Fine-scale movements, three-dimensional habitat use and acoustic environment of humpback whales in NW WA

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Project Objectives:

The objectives of this project are to gain an understanding of:

1.     the fine scale movements and habitat-use of humpback whales in regions slated for development activity (e.g. port construction, oil and gas exploration, shipping) in NW WA.

2.     the ambient ocean noise in these regions and the extent to which humpback whales will be exposed to increased noise derived from ship traffic and from near-shore and offshore construction activities.

Researchers:
Prof. Peter Madsen (Aarhus University and Murdoch University), Prof. Lars Bejder (Murdoch University), A/Prof. Dave Johnston (Duke University and Murdoch University) and Dr. Josh Smith (Murdoch University).

Anticipated outcomes:
Our research will provide important information on: the probability of whale ship strikes; behavioural responses of whales to man made noise; and information on the behavioural ecology of humpback whales in the North West of Western Australia. The information will aid management agencies (e.g. Department of Parks and Wildlife; Federal Government) and industry in developing regional conservation strategies to project humpback whales in areas of rapid coastal development.

Project duration (2013-2015):
The project commenced in Exmouth in September 2013 and is currently ongoing. Subsequent field efforts will concentrate in areas off the Pilbara coast and the Kimberley.

Background to the project:
There are increasing conflicts between coastal development and marine species in Western Australia (port construction, oil and gas exploration, shipping). Little is known about the fine scale movements and habitat-use of humpback whales in regions slated for development activity, including associated increases in ship traffic. Furthermore, little is known about ambient ocean noise in these regions and the extent to which humpback whales will be exposed to increased noise derived from ship traffic and from near-shore and offshore construction activities. The purpose of this research project is to improve our understanding of the baseline ecology and behaviour of humpback whales in the Exmouth, Pilbara and Kimberley region; and to gain an understanding of how human activities (e.g. shipping; acoustic stimuli) may influence these baseline behavioural patterns. We hypothesize that the response of these animals to such stimuli will vary depending on the ecological characteristics of their environment. This research will add to our knowledge of humpback behaviour and ecology and to the conservation of this species.

Dtag compilation image

A compilation image showing the tagging pole, the DTAG, and the tag attached to a humpback whale.

The study involves attaching a digital acoustic recording tag (DTAGs) to humpback whales to monitor fine-scale movement in three dimensions, vocal behaviour and the acoustic environment.  The non-invasive tags will be attached to whales for periods of up to 24 hours using suction cups.

The core of this project is built around an established, non-invasive research protocol that has been developed over the past 15 years. Thanks to the work of many investigators, the application of these tags is now considered a routine research method for many species. Members of our research team have conducted research using DTAGs since the tag was first developed in 1999 and have successfully deployed the tag on 13 marine mammal species, including humpback whales in Antarctica, Greenland and USA.

DTAG description:
DTAGs are small (15cm x 8cm x 3cm), light-weight (200g in air; slightly buoyant in water), non-invasive archival tags that attach to study animals via small (30 mm diameter) silicon suction cups. The tags can be programmed to remain on a whale and collect data for up to 48 hours (we will limit our observations to 24 hours). Based on extensive experience with this tag on large whales, there is no evidence that the drag of the tag affects the swimming behaviour of a tagged whale. The DTAG measures and records water depth (via a pressure sensor), water temperature, and the swimming orientation in three-dimensions of the tagged animal at 800 samples/sec. The tag also records sound up to a frequency of 192 kHz, which is sufficient for measuring sounds both made and heard (e.g., vessels) by the whales. All data are stored on the tag and downloaded for analysis. The tag contains a VHF transmitter that is used to follow the tagged whale whenever it is at the surface and to aid in tag retrieval. A programmable release mechanism allows tags to release at a predetermined time.

DTAGs are attached with suction cups to whales:
DTAGs are attached to a whale with four silicone suction cups using a 6-12 m handheld carbon fibre pole. With the use of the poles, the tag is delivered without encroaching over the flukes of the animal.  The tags are programmed to release from the animal by venting the suction cups at the end of the recording time. A VHF beacon in the tag aids in tracking and recovering the device. Once recovered, tag data is off-loaded to a computer.

How do we get the DTags on the whales?:
The DTAG is noninvasive and is attached to the whale with 4 silicone suction cups using a 6-12 m handheld carbon fibre pole.  With the use of the pole, the tag is delivered without encroaching over the flukes of the animal.  The tags are programmed to release from the animal by venting the suction cups at the end of the recording time.  A VHF beacon in the tag aids in its tracking and recovering. Once recovered, the tag data is off-loaded to a computer, checked for errors and archived.

DTAGs are attached to the whales in a manner that minimizes the potential for disturbance. We will attempt to tag humpback whales by approaching them slowly in a small vessel and using the hand-held poles for attachment.  The tagging vessel must approach within 10 m for attachment using the hand pole. DTAGs are typically attached on the dorsal surface of the animal, caudal to the blowhole.

tagging picture

A tagging event of a beaked whale.

Observers select an animal for tagging and monitor this animal before tagging so we can test for any effects of tagging. Both males and females are approached for tagging. The tagging vessel approaches slowly, typically from behind and to one side of the animal, and move into a position to allow attachment of the tag. We obtain photo-identification images of all animals that we tag or attempt to tag. We use photos to identify the tagged animal by comparing with photo-identification catalogues and to prevent duplicative tagging.

We attach DTAGs to humpback whales for periods of up to 24 hours. We employ a release mechanism that incorporates an electrically corroding wire assembly to release the tag package from the animal at a predetermined time. The corroding wire assembly opens a tube to release the suction and is not in contact with the animal at any time. Because the tag is attached behind the blowhole it has no chance of interfering with breathing if the tag migrates (it will always move towards the tail of the animal). The entire tag releases from the animal, leaving no equipment behind.  Detached tags float to the surface and are located by sight or using the VHF transmitter. To facilitate tracking (and subsequent retrieval) of the tag, we will use VHF radio receivers and antennas to detect signals from the tagged whale when the transmitting antenna emerges from the water. Madsen and Johnson have followed hundreds of tagged whales with this system with virtually no tag loss. VHF tracking can be conducted from smaller vessels or from land.

Permits:
This research is being carried out under permits from the WA Department of Parks and Wildlife (# SF009373 & CE004048) and a Murdoch University Animal Ethics permit (#R2594/13).

Funding:
This research is being funded through two sources: Murdoch University and the National Danish Research Council for Natural Sciences.

Contact details: Lars Bejder l.bejder@murdoch.edu.au

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