A mysterious beaked whale in the South China Sea

A mysterious beaked whale in the South China Sea

Introduction

Recently, the Institute of Deep-Sea Sciences and Engineering in the University of Chinese Academy of Sciences published a research paper in the journal Integrative Zoology, titled as “First live sighting of Deraniyagala’s beaked whale (Mesoplodon hotaula Deraniyagala, 1963) or ginkgo-toothed beaked whale (Mesoplodon gingkodens Nishiwaki & Kamiya, 1958) in the western Pacific (South China Sea) with preliminary data on coloration, natural markings and surfacing patterns“.

The research team witnessed three free-ranging beaked whales during the dedicated marine mammal vessel survey carried out in the northern waters of the South China Sea from April to May 2019. (Read more about “cetacean survey in the south china sea”).

The preliminary judgment of this sighting is that they would be ginkgo-toothed beaked whales (Mesoplodon gingkodens, [Nishiwaki & Kamiya, 1958]) or Deraniyagala’s beaked whale (Mesoplodon hotaula [Deraniyagala, 1963]).

Photographic sequence of respiration surfacing of the ind#2. The general body profile is similar to the typical shape of
Mesoplodon species.
Figure 1. Photographic sequence of respiration surfacing of the ind#2 (typical shape of
Mesoplodon species.)

Regardless of whether it is a Ginkgo-toothed beaked whale or a Deraniyagala’s beaked whale, they are the least known of all marine mammals. The understanding of these animals only relied on the knowledge of a few stranded individuals.

This clear sighting is the first preliminary study of living individuals of Ginkgo-toothed beaked whale and Deraniyagala’s beaked whale. This research paper is also the world’s first preliminary descriptions to examine the body color patterns, scar patterns and surface behavior of these mysterious beaked whales.

Why beaked whales are so mysterious?

Coincidentally, on the morning of November 17, 2020, 100 miles (about 160 kilometers) north of the San Benito Islands in Mexico, foreign scientists participated in the “Martin Sheen” of the Marine Guardians Association. This sailing ship also witnessed three mysterious beaked whales appearing in the nearby waters.

According to the recorded animal sound signals, the physical characteristics of the sound signals emitted by the mysterious beaked whales do not match the sound signals of any other known species of beaked whales.

Researchers believe the photos were taken and the sound recorded of the mysterious beaked whale is likely to be a new species. In addition, the researchers also sampled the DNA of the sighted animals, and the relevant data is being analyzed.

Beaked whales are the collective name of the cetacean suborder beaked whales. It is currently representing a total of 22 species in 6 genera, accounting for around 25% of the known extant cetaceans.

Beaked whales mainly live in deep waters and perform long-term deep diving for food. Its mystery is not only because there may be potential new species that have not been discovered, but also that its living body is difficult to be observed in the wild.

In fact, in the past two decades, people’s awareness of beaked whales has gradually improved, but there are still few studies on most species of beaked whales. Much of the cognition simply relies on the study of a few stranded individuals.

So far there is no exact records of individual sightings at sea and the collection of basic biological and ecological information obtained due to the difficulty of surveys and identification of most beaked whales species include Ginkgo-toothed beaked whales and Cuvier’s beaked whales.

Findings of the current survey on beaked whales in the South China Sea

The three beaked whales in the South China sea witnessed by the research team in the Chinese Academy of Sciences were similar in size, with a visually estimated body length of 4.5 to 5 meters. Two of them were taken with high-definition quality photos, denoted as ind#1 and ind#2.

The medium-sized sickle-shaped dorsal fin is located at about two-thirds of the body length (see Figure 1). The body surface has a similar body color pattern, and the back is gray-brown. The upper jaw is brown without white edges. The lower jaw and cheeks are pale; yes slight dark eyespots; small dents behind the arched upper lip; ind#2 has protruding teeth (see Figure 2).

Both animals have cookie-cutter shark bites marks on their bodies, and the shark bite marks appeared as white healing scars on its body, and most of the healing scars are the same color as the surrounding skin (see Figure 2).

