A Drone Study of Sociality in the Finless Porpoise Neophocaena asiaeorientalis in the Ariake Sound, Japan
Round 1
Reviewer 1 Report
The study was aimed at studying the sociality of the finless porpoises Neophocaena asiaeorientalis based on the description of the spatio-temporal structure of the free-living population of the species. In this aspect, the study is pioneering. The use of a drone in the field has shed light on gaps in the spatial distribution of individuals and gained valuable experience in collecting empirical data, which underlines the dignity of the study and the value in the conservation of a rare species of marine mammals.
Dear authors, please find my comments below in the attached file.
R
Comments for author File: 
Comments.pdf
Author Response
Responses to Rviewer1
Header
L 2-3.
According to the rules for authors of Drones, the title should be short. I propose a different title:
A drone-assisted study of sociality in the finless porpoises Neophocaena asiaeorientalis in the Ariake Sound, Japan.
>>>Title was shortened as “A drone study of sociality in the finless porpoise Neophocaena asiaeorientalis in the Ariake Sound, Japan.”
Abstract
L 17.
After the common name, the Latin name of the species is necessary.
>>> L15. Added the Latin name of the species.
L 20.
After Ariake Sound, insert the name of the country – Japan.
>>> L20. Inserted “Japan”.
Keywords
L 29-30.
It is desirable that the keywords do not match the words in the title.
>>> L28. Changed the keywords as “Neophocaena asiaeorientalis; UAVs; population distribution; sociality; group cohesion”.
Introduction
L 52.
Please insert the link at the end of the sentence if possible.
>>> L48-51. The sentences were revised vastly for making them more readable to the reader.
L 65-66.
Here you can specify the subspecies of porpoise, accompanied by a link, for example, Zhou X., Guang X., Sun D., et al. 2018. Population genomics of finless porpoises reveal an incipient cetacean species adapted to freshwater. Nature Communications 9(1): 1276. doi:10.1038/s41467-018-03722-x
It is also helpful to say why you studied the subspecies Neophocaena asiaeorientalis sunameri (1-2 sentences).
>>> L61. Inserted the subspecies of porpoise as Neophocaena asiaeorientalis sunameri.
L 67.
Please rephrase the beginning of the sentence, for example, It was found [16] that stable social bonds form, at least, between mothers and calves, based on an aircraft survey.
>>> L65-67. The sentences were revised vastly for making them more readable to the reader.
L 73-76.
I would remove those two sentences as they don't fit in with the above text, or add more clarity to the end of this paragraph.
>>> Deleted those sentences.
L 77 and L89.
Therefore, the present study aimed to … Please review this paragraph (L 77-92) to avoid repetition and to clearly state the purpose of the study. You can also combine L 77 and L89 into one sentence - the purpose of the study - and place it at the end of the paragraph.
I propose to move L 78-81 to L 109.
>>> L61-82. The paragraphs were revised vastly for clarifying the aims.
L 91-92,
I propose to move the null hypothesis to the Materials and Methods section or to L 88.
＞＞＞Moved the null hypothesis to L152.
Materials and Methods
L 94.
Please replace Study Site with Study Area.
>>> L84. Replaced as “Study Site with Study Area”.
I propose to move L 95-96 to the Introduction section on L 66.
>>> Moved the sentence to L60-61.
I suggest moving L 99-100 to L 143.
>>> L129-132. Moved and revised the sentences vastly.
L 102.
In figure 1, in the upper right corner, I would like to see an inset that shows in which part of the Japanese archipelago this study was conducted?
>>> Added the Japanese archipelago in Figure 1.
L 105.
I suggest another version of the caption, for example, Figure 1. Study Area in Ariake Sound, Japan. Solid lines indicate the North, Yushima and Area flight routes …
In general, section 2.1 at L 94-107 would like to see more information about the habitat of the finless porpoise and what ecosystem services do they use, are they found year-round or seasonally, where do they breed? The reader may be interested in information, what species of marine mammals are also found in the study area? Please add some sentences.
>>> L92-94. Revised the caption of Figure1. The information on the habitat of the finless porpoise was difficult to add because of reducing the total word number. But, the sentences at L61-69 were revised vastly for more informative.
L 108.
I propose another heading: Drone use and flight routes.
