Toxoplasmosis in Indo-Pacific humpbacked dolphins (Sousa chinensis) from Queensland

Objective: To describe the clinical signs, gross pathology, serology, bacteriology, histopathology, electron microscopy and immunohistochemistry findings associated with toxoplasmosis in four Indo-Pacific humpbacked dolphins (Sousa chinensis) that stranded in Queensland in 2000 and 2001. Design: Clinical assessment, gross necropsy, and laboratory examinations. Procedure: Necropsies were performed on four S chinensis to determine cause of death. Laboratory tests including serology, bacteriology, histopathology and transmission electron microscopy were done on the four dolphins. lmmunohistochemistry was done on the brain, heart, liver, lung, spleen and adrenal gland from various dolphins to detect Toxoplasma gondii antigens. Results: Necropsies showed all of four S chinensis that stranded in Queensland in 2000 and 2001 had evidence of predatory shark attack and three were extremely emaciated. Histopathological examinations showed all four dolphins had toxoplasmosis with tissue cysts resembling T gondii in the brain. Tachyzoite stages of T gondii were detected in the lungs, heart, liver, spleen and adrenal gland, variously of all four dolphins. Electron microscopy studies and immunohistochemistry confirmed the tissues cysts were those of Tgondii. All four dolphins also had intercurrent disease including pneumonia, three had peritonitis and one had pancreatitis. Conclusion: Four S chinensis necropsied in Queensland in 2000 and 2001 were found to be infected with toxoplasmosis. It is uncertain how these dolphins became infected and further studies are needed to determine how S chinensis acquire toxoplasmosis. All four dolphins stranded after periods of heavy rainfall, and coastal freshwater runoff may be a risk factor for T gondii infection in S chinensis. This disease should be of concern to wildlife managers since S chinensis is a rare species and its numbers appear to be declining.

Survival of bottlenose dolphin (tursiops sp.) calves at a wild dolphin provisioning program, Tangalooma, Australia

Mortality of calves born to provisioned mothers is identified in the literature as an issue of concern in dolphin provisioning programs. Wild dolphin provisioning at Tangalooma, Moreton Island, Australia has been occurring since 1992. Each evening, up to eight dolphins are provided with fish in a regulated provisioning program. In this paper, calf survival at the Tangalooma provisioning program is reported and contrasted with that from wild populations and from a similar provisioning program at Monkey Mia, Western Australia. At Tangalooma, the calf survival rate is 100%, including both orphaned and first-born calves, both of which are expected to have relatively low survival rates. Possible explanations for the high calf survival rate are explored. These include site attributes such as isolated location and high water quality, aspects of foraging ecology likely to benefit calves of provisioned mothers, and the management regime used in the provisioning program (e.g., duration and timing of provisioning; quality of provisioned fish).

"Gift Giving" by wild bottle-nose dolphins (tursiops sp.) to humans at a wild dolphin provisioning program, Tangalooma, Australia

Since 1992, wild dolphin provisioning has occurred on a nightly basis at Tangalooma, a resort located on Moreton Island, Australia. Each evening at dusk up to 12 bottlenose dolphins (Tursiops sp.) are provided with fish in a regulated provisioning program. Since July 1998, biologists managing the program have documented 23 occurrences of "gift giving," when several of the provisioned dolphins have offered wild-caught cephalopod or fin fish species to staff members. The characteristics of each of these events are presented, and we explore the relationships between these events and their temporal patterns, and the age and sex of the dolphins involved. We also consider the behavioral explanations for the "gift giving," including prey sharing, play, and teaching behaviors, which have previously been described for cetaceans and other higher mammals. Gift giving may occur either as a discreet behavior (that may be a sequel to one or more other behaviors such as play or food preparation), or as a part of other behaviors, such as play and/or food sharing. It is most likely a manifestation of the particular relationship between the provisioned dolphins and the human participants in the provisioning. Gift giving has become an established but infrequent part of the culture of the provisioned dolphins at Tangalooma. © ISAZ 2012 Printed in the UK.

Bycatch and strandings programs as ecological indicators for data-limited cetaceans

An integrated approach of using strandings and bycatch data may provide an indicator of long-term trends for data-limited cetaceans. Strandings programs can give a faithful representation of the species composition of cetacean assemblages, while standardised bycatch rates can provide a measure of relative abundance. Comparing the two datasets may also facilitate managing impacts by understanding which species, sex or sizes are the most vulnerable to interactions with fisheries gear. Here we apply this approach to two long-term datasets in East Australia, bycatch in the Queensland Shark Control Program QSCP, 1992–2012) and strandings in the Queensland Marine Wildlife Strandings and Mortality Program StrandNet, 1996–2012). Short-beaked common dolphins, Delphinus delphis, were markedly more frequent in bycatch than in the strandings dataset, suggesting that they are more prone to being incidentally caught than other cetacean species in the region. The reverse was true for humpback whales, Megaptera novaeangliae, bottlenose dolphins, Tursiops spp.; and species predominantly found in offshore waters. QSCP bycatch was strongly skewed towards females for short-beaked common dolphins, and towards smaller sizes for Australian humpback dolphins, Sousa sahulensis. Overall, both datasets demonstrated similar seasonality and a similar long-term increase from 1996 until 2008. Analysis on a species-by-species basis was then used to explore potential explanations for long-term trends, which ranged from a recovering stock (humpback whales) to a shift in habitat use (short-beaked common dolphins).