The Miistakis Institute has concluded their study on protecting trees with sand paint and decided against it. Latex paint contains Titanium Dioxide which is toxic to rats in fairly small doses.
Lethal Dose, 50% (LD50) for titanium dioxide for a rat = >5000mg/kg
(please see Appendix 2 for the Safety Data Sheet (SDS) for No.4050 Ultra
Pure White® and No. 4400 Medium Base),
They infer that the average weight for a small beaver is 12kg and by extension a beaver could be poisoned by eating the bark of three painted trees.
There is a risk that the beaver may test the painted trees and
consume the painted bark in amounts that may be lethal, based on our
calculations. Our research shows that a beaver consuming the bark of 3
painted trees would reach a lethal dose (LD50) of titanium dioxide. Given the
small number of painted trees needed to be consumed to reach LD50, along
with the lack of safe alternative adhesives we conclude that the use of a
sand/paint textural repellent as a technique to protect trees cannot be
recommended
It’s a sound inference based on the toxic nature of the substance. But it doesn’t make sense to me who watched our beavers deal with our stand of of painted trees for nearly a decade. When the tree grew and the sand got farther apart and less off-putting, our beavers might ‘nibble’ to test it out, but I never saw them eat entire trunk of the tree or indeed the entire trunk of ANY tree. They were far more interested in the tasty smaller branches higher up.
I checked in with resident researcher and physician Rick Lanman to ask his thoughts. Here’s his response:
The Mistaakis Institute is sorely mistaken (pun intended). They used 2 gallons of paint to cover 167 trees (presumably they only painted the bottom four feet or so of each tree trunk). Their error was that they assumed the beaver would eat ALL the bark on each tree. Instead a beaver would typically not even eat the bark on the tree trunk, and instead fell the tree (spitting out the wood chips), then the beaver would go for the tender bark on the slender twigs and branches.
Even if the beaver accidentally consumed some of the trunk bark this would be a miniscule part of the area of bark on the tree. The notion that a beaver would remove all the bark from a four foot section of tree to fell the tree is ridiculous. Rough guess (for a 4 foot section of tree and using largest tree girth of 25 cm which is radius of about 5″) is they might eat a few % of the area of tree bark.
Let’s do the math: area of bark = π r squared x height = 48″ high x 3.14159 x 5″ x 5″ = 3,769 sq inches or about 26 square feet). I expect they might eat 1 square foot of bark of that 26 square feet of latex painted bark per tree or 1/26 of the painted bark per tree. So they’d have to eat 78 tree trunk sections each 4 feet long to hit that LD50, not three trees. Not even remotely close.@Heidi Perryman
Thank you Dr. Rick! You are the very first person to use pi on behalf of beavers on this website. Maybe ever. And now stop it. Because I came into this work to get AWAY from math. Sheesh.
For the record, I agree with Rick here. Beavers are not going to consume all the bark at the base of the tree when they have all those sweet upper branches at their disposal. But it is icky that paint is toxic. Stop that will you? Apparently the Tintanium dioxide is a pigment stabilizer so it makes your perdy living room just that right tone to match the sofa.
Surely they can invent some kind of icky unstabilized color that’s non toxic, right?