>>> L95. Revised as “Drone use and flight routes”.
L 124- 125.
I propose to indicate the coordinates of the extreme points of the surveyed rectangle (n=4), then the coordinates of the center of the surveyed territory (n=1) can be deleted.
>>> L111-113. Described the 4 coordinates of the surveyed rectangle.
L 134.
Another heading is suggested: 2.3.1. The size of the animal aggregations. In the same subsection, it is useful to explain that the study used a division into individuals and groups, aggregations, ranging in size from ... to ...
>>> L121. Revised the heading of 2.3.1. as “The size of the animal aggregations”
L 162-163
combine into one paragraph of subsection 2.4. statistical analysis.
>>> L142-152. Combined the sentences into one paragraph.
L 164-169
(Ethics Statement) should be transferred to L 373.
>>> Moved the ethical statement to L378-382.
Results
L 172.
Please place table 1 after the first mention of it in the body of the manuscript.
>>> Confirmed that Table 1 already is placed immediately after the first mention (L155).
L 173.
Here and below, area must be replaced by Area route.
>>> In the present study, we distinguished between two survey types, the area and line surveys. Each survey had flight routes as the North and Yushima routes in the line survey, and the Area route in the area survey. We referred the area survey simply because the comparisons were done between the surveys. We also revised the manuscript with attention to the points.
L 213.
Figure 3. I propose to change the color of the drone flight paths from gray to yellow or white in each session presented (1, 3-7).
>>> We think the original style (white line with transparent effect) is suitable to see the figure. Without a transparent effect, the flight line covers the heatmap. Yellow line can be mixed with the heatmap as shown below;
White without transparent Yellow with transparent
Discussion
L 266-267.
Avoiding repetitions (L 377), I suggest deleting the fragment: Though the methods employed during the study had limitations, such as inability to identify specific individuals, the present results.
I also suggest combining two sentences into one sentence (L 265-268): Findings in the present study illuminated the dynamic spatiotemporal variation of finless porpoises’ distribution and provide novel data on the total number of individuals and frequencies of aggregation sizes in this area.
>>> L247-258. Deleted the sentence, “Though the methods employed during the study had limitations, such as inability to identify specific individuals,”, and revised the paragraph significantly.
L 318.
I propose to delete STILL.
>>> Deleted “Still” and revised vastly the Discussion section for making them more readable to the reader.
I propose to transfer L 319-320 to L 336, which refers to restrictions.
>>>L322-341 Revised on the limitation of the present study vastly in the paragraph of the Discussion section.
L 336.
Delete word HOWEVER.
>>> Deleted “However” and revised vastly the Discussion section for making them more readable to the reader.
I propose to merge L 334-336 and L 345-349 into one paragraph and place it at the end of the Discussion section.
>>> L342-352. Merged the sentences and revised the paragraph significantly.
Reviewer 2 Report
I have reviewed the manuscript "Investigation of finless porpoises’ sociality through a population distribution survey using a VTOL drone in Ariake Sound, Japan". I found the manuscript generally very interesting, using a fixed-wing drone to monitor and observe a porpoise off the coast of Japan. While I found the methods comparing two different survey designs interesting, and the analysis of sociality an interesting outcome of the study, I believe the conclusions drawn are not always supported by the data and analysis. I believe the manuscript could be improved by shifting focus to concentrate less on the sociality of the species (which I think support for with the data collected is weak), and shift more towards the value of this methodology for monitoring species occurrence and seasonal changes in occurrence in the coastal ocean for a species that is otherwise difficult to observe. I do believe this manuscript is appropriate for publication after some concerns are addressed and am therefore recommending revisions. I have included additional comments in the attached document.
Comments for author File: Comments.pdf
Author Response
Responses to Rviewer2
L20
Suggest adding a bit more information about where this is geographically for readers unfamiliar.
>>> L20. Added “coastal” to the sentence.
L47
I don't understand the points you are trying to connect and tie together in this sentence.
>>> L 47. Deleted the sentence “even if most marine mammals are highly mobile in three spatial dimensions across large areas and spend the vast majority of their lives completely underwater [3]”.
L59
To contrast with multirotor drones (which also can be considered vertical take-off and landing), you should specify here if you mean fixed-wing VTOL drones. That is my impression what you are describing, especially given the instrument you use, but the terminology you are using here isn't clear.
