Jeroen Speybroeck wrote:Thanks a lot for your replies! I enjoy this kind of knowledge exchange very much, although I hope the berus lovers don't mind we discuss all these details on the forum
I really hope the others are as happy about the discussion as I am. And hey, this is a forum about field herping and not just about vipers. lol
Jeroen Speybroeck wrote:I don't do larval counts, because it's too much to handle already + it has been demonstrated that larval numbers are not really a good proxy for adult population size.
I only did it once, because I was interested in the number of alpine newt and fire salamander larvae as well as the number of adult newts in the basin. We counted almost 860 alpine newt larvae in three basins and only 110 fire salamander larvae.
Jeroen Speybroeck wrote:Me too, I have not really been out there immediately(!) after a summer thunderstorm, yet. I would assume that the effect of major activity on the 1st(!) rainy night after a dry period would be more different than that of the subsequent nights, in comparison with spring and autumn.
I will definitely put that on my list this year. I just went through my data and fear I've been kind of sloppy in 2011 and 2010.
Jeroen Speybroeck wrote:What's with the focus on albino larvae?
I was just wondering with the large amount of alpine newt larvae, how many I may find that have a pigmentation defect. I don't know how common it is, but I have been very unsuccessful so far. Same goes for blue water frogs.
Jeroen Speybroeck wrote:Is Hymenochirus an alien invasive in your area!?
Gladly it isn't. There was one found in August 2010. I only saw a picture of it, because the photographer thought it was a weird looking R. temporaria. But the R. temporaria tads usually don't make it through metamorphism in the basins because the bit of spawn is eaten by the newts and the small amount of tads that make it get eaten by dragonfly larvae or backswimmers. It turned out to be a small dwarf frog and unfortunately we couldn't find it again. I assume it died anyway, because it looked really weak and skinny in the pic already.
Jeroen Speybroeck wrote:Why do artificial ponds yield more juveniles? And how do you find juveniles (+ how do their numbers relate to adult numbers in %)?
The artifical ponds are stone basins, so they have water from March to the end of October. They don't dry out, because they are filled by the owners. So when we have a dry period during summer, the small creeks in the area dry up, the larvea in the creeks die, while the ones in the stone basins survive.
Finding juveniles is not so difficult. The stone basins are surrounded by old sandstone walls and you have a higher level above the area with the basins with more sandstone walls and another level below the area with the basins, and again many sandstone walls. There are many alpine newts living in tunnels and holes inside these walls and many adult salamanders (but I think there are way more newts). So when we went out in October 2009 about 80 salamanders of the 150 were juveniles. They were about a couple of days to a couple of weeks old. At a later stage of the year, I can often encounter them in front of these walls. The walls seem to be favored as wintering dens.
Unfortunaetly I am missing data from autumn 2010 and 2011, I may need to ask a friend of mine, 'cause I think she counted the individuals in september last year. Oct. 2010 had a smaller amount of animals because it was a lot drier compared to 2009, but I think we were also out in Nov. 2010 and we had a nice amount of adults and juveniles. But I don't remember the statistics.
The only counts I have at the moment are: 27 Dec. 2011: 2 subadults and 7 juveniles; Jan. 1st 2012: 14 adults, 12 subadults and 11 juveniles of late 2011 (still very small); Feb. 25th: 29 adults, 5 subs, 13 juveniles of late 2011. So I definitely need to get more data for spring, summer and autumn this year as the temperatures were just rising again after a cooler period in February.
>So you don't agree that these high abundances are rather norm than exception in good natural habitat? I believe they are and that people underestimate abundance of >terrestrial salamanders very often, due to their secretive habits.
No, I wouldn't say that because I obviously have a lack of data. I think the question is, is the habitat I often visit a good natural habitat, because everything is obviously controlled by human structures? I know a guy that says that the location has sort of a "tank effect". I don't know a good expression for the German terminus "Kesselwirkung". This is due to the location having lots of stairs to get from one level to another and having streets between this area and the forest. So it is more of a question of how much individuals can this place hold and how many can get out or come in during migrations.
Jeroen Speybroeck wrote:> which was in early May 2009 or 2010
That would be rather late in my area, but maybe the big numbers are earlier near me (although that does not show from your posts)?
Maybe the elevation of the area has an effect on that? The woman that organizes the helpers during amphibian migration says that the main migrations usually end with a large amount of salamanders crossing the road in the more elevated forest areas (around 400 to 500 meters above sea level) in May. I have not seen this myself and don't know what to think of it, but from that one experience at the other localion, they obviously do still move in larger numbers at this time of the year in our area.