There
are numerous plants that are poisonous to animals (many are also poisonous to
the two legged animals known as humans).
Of those that grow in the Western United States, Water Hemlock (Cicuta douglasii) is the granddaddy of
them all. It causes the violent signs,
and more often than not leads to death of the animal. It only takes a little bit of the toxin,
called cicutoxin, to be fatal.
Cicutoxin
is a neurotoxin, which means that it affects the nervous system. In this case it affects the brain, rapidly
causing severe seizures, coma, and death.
Animals begin showing signs within a few minutes to a few hours after
eating the plant, and can die as soon as 15 minutes after showing signs.
Poisonings
are likely in the spring when it first begins to grow. The early leaves tend to have a very high
concentration of cicutoxin. Any animal
that grazes on it is potentially susceptible.
I have even heard of geese being poisoned from eating the young plants
in the early spring. Poisonings also
occur later in the year, particularly when the roots are larger and become
available due to plowing, tromping in stream beds, cleaning ditches etc.
Human
poisonings may occur, because people mistake it for wild parsnips or other potentially
edible plants. The toxin is particularly
concentrated in the root, and has been reported to have a carrot-like
odor. I recommend growing your own
carrots and parsley (or buying them from your local grocer).
This
is another situation where prevention is the most effective means of
control. Don’t graze animals where water
hemlock is growing. Another means is
just plain luck. In the lab where I am
working there is a photograph of a field with more water hemlock than grass,
and cattle are happily grazing around the plants. If you try that technique I hope your luck is
better than most farmers.
So water hemlock is not a plant that animals recognize as hazardous to their health?
ReplyDeleteOften, animals must be conditioned through some negative experience, to stop eating toxic plants. This one tends to be a little difficult, due to the fact that many animals that eat enough to have a "negative experience" don't live long enough to change. There are reports of wildlife dying from water hemlock.
ReplyDeleteReading through your posts I have wondered what natural selection processes have occurred in response to these life threatening poisonous plants? Natural selection must have selected for traits that can smell poison, or taste it. I know much is conditioned but in many cases the conditioning is useless as they will die with only one exposure. Some poisonous plants are bitter to the taste and therefore make them undesirable for consumption. Do you know of any species that have adapted to the threat of poisons in their ecosystem? What adaptations if any do humans have to these potentially lethal poisons?
ReplyDeleteIn what areas of the US is water hemlock most prevalent? I am not familiar with this plant. Public health authorities should warn and educate endangered populations of the risks to humans and animals and provide advice on how to avoid these risks. What is disconcerting is that a carrot-like smell to the plant makes it seem palatable and even appealing.
ReplyDelete