Changing Butterfly Distribution

Butterfly distribution is in a constant state of flux because their environment is changing in one way or another on a continuous basis. Measurements are visible sometimes only after many years......when species numbers blossom or diminish or even disappear. Many factors play a roll in the pattern of distribution such as loss of habitat, weather, predators and a natural ebb and flow brought about by more obscure influences. In no way is it the intent of this page to trivialize the complexity of this issue, however, it is the observations of amateurs that can serve as early indicators.

Over the last decade there have been surveys in North America and Europe that have studied, in considerable detail, the distribution of many butterflies. As a result it has been determined that as many as two thirds of the butterflies, identified as possible candidates for territorial expansion, had indeed expanded their range northward. In some cases as much as 250 km. Evidence would indicate that global warming would be the primary contributor to such movement. However it must be noted that the appropriate habit must be present in order for this to occur. Weather as the primary catalyst will not typically drive butterflies to adapt to inappropriate habitats. Only in rare circumstances has it been documented that butterflies have adopted new hosts in order to comply to environmental situations. The only butterfly I am aware of that has performed this transition, here in Canada, is Henry's Elfin adapting to Black Buckthorn as a larval food plant.

In Canada we have seen two butterflies recently expand their colonies in Ontario. Both these butterflies, the Gorgone Checkerspot and the Delaware Skipper, appear to be responding to warmer climactic trends. The Gorgone Checkerspot had not been seen in eastern Canada since the late 1800's. In the mid 90's it was discovered that it now inhabits several locations in eastern Ontario. In the case of the Delaware Skipper, typically it has been limited to the more extreme southern areas of Ontario but now can be found as far north as Ottawa. As well, the Tawny-edged Skipper is now double brooding where, in the past, it was propagating only once a season in it's northern most range. Are these the early indicators of the results of global warming? Well it is too early to tell but data such as this would indicate that it is a distinct possiblity.

Ontario has recently lost three butterflies to the influences of habitat destruction; the Karner Blue (last seen in Ontario in 1991), Frosted Elfin and the Persius Duskywing. All three of these butterflies are closely connected to lupines which are virtually non existent in Ontario now due primarily to habitat destruction. Interestingly enough a contributing factor to the habitat destruction, aside from the obvious urbanization, is man's ability to control and arrest wildfires......an accomplishment in which we take great pride and rightfully so. Wildfires, however menacing to humans, are an essential element to the continuance of lupine ecology. Wildfires are responsible for suppressing competing growths which take over and choke the lupines out of their preferred environment. Since southern Ontario is one of Canada's most rapidly developing areas it is probably only a matter of time before other butterflies such as the Wild Indigo Duskywing, Sleepy Duskywing, Mottled Duskywing, Scalloped Sootywing, Duke's Skipper, Dusted Skipper and the Garita Skipper (all of which are on the endangered list) succumb to the pressure unless dramatic steps are taken.

Across the northern United States there are several attempts underway to reintroduce the Karner Blue ......a butterfly once found from the Atlantic in New England west to Wisconsin and from Pennsylvania north to southern Ontario and who's numbers have diminished by more than 90 percent in the last 15 years alone. Recent attempts in Ohio have had colonies successfully reestablish themselves in several locations through the efforts of various interest groups and the Toledo Zoo.

Since the mid 90's a cooperative effort between the Pinery Provincial Park, the Toronto Entomologist Assoc., MNR, Canadian Nature Federation and the Toronto Metro Zoo has been implemented in Ontario. Perceived success of this program has still to be determined. Currently, at the Pinery and Port Franks, plantings of lupines and restoration of the oak savanna meadows continues. Controlled burns, removal of pine plantations and the culling of the deer population is the extent of the project's work so far. At this point the project remains in the monitoring phase prior to the introduction of Karner larvae. The recovery team is currently negotiating to acquire and import this endangered specie. The shipment will consist of up to two dozen females which will lay the eggs that will become the breeding stock. Of these approximately 500 larvae will be released each year over the short term. St. Williams and High Park, in Toronto, have also been identified as potential future site for restoration if phase one is successful.

Even if these programs are deemed successful an uncontrollable element may have the final say in the equation anyway. Since Karner second brood eggs overwinter their survival rate has been hampered by the exceedingly mild and virtually snowless winters of late. Without the protective blanket of snow survival rate is poor at best. That does not mean that we should abandon these efforts. Quite the contrary. If we capitulate now the outcome is then guaranteed for this venture and any other reintroduction program that is bound to face obstacles along the way.

With the continual urban sprawl (loss of habitat) and persistent climactic trends of the last couple of decades I have been curious to discover if the long term effects have shown any positive changes in the butterfly distribution in our area of south Central Ontario but not strictly limited to that area. There have been numerous species of butterflies that have frequented the southern tip of Ontario and along the north shore of Lake Erie but, in years past, have refused to venture any further east. One would expect that casual or even long term expansion into this part of Central Ontario, in particular along most of the north shore of Lake Ontario, is possible due these pressures. No doubt, in some cases, habitat will play a roll in territory expansion for some of these butterflies. In general though, the same Carolinian Woodlands exists throughout this area.....albeit a fairly narrow band that is tragically fragmented by urban development. Obviously the Great Lakes form very narrow corridors of entry into these regions for those unable to commit to flying over large bodies of water. Also, it is a distinct possibility that the largest urban concentration in Ontario provides an impassable gauntlet, for those trying to relocate, accept for the very odd stray. Perhaps in your area butterflies have quite different obstacles to face.

In any case butterflies that I would be on the lookout for here in southern Ontario are the American Snout, Delaware Skipper, Fiery Skipper, Little Glassywing, Gorgone Checkerspot, Giant Swallowtail, Zebra Swallowtail, Pipevine Swallowtail, Spicebush Swallowtail, the Tawny Emperor and Hackberry Emperor. Most of these butterflies are fairly plentiful in the northern States and do frequent Ontario's most southern reaches. Of these the Fiery Skipper was recorded in 1999 at Presqu'ile and along the Moira river the Hackberry Emperor (which, by the way, appear to have setup regular colonies here) and the American Snout. However, no long term or centralized records (for this region) of these butterflies exist to indicate whether or not they are isolated sightings. If you could apprise me and other visitors to this site of any of these butterflies, east of Toronto, please write about your sightings or you can read what others have observed by following the link at the end of this page.

Basically what is happening here is that nature's system of checks and balances are in turmoil not just for butterflies but for every inhabitant on this planet. From the beginning of time nature has made adjustments and evolved to suit these situational changes over time. In the past nature has had the luxury of time, in most instances, for evolution to occur. Now things are different. With man's influences, the speed at which nature is required to make these changes is unattainable.......especially if the present pace and course is maintained. The cost of speed; extirpation rates are on the rise and for all intents and purposes unstoppable for most species which are on endangered lists and for many more that are bound to the inevitable. We almost find ourselves in a damned if you do damned if you don't situation now. For every situation we try to repair it seems several more pop up in it's place. Is this the cost of progress or another example of "too soon old too late shhhmart"?

For visitors from other areas please feel free to include your views on this topic, along with interesting observations such as early, late, favourite or other unusual sightings. As well, if you can identify cause(s) that could be a contributing factor to your observations. Remember it is not necessary that comments be restricted to my particular region of interest.

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