this. Since 2007, Dr Holly Raudino and myself have seen several dolphins feeding on cuttlefish after popping out the cuttle bone. This is a specialised feeding technique, which in Australia, has only been reported previously in Adelaide.
Another, specialised feeding technique, which occurs in Bunbury, is what we have termed “octopus tossing”. The dolphins repeatedly toss octopus several meters into the air making sure the octopus becomes limp. We have seen this event on multiple occasions even prior to 2007 from Dolphin Discovery Centre volunteers and SWMRP researchers. Our last occasion to witness this event was in October, where an adult male “Quicksilver” was tossing an octopus. Quicksilver did not appear to be concerned by the boat or the fact that he had a large shark bite on his side of his body.
In addition to “Quicksilver’s” shark bite, we have also recently seen “Gem” a juvenile female and “Harvey” an adult male with shark bites. We keep track of these dolphins and record the healing rate of their scars.
Apart from sharks, dolphins also have to watch out for other dolphins, especially male alliances. In October, we saw a male alliance approach another male alliance. These alliances greeted head on and began intensely interacting. The dolphins were chuffing (forced exhalations that created a loud sound), splashing and blowing bubble rings. “Razor” and “Star” reared up at “Hockey” and “Shaka” appearing to ram them out of the way (see the main image at the top of this blog).
Summer has now begun and I have trained up Krista Nicholson who will be conducting my field data collection for a few months. I have been given the opportunity to attend classes on habitat modelling at Duke University. I will work with Dr David Johnston, who is a lecturer at Duke University. As my PhD is based on habitat modelling this is a special opportunity for me. However, I will miss being on the water each month with the dolphins, whales, hammerhead sharks, flying fish, fur seals, sea lions and little penguins.