Impact of severe storms on butterfly populations

Share your notes and experiences in the field
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Chuck
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Impact of severe storms on butterfly populations

Post by Chuck »

Forever I thought that when storms are coming the butterflies do what the other animals do- seek shelter. And, I presumed after the storm passes, they all come out, minus an unfortunate few, and resume life.

However, in the past few years of focus specifically on Tiger Swallowtails I've become more attuned to the environment and the Tiger population. My observations following severe storm fronts:

1. Population of Tigers drops 90% in the days immediately following severe storms, inferring a far higher loss rate than I'd previously thought.

2. Two or three days following the passing of a severe front, Tiger individuals fall into two categories: (a) fresh and recently emerged, and (b) extremely damaged, far more than flight wear or bird damage.

The above two observations I take to indicate that Tigers (specifically) are not adept at protecting themselves as might other Leps (e.g., Catocala and grass-hidden Speyeria)and thus suffer a high mortality rate as a result of severe storms.

Last year the southern shore of Lake Ontario (New York) was swept by a series of severe storm fronts every week or so. Each time the Tiger population plummeted, then slowly rose, only to be knocked down again. In both 2020 and 2021 severe storms in mid-August spelled the end of Tiger observations, whereas in past years with "good" weather they'd be on the wing until the first week of September.

Your thoughts/ observations?
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wollastoni
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Re: Impact of severe storms on butterfly populations

Post by wollastoni »

We don't have severe storms here in W. Europe vs what you have in N. America, but I am sure large wings butterfly species like Papilio glaucus must be severely hit by storms. As you said, they can't protect themselves.

A question though : are they killed by the storm, or transported kilometers away from their original spot ? I read about some Danaus plexippus brought to Europe by strong winds.

Micro GPS chips could help us in the future to better understand that.
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kevinkk
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Re: Impact of severe storms on butterfly populations

Post by kevinkk »

Environmental factors and the effect on populations is interesting, here in the west, we get some severe weather in the summer, but nothing
like what I saw the summer I spent in Indiana, I get asked sometimes "where do butterflies go when it rains?" I really don't know- under a big
leaf probably.
What has interested me lately, is the impact of wildfires, some of my favorite collecting spots are still closed 2 years after the apocalyptic
fires in 2020, last season driving through some of the areas, I never saw anything flying, while fire may open up land for wildflowers and
underbrush to get a foothold, the animals still need to recolonize. I'm hoping this next season we can get to the closed areas again. I kind of
expect at some point there will be a higher amount of insects in these areas, besides the open land, there's a lot of dead timber lying about.
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chulrich
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Re: Impact of severe storms on butterfly populations

Post by chulrich »

While living in Taiwan I experienced a couple of Typhoons; one of them was during the month of July in the south of the country which is quite tropical. The storm killed at least 80% of the butterfly population (bigger butterflies).
Chuck
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Re: Impact of severe storms on butterfly populations

Post by Chuck »

I’ve seen a number of Papilios
Sheltering under a leaf.

In fact, my most amazing story about human eyesight and shape recognition involves this. Munda, Solomon Islands a storm was coming and already raining. In the gloom, Looking down a single file trail I swore that 75m away there was a Papilio under a leaf. We’ve all done similar- nope, just a leaf typically. But it bothered me so despite the pending storm I hiked down that trail and sure as heck it was a female Ulysses. From 75m, in bad light. Despite their stupidity, human capabilities are astonishing
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