The Contribution of Desert-Dwelling Bats to Pest Control in Hyper-Arid Date Agriculture

Round 1

Reviewer 1 Report

 

This study examines bat community response to date plantations before and during harvest and also documents the pest prey community sampled by those bats. One of the three plantations was conventional, the other two were organic. Overall, the manuscript is well written and very interesting. I have some questions about the methods and concerns about the implications of those methods on interpretation of the results.

 

The closest plantations (in the south) were only 400 m apart, the same distance between detector locations within each site, so I question how independent the bat communities would be between the two sites. Looking at the area on Google Earth, it doesn’t look like there is any separation between the two southern sites.

 

It appears that the reason activity was not significantly higher during harvest is due to high variance. Richness also seemed to vary by sampling plot, suggesting that sampling plot siting had a large effect on the overall results. How were the acoustic plot locations chosen? Were there any characteristics implied by the plot locations that could explain these differences? Were the locations during harvest near the actual mechanical harvesting activity? I would imagine that bats could easily find harvest activity given the lights and noise. It would be helpful to address this in the discussion.

 

Line 80: With a sample size of three, it’s difficult to say how much we can infer about the difference between organic and conventional habitats.

 

Line 138: I don’t understand this sentence. Which nights were missed, from which locations? How is this different from the detector malfunction at Elifaz?

 

Line 160: Please provide more information about the netting sites. Of the seven within plantations, how were these distributed across the three plantations? Where were the adjacent sites, and why were these chosen? Were bats netted on the same night as the acoustic sampling?

 

Line 207: Is the average plantation species richness before or after harvest the mean of spp at each of the 5 detector locations?

 

Line 304: The results don’t show that rates increased significantly.

 

Figure 2: Please keep the y-axis scales the same across stages

 

Table 1: Are these total bat passes the sum from the 4 or 5 detectors per location over the 5 nights? Were the nights contiguous? If not, how were they chosen?

Author Response

Response to Reviewer 1 comments

 Dear Reviewer

Thank you very much for taking the time to read our manuscript. We appreciate your comments and suggestions. Below you can find a point-by-point reply to all of your comments. We left track changes on for you to find all changes made easily. In addition, the manuscript underwent English proofreading by a professional English editor (no track changes).

 

Reviewer 1

This study examines bat community response to date plantations before and during harvest and also documents the pest prey community sampled by those bats. One of the three plantations was conventional, the other two were organic. Overall, the manuscript is well written and very interesting. I have some questions about the methods and concerns about the implications of those methods on interpretation of the results.

The closest plantations (in the south) were only 400 m apart, the same distance between detector locations within each site, so I question how independent the bat communities would be between the two sites. Looking at the area on Google Earth, it doesn’t look like there is any separation between the two southern sites.

Response: Thank you for your comment. Indeed, both plantations are close to each other, and the bats can easily fly between them. We took it into account when we selected the recording plots and the distance between the nearest recording plot in Elifaz and Samar was more than >1000 meters. We added the explanation to the methods (lines 138-141) and we refer to this point in the discussion (lines 310-312).      

Reviewer: It appears that the reason activity was not significantly higher during harvest is due to high variance. Richness also seemed to vary by sampling plot, suggesting that sampling plot siting had a large effect on the overall results. How were the acoustic plot locations chosen? Were there any characteristics implied by the plot locations that could explain these differences? Were the locations during harvest near the actual mechanical harvesting activity? I would imagine that bats could easily find harvest activity given the lights and noise. It would be helpful to address this in the discussion.

Response: Thank you for your suggestion. In the selection process of the recording plots, we only selected plots of adult trees. However, in the vicinity of some of the plots, there were plantations with young trees or subadult trees. These nearby plantations could contribute to the variance between the recording plots. We discuss it in the revised manuscript (lines 343-349).        

Reviewer: Line 80: With a sample size of three, it’s difficult to say how much we can infer about the difference between organic and conventional habitats.

Response: The reviewer is correct. However, in the Arava valley, we only have two organic plantations which also differ from each other. In the revised manuscript we now refer to this comment. (lines 119-120).      

Reviewer: Line 138: I don’t understand this sentence. Which nights were missed, from which locations? How is this different from the detector malfunction at Elifaz?

