Where have all the monarch butterflies gone?

Monarch butterflies have been tough to come by in southern Ontario so far this summer.

Early July is normally the time of year when the black and orange butterflies start showing up in Windsor and Essex County, but so far they have been largely absent.

Chip Taylor is founder and director of Monarch Watch and a professor in the department of ecology and evolutionary biology at the University of Kansas.

He said monarchs are off to a slow start this year, with the number moving north in May at an all-time low.

The Ojibway Nature Centre in Windsor held its annual butterfly count July 7 and spotted just one adult monarch.

Vic Bernyk owns Native Trees and Plants, a hobby nursery in Amherstburg, Ont., that specializes in creating butterfly gardens. He has yet to see a monarch.

'Normally at this time of year, I'd see hundreds.' Joe Derek, butterfly enthusiast

"This year, there seems to be some sort of delay in their arrival. It could be weather, loss of habitat, those kind of things," Bernyk said.

Butterfly enthusiasts across neighbouring Michigan also want to know where the monarchs are.

Data is being collected by monitoring groups around the state, but anecdotally its not looking great.

Butterflies are absent from Joe Dereks naturally landscaped property in Farmington Hills, where he grows two acres of native plants known to draw the insects.

"Normally, at this time of year, Id see hundreds," Derek, former naturalist for the City of Farmington Hills, told the Detroit Free Press "In my life, Ive never seen a season where were not seeing butterflies really of any kind."

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Holli Ward, executive director of the Michigan Butterflies Project, said she has seen few monarch butterflies this summer, the type she studies most.

"On a good day, were looking at hundreds of milkweed stalks every week, twice a week since early June," she said. "We have not seen a single egg or caterpillar."

Ward hopes it will get better later in the season, but she has doubts.

Some butterfly experts and enthusiasts are blaming changing weather patterns and drought in the U.S. for the lack of monarchs. Others blame herbicides for wiping out their natural habitat, namely milkweed.

"They depend on one species only: the milkweed plant," Bernyk said.

The monarch feeds and breeds on butterfly, swamp and common milkweed.

Milkweed crop has 'crashed'

"Loss of habitat is the major reason monarchs are declining. People have to remember this is a continental species and what happens locally is only a small part of the story," Taylor wrote in an email to CBC News. "Just because there is a lot of milkweed in some areas of Ontario does not mean this applies everywhere. The northeast has been relatively untouched by changes in agriculture and there is still lots of milkweed, but it's not a big monarch production area.

"It's what happens in the corn belt that determines the size of the monarch population and milkweeds have crashed in this area."

Elizabeth Howard, who directs the monarch research group Journey North, told Minnesota Public Radio News that milkweed plants weren't far enough along in Texas this year because of a cold spring, so the butterflies couldn't lay eggs. She said a generation of monarchs may have been lost.

"Because of their long journey from central Mexico, theyre prone to climatic changes," Bernyk said.

Storms and drought can wreak havoc on the insect and its food source.

Bernyk is encouraging residents in Windsor-Essex to plant milkweed in their gardens.

"Theres been a continuous loss of habitat. Without the milkweed, the reproduction of monarchs becomes very difficult because they depend solely on this plant for reproduction," Bernyk said.