MadSci Network: Zoology

Re: How much defacation does a Canada Goose produce,& Ecoli

Date: Tue Sep 18 13:58:49 2001
Posted By: Dean Cliver, Faculty, Food Safety Unit, Uiversity of California, Davis
Area of science: Zoology
ID: 1000066240.Zo

	With the help of an excellent reference librarian, I have found two 
original research publications that appear to address this question.  They 
* Alderisio, K. A., and DeLuca, N.  1999.  Seasonal enumeration of fecal 
coliform bacteria from the feces of ring-billed gulls (Larus delawarensis) 
and Canada geese (Branta canadensis).  Appl. Environ. Microbiol. 
* Bedard, J., and Gauthier, G.  1986.  Assessment of faecal output in 
geese.  J. Appl. Ecol.  23 (1):77-90.

The 1986 report was about how often geese defecate and was done by 
observing greater snow geese in Canada (i.e., not Canada geese as such).  
While feeding, the geese averaged from 5.23 to 18.79 defecations per hour, 
depending on the feeding site and the year of observation.  Unfortunately, 
the authors do not indicate how many hours per day the geese were likely to 
feed, nor whether they also defecated when not feeding.

The 1999 report was about how much the average Canada goose fecal deposit 
weighed and the level of fecal coliform bacteria it contained.  Average 
weights ranged from 5.85 to 9.98 grams, depending on the season.  Fecal 
coliform bacteria contents (probably mostly Escherichia coli) averaged from 
4,500 to 24,200,000 colony-forming units per gram of feces, depending on 
the season and year of observation.  The bacterial levels were consistently 
lower than those for the seagulls that were observed in the same study, 
supposedly because the geese are largely vegetarian grazers.

If we assume the a goose's daily fecal output is the equivalent of 6 hours 
of grazing, the 24-hour total might be as much as 126 to 451 defecations, 
with weights ranging from 5.85 to 9.98 grams.  The smallest number times 
the smallest weight gives 737 grams (~1.6 pounds); the largest number times 
the largest weight gives 4501 grams (~9.9 pounds).  Using a mid-range value 
for each (288  7.9) gives 2276 grams (~5.0 pounds). For a mid-range value 
of 300,000 colony-forming units per gram, this would be about 683 million 
colony-forming units per day, which may or may not be a leading source, 
depending on what else is going into the water.

At least you can see that the estimate of 46 pounds of fecal output per day 
is about 10 times too high.

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