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The one species of rattler that's range approaches a reasonable driving distance from where I live is C. viridus. Today, while attending the Albertan Herpetile Group meeting (bunch of biologists discussing their herp work) I found out some really interesting stuff on this snake.

In southeastern Alberta, on a Reddeer river tributary is the northern most border to the rattler's range. It's also home to the largest rattler hibernaculum in Alberta, probably Canada, and questionably North America. Study numbers from the last 4 years give a pretty good approximation of 1000 /- snakes using this den. It's interesting that such a large den is on the very edge of the range. Are these numbers surprising at all for you Americans? Is this huge for C. viridus? For any crotalus?

Also very interesting was the size of these animals. I know prairie rattlers to be about 75cm - 90cm and about 500-600grams tops. I found them in close proximity to an urban center (Lethbridge), and similar "small" snakes were discovered by a different biologist in Medicine Hat. The snakes in this large, very rural den averaged well over a metre when adult; the largest was 173cm and over 2kg! That's huge for any viridus! It's theorisized that urban sprawl selectively kills larger snakes, which in the end, puts a population's reproductive ability at risk. This of course, is unproven, and will likely be the target of a future study.

So thanks for listening and responding to what I hope comes across as an enthusiastic rant, and yes I know, I'm spelling viridus wrong.

I'd love everyone's take on these topics! If it doesn't conflict with exams, I'm hoping to attend the spring treck to this den.

Ian

I have noticed several species with a higher density found at the edge of their range. This could be due to geographical or habitat reasons.
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Tim Cole
www.Designeratrox.com/
www.AustinReptileService.net
www.AustinReptileExpo.com/
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Conservation through Education

i think it's an interesting point tim-about the 'fringe' populations being the largest in many/some cases-can you be more specific?because it seems to me if a popualtion is really on the edge/fringe of a specie's range,my initial thought is that it would presumably be a smaller population,and the density would be highest naturally more towards the middle of it's range,or at least away from the edges-i would think it either signifies an extension of the already known area-i.e. newly dicovered range extension......or the species' range is moving/morphing-spreading out,shrinking(moreso than usual,that is)...but joey-yeah that would be a new record size for a viridis.......viridis is well known to be one of the two most gregarious crotalid species(horridus is the other);regardless,yes that's a big-ass den(better keep that locale to yourself,lol)....p.s. here's an old famous pic of a prarie rattler den slaughter.(courtesy a.m. jackley)

dead viridis at a den

Possibly areas on a species fringe could lead to higher densities because on the fringe less of the habitat is suitable for providing the species with all that it needs. Proper microhabitat and resource availability could be limited on the fringe. Even species who have wide distribution maps do not use all habitats encompassed in the man made shaded area of the map because it does not provide everything they need to survive. Suitable den sites could be one of the limiting resource which causes this to be the species fringe area. Maybe areas that people would think would be good den sites dont provide what the snake needs farther north to survive the winter? So with less suitable sites to den these fringe zone dens have to be used by more snakes because there are less quality dens on the fringe available than there are in the middle of the species distribution. Just my guess. Take care.

Chip

n/m

His theory about such a large den being on the very edge of the range is perhaps that as snakes keep spreading northward there is a certain limit to where their needs aren't met. Thus, the majority collect at the fringe, and the minority that continue to move north die. The fact that this is a perfect, and huge den, allows the collection to comfortably house many snakes.

I hope to attend a spring count, if I do, perhaps I'll have some pictures to share

Ian

....and i should have the same,from the east;watching that calender...
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"with head raised regally,and gazing at me with lidless eyes,he seemed to question my right to trespass on his territory" Carl Kauffeld