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Wednesday, September 8, 2010

Mohave Rattlesnake revisited

Ten days ago, Frodo, our youngest dog and son of a feral coyote half-breed got his fourth snakebite in as many years. He started his snake encounters as a tiny pup. To him, most bites do not seem much worse than a nasty bee sting, hardly interrupting his play. This time however, he was distraught enough to leave his breakfast to Montana the Husky, so we took him to the vet, just in case. When we got there his hugely swollen head was already returning to normal (I didn't have the heart to document his misery on film) and all he needed was an antibiotic and a painkiller. Presumably all four bites were administered by Western Diamondbacks. Two of them we caught just after the attacks.

Frodo, Tana and a day-time visitor. Nocturnal ones are much more ominous.

Three days ago, at four in the morning, the snake alarm went off again: Frodo’s sharp rhythmic barks. All three outdoor dogs were pointing at a snake from a save distance this time. I’d just returned from an exhausting two day field trip the evening before. Getting out of bed and keeping my eyes open proved rather difficult. The first attempt to noose the snake with the snake-stick failed. The sudden notion that this was no ordinary Diamondback, but probably a Mohave Rattler gave me enough of an adrenalin boost to reopen the noose and place it safely this time. By then, Randy had arrived with the transport bin. The snake securely stored, we went back to bed.

Mohaves are rare here. Some 15 miles further south the herpetologists of the Arizona Sonora Desert Museum have been keeping records for years, and they never got anything but Western Diamondbacks.









When I mentioned a Mohave Rattlesnake in one of my earlier blog chapters, some readers correctly pointed out that I couldn’t be completely sure of the identification just by looking at the relative width of the tail-bands alone. So while I’m still not getting close enough to a rattler’s head to count the scales between the eyes, this time I took some pictures to enlarge the details later. Yes, it’s clearly a Mohave Rattler Crotalus scutulatus. Where this one has two big scales, the Western Diamond-backed Rattlesnake Crotalus atrox has a row of 4 or more small ones.











Thinking about the possibility that this snake is not only producing hemorrhagic venom (which is bad enough by itself) but also a more deadly neurotoxin, we felt our resolution to simply remove snakes from the premises waver. But finally Randy carried him just especially far away from the house to an out-of the way part of the State Trust Land and the border of an old lime-stone quarry. Laika, our wolf-dog, trotted along on his heals. When he released the snake she respectfully stood aside. She’s much too smart to get too close to any snake that she’s aware of.

Note the wide white bands of the tail, another characteristic of the Mohave Rattler that is less reliable but easier to see than the facial scales.

13 comments:

  1. Thanks for the lesson which I hope never to have to use in practice! Poor doggy. Glad he's OK.

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  2. Baubo Bittern said via flickr:
    Good job on the snake ID after the picture rather than going there with your nose. I often do use a similar technique even on the most harmless of subjects, just to avoid getting off the path and trampling the environment.

    So this is a rare snake that graced you with a visit, or just one doing well and expanding it's range towards your area?

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  3. I can not tell that the distribution changed. I think we always had a few Mohaves around. We also once had a Tiger Rattlesnake. M. Rubio, author of several books on Rattlers, lives only a couple of miles down the road (SE). He says among 100 rattlers that he saw on his property was one Black-tail, no Mohaves, all the others were Diamond-backed. Subtle differences in vegetation, soil structure, temperature may make the snakes (or their prey animals)prefer one area over the other.

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  4. Margarethe...so glad Frodo is OK once again! My kid caught a baby rattler on our back porch last weekend...another herpetologist friend thought the markings were unusual for a Diamondback..I'm going to post a picture on Flickr, if you wouldn't mind taking a look...

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  5. Barabara Robeson said via flickr:
    Most interesting blog entry. So, do you suspect that this snake bit your dog? Or is the bite so venomous that he would not have survived? Quite a story!

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  6. No, we got the one that bit him, it was a Diamondback.
    As for the Mohave venom: they may have neurotoxin, or they may not. A Texas A&M Studie showed that over time, the Mohaves in Texas evolved to have more of the neurotoxin (besides the hemotoxin) when the squirrels developed immunity to the hemotoxin. Traditional round-ups of thousands of snakes in Texas communities seemed to hasten those changes.. If one removes many old territorial rattlers, many more young ones survive and get established. This shortens the generation-sequence and can speed up adaptive changes.
    SE Arizona Mohaves have also been shown to have a neurotoxic component in their venom.

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  7. Frodo must be one tough cookie! I hope she is fine now.

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  8. Another interesting post on this snake. I like the photos of Randy carrying the snake away in the garbage can, with Laika following, and then releasing the snake. Interesting that Frodo's reaction to the diamondback bites has been so mild.

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  9. I have an old australian shepherd that has been bitten 4 times. The first three he had minimal swelling and lost some hair, but no skin. The last time he was struck in the neck and was very sick. He ended up getting abx, steroids and pain meds. He lost hair and a big chunk of skin that died and had to be cut off by the vet. We figure that the first three bites must have been "dry" bites, and the last one was a venom filled one :( We usually let snakes just move on out to Saguaro west. In one week we saw a black King snake (my first!) FOUR different bull snakes and two rattlers. Seems to be snakey out all of a sudden.
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  10. Reb: Yeah, same Saguaro West area here, and we've had two more Diamondbacks, a black racer, a baby king and a Long-nosed snake since I posted.
    If your dog showed swelling at all, the bites were not dry, but maybe the venom dose was low. Our vet made the experience that bites to the face usually do not cause tissue loss, but elsewhere on the body they are more likely to cause necrosis. The progressing age of your dog may also play a role.

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  11. That makes sense....he's a young 13 year old :)
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  12. Margarethe,
    Unbelievably, the old guy got bitten again yesterday! Not a bad bite this time. Minimal bleeding and swelling, but I put him on abx again because it is on a lower leg. I swear he's really smart about everything except snakes!
    Reb

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  13. Oh, no! Poor guy! This is just a crazy year - so many rattlers, right now we are finding them in pairs. I hope the cooler weather will send them hibernating!

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