Guano extraction becomes more common these days, the needs of the very populations near caves is increasing, and soon realize that it is good business. It is necessary to determine how much manure is produced and how much is feasible to extract and teach the people how to get it before it starts further disruption. Besides that chances of contracting this disease and an alternative to preserve the cave and bat community are avoided.
I have never worked with guano, but I would imagine a similar protocol for calculating deposition as for calculating deposition of leaf litter in a forest, which I do quite often. The method is very simple...you put out a several collection trays (nets in the case of leaves so water can seep through) of a known area randomly situated in the area of interest, and then collect them after a known amount of time. Take the total amount of guano on the collection tray, and extrapolate based on the area and time to get rates of deposition per area.
You're very kind to answer, thank you !. Initially, if you had meant to follow as a guide, the method for calculating biomass through leaf litter. But the guano contains certain moisture level, much higher than the leaf litter, the paths followed us droppings falling is vertical, by the flight of bats. So far, I have not found literature, quotes specific to talk about how to calculate the deposition rate as well as an efficient method !. That's what I'm looking for, especially a method to their respective appointment.
Calculating guano deposition is very tricky and it depends upon the species occupying the cave, the diet (insects, pollen, nectar), the number of bats roosting, and where you put your collecting trays. I have placed metal trays under roosts containing thousands of bats, only to find the trays were buried under mounds of guano and had to be dug out. So, at a minmum, you will have to establish: the size of your collecting trays (or tarps), the frequency of collecting the samples so they are not totally buried under guano, and the estimated density of bats roosting above the collection trays. You could randomly place trays around the cave; however, the deposition may not be as constant as it would be if you placed them under a roost. An interesting place could be at the entrance and under one or several roosts since that is where guano miners typically collect and bag guano.
You could place grids on the collecting pans and estimate dried biomass and/or number of pellets per grid per tray per sampling session. Or, you could do the same for the entire tray assuming guano covers all surfaces. You may have to experiment a bit with collection times (sampling sessions) to see what works best. However, I urge caution that you do not overly distrub the bats, or collect when flightless pups are in the nursery roosts, and that you use red lights or night vision gear when inside the cave so that you reduce bat disturbance as well as reduce additional guano deposition on your trays by frightened bats.
If you have not already done so, you may want to visit Bat Conservation International website www.batcon.org and contact one of the biologists. they may be able to direct you to their Latin America Bat coordinator or bat researchers in your region.
Good luck!
Awesome experience Charles. Digging collection trays out of a sea of guano sounds like quite the field experience! :)
Thanks Noa. Yeah, researching bats are fun and researching caves are fun...combining the two = heaven. You guys have some beautiful caves!
One thing I forgot to mention was that you should measure the areal extent (and depth if feasible) of the existing guano mounds and attempt to place collecting trays at random spots on the mound. The bigger the mound, the more trays you need to deploy.
Thank you very much, Charles. In the cave is a community of insectivorous bats. The colony did not have succeeded as to calculate numerical values but may be close to 1 million individuals, we are around trying to tell through video recordings when they start out.
1 million- I suppose these are Tadarida brasiliensis?
If so, the mammalian species account attached gives an annual estimate of guano deposit of 18,700 metric tons in northern Mexico and 22-99 tons per cave in Texas. I'm not sure how this was calculated and how accurate it is.
With that many bats in your study site, I bet the guano mound is huge and the deposition is rapid. So, your sample collection session will probably be short (5-7 days). Another consideration for you is that microscopic and invertebrate communities feed on the guano, rapidly breaking it down. This may affect your samples if you leave the collection trays out too long.
As I mentioned earlier, contact Bat Conservation International because they own a Tadarida cave in Texas with millions of bats in it during the summer. This cave has had commercial guano mining in the past and they currently allow low level mining during the winter. Perhaps they can give you some insight on the impacts and their view of deposition for that species.
http://www.science.smith.edu/msi/pdf/i0076-3519-331-01-0001.pdf
Yes, it is a large colony, but my study area is in the center of Mexico and in the tropics. We have found until now 4 species of bats Pteronotus personatus, P. and P. parnellii davyi, also Mormoops megalophylla. Thanks for the tips. We would like to quote or try any of the methods already used before. So far we have not found any article that tells us how to calculate it and how? Even well to quote them in our work.
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