Using photography to study the conservation biology of bottlenose dolphins in southern New Zealand.

Abstract

Photography is a key tool in conservation science and has numerous applications. In the present study, photography and photogrammetry are used to provide new abundance estimates for the populations of Doubtful and Dusky Sounds, and to determine potential causes of the dramatic variation in reproductive success of females in Doubtful Sound. Additionally, this thesis aims to document the presence of an unstudied population of bottlenose in the Stewart Island area.

Mark-recapture analyses of photo-ID data show that bottlenose dolphin abundance in Doubtful and Dusky Sounds for 2012 were 61 (CV=0.5%) and 116 (CV=0.2%) respectively. Both populations underwent a decline between 2011 and 2012, and have a history of previous declines. To aid our understanding of the causes of these declines, a stereo-photogrammetric system was built, and calibrated, to measure dolphins in the field. Repeated measurements of all individuals within the population of Doubtful Sound produced a mean CV of 2.43%. Analysis of a range of factors potentially influencing calf survival showed that survival to 1 year depended primarily on being born at the optimum time (January). Survival to 3 years was predicted by the size of the mother (larger=higher calf survival) and the sea water temperature at birth (warmer=higher calf survival).

Frequent reports of sightings suggested the presence of a previously unstudied population inhabiting the south-coast coast of the South Island. Surveys of Paterson Inlet, Stewart Island resulted in an abundance estimate of 18 (95%CI= 15-20) regular users of the area. Results from this thesis indicate that the Fiordland populations are still vulnerable to population decline, and provide insight on why this is so. The repeated observation of dolphins at Stewart Island provides new information as to the distribution and abundance of this threatened species in NZ waters.