>>> L54, 97, 249, and 342. Added “fixed-wing“.
L72
I do not follow the justification that coincident diving in response to a disturbance (boat) suggests sociality.
>>>L61-69 Rephrased this sentence and revised vastly the paragraph in the Introduction section.
L110
Suggest mentioning this is a fixed-wing.
>>> L97. Inserted “fixed-wing” into the sentence.
L137
Earlier you mention you are not able to identify individuals using your method, however here you indicate individuals are not counted twice. This is a major discrepancy and point of confusion that needs to be addressed.
>>> L122-132. The paragraph is a description on how to count the number of individuals for each aggregation. Double counting could happen across solitaries and aggregations but tried to avoid double counting within an aggregation. The risk of double counting was clarified and discussed at L130 and L311, and313.
L143
What is the possibility that for a large aggregation, you are double counting individuals. For example that a porpoise counted early in a photo sequence has enough time to dive and then resurface to be counted again before the "aggregation" photo sequence was ended with the seven consecutive empty photo cut-off.
>>> Revised the manuscript vastly with careful attention to the possibility and risk of double counting, especially at L130 and L311, and313. The focus of the present study was a variety of aggregation sizes. Even if we did double counting, the aggregation sizes varied from single to 9 individuals or up to 33 individuals was concrete evidence as the aggregation size and its variation, which was completely different from stable social bonds limited to a dyad between mothers and calves, mentioned in a previous study.
L156
Unless I'm missing something this sentence seems redundant to earlier sentence.
>>> L142-152. Revised vastly the descriptions of the statistical analysis paragraphs.
L185
This information may be better suited for the discussion section.
>>> L326-331. Moved the sentences in the Discussion section and revised the descriptions significantly.
L213
I suggest labeling these with the date for comparison across time.
>>>Added the date labels to Figure 4.
L213
This figure needs a legend for the heatmap to understand the scale of observations among flights.
>>> L198. Rephrased the legend.
L216
It is unclear to me how the likelihood that you are tracking the same aggregations of porpoises moving throughout the study area over and over influences your results/conclusions. It seems like a very important consideration as an aggregation of porpoises moving through the area would be captured over and over as the drone surveyed back and forth.
>>> L170. Added a sample picture of the present study as Figure 2. We have observed a similar huge aggregation of over 50 individuals mostly every year at the Misumi West Port of Ariake Sound.
L276
very difficult to conclude anything about social relationships, which implies choice, from a dataset where you are unable to identify repitition in association between individuals. Here, your dataset could simply reflect the tendency for dolphin aggregation size to change in response to external environmental conditions, and not social choice.
>>>We agree with the points. Again, the focus of the present study was a variety of aggregation sizes. The findings of the present study illustrated that the aggregation of finless porpoises was completely different from stable social bonds limited to a dyad between mothers and calves. We also emphasized the limitations of the present study in the Discussion section at L311-322.
L278
How long can these porpoises hold their breath? What is the chance that aggregation size may be skewed by differences in vertical behavior. For example an aggregation may be stacked vertically with a few porpoises near the surface and visible to the drone imagery, with other porpoises swimming below, not surfacing until the drone had passed (for whatever reason). These arguments could be improved by providing the reader with a better sense for the speed of the drone survey compared to the speed of porpoise travel and time spent below the surface and out of the visible range of the drone.
>>> Added Figure 2 for additional information.
L317
I do not agree that primarily observing solitaries and pairs and an occasional larger group indicated unexpected complexity at all. It seems to me to support transient social relationships in a simpler social structure.
>>> Added Figure 2 for additional information.
L323
Could that just be seasonality or variability in the occurrence of the species, and not necessarily differences in visibility? Seems like both would be variable. Your sample size of flights is small, so it will be tough to distinguish factors affecting variability and presenting additional alternative explanations would be preferable.
>>> There has been no study for monitoring the distribution of finless porpoises in the same sea area of Ariake Sound on a relatively large scale repeatedly within and over the years. Seasonal changes in ecological and environmental conditions are very important but mostly anecdotal. We agree with the limitation of the present study as mentioned in the Discussion section at L311-322.
