Mystery of Small Tortoiseshell decline solved?

[Pete Eeles]

See http://www.butterfly-conservation.org/a ... ists_.html

Also in lots of press today.

Cheers,

- Pete

[Trev Sawyer]

Wasn't it a parasite which was responsible for the decline in the Large Tortoiseshell?...
I think I read that towards the end of their time in the UK, caterpillars were quite numerous, but VERY few survived to form an adult butterfly. Hopefully, with new technology and understanding, we can stop the same thing happening to the small Tort. They were certainly the most common butterfly in Cambridge when I was a child and it would be terrible to lose such an attractive butterfly.

Trev

[Padfield]

This is an interesting article. I find the link to climate change entirely speculative, though, unless they know something they are not telling us. Far more probable seems the accidental transport of the parasites via southern stock, especially given the increased popularity of butterfly releases, butterfly rearing &c. Certainly, if Sturmia bella came to Britain under its own steam it missed a great opportunity on the way: the Rhône Valley in Switzerland, with a near Mediterranean climate and butterflies every month of the year, is almost literally humming with small tortoiseshells!

Everything gets blamed on climate change nowadays (some things rightly, of course), and sometimes this becomes a bit of a smokescreen; humans go around stomping on the countryside, messing about with nature and generally trashing things far faster than a gently warming climate can do the job!!

Guy

[Paul]

I think we can all see them declining... last year I counted them in overwintered ones & twos in the garden through 'til late june, when the
first brood arrived, peaking at only x10 individuals in late July, with a second September emergence peaking with just 8 individuals. Far fewer
than maybe 10-15 years ago. I had x3 pupate in my shed in 2006, none of which produced adults.. ? due the fly. on the other hand, our winters have become milder & wetter, something I've seen blamed for the lack of other species which happily exist at more Northerly latitudes elsewhere in Europe.



Wouldn't it be a disaster if they disappeared.

[Dave McCormick]

It would be a dissappointent if they disappeared, but last year, in a very small area (around 8-10ft) I saw around 25-30 small tortoiseshell, seem to be increasing in numbers here iN Mountstewart, found a huge nettle patch which was nearly black with amount of cterpillars of the small tortoiseshell and peacock. Hope nothing happens here to these numbers too much. Seemed to be as common around here as ringlets or meadow browns which are very common here too.

[Susie]

There is an interesting article in my local natural history society magazine this month in which one member writes about the importance of wildlife recording. In it he shows a graph on which he has recorded the number of Small Tortoiseshells in his garden since 1990. There are very distinct highs and lows, with some years there being next to none and other years, such as 2003, when there were close on 200. What it does show is that there appears to be a six year cycle going on with this species and the next good year will be 2009. I do hope he is right.

[bugmadmark]

True - but I read that whilst these peaks and troughs appear to be the norm, the major concern was that the last peak was significantly smaller than expected. The Telegraph in also points this out but not sure of the source of this data - presumably Oxford Uni? http://www.telegraph.co.uk/earth/main.j ... fly129.xml mark

[KeynvorLogosenn]

that would explain why I am not coming across many at all, plus I live in the worse affected area, south east England
Mouse

[thepostieles]

hi mouse, we did see loads of small tortoiseshells while we were on hols in skegness nectering on late buddlia.mustve counted over 30 on couple of bushes

[KeynvorLogosenn]

I found one today, but just the one, That makes two all season

Mouse

[bugmadmark]

Hi Mouse

Im in SE too (East Anglia) and I'd seen no Tortoisehells all year. Then when everyone on here was getting excited about the idea of us having sun this w/end and talking about going out hunting for whatwever they could find - this inspired me to do the same. In fact I didn't have to look hard at all. On the way to collecting my son from his tennis lesson at 11am Sat the Buddleia and Ice Plants opposite the playing field were 'covered' with butterflies. I thinks we saw ~30 Small Tortoiseshells, 1 Red Admiral a couple of Commas and loads of Large/Small whites. The villagers were wondering what on earth was going on. I was kneeling on the road laden in camera gear (trying out my new monopod). I had my 4 year old daughter running up and down shouting out when she saw a butterfly she liked and my older son was at the other end taking his photos which i uploaded to September sightings today. Meanwhile the 16 month old was sat in his pushchair smiling away and pointing at the butterflies calling them 'ish' (everything that moves in our house is a fish or 'ish' at the mo.) By the time we finished an hour or so later my 4 year was correctly identifiying them all - so something really good came out of the day Mark.

[KeynvorLogosenn]

Thats great Mark, I normaly come across things when I go out and look from them. Then I am concerntrating purely on it. But what a great site that would have been! Nice memory for sure

Mouse

[KeynvorLogosenn]

And here is another one. I guess that this is the same one that is always there!

Mouse

[Dave McCormick]

I was just thinking of something... if the fly is responsible for the decline in small tortoiseshell numbers, why are other nettle feeding species such as Red Admiral or Comma not affected by it? In fact, the comma numbers have been on the increase this year as far as I know and I have not seen a decline in Red Admirals, although they are a migrating species, but the question is still valid. The caterpillars eat the eggs of the fly and they hatch inside the caterpillar... so why don't comma or red admiral caterpillars suffer same fate as small tortoiseshell? Or am I missing something here?

[Tony Moore]

Hi Dave,
I think that most parasites are host specific. Other caterpillars may not find the eggs palatable, or the eggs may not hatch in a different gut. There may even be bacteria in the alimentary tracts of the other butterflies, which would attack the eggs. I guess the research presently being undertaken will answer all these questions, in due course. Evolution ain't half clever!
Tony M.