Caterpillar observation/disappearance

[froglegs]

Finally after several years of waiting, I finally achieved success; counted as many as 18 caterpillars on my common milkweed.
May be a common observation, but I noticed they move around a lot, and many disappeared for most of the day, no where to be found on the milkweed, only to reappear in the later afternoon. I found one on an adjacent purple milkweed one day.
Unfortunately, I do not think any survived. A large flock of grackles/starlings descended, and when I looked later, not a cat to be found.
In past years, I could sometimes find large aggregations of Monarchs the last week of August at a remnant prairie site. No luck this year, will try again tomorrow.

[Mona Miller]

This is why many of us take them in to raise them. Predation is pretty high outside and this year it seems worse than the past years.

http://www.monarchwatch.org/rear/index.htm
Rearing Monarchs

I know that Monarchs in the Classroom monitoring project usually leaves them out.

http://www.mlmp.org/
Monarch Larva Monitoring Project

[midimatt]

I've collected butterflies and moths in my younger years, but I hadn't specifically searched for monarch caterpillars until this year after attending a tagging session through a local nature center.

Although the number of monarchs I see this year seems low compared to other years, I found a field at a local park (maybe four acres) that is plentiful with milkweed and monarch caterpillars. I took around 100 of the caterpillars home (over a span of three weekends; about three hours of collection per weekend) along with around a dozen chrysalises to raise, and most of the caterpillars have thus far turned into chrysalises. I released ten adults a few days ago. I've seen more caterpillars than adults this year by far.

Unfortunately there were some fatalities. The mortality rate I'm seeing in the caterpillar stage is around 20-25%. Is this normal? I noticed that a few died with larvae (perhaps of a wasp) in them. I've heard of there being a virus that monarch caterpillars are prone to, however I'm not sure what the normal mortality rate is. Does anyone know what I should expect?

[Mona Miller]

It varies from year to year and location. The level of OE is higher in CA and FL year round. I feel after rearing in an area for a while the predators build up. I think that is why they have a difference preference for milkweed from year to year. Keeps those predators guessing.