Response: We rephrased the explanation in the methods. For each of the three plantations, we had 5 recording sites where we recorded each for 5 nights. In total, we should have 75 recording nights (3*5*5) before the harvest and another 75 nights after the harvest. However, due to technical issues, we recorded in total 129 nights instead of 150. (lines 149-150)

Reviewer: Line 160: Please provide more information about the netting sites. Of the seven within plantations, how were these distributed across the three plantations? Where were the adjacent sites, and why were these chosen? Were bats netted on the same night as the acoustic sampling?

Response: Nets were set up at locations within the plantations where possible. Adjacent sites are located within 1km of date plantations as this distance is likely to include the ‘nightly foraging area’ of any given bat caught there. These sites were therefore included to increase the dataset on the diet habits of the bats (lines 172-174). See also supplementary table 1.

Reviewer: Line 207: Is the average plantation species richness before or after harvest the mean of spp at each of the 5 detector locations?

Response: It is the total cumulative number of species (see Table 1). The averages are presented in Figure 2 and Table 2.

Reviewer: Line 304: The results don’t show that rates increased significantly.

Response:  This is indeed true. Hence, we wrote that bat activity did not differ between the plantations before and during harvesting (lines 224-226, 229-231, 234-236).

Reviewer: Figure 2: Please keep the y-axis scales the same across stages

Response: Done

Reviewer: Table 1: Are these total bat passes the sum from the 4 or 5 detectors per location over the 5 nights? Were the nights contiguous? If not, how were they chosen?

Response: Yes these are total bat passes from the 4-5 detectors per each date planation for the two periods of the study (before and during harvesting). Yes, the nights were contiguous.

Reviewer 2 Report

This study makes an important contribution to the growing evidence that bats play an integral role in agriculture as natural enemies of crop pests. The authors make a strong case for bats’ indirect positive effect on date plantations (possibly date yield) by providing descriptive data on bat activity across multiple date plantations and molecular evidence of date pests in these bats’ diet. This study is especially interesting in that it emphasizes the role of isolated agricultural oases in desert landscapes as a critical resource for bat foraging, and as a result may magnify their impact on crop pests. Despite the lack of insect composition and abundance data, and a modest sample size (only 3 date plantation sites), this study offers novel and useful information for the scientific community, as well as for date growers.

In addition to the minor comments below, the authors need to provide more details on the acoustic bat activity data collection (lines 128-135). For example, it was not clear if they monitored bats for five nights in July and again and September, or five nights overall. Did they sample in all three plantations simultaneously? Did they rotate sampling among them? Within each plantation, were the detectors moved nightly?

Minor comments:

Line 195: “acoustic”

Figure 1: Indicate whether the site was organic or conventional in the caption.

Figure 2: These plots might be more informative if combined given that differences between “stage” had the largest effect in the model—for example, compare bat activity before and during harvest by plantation.

Table 1: Given that sampling effort differed among “stage” and plantation, I would suggest including passes/night as well as total numbers for each bat species.

Lines 307-319: I am not familiar with the timing of bat reproduction in this part of the world; however, it occurs to me that another reason for increased activity could be newly volant young.

Author Response

Response to Reviewer 2 comments

 

Dear Reviewer

Thank you very much for taking the time to read our manuscript. We appreciate your comments and suggestions. Below you can find a point-by-point reply to all of your comments. We left track changes on for you to find all changes made easily. In addition, the manuscript underwent English proofreading by a professional English editor (no track changes).

Reviewer 2

This study makes an important contribution to the growing evidence that bats play an integral role in agriculture as natural enemies of crop pests. The authors make a strong case for bats’ indirect positive effect on date plantations (possibly date yield) by providing descriptive data on bat activity across multiple date plantations and molecular evidence of date pests in these bats’ diet. This study is especially interesting in that it emphasizes the role of isolated agricultural oases in desert landscapes as a critical resource for bat foraging, and as a result may magnify their impact on crop pests. Despite the lack of insect composition and abundance data, and a modest sample size (only 3 date plantation sites), this study offers novel and useful information for the scientific community, as well as for date growers.

 

In addition to the minor comments below, the authors need to provide more details on the acoustic bat activity data collection (lines 128-135). For example, it was not clear if they monitored bats for five nights in July and again and September, or five nights overall. Did they sample in all three plantations simultaneously? Did they rotate sampling among them? Within each plantation, were the detectors moved nightly?

Response: Thank you for your comment. We added all the relevant details on the acoustic recordings (lines 136-141).

Reviewer:

Line 195: “acoustic”

 

Response: Fixed

 

Reviewer: Figure 1: Indicate whether the site was organic or conventional in the caption.

