Scientific Literature: Searchable Database

Executive Summary of results and recommendations Distribution and Abundance ~ About 80 whales visit Kaikoura in any one season ~ 119 sperm whales were photographically identified at Kaikoura between 1988 - 96 ~ Individual whales may visit for only a few hours or days, or may stay several months over periods up to 5 years ~ Marks used to identify these whales are very stable. No individual has gained a mark sufficiently large to obscure those by which it was first identified ~ Individual resident whales are routinely found in specific places ~ Resident whales tend to be found inshore, while transients are typically seen only offshore Population structure ~ A boat based, stereo-photographic measurement system was developed and used to measure 41 individual sperm whales ~ Size measurements show that sperm whales at Kaikoura are predominantly, if not exclusively, males. This concurs with whaling data from this area in 1963 - 64 ~ Most are in the size range of pubescent of sexually mature males. Very few are sufficiently large to be "socially mature" (breeding with nursery groups) ~ About half the population have dorsal calluses ~ Several sexually mature males have dorsal calluses. This observation substantially reduces confidence in using this feature to identify sex. Acoustic censusing ~ Sperm whales at Kaikoura typically dive for about 40 minutes and rest at the surface for about ten minutes before diving again ~ These whales start clicking within a minute of diving, and while underwater, vocalise almost continuously - with only short periods of silence. Normally they are silent for the last 3 - 5 minutes immediately before surfacing ~ Software was developed (Moby Click) allows automated analyses of click rate, for acoustic censusing via click counting ~ During bouts of regular clicks, mean click rate is around 1.25 clicks/sec (cv = 27.5%). Excluding buzzes, which are usually too faint to allow click counting, but including short silences, mean click rate of a lone whale over one entire dive was 0.88 s_1 (2244 clicks in 42.25 minutes) ~ Detailed studies of high-resolution recordings refute the idea that timing of multi-pulse echoes provides information on whale size. Recommendations ~ Current studies should continue to allow further development of acoustic censusing systems and better understanding of what drives fine scale patterns of habitat utilisation ~ Installation of a three dimensional hydrophone array on the Conway Ridge at Kaikoura would provide, for the first time, a detailed insight into what sperm whales do at depth. This system could also be used to investigate changes in behaviour caused by whale watching