Hibernation Hypothesis

[Jack Harrison]

I have often suspected that in some species, the percentage of hibernators has some correlation to the population the previous summer. I will try to elaborate with examples.

Last summer Small Tortoiseshells were scarce. Yet this spring, there have been plenty of reports of sightings. So perhaps, because numbers were low last summer, there was somehow a greater instinct to feed up quickly and enter hibernation without undue delay. I have often been surprised with other species too, eg Commas that don't have a particularly good showing in late summer are often seen in numbers the following spring.

Clearly it is a complicated matter with no simple explanation. Any thoughts?

I had a Tortoiseshell emerge from my garage this morning in a very "groggy" state. I let it warm up (away from cats) and after half an hour it flew off strongly.

Jack

[Padfield]

That's an interesting theory! I'm not quite sure if I understand you right, so you might have to elaborate a little more! I also suspect it varies from species to species.

Some species, like peacocks, don't fit in a purely breeding summer generation, so all the offspring of the spring butterflies have to hibernate or die without descendents. Others, like small tortoiseshells and brimstones, do generally fit in a breeding generation over the summer. Are you suggesting that in a bad summer a greater percentage of pupae hang on until the autumn (then hibernate) and effectively miss out on their breeding summer? Or do you think they emerge on time and opt to hibernate already (in June) rather than expend energy on breeding?

I never see hutchinsoni commas in the spring, so I take it this generation never overwinters as an adult. But it is possible that a greater percentage delay their emergence in bad summers and so the hibernating generation is augmented.

I'd be interested in your further thoughts on this.

Guy

[Jack Harrison]

I'll try to explain again using an example.

Last summer/autumn, Small Torts were very thin on the ground. Yet this spring - and not just personal observations - they have been more numerous than for many years. So I have to wonder when autumn numbers are low, a greater percentage feed very quickly and enter hibernation with little delay. With this strategy, a larger number would survive into the next year. On the other hand, when autumn numbers are good, somehow, they don't feel the need to feed quickly and to hibernate almost immediately - they and in effect "enjoy themselves feeding" as losses in an autumn of abundance are far less critical to the species.

Brimstones seem to feed quickly and hibernate as a matter of routine. Although of course, they are around in late July and August, they seem more abundant in the spring. Now of course in total numbers, that is impossible. So maybe Brimstones have evolved to feed up quickly and enter hibernation with minimal delay.

I must have misunderstood you Guy, but you said:
"Others, like small tortoiseshells and brimstones, do generally fit in a breeding generation over the summer"

I don't think Brimstones do that in Britain. Of our species that hibernate as adults, Peacock, Small tort, Comma and Brimstone (ignoring Red Admiral which I don't think hibernates in the true sense) only Comma and Small tort (and not even Small Tort in Highland Scotland) have an intermediate generation. It is these two species which can seem to bounce back with good numbers in the spring following an apparently poor autumn.

Incidentally, I notice a lot of posts this Sunday morning. The weather here in Cambridgeshire is I guess typical across the country. Tantalizingly bright and warmish but I don't think much will be flying. So like a lot of saddos, I am at the computer catching up while I live in hope of some sunshine. I might even be really sad and watch the snooker final later!

Jack

[Martin]

So I have to wonder when autumn numbers are low, a greater percentage feed very quickly and enter hibernation with little delay. With this strategy, a larger number would survive into the next year. On the other hand, when autumn numbers are good, somehow, they don't feel the need to feed quickly and to hibernate almost immediately - they and in effect "enjoy themselves feeding" as losses in an autumn of abundance are far less critical to the species.

What kind of percentages are you thinking? And so, even if double the percentage went for the feed and hibernate quickly route, would you say 50% of a poor year would be more than maybe 20-25% of a good year?

Martin. (who will going to his allotment...NOT watching the snooker! )

[Jack Harrison]

"What kind of percentages are you thinking? And so, even if double the percentage went for the feed and hibernate quickly route, would you say 50% of a poor year would be more than maybe 20-25% of a good year?"

I don't offer any numbers, just a broad idea.

Jack

[Padfield]

I must have misunderstood you Guy, but you said:
"Others, like small tortoiseshells and brimstones, do generally fit in a breeding generation over the summer"

No it was my mistake. I always thought brimstones were single-brooded, but I checked on these pages and over-hastily misread the graphic:



(I'm still not quite sure what all those second generation eggs are doing in August and September... Is that a mistake or do they really exist?)

My next question/observation is this. It makes sense to me that if numbers are low in the autumn a greater percentage should hibernate immediately - a kind of inbuilt urgency to make it through to the next season. But a greater percentage of a smaller number does not automatically mean greater numbers, in absolute terms. It seems counter-intuitive that in a good summer the creatures are so complacent that a smaller absolute number survives to pass on the genes to the next generation.

I haven't kept any kind of count of small tortoiseshell numbers in the past, so I haven't got any real data to see how your observations fit with the empirical evidence over here. But my impression is that we have never seen so many spring small tortoiseshells as this year - and last summer was certainly a washout.

Guy

[Pete Eeles]

I'm still not quite sure what all those second generation eggs are doing in August and September... Is that a mistake or do they really exist?)

It's a mistake - thanks for pointing it out. Fixing now!

Cheers,

- PEte

[Jack Harrison]

Guy wrote:
"No it was my mistake."

One all now. My "Large White" that wasn't was kindly pointed out by you.

This is a REAL Large White (a few days ago)

Now I have a caterpillar picture - after that lovely Children's Book "The Very Hungry Caterpillar".

Not posting here to spare sensibilities but can be seen (for a few days anyway until I remove) at but BE WARNED:

http://s214580749.websitehome.co.uk/pho ... pillar.jpg

Jack

[Padfield]

Shocking!!

You don't seem to have an avatar yet, Jack. That caterpillar would be quite original, to give us an image to think of you by!

Guy

PS - It makes more sense to me after that change, Pete!

[Jack Harrison]

I believe Pete had thoughts about photos of foodplants.

So I start the ball rolling. I doubt that my angry caterpillar uses that particular plant - if he did, it would be the "very happy caterpillar"!

Jack

[Jack Harrison]

Guy suggested an avatar so here is a sanitised version as per his suggestion. 80 x 80 pixels.

Jack

[Martin]

Great avatar...shame you cut the text out!

[Jack Harrison]

Some of you probably don't know the background but I do have to be careful. On another lepidopterists' group, the moderator objected to my puerile vulgarity when I told a bad joke. He subsequently threw me off for calling him a "stuffy old f-rt"!

Jack