Response: Done

 

Reviewer: Figure 2: These plots might be more informative if combined given that differences between “stage” had the largest effect in the model—for example, compare bat activity before and during harvest by plantation.

 

Response: We revised the figure to show the same scale. The difference between the stages is now clearer.

 

Reviewer: Table 1: Given that sampling effort differed among “stage” and plantation, I would suggest including passes/night as well as total numbers for each bat species.

 

Response: The information is included in the last row for each plantation.

 

Reviewer: Lines 307-319: I am not familiar with the timing of bat reproduction in this part of the world; however, it occurs to me that another reason for increased activity could be newly volant young.

Response: Thank you for the suggestion. We added it to the discussion (lines 327-329).

Reviewer 3 Report

This research demonstrates the ecosystem services of bats in date farms. This is an important contribution to the growing body of literature on how bats are economically valuable through pest control services to agriculture. The study methods of pairing acoustic monitoring, captures, and barcoding for dietary analysis is clean and clear. The manuscript is very well-written, concise, and easy to read.

I have a few very minor suggested revisions to the manuscript highlighted in the attached PDF.

My one concern is about log-transforming the data. This is generally not the correct method for ecological data (O’Hara & Kotze 2010). Which data was log-transformed? Be specific.
Please review if the statistical methods are appropriate. Acoustic data usually requires a zero-inflated model or negative binomial model and can require a quasipoisson distribution.

Figure 1: Add a description of which plantations are conventional or organic in the figure legend. Change the colors of the red icons to match the site colors used in Fig. 2.

Figure 2: Make the y-axes scales the same between A&C and B&D. Add your sample sizes (N=# nights) to the figure legend. Add a column label above A&B for “Before Harvesting” and above C&D “During Harvesting.”

I’m not convinced that Table 1 is the best way to present this data.

For the discussion, expand on which species are aerial hawking and which are gleaning, and why this is relevant. The intro or the discussion is also the place to mention (and reference) which species is smallest or rarest or largest and relate it to diet and/or your results.

 

O'Hara, R., & Kotze, J. (2010). Do not log-transform count data. Nature Precedings, 1-1.

Comments for author File: Comments.pdf

Author Response

Response to Reviewer 3 comments

 Dear Reviewer

Thank you very much for taking the time to read our manuscript. We appreciate your comments and suggestions. Below you can find a point-by-point reply to all of your comments. We left track changes on for you to find all changes made easily. In addition, the manuscript underwent English proofreading by a professional English editor (no track changes).

Reviewer 3

This research demonstrates the ecosystem services of bats in date farms. This is an important contribution to the growing body of literature on how bats are economically valuable through pest control services to agriculture. The study methods of pairing acoustic monitoring, captures, and barcoding for dietary analysis is clean and clear. The manuscript is very well-written, concise, and easy to read.

Reviewer: I have a few very minor suggested revisions to the manuscript highlighted in the attached PDF.

Response: All the minor suggestions in the PDF file were taken into account.

Reviewer: My one concern is about log-transforming the data. This is generally not the correct method for ecological data (O’Hara & Kotze 2010). Which data was log-transformed? Be specific.
Please review if the statistical methods are appropriate. Acoustic data usually requires a zero-inflated model or negative binomial model and can require a quasipoisson distribution.

Response: We rechecked the data and the data are not zero-inflated. The sentence on log transformation was deleted.

Reviewer: Figure 1: Add a description of which plantations are conventional or organic in the figure legend. Change the colors of the red icons to match the site colors used in Fig. 2.

Response: Done

Reviewer: Figure 2: Make the y-axes scales the same between A&C and B&D. Add your sample sizes (N=# nights) to the figure legend. Add a column label above A&B for “Before Harvesting” and above C&D “During Harvesting.”

Response: It is stated in the figure legend and therefore, we did not add the column label. The number of sampling nights was added to the figure legend.

Reviewer: I’m not convinced that Table 1 is the best way to present this data.

Response: We still present the data in Table 1 but formatted all tables better and think that it is clear now. We added the information about the foraging mode of each of the recorded species to Table 1 as suggested by the other reviews.

Reviewer: For the discussion, expand on which species are aerial hawking and which are gleaning, and why this is relevant. The intro or the discussion is also the place to mention (and reference) which species is smallest or rarest or largest and relate it to diet and/or your results.

Response: Done, the information was also added to Table 1.

Round 2

Reviewer 1 Report

The authors made sufficient changes to the manuscript to address questions and concerns I raised in my review.