Monday, July 7, 2014

Mange in Urban Coyotes

This article has been updated. Read more about rat poison 's link to mange and death in local wildlife:  Household rat poison linked to death and disease in wildlife
(Thanks to one of my readers for sending the link.)

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I've seen a whole lot of mangy coyotes this year in my Altadena foothills neighborhood, a lot more than last year. And nocturnal coyote songs and yips have all but disappeared. Is there a relationship?  Apparently so.
Coyote with sarcoptic mange

Coyote with healthy coat
Photo Source: Jim Coda
Sarcoptic mange (not to be confused with the less serious demodectic mange) is a highly contagious infestation of a burrowing mite. The little fiends dig into the skin causing intense itching, pustules, skin crusting, hair loss and secondary infections that can lead to death in some animals.  Sick animals move closer into the neighborhoods to find easier sources of food and water, and exhibit unusual behaviors like lethargy and lack of wariness.
This poor little fella has advanced stage sarcoptic mange.
You can see why hairless coyotes
gave rise to the Chupacabra legend.
As bad as these animals look, only about 20% die from mange or conditions directly associated with it. In really bad epidemics it can be as high as 50%,  In those that die, it will take anywhere from  a few months to over a year.  Less than 15% recover and regrow hair.

Under normal circumstances mange drastically affects population size because infected females either reabsorb their fetuses, or give birth to pups that usually don't survive. However coyotes eating rats that have ingested anticoagulant poisons are significantly more likely to suffer and die from mange. (Read more here), Although I couldn't find any literature on mange and coyote population reduction, in a  red fox study, the population was reduced by as much as 90%. 
Source: Mary Cummins
When animals overpopulate a territory, resources gets scarce causing immune systems to weaken. The incidence of mange increases and the coyote population plummets. As the infestation recedes, the population increases.

The incidence of mange fluctuates, but is likely always around.  According to a long range study in Canada, 24% of the population consistently harbored sarcoptic mange mites. In comparison, a really bad epidemic can affect 70% of the population (Texas, 1980s).  I couldn't find any studies that said how bad it is in our area right now.  

Will your dog get mange mites from coyotes traveling through your yard?  They could, especially if the coyote is nesting there at night.  But researchers think it's not likely because monthly application of tick and flea meds may control mange mites in companion dogs.

So Dr. Barkman says: Don't buy or use anticoagulant poisons for rodent control. Keep your dogs up to date on their flea and tick meds. Don't leave food out for coyotes no matter how destitute they look.  And maybe, until the coyote population increases again, we can let our cats go outside.

If you want to read more, I recommend a thesis paper by Evan C Wilson, The Dynamics of Sarcoptic Mange in an Urban Coyote Population. Although the study took place in the Chicago area, much of the information can be applied to local populations here.  This KCET article is about how rat poison is increasing  immune system dysfunction, sarcoptic mange and death in California bobcats. 




3 comments:

  1. A rather nasty albeit natural way of containing a population. Interesting post!!

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  2. I have read about the connection between bobcat and mountain lion exposure to anti-coagulant rat poisons and mange, and it seems likely that these coyotes with mange are suffering the same fate- eating easy prey that has been poisoned, which over time weakens their immune systems, leaving them vulnerable to opportunistic organisms like mange mites. I spoke with a wildlife rehabber after finding a near-death bobcat covered with mange, and she told me that severe mange infections affect much more than just the skin, and can cause blindness and deafness, a terrible fate for any animal, especially a wild predator. Anti-coagulant rat poison has certainly had some far-reaching unintended consequences.
    Beth

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    Replies
    1. That's very interesting and seems likely to be the cause of our very bad infestation here. If you have links, please send and I'll add them to the body of the post.

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