Reviewer 3 Report
The manuscript discusses the use of drone for investigating the finless porpoise social behaviour in Ariake Sound, Japan. Overall study is interesting and the manuscript is relatively well organized. However, there are few sections that require improvement before publication.
In general text needs editing for English, some section and sentences are confusing to understand. The material and method section needs to be considerably improved.
Title: I would suggest to reduce the number of words and make it shorter. For example VTOL is not necessary and is acronym which results in confusion in title.
Lines 78-87: These lines can go further up into introduction or into discussion. In the last paragraph just focus on telling what you will study and why.
- Please mention in the introduction why the study has been conducted and the in the discussion mention what is the significance of your finding and how can be utilized.
Lines 111-139: The information regarding the flight pattern is unnecessary since the authors are showing the pattern on the map.
Material and methods: The Hero 5 does not have a GPS. So, how the position of the drone incorporated with the images ? It is not clear how the GPS location of the animals have been acquired. Have you stitched the images and interpolated the coordinates on the pixels ? which software you used ? All needs to be clear otherwise measuring distances will be all relative.
- What would be the accuracy of detection in the images ? Please include few images from this survey.
- The study has been conducted between the June 2023 and Jan 2023, how did you separate the aggregations over time ?
- How did you compare the sessions over time ? knowing that these animals moving around ?
- Figure 2, what is areal and line survey ? this has not been mentioned in material and method section.
In general text needs editing for English, some sections and sentences are confusing to understand.
Author Response
Responses to Rviewer3
Overall study is interesting and the manuscript is relatively well organized. However, there are few sections that require improvement before publication.
In general text needs editing for English, some section and sentences are confusing to understand. The material and method section needs to be considerably improved.
>>> The manuscript was reviewed by an English editing service supported by the Edigate Co. Ltd.
Title:
I would suggest to reduce the number of words and make it shorter. For example VTOL is not necessary and is acronym which results in confusion in title.
>>> The title was revised as “A drone study of sociality in the finless porpoise Neophocaena asiaeorientalis in the Ariake Sound, Japan.”.
Lines 78-87:
These lines can go further up into introduction or into discussion. In the last paragraph just focus on telling what you will study and why.
- Please mention in the introduction why the study has been conducted and the in the discussion mention what is the significance of your finding and how can be utilized.
>>> L70-82. Revised the objective in the Introduction section.
Lines 111-139:
The information regarding the flight pattern is unnecessary since the authors are showing the pattern on the map.
>>> L110-113. Revised the sentences by describing the coordinates of the surveyed rectangle, and also revised the subsection 2.2 for clarifying the flight conditions.
Material and methods: The Hero 5 does not have a GPS. So, how the position of the drone incorporated with the images ? It is not clear how the GPS location of the animals have been acquired. Have you stitched the images and interpolated the coordinates on the pixels ? which software you used ? All needs to be clear otherwise measuring distances will be all relative.
>>> We confirmed the GPS function through the below link;
https://www.manua.ls/gopro/hero-5/manual?p=8
- What would be the accuracy of detection in the images ? Please include few images from this survey.
>>> L170. Added a sample picture of the study as Figure 2 for additional information.
- The study has been conducted between the June 2023 and Jan 2023, how did you separate the aggregations over time ?
>>> L122-132. Revised carefully the description of subsection 2.3.1.
- How did you compare the sessions over time ? knowing that these animals moving around ?
>>> Revised the description on the limitation of the present study as mentioned in the Discussion section at L311-322.
- Figure 2, what is areal and line survey ? this has not been mentioned in material and method section.
>>> L95-119. Revised the description on the flight routes in the subsection 2.2.
Round 2
Reviewer 3 Report
The manuscript overall improved since the first submission. However, there are still few things need to be addressed.
The English still needs editing. I raised this issue before. Although some parts have been changed, the text still needs work. There are many similar sentences and long unclear paragraphs that can be reduced in size. Please be specific about your data and findings. The discussion part at the moment is confusing. Focus on presenting and discussion your main study which is the " sociality in the finless porpoise" as stated in title. The aim of the study should be Cleary stated at the end of introduction, and the correspondent results should be provided. Anything about details of the method should go to the material and methods. I suggest to remove anything else that is not related to your study purpose.
The main issue I see at the moment is the material and methods and analyses. As a reader is not clear how the information and location data has been gathered and how those calculations has been made.
