Are female monarch butterflies declining...

[Mona Miller]

http://rsbl.royalsocietypublishing.org/ ... 2e034a5a07
Are female monarch butterflies declining in eastern North America? Evidence of a 30-year change in sex ratios at Mexican overwintering sites
Andrew K. Davis,* and Eduardo Rendón-Salinas
Every autumn the entire eastern North American population of monarch butterflies (Danaus plexippus) undergoes a spectacular migration to overwintering sites in the mountains of central Mexico, where they form massive clusters and can number in the millions. Since their discovery, these sites have been extensively studied, and in many of these studies, monarchs were captured and sexes recorded. In a recent effort to compile the sex ratio data from these published records, a surprising trend was found, which appears to show a gradual decline in proportion of females over time. Sex ratio data from 14 collections of monarchs, all spanning 30 years and totaling 69 113 individuals, showed a significant negative correlation between proportion of females and year (r = −0.69, p = 0.007). Between 1976 and 1985, 53 per cent of overwintering monarchs were female, whereas in the last decade, 43 per cent were female. The relationship was significant with and without weighting the analyses by sampling effort. Moreover, analysis of a recent three-year dataset of sex ratios revealed no variation among nine separate colonies, so differences in sampling location did not influence the trend. Additional evidence from autumn migration collections appears to confirm that proportions of females are declining, and also suggests the sex ratio is shifting on breeding grounds. While breeding monarchs face a number of threats, one possibility is an increase in prevalence of the protozoan parasite, Ophryocystis elektroscirrha, which recent evidence shows affects females more so than males. Further study will be needed to determine the exact cause of this trend, but for now it should be monitored closely.

[Paul Cherubini]

The sex ratio at both winter and autumnal cluster sites varies depending on a wide range of sampling variables such as calendar date, temperature, sunny vs shaded area within the colony, size of the colony, or cluster etc. Since sampling procedures were not identical over the 30 year study period, it's not surprizing that sex ratio differences were found which may simply be just artifacts of the sampling procedure differences.

[summerluver]

I've just sorted through this report, and it seems to be pretty scientifically balanced, with the results showing accuracy. I know that I've keept track of what I raise here in NJ over the past 4 years as far as the date and sex of each butterfly as it ecloses, and had initially found that in the beginning of the season I had a ratio of more males than females. Towards the end of the season, I had almost all females. I post the results on a sign in my yard with daily updates, and all the kids of the neighborhood anxiously keep score to see if the boys or girls are winning. The boys have always had higher numbers until the end of August when the numbers shift over to mostly females. (The girls relish this victory, and I know it's coming, but they haven't figured it out yet.) This year, however, I'm suprised to find that I'm getting more males. I've been catching wild ones and tagging them over the past 3 days as they're migrating through here, with the ratio being almost even, instead of the usual predominently female counts. I've still got about 10 chrysalises to go here, so the neighborhood excitement is high that the boys may win, which would be a first.

[Paul Cherubini]

How many Oe spores justifies killing a newly emerged monarch?

a) 1
b) 2-9
c) 10-99
d) 100-999
e) 1,000-9,999
f) 10,000-99,999
g) 100,000 or more?

[Mona Miller]

What happens to one spore that a caterpillar eats?

Same numbers. Wake up.

This isn't about commercial gain. The USDA is not going to open up that divide because you prove that OE doesn't matter. Or butterflies migrate from one side to the other. Remember I was there talking with you and Linda and Chris at one point.

[Paul Cherubini]

What happens to one spore that a caterpillar eats? Same numbers. Wake up.

I'm not aware of any study that has demonstrated what happens to one spore that a WILD monarch caterpillar eats in the WILD. I'm not aware of any study that has demonstrated Oe is commonly lethal to migratory monarch caterpillars in the WILD.

I do know that 80% of the 1,000,000 migratory, overwintering monarchs in California have a spore load of between 1-999 Oe spores on their bodies; i.e. are spore positive:

http://i636.photobucket.com/albums/uu87/4ALC/nb75b.jpg
http://i636.photobucket.com/albums/uu87/4ALC/spore.jpg

So If it was logiscally feasible to kill all spore positive monarchs in California (all 800,000 of them)
the overall western population would suffer a drastic 80% drop.

Conversely, if it was logiscally feasible to rear and release 800,000 spore positive monarchs in California (with spore loads of between 1-999), the overall western population would be boosted by a huge amount (around 80%).

Reasonable Conclusion: Rearing a releasing western monarchs with spore loads of between 1-999 will HELP the western monarch population grow.

[texas butterfly]

It seems that rearing and releasing OE negative Monarchs would be the best way to increase the numbers of the Western population or any wild population.

0 or Zero would be best

[summerluver]

I agree. How many spots did someone in my kids have to have from chicken pox to be contageous, and spread it around to everyone? If the OE bacteria, or any for that matter, is going to release spores in its efforts to reproduce and spread, what's the point in counting spores? All I know is that I've seen the results of having it infect my entire breeding population this summer, and finally died out with the last cat that had it, losing about 60. I didn't perform autopsies to count how many spores they had on them to see that the results were devastating to my entire population.

[Mona Miller]

Your experiments haven't proved to me that wild populations find it any easier than captive populations. Releasing a bunch of caterpillars out in the wild, coming back to find adults without OE. Anything can happen in that area. Absolutely, no control.

Telling people it doesn't matter if they raise and release infected butterflies is unethical.

[Paul Cherubini]

Releasing a bunch of caterpillars out in the wild, coming back to find adults without OE.

The adults I found were newly emerged adults. I knew the date I had released the caterpillars so I knew the date the adults would be emerging. There were no wild caterpillars to be found that year because the wild populations were low, so there was no need for a "control".

I did not even know these newly emerged adults had no OE until after I shipped them to a commercial breeder here in California who had a microscope and was experienced in doing spore counts. And this breeder actually USED these butterflies successfully for breeding stock.

I did not inform this breeder that these OE free butterflies were actually derived from hundreds of caterpillars I reared during the 1st-4th instars in extremely crowded, filthy conditions where the caterpillars consumed dozens, if not hundreds of spores. I told her this only AFTER she had successfully used the adults as breeding stock. She was pissed to learn I had given her breeding stock with such horrible background, but the experience taught her and me that caterpillars that consume
spores don't necessarily develop into adult butterflies that have alot of spores.

Sonia Altizer and the other OE scientists havn't ever conducted actual field trial experiments like this.

Citizen scientists seem to always be the ones who make the major Monarch discoveries; e.g. that monarchs breed WITHIN the Rocky Mountains, that milkweed grows up to 10,600 feet, that monarchs can fly NORTHWEST in the autumn, that some western monarchs migrate to central Mexico for the winter and so forth.