Kyoichi Mori

First-ever observations of a live giant squid in the wild

The giant squid, Architeuthis, is renowned as the largest invertebrate in the world and has featured as an ominous sea monster in novels and movies. Considerable efforts to view this elusive creature in its deep-sea habitat have been singularly unsuccessful. Our digital camera and depth recorder system recently photographed an Architeuthis attacking bait at 900 m off Ogasawara Islands in the North Pacific. Here, we show the first wild images of a giant squid in its natural environment. Recovery of a severed tentacle confirmed both identification and scale of the squid (greater than 8 m). Architeuthis appears to be a much more active predator than previously suspected, using its elongate feeding tentacles to strike and tangle prey.

Observations of wild hunting behaviour and bioluminescence of a large deep-sea, eight-armed squid, Taningia danae.

Our newly developed underwater high definition video camera system took the first live images of adults of the mesopelagic large squid, Taningia danae, between 240 and 940 m deep off Ogasawara Islands, western North Pacific. The resulting footage includes attacking and bioluminescence behaviours, and reveals that T. danae is far from the sluggish neutrally buoyant deep-sea squid previously suspected. It can actively swim both forward and backward freely by flapping its large muscular triangular fins and changes direction quickly through bending its flexible body. It can attain speeds of 2–2.5 m s−1 (7.2–9 km h−1) when attacking bait rigs. They emitted short bright light flashes from their large arm-tip photophores before final assault, which might act as a blinding flash for prey as well as a means of measuring target distance in a dark deep-sea environment. They also emitted long and short glows separated by intervals while wandering around the double torch lights attached to the bait rig, suggestive of potential courtship behaviours during mating.

Measurement of swimming speed in sperm whales

Cetaceans spend their entire life in the water. Hence these animals represent important models for studying adaptations for aquatic environment. Although many scientists have been interested in how fast they can swim, accurate swimming speed measurements of free-ranging cetaceans are rare because it is difficult to observe them continuously. In particular, little is known about routine swimming speed of deep diver, such as sperm whales. To measure swimming speed of the sperm whales, we attached two-type suction-cup-attached tags including a data logger to sperm whales. One type was similar to that employed in several other studies (Type A). The other type was modified by us to get more precious velocity data (Type B). We attached the two-type tag to a total of 11 sperm whales (8 Type A and 3 Type B) and, obtained accurate swimming speed with 8 whales of them (5 Type A and 3 Type B). A total of 136 hours of accurate swimming speed data including 137 dives was obtained. Average velocity during the dive was 1.77 plusmn 0.39 m s-1 (n =137). Maximum velocity of each whale was 4.2-9.6 m s-1 (n = 8). In addition, we found the oscillations caused by the tail beat in the time-series velocity data, which was obtained by modified suction-cup-attached tags (Type B). The modified tags provide us routine and maximum swimming speed of the whales as well as the information of the tail beat.

Differences in sperm whale codas between two waters off Japan: possible geographic separation of vocal clans

Abstract The sperm whale (Physeter macrocephalus) clan is a social unit that shares a similar repertoire of vocalizations called codas. Coda repertoires and clan structure are well studied in sperm whales of the eastern tropical Pacific, but information is limited in the western North Pacific. We compared sperm whale codas recorded from female and immature sperm whales in 2 areas near Japan, off the Kumano Coast and off the Ogasawara Islands, to determine whether different clans exist in these waters. Repertoires of coda types were different between the 2 areas, and the lengths of codas consisting of the same number of clicks were longer in duration near Kumano than near Ogasawara. Our results suggest that different vocal clans inhabit in these 2 areas. Such clear geographic structure of clans is not known in other waters in the Pacific and distinct environmental features may favor a clan in which members share a specific foraging strategy and coda repertoire, both of which likely are transmitted through social learning.

Change in singing behavior of humpback whales caused by shipping noise

Reactions of singing behavior of individual humpback whales (Megaptera novaeangliae) to a specific shipping noise were examined. Two autonomous recorders separated by 3.0 km were used for the acoustic monitoring of each individual song sequence. A passenger-cargo liner was operated once per day, and other large ship noise was excluded given the remote location of the Ogasawara Islands, 1000 km south of Tokyo. In total, locations of between 26 and 27 singers were measured acoustically using time arrival difference at both stereo recorders on the ship presence and absence days, respectively. Source level of the ship (157 dB rms re 1μPa) was measured separately in deep water. Fewer whales sang nearby, within 500 m, of the shipping lane. Humpback whales reduced sound production after the ship passed, when the minimum distance to the whale from the ship trajectory was 1200 m. In the Ogasawara water, humpback whales seemed to stop singing temporarily rather than modifying sound characteristics of their song such as through frequency shifting or source level elevation. This could be a cost effective adaptation because the propagation loss at 500 m from the sound source is as high as 54 dB. The focal ship was 500 m away within several minutes. Responses may differ where ship traffic is heavy, because avoiding an approaching ship may be difficult when many sound sources exist.

Underwater drone for bio-logging of sperm whale

Bio-logging enables zoologists to reveal the many mysteries of free-range animals. It enables valuable scientific data to be gathered without disturbing their daily life, using a small data logger attached to their body. Several zoologists have applied the bio-logging approach to reveal the behavior of sperm whales by attaching data loggers onto their backs. However, no one has been able to observe their predatory activity, which can be considered as fighting and eating giant squids, because of the darkness of the deep sea. In this paper, to tackle the problem, we propose a novel concept with an underwater drone. The underwater drone carries a camera logger and directly attaches it to the area around the mouth of the whale. To implement the concept, we have designed and partially developed a prototype of the underwater drone. The prototype has six thrusters to enable six degrees of freedom omnidirectional motion in water. It has been designed with a maximum speed of 1.2 m/s to chase the sperm whale. The underwater drone will be teleoperated by an operator on a boat through a cable. The details of the prototype design are described in this paper.

An attempt to estimate ship noise effect on humpback whales in Japan

Ocean noise pollution is getting to be a major issue for the environmental assessment of maritime transportation and engineering. Evidences to estimate the effect of noise on marine creatures are urgently required. A Japanese team consist of government agency, universities, and research institutions launched a new project to observe possible effects of ship noise on humpback whales in Ogasawara archipelago. Radiated noise from a ship was measured according to the ISO standard protocol in deep water. The position and operational conditions of the ship during the daily voyages were precisely monitored onboard. Sound field within 10 km from the voyage route was calculated by numerical simulation. In parallel, land-based visual observers tracked humpback whales by a theodolite to locate surface position so that the exposure level at the animal can be estimated. Two autonomous stereo recording systems were deployed in the focal area to monitor the phonation behavior of singing whales simultaneously. As the fir...