Executive Summary on the Status of the Taylor’s Checkerspot Butterfly

From Ann Potter, WDFW

The Taylor’s Checkerspot, a Pacific Northwest endemic butterfly, was historically found in grassland habitats from southeastern Vancouver Island, British Columbia, south through the Puget Trough in western Washington, and into the southern Willamette Valley in Oregon. Today, the butterfly is restricted to 11 known populations: eight in Washington, one in British Columbia, and two in Oregon. Current distribution within Washington is greatly reduced from historical and limited to two geographically isolated areas: the south Puget Sound region (Pierce County), and the northeastern Olympic Peninsula (eastern Clallam County). In addition to the eight naturally occurring populations, efforts to reintroduce the butterfly are underway at four sites in the south Puget Sound region. Taylor’s Checkerspot was listed as an endangered species by the Washington State Fish and Wildlife Commission in 2006, the Committee on the Status of Endangered Wildlife in Canada in 2011, and the U.S. Fish and Wildlife Service in 2013.

When listed endangered by the Washington Fish and Wildlife Commission in 2006, Taylor’s Checkerspot was known to occur on 10 Washington sites in Clallam, Pierce, and Thurston counties. Since then, extirpation of the butterfly has been observed on seven of the 10 sites. Also during this period, searches continued for Taylor’s Checkerspot on the Olympic Peninsula, and five new sites were located within Olympic National Forest. No new populations have been found since 2009.

Grassland dependent butterflies in the Willamette Valley-Puget Trough-Georgia Basin ecosystem, including Taylor’s Checkerspot, have declined dramatically due to widespread habitat degradation and loss of prairie-oak ecosystems from development, invasive species, and loss of beneficial disturbance mechanisms. Habitat enhancement efforts for Taylor’s Checkerspot since 2006 have been significant, however, the amount of fully-restored habitat relative to need is low, and the configuration of habitat remains fragmented and isolated.

Research in the Prairies of Western Washington

The following is a brief summary of some research being done on the Taylor’s Checkerspot and its host plants. This information was taken from a recent presentation given by Dr. Jon Bakker of UW, to the Seattle chapter of the Native Plant Society titled “Prairies of Western Washington”. The talk was packed with information about our northwest prairies and the research that he and a team of people are doing in the South Sound prairies, Whidbey Island, and in the San Juans, both in restoration and in monitoring two endangered species that depend on the prairies: the Taylor’s Checkerspot, a subspecies of the Edith’s Checkerspot (Euphydryas editha taylori); and the Golden Paintbrush (Castilleja levisecta).

One study looked at the butterfly’s host plant preferences. The Taylor’s Checkerspot uses host plants that contain iridoid glycosides, which the larvae sequester. These are toxic and unpleasant to taste giving the larvae protection from predators. (This is similar to what Monarch larvae do by eating milkweed.) Prairie plants which are high in these chemicals are: Golden Paint- brush, Harsh Paintbrush (Castilleja hispida) and Narrow-leaved Plantain (Plantago lanceolata). Historically the Taylor’s Checkerspot used C. hispida. However, it has been documented using all three as a host in the wild. In their research, it survived better on Plantain, although the Plantain is not native. One possibility is that it has switched hosts, and could switch back to the Castillejas. Of note, their research showed that while Plantain has higher levels of iridoid glycosides, repeated burning can lower its iridoid glycoside levels.

Castillejas are hemiparasites, meaning that they can live independently but may grow better by getting resources from a host plant. Castilleja roots can penetrate the roots of other plants drawing nutrients from them. In another study the researchers asked the following question: if the butterfly is using Castillejas, does the identity of the Castilleja’s host plant impact the butterfly larvae? Research showed this to be the case-the checkerspot larvae growth varied with host plant of the Castilleja. This is an example of an indirect effect in which the Castilleja is the mediator through which its host plants affect the butterfly larvae even though the larvae don’t eat those plants. This would be similar to a situation in which the plants that a herbivore eats affect the carnivore that eats the herbivore. Some host plants are better hosts than others, thus the Castilleja will be more or less healthy depending on the host. The researchers found that in the prairie, yarrow was the most beneficial host to the Golden Paintbrush of the plants they were testing, and the yarrow stood up well as a host. It is also interesting to note that the Castilleja may parasitize several hosts at the same time if a variety of plants are nearby!

The 4th instar of the Taylor’s Checkerspot overwinters from July through February. Adults usually emerge during April and May. Eggs are laid and the larvae feed until the 4th instar or 5th instar goes into diapause around July. 

At the time the butterfly emerges from diapause in early spring, it may use different hosts than it had been using earlier. Historically it has also used annuals in the spring, but today there are fewer annuals in the prairie due to less disturbance to the ground, such as no harvests of camas bulbs by Native Americans, reduced populations of gophers, and fewer fires. There are many different factors to consider with this butterfly and the prairie that are unknown. Research is an ongoing process.

I applaud the efforts that these researchers are making to tease apart the interdependent details of the prairie system and proceed in supporting the plants and animals of this fragile habitat.

~Thanks to Jon Bakker for kindly fact checking and making editorial comments for this summary.

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