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The Karner blue butterfly, behaviour, and the role of fire in managing a reintroduced population.

Abstract

The Karner blue butterfly (Karner blue) [Lycaeides melissa samuelis] was extirpated from the oak savanna of Ohio, USA in 1989, and the butterfly was later reintroduced with little knowledge about how Karner blues respond to habitat management. While burning maintains the oak savanna habitat of the Karner blue, the consequences of burning on the butterfly remains unknown. The objective of our study was to determine the effect of prescribed burning on Karner blues. Each of the four study sites had host-plants of which 1/3 were burned, 1/3 were mowed, and 1/3 were left unmanaged each year. These treatments had been rotated within each site, to create a chronological order of succession (0-4 years since burning). We used surveys and behavioral observations to determine the effect of management on Karner blues. Our survey results showed Karner blues were not consistently selecting for management treatments. However, the oviposition rate in the unmanaged treatments was so low that only 5 of 127 eggs were oviposited in these treatments. Overall, the management strategy allowed for Karner blues to recolonize burned treatments and provided butterflies with the opportunity to make behavioral decisions that could potentially maximize their reproduction. In conclusion, we recommend burning oak savanna on a 3-4 year interval based on the Karner blue's lack of reproduction in savanna left unburned for [greater than or equal to]4 years.

Introduction

The Karner blue butterfly (Karner blue) [Lycaeides melissa samuelis] is one of the first insects of conservation concern to be reintroduced in the United States. The Karner blue is an endangered species that inhabits early successional oak savanna and pine barrens ranging from New Hampshire to Wisconsin. The average lifespan of the butterfly is only 3.5 days (Knutson et al. 1999) and its wingspan is about 2.5 cm. This small butterfly has two distinct broods per year with separate generations of adults flying in May and July. Much of the ecology of the Karner blue revolves around the fact that it is a larvae host-plant specialist that relies solely on wild blue lupine [Lupinus perennis], which lives in disturbed areas and nutrient poor soils associated with fire-prone ecosystems (U.S. Fish and Wildlife Service 2003).

The reasons for the butterfly's endangered status stem from massive land use changes associated with agriculture and extensive fire suppression throughout the 1900s. Fire is well known to be critical to maintain the oak savanna community (Davis et al. 2000; Peterson & Reich 2001),

and many of the rare, early successional species depend on fire to create proper habitat conditions. In particular, the Karner blue once inhabited the oak savanna of the Midwest, which has largely been converted to either agricultural lands or oak forests due to decades of fire suppression. In fact, only about 0.02% of historic oak savanna remains in the Midwest (Nuzzo 1986), and this ecosystem is home to many plants, insects, and birds of high conservation concern in the region (e.g. lark sparrow [Chondestes grammacus], red-headed woodpecker [Melanerpes erythrocephalus], frosted elfin [Callophrys irus], and hundreds of rare plant species).

[FIGURE 1 OMITTED]

In Ohio, the Karner blue was extirpated in 1989. The cause of extirpation remains unknown, but it was likely a result of dramatic habitat loss due to fire suppression, agriculture, and development. The resulting small population was then subject to poor weather conditions (i.e. drought), and this probably eliminated the final few Karner blues in Ohio. After years of its absence from the region, a group of experts studied the possibility of reintroducing the species into northwest Ohio. Finally, in 1998, the Toledo Zoo, The Nature Conservancy, and the Michigan and Ohio Departments of Natural Resources decided to capture first brood Karner blues at Allegan State Game Area in Michigan (Figure 1), breed them in captivity at the Toledo Zoo, and then release the butterflies into the wild in Ohio during their second brood. The methodology included bringing butterflies into captivity, assuring proper breeding, and collecting oviposited eggs on host-plants within a greenhouse environment. One particular area was deemed most suitable for the Karner blue which was located at The Nature Conservancy's Kitty Todd Preserve in Lucas County, Ohio. At this preserve, The Nature Conservancy owns one of the largest pieces of oak savanna in Ohio. The Nature Conservancy had also instigated a prescribed burning program over the past several years prior to the butterfly's return. Additionally, the most well known factors affecting the butterfly, canopy cover and the presence of wild blue lupine, appeared most suitable at the Kitty Todd Preserve. The first reintroduction took place at one site within Kitty Todd