The distance between ind#1 and ind#2 is less than one of its body size, and ind#2 is obviously in escort. The three beaked whales exhibited synchronized surfacing behavior.

They respectively performed three consecutive dives (shallow dives) for approximately 15.1, 16.7, and 13.7 minutes respectively. The fourth was a deep dive and then disappeared.

Before the second, third, and fourth dives, the three recorded times to the surface were 1.5, 2.0, and 4.5 minutes, respectively. The breathing rate is about 10 breaths per minute. In addition, no other surface behavior events were observed.

Photographic sequences of ind#1 and ind#2. The two individuals showed similar pigmentation patterns.

Figure 2 Individuals of ind#1 and ind#2 show similar body color patterns

Figure 2 The photos of the front of ind#1 taken under different lighting conditions. The photo shows that there are few typical white healing scars in the healed Dharma shark bite marks (see white in the left picture), and most of the healed scars are the same color as the surrounding skin (see the small round bump in the right picture).

Photo comparison of Ginkgo-toothed beaked whale and Deraniyagala’s beaked whale

The researchers compared the photos taken this time with the previous photos of Ginkgo-toothed beaked whales and curvier’s beaked whales. The following are some obtained insights related to photo comparison of these two beaked whales:

  1. Due to differences in the shape and body color of the head and mouth, Individuals of Ginkgo-toothed beaked whales and Deraniyagala’s beaked whales can be easily distinguished from other beaked whales. From the appearance and skin color, the beaked whales witnessed this time should be Ginkgo-toothed beaked whales or Curvier’s Beaked whales.
  2. Although the quality of the photo data collected in this study is relatively high, due to the high degree of similarity in body color patterns and scar patterns between species, it is impossible to compare the Deraniyagala’s beaked whale and living Ginkgo-toothed beaked whale’s color pattern.
  3. The preliminary collected data on diving and surface behaviors are similar to those observed in other beaked whales, which indicates that the chances of encountering ginkgo-toothed beaked whales and Deraniyagala’s beaked whale are consistent. The accessibility may be similar to that of other beaked whales.
  4. Future research should verify whether mouth line indentations are normally present in the ginkgo tooth beaked whale and the Deraniyagala’s beaked whale specimens are normal. In fact, the presence of an indentation may be caused by fishing gear or marine litters.

Overview

The beaked whales in the South China Sea & Southeast Asia are very vulnerable to marine debris because this sea area is one of the major areas of marine plastic waste pollution in the world.

According to the scientific committee of the International Whaling Commission, similar to other beaked whales, the ginkgo-toothed beaked whale or Curvier’s beaked whale may also be susceptible to sounds from naval sonar and seismic research.

Therefore, there is an urgent need to further understand the distribution, number, and structure of the little-known beaked whale populations in the South China Sea and the entire Southeast Asian waters in order to scientifically assess the impact of various potential threats on these marine mammals.

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Reference

ROSSO, Massimiliano, Mingli LIN, Francesco CARUSO, Mingming LIU, Lijun DONG, Anna BORRONI, Wenzhi LIN, Xiaoming TANG, Alessandro BOCCONCELLI, and Songhai LI. “First live sighting of Deraniyagala’s beaked whale (Mesoplodon hotaula) or ginkgo-toothed beaked whale (Mesoplodon ginkgodens) in the western Pacific (South China Sea) with preliminary data on coloration, natural markings, and surfacing patterns.” Integrative Zoology (2020): 1-11.

Photo source credit and disclaimer

All the photos of the article are from the referenced research article and I’m grateful to the Mingli Lin original owner for the use of his picture as a featured image in this article. If you have any copyright issues, please contact us.

Rajitha Dissanayake

Researcher in the field of Marine Mammals and Bio-acoustic

I'm a Master’s student in marine mammals and bio-acoustic laboratory, Institute of Deep-Sea Science and Engineering (IDSSE), Chinese Academy of Sciences (CAS) and focusing on the sustainable environmental application, conservation, and exploring all aspects of the ecology and behavior of marine mammals.

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