Proposed Tests to Determine if Geotextiles Are Nutria-Resistant

by Dr. Adrian Lawler
(retired) Aquarium Supervisor (l984-l998) J. L. Scott Aquarium Biloxi, Ms 39530

Original to Aquarticles

There are various ways a geotextile (GT) can be tested for effectiveness against digging nutria. Installation in the environment along a bank where nutria are known to occur is one way. However, this field test may take a while as there is no way of telling if, and when, nutria may try to dig where fabric is installed (unless the installed geotextile has covered up an already-existing nutria burrow).

Due to money involved, production schedules, etc., there should be ways for a company to ascertain fairly quickly if their geotextile product is resistant to nutria digging and thus marketable as such. Thus, I designed a few ways to ascertain the nutria-resistance effectiveness of the geotextile fabric fairly quickly in field and laboratory (captive nutria) tests. Some tests are based on using some favorite food (sweet potato, carrot, turnip, etc.) to attract nutria to the test, and require that nutria try to break through the geotextile being tested in order to obtain the food. The test/area containing food should be fairly near the water so nutria can easier detect the food as they swim along bank. Since nutria appear to favor digging under a solid object, another type of test involves a concrete pad or metal plate placed over installed geotextile, and seeing if nutria dig under pad/plate and then through geotextile. Other tests use captive nutria, and challenge such nutria to break through geotextile to get to a female, food, or freedom; these can be the quickest tests because the captive nutria are already available for testing.

Nutria breaking through the fabric would be considered a failure for the geotextile. There can be several levels of testing results from nutria trying to get through geotextile:

     ---Little or no effect on geotextile. (Nutria-excluding)
     ---Puncture or small hole in geotextile made trying to get to food, etc. Did not get food or escape/dig
          through fabric. (Nutria-resistant.)
     ---Large hole made in geotextile. Got food, or escaped/dug through fabric. (GT failure.)
     ---Geotextile ripped to shreds. Got food, or escaped/dug through fabric. (GT failure.)

Only those geotextiles that prevented nutria from getting food, or digging through fabric should be labeled and sold as "nutria-resistant," or "nutria-excluding." Those geotextiles that fail the nutria tests may, however, be strong enough to pass tests using rats or mice, and thus these geotextiles may be sold and used in areas that nutria do not occur as "rodent-resistant" or "rodent-excluding."

See the figures below on some testing procedures proposed for nutria. Geotextile (GT)-covered stainless steel framed food cube used for testing in marsh (Figure 1). Some ways to test GT by installing/burying it in a flat area (Figure 2). Some ways to test GT on a slope or bank (Figure 3). Test of GT under a pad (Figure 4). Some ways to test GT with captive nutria (Figure 5). One can test nutria in field (Figures 1-4), or captive nutria (Figure 5). These tests may also be used with other rodents.

I am submitting these tests to the public domain in hopes we develop/find better controls for nutria digging into levees, pond banks, banks of waterways, etc., thus saving areas from flooding, severe erosion, loss of fish, loss of plants, etc.

Copyright 2007 by Dr. Adrian Lawler, Author Copyright 2007 by Aquarticles, Internet Sponsor

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