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Nice work, few queries

Posted by JLin1 on 18 Feb 2009 at 22:42 GMT

I enjoyed reading your paper. It is rare to find research done extensively among bats in regards to geophagy. I especially appreciated the comparison drawn between ominivorous and frugivorous bats to examine the role of mineral licks, rather than studying only a single bat species. I have a few questions: 1.) As a part of your method, I wondered why you measured nitrogen isotope ratio in the bat tissues. Why not measure sodium levels to determine if they visit licks for salt, a more prevalent reason of mineral supplementation used for comparison (Gilardi et al 1998). 2.) Also, it would be really interesting to examine the effects of seasonality such as year long observations to determine which months the bats visit the mineral licks the most rather than a month long study. In some studies, weather affects geophagy behavior, such as birds visiting licks less on mornings following rain the previous night (Brightsmith 2004). It would also be interesting to include a detailed description of how young/old the plants are and the kinds of fruit consumed. Young plants synthesize secondary toxins to protect themselves which have negative effects on predators’ intestines once consumed. These factors can be used to compare with geophagy behavior among other animals and even humans. 3.) Furthermore, I noticed that you briefly stated pathogen binding capacity, but I was curious about the details of it and how it explains geophagy among animals. Maybe you can look at another Plos One article that discusses the methods of collecting and analyzing pica substances (Young et al 2008). I was interested in seeing if a mineralogical analysis was done to determine the kaolin and smectite composition. This could confirm the pathogen binding capacity of the consumed pica substances.

Brightsmith DJ, The Wilson Bulletin (2004) Effects of Weather on Parrot Geophagy in Tambopata, Peru.

Gilardi JD, Duffey SS, Munn CA, Tell LA (1998) Biochemical Functions of Geophagy in Parrots: Detoxification of Dietary Toxins & Cytoprotective Effects. http://www.springerlink.c...

Young SL, Wilson JM, Miller D, Hillier S, Plos One (2008) Toward a Comprehensive Approach to the Collection and Analysis of Pica Substances, with Emphasis on Geophagic Materials.

RE: Nice work, few queries

CCVoigt replied to JLin1 on 19 Feb 2009 at 14:58 GMT

Dear JLin,
I am glad that you liked the article. Please find my responses to your queries below:
1) We have used stable nitrogen isotope ratios as an estimate of the portion of insects in the diet of bats. The more an animal feeds on an animal-based diet, the more enriched its body is in 15-nitrogen in relation to 14-nitrogen. We expected animals feeding on mineral-depleted insects to visit the mineral licks; the reverse of what we found in our study. Mostly fruit-eating bats with a low enrichment of 15-nitrogen in relation to 14-nitrogen were found at mineral licks.
2) I agree that it would be very interesting to look at seasonality, the adverse effects of secondary plant compounds etc. This work is in progress.
3) We haven't mentioned pathogen binding capacity in our article. Actually, the bats are facing the very opposite problem, i.e. they may pick up gastrointestinal helminths at mineral licks, see Nogueira MR, deFabio, SP, Peracchi, AL (2004) Gastrointestinal helminth parasitism in fruit-eating bats (Chiroptera, Stenodermatinae) from western Amazonian Brazil. Rev. biol. trop. 52(2) [PMID: 17354389]
Best regards,
Christian Voigt