Where and Whither the Monarch?

One phenomenon I can usually count on every late summer/autumn is a sudden swelling appearance of Monarch butterflies as they begin to make their long migratory journey southward for the winter.  During the summer, I see them flitting about in my garden, and spot the caterpillars munching away on their wild host plants (milkweed).

Male Monarch butterfly in my garden in September 2011.

This summer, though…nada.  Nothing. Zip.

Honestly, I didn’t see a single caterpillar, and although I remember thinking I might have had a glimpse of one adult flying across my road in August, it seemed small and could easily have been a mimicking Viceroy.

It wasn’t until just a few days ago that I found this:

Monarch butterfly (Danaus plexippus)

I found it lying back-up in the middle of the rarely-used old gravel road where I take my dogs for walks.

It was sad and beautiful: starkly, vividly orange on top of the dirt and scattered brown leaves. It was also dead. I gathered it up carefully in my gloves and walked it home. I felt it would be a waste to leave it there to be stricken by the elements since there was no other insect life out that might otherwise scavenge the body. Frankly, I was quite shocked to see it there at all, given the cold weather and heavy overnight frosts we’ve been experiencing of late.

So now it’s on a pin. Other than a couple of scales scuffed off on the top edge of the right forewing, it’s in excellent shape overall – no tears or tattered wing edges. I’m not usually one to pin butterflies (I find spreading wings fussy – the scuffed scales on the left wing were my own clumsy fault), but the utter absence of Monarchs this year made me think that this one was worth preserving.

Any casual observer of wildlife has noticed that the number of Monarchs in Ontario/eastern Canada has been way down this year.  I just went to ebutterfly.ca, a great new citizen science initiative, and drew up some maps comparing the reported observations of Monarchs in Ontario from May-October in 2012, and in 2013.  The difference is pretty remarkable:

Citizen science reports of Monarch butterflies (from http://www.ebutterfly.ca) in southeastern Ontario in 2012 (L) and 2013 (R). There are also a few points to the northwest on the 2012 map that aren’t shown here. You can click to embiggen.

I made sure to add my “dot” to this year’s map.

Researchers suggest that this big change is likely due to a combination of less-than-ideal climate and a lack of habitat, and therefore of host plants. Here in the north, we get the last round of breeding adults; generations of butterflies progressively make their way northward throughout the breeding season, starting way down in the southern US.  Although we’ve previously thought that breeding grounds in the central US were the most critical for their success, new research by a team at the University of Guelph suggests that the entire breeding range is actually quite important. These scientists feel confident that the population will rebound, though perhaps not to the same historically high numbers.

Labidomera clivicollis, a milkweed specialist leaf beetle

I live in a rural area with lots of old fields and unmanaged roadsides: perfect places for milkweed to grow and so perfect places to observe its characteristically-coloured red/orange-and-black insect fauna.

One interesting thing I observed this summer was an absolute gangbusters number of specialist milkweed leaf beetles, Labidomera clivicollis.

I usually see a couple of them here and there but the milkweeds were covered in them this summer. Perhaps they were doing better with reduced competition? I’d be curious to know if others elsewhere observed the same thing.