Mice and butterflies

[Stan Gorodenski]

I don't have any information on mice predation on other butterflies, but 
I wonder if the following observation from Monarch Watch can be a valid 
argument against forest thinning:
"Other characteristics may affect the amount of predation too. The edge 
or periphery of the roost faces higher levels of predation than the 
center. Thus, small roosts, with a larger edge to interior ratio, face 
higher overall predation than larger roosts, which have a lower edge to 
interior ratio. Forest thinning, due to natural causes such as 
streambeds or human-induced causes such as selective logging or brush 
clearing, also increases predation. Thinning increases the surface area 
of the roost and makes the top side of the roost more accessible to 
predators."

My question is:  Are these observations made on large and small roosts 
that are separated from one another to such a degree that the same bird 
population would not likely feed on more than one roost? The cited part 
of Monarch watch does not make it clear if they are or not.

If roosts are separated from one another to such a degree that the same 
bird population would not likely feed on more than one roost, then these 
observations could be viewed as a valid argument against thining.  On 
the other hand, if the same bird population can feed on both large and 
small roosts in the same study area, then it is questionable that the 
observations are a valid justification against thinning. It may be that 
smaller roosts have larger overall predation than larger roosts because 
it is easier for the bird to get to the Monarch.  If  a bird had a  
choice of doing something easy or hard, I would guess it would choose 
the easy way.  Hypothetically, if smaller roosts disappeared, i.e. no 
longer existed, and all roosts were large, it does not seem likely the  
large roosts would still experience the same level of predation as they 
had in the presense of small roosts.  The birds could and probably would 
modify their predation techniques  so that the large roosts would 
experience the same level of predation, or close to it, as the smaller 
roosts.

I know very little about this subject, and so these are questions I have.
Stan

Staffan Forssell wrote:

>Hi, 
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>I found this on http://www.monarchwatch.org/biology/pred2.htm
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>... Five species of mice are known to be abundant near the Mexican overwintering roosts of Monarch butterflies. Of these five, only the scansorial black-eared mouse, Peromyscus melanotis, eats Monarchs. Several studies have investigated how P. melanotis avoids poisoning, the impact Monarch consumption has on the mouse, and the impact mouse predation has on the Monarch population.
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>This predation may also have helped mold Monarch behavior in winter roosts. For example, Monarchs generally crawl up vegetation. Moving up might help protect Monarchs from both freezing temperatures near the ground and from greater mouse predation. On a conservation note, this means that it is important to also protect the understory vegetation in winter roosts so that Monarchs can escape mouse predation more easily ....
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>Question: do we know of other mice predators on other butterflies? Be it in the US, Latin America, Africa, Asia or Europe? 
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>Best wishes 
>
>Staffan in Sweden 
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