Wednesday, June 6, 2012

Caterpillar soft science

My colleagues and I have been looking for caterpillars in recent (<12 year-old) openings (0.5-2 ha clearings created by timber exploitation) in the forests north of Lausanne Switzerland. We randomly selected 19 such openings and looked for caterpillars for 2 hours in each. We found 5 occupied openings. It will probably come as no surprise to most of you, but Emperors seems to prefer young to middle aged openings. To young = no sallows, to old = sallows have been cut down to promote more profitable woods. Given the rythm of interventions in Swiss forests, the optimal stage seems to be around 6-8 years after timber exploitation (sory, the legends are in french...).

What's interesting for me is:
  • we can find caterpillars in randomly selected sites, which suggest a relatively high larval density in these openings (there must be false absence in our dataset too) 
  • we have shown this (serious-looking) graph to foresters and it helped making them understand the importance of keeping sallows in regeneration patches and it increased there awareness of the woodland butterflies (most of them were unaware of the existence of these beauties at all, the less so in their own woods)
NB: we did not look for caterpillars in edges, lanes and other potential places, so these results are probably very local/regional and will differ depending on where you study them.

Any input, thoughts, similar results would be greatly appreciated.


irisscientist said...

Dear Jérôme,

Many thanks for uploading your recent iris larvae data. Your initial conclusions appear to mirror the results obtained by Kobayashi (2008, and 2009), who has studied forest patterns that are important to the Japanese Emperor, Sasakia charonda. In his papers, Kobayashi concluded that host trees on the edges of large, recently disturbed (secondary) forest areas were preferable as they enabled the growth of optimum height, host trees (greater than 2M tall) and were also in easy flying distances of larger broadleaf sap-rich feeding trees, which are utilized by the adults for both feeding and roosting. Further inside the forest, growth of the optimal sized host tress becomes restricted by surrounding vegetation and consequently their presence becomes considerably rarer. Kobayashi also reported that larger quantities of over wintering/diapausing larvae were found in riparian forest (forest land adjacent to water) areas than in the secondary forest areas. This data could however easily be explained due to high/increased larval predation rates in the open surveyed areas.

Kobayashi’s paper abstracts can be found at the links below. If however you would like to view full copies please send just me an email.

I hope this is interested to your recent studies?


Jérôme Pellet said...

Thanks for the links. Very usefull indeed.

dennis said...

Hello Jerome,
Very interesting indeed; I'd like to tell you about my Swiss experiences over 22 years [1981 to 2002] in woods around Basel; may I have your e mail address please?

Dennis Dell

Jérôme Pellet said...