An international research collaboration has used an omnidirectional camera attached to a humpback whale to reveal how these creatures lie underwater. These findings show how wide-angle lens cameras can be useful tools for illuminating the ecology of hard-to-see animals.
The research group included Professor Takashi Iwata from Kobe University Graduate School of Marine Sciences, Researcher Martin Biuw from the Norwegian Institute of Marine Research, Professor Kagari Aoki and Professor Katsufumi Sato from the Atmosphere and Ocean Research Institute, University of Tokyo, and Professor Patrick Miller from the University of St Andrews.
These search results were published online at Behavioral processes on February 25, 2021.
Key points
- The researchers attached an omnidirectional (360 °) camera to a humpback whale and found that these animals rest while moving underwater. Whales can rest either on the surface or underwater, and it is believed that they choose which of these different environments to rest according to the situation.
- The omnidirectional camera recorded a wide range of information about the environment around the tagged whale, revealing that humpback whales lie in groups rather than alone.
- These results have proven that animal-carried omnidirectional cameras are useful for learning more about hard-to-see animals.
Research Background
It is difficult to see the ecology of cetaceans directly because they spend most of their lives underwater. However, recent studies have been carried out on the ecology of hard-to-see marine animals, using a method called bio-logging. This method involves attaching a camera to an animal and recording environmental information related to the behavior and its surroundings. Different types of data can be recorded and measured, and this information can be used to understand things like animal behavior and diving psychology. Such data include depth, swimming speed, acceleration (which can be used to understand the position of the animal and precise movements), voices, heart rate and GPS positioning data (Global Positioning System) .
Cameras in particular are a powerful tool as they allow researchers to look at the environment of the individual animal, which in turn helps them to understand the animal’s behavior. However, the limited view of the camera has been a problem with animal-carried cameras so far. For example, research using a camera attached to a humpback whale (Megaptera novaeangliae) showed that if a competitor were present, the whale would move away quickly from hunting sites. However, the competitor was invisible due to the small size of the camera, so its presence was not accepted. So a camera with a wide-angle lens is needed to record what is around the animal.
This research focused on the humpback whale, a species of baleen whale found in oceans around the globe. Using bio-logging, researchers have learned more about the hunting habits of humpback whales, but little is known about their resting behaviors. Detection events can be identified from the recorded depth, swimming speed and acceleration (movement) of the whale which are common indications that it is running a prey. However, researchers have not identified the usual symptoms for relaxation, and the differences between relaxation and slow swimming are not fully understood. Information about an animal’s resting behavior is needed to understand their ecology. For example, if we consider the behavior of animals according to their time budget, the percentage of time for other activities such as hunting decreases if their rest periods increase. Even though knowledge of resting behaviors is essential to understanding the ecology of animals, one is hardly aware of the resting practices of baleen whales.
This research group used an omnidirectional camera (with a 360 ° view on land and a 270 ° underwater field view) and a behavioral data recorder to elucidate the resting behavior of humpback whales.
Research Methodology and Findings
RICOH provided the basic THETA camera model for this research, which was made against pressure and waterproofing using epoxy glue by Little Leonardo Corp., which led to the development of a new type of omnidirectional camera carried by animals. A switch cup tag was made of influential materials that can be attached to the whale. The tag included an omnidirectional camera, a behavioral data recorder and a radio transmitter.
The field survey was conducted in January 2016, off the coast of Tromsø in Norway. To tag the whale, the researchers approached it in a small vessel (5-6m) and used a 6m pole to attach the tag to the animal. The tag was designed to fall off naturally after several hours and go up to the surface. The tag was then detected by verifying its position through the signal from the transmitter.
The research team was able to tag one person, receiving about an hour of video data and about eleven hours of behavioral data. From the behavior data, the researchers found that the whale was inactive in the first half of the recorded period and showed active behavior in the last half.
Based on previous research, this active shift in the latter half was assumed to be a procurement activity. The video data was captured in the first half of the behavioral data recording period when the whale did not move much. In this video period, the whale had the deepest dive on average 11m and his average swimming speed (trip speed) was 0.75m / s-1. The regular swimming speed of humpback whales was reported to be 1.45m / s-1, but the tagged whale was moving much more slowly at this time. Whales usually move their flukes (tails) when swimming but there were no signs that the individual whale moved its fluke in the behavioral data recorded in the video time. In the film, two other whales are seen moving underwater without moving their flukes. The tagged person was also confirmed to be moving underwater from his slow swimming speed, the lack of flu motion and the constant presence in other moving video footage. Species of seals, sperm whales and loggerhead turtles are known to move underwater while resting. Therefore, it is believed that the tagged whale in this study was also resting. Previous research has reported that baleen whale species lie on the surface but this study has shown that they also rest while moving underwater. Whales are thought to consider factors such as the position of the sea and their physical condition when selecting from both resting environments: on the surface or underwater. In addition, the images from the omnidirectional camera show that whales lie underwater in a group rather than alone.
More research
Researchers have been using animal-carried cameras as a tool to study the ecology of marine animals. For example, a front-facing camera attached to a mother seal recorded images of a puppy swimming behind it. However, to find out the meaning of these images (for example, whether or not the mother taught the puppy how to hunt) it is necessary to use a panoramic camera so that we can experience the environment. around. Still camera images of friction behavior between whales were recorded; however, a wide-angle lens camera would help researchers determine how often this behavior occurs. These examples illustrate the importance of wide-angle cameras, such as omnidirectional cameras, for studying the ecology of marine animals. Cameras like this allow researchers to record the environment around the tagged animal, allowing them to find out if other individuals (such as competitors, colleagues, or predators) present or not, and understand the frequency and circulation of food sources.
This research group said the selected whale was resting based on the capture of nearby people at rest, demonstrating the usefulness of omnidirectional cameras. It is hoped that these cameras can be used to illuminate the ecology of cetaceans.
Video of whale tagging: https://www.youtube.com/watch?v=oCESDySblqM