I therefore repeat my previous comments that hasn't been answered in the manuscript:
- Material and methods: The Hero 5 does not have a GPS. So, how the position of the drone incorporated with the images? It is not clear how the GPS location of the animals have been acquired. Have you stitched the images and interpolated the coordinates on the pixels? which software you used? - What would be the accuracy of detection in the images? All needs to be clear otherwise measuring distances will be all relative. If the camera has gps, you still need to explain the rest in the manuscript.
Authors reply:>>> We confirmed the GPS function through the below link;
https://www.manua.ls/gopro/hero-5/manual?p=8
Unfortunately, providing me with the manual of the camera, doesn't improve your manuscript. The point is to clarify the methods for the readers.
- The comparison of line and area analyses is confusing. The comparison of these methods has not been identified in the introduction as part of this study and authors state in line 237 "the analyses focused on the area survey", so it is not clear then why the line analyses has been discussed.
Here is some more specific comments:
References: Please check all references carefully, there are several repeats and errors.
lines 153-156: they don't belong here. I would suggest moving to acknowledgements.
Styles of the figures 5-7 needs improvement.
The text English still needs editing. I raised this issue before. Although some parts have been changed, the text still needs work. There are many similar sentences and long unclear paragraphs that can be reduced in size.
Author Response
Response to Reviewer #3
The English still needs editing.
>>> The original version of the manuscript had been edited by a commercial English editing service. Additionally, one of the coauthors, who is an English native and has experience with several English publications in high-impact scientific journals, had carefully checked throughout the revision. We have completed what the Reviewers pointed out about English for the revision.
- Material and methods: The Hero 5 does not have a GPS. So, how the position of the drone incorporated with the images? It is not clear how the GPS location of the animals have been acquired. Have you stitched the images and interpolated the coordinates on the pixels? which software you used? - What would be the accuracy of detection in the images? All needs to be clear otherwise measuring distances will be all relative. If the camera has gps, you still need to explain the rest in the manuscript.
Authors reply:>>> We confirmed the GPS function through the below link;
https://www.manua.ls/gopro/hero-5/manual?p=8
>>>> GoPro Hero 5 has a GPS function. The function can be confirmed in the user’s manual via the above link. The GPS location can be extracted from each image data through a property function supported by Windows/Apple OS. The function is well-known among public users. Thus, we have mentioned simply “were collected from a single photograph.” (L134)
Additionally, the GPS location data was associated with a single individual or an aggregation of several individuals. We did NOT estimate the coordinates for all the individuals observed. As Reviewer #3 mentioned, the distances across individuals and aggregations were estimated on a relative scale. In many cases, no individual was on the exact location of the GPS point, as described “the location was chosen as the photograph with the largest number of individuals in a single image.” (L138-139). It is also impossible to take all photographs of a single finless porpoise by centering the individual in the photo frame under an automated flight. This estimation was very useful for describing the distribution patterns of animals spread over an area of 68 km2 or a line of 15km. We carefully rephrased the descriptions of the subsection “2.3. Data Analysis” in the revised manuscript submitted on June 12, 2023. We also clarified the limitations of the present study at L 305-322.
- The comparison of line and area analyses is confusing. The comparison of these methods has not been identified in the introduction as part of this study and authors state in line 237 "the analyses focused on the area survey", so it is not clear then why the line analyses has been discussed.
>>> No description at L237 as "the analyses focused on the area survey" in the revised manuscript submitted on June 12, 2023. We have carefully revised the descriptions of the line and area surveys in the subsection of “2.2. Drone use and Flight Routes” in that revision.
Screenshot of L227-241.
Here is some more specific comments:
References: Please check all references carefully, there are several repeats and errors.
>>> We have confirmed again all references throughout the revised manuscript.
lines 153-156: they don't belong here. I would suggest moving to acknowledgments.
>>> L153-156 is the beginning of the Results section as shown below. It is difficult to move to the Acknowledgements section.
Screenshot of L153-160.
Styles of the figures 5-7 needs improvement.
>>> Reviewer#3 did not mention the points in the review process of Round 1st. The comment is too ambiguous to revise the manuscript at the 2nd round.
[EON]
Author Response File: Author Response.pdf
