Foraging activity of sperm whales (Physeter macrocephalus) off the east coast of New Zealand

Giacomo Giorli,Kimberly T Goetz

doi:10.1038/s41598-019-48417-5

Abstract

The occurrence and distribution of sperm whales in New Zealand waters is mainly known from whaling records or opportunistic sightings by the public and a systematic estimation of the abundance and distribution has never been conducted. In this study, we investigated the foraging activity and occurrence of sperm whales off the Eastern coast of New Zealand using passive acoustic monitoring techniques. Three acoustic recorders were moored to the ocean floor at different locations on the east side of the North and South Island to collect passive acoustic data from June 2016 until August 2017. A total of 53,823 echolocation click trains were recorded and analyzed to understand the spatial and temporal variation of sperm whale foraging activity. No difference in the foraging activity was found between night-time and day-time periods at any of the locations. Click train detections increased toward the south, suggesting increased foraging activity near Kaikoura. At each station, sperm whale foraging activity varied by month.

Highlights

The occurrence and distribution of sperm whales in New Zealand waters is mainly known from whaling records or opportunistic sightings by the public and a systematic estimation of the abundance and distribution has never been conducted
Most of the information available are from historic whaling records, opportunistic sightings reported by the public or studies conducted in a known “hot spot” area offshore of the Kaikoura peninsula
Data from the Mediterranean Sea and the Gulf of Mexico revealed similar dive patterns with sperm whales diving to depths ranging between 700 and 1100 m18, a behavior the was consistent with data from Papua New Guinea[19], the Atlantic Ocean[17] and New Zealand[20,21]

Summary

Introduction

The occurrence and distribution of sperm whales in New Zealand waters is mainly known from whaling records or opportunistic sightings by the public and a systematic estimation of the abundance and distribution has never been conducted. We investigated the foraging activity and occurrence of sperm whales off the Eastern coast of New Zealand using passive acoustic monitoring techniques. Occurrence, distribution, and foraging behavior of sperm whales in the New Zealand Exclusive Economic Zone (EEZ) are sparse or lacking. Seasonal and spatial occurrence of beach-cast animals showed that sperm whales stranded on both the North and South Island, with no apparent seasonality[9]. In a similar study carried out between 1990 and 1998, sperm whale abundance around Kaikoura was not found to vary seasonally, but differences between their summer and winter distribution were evident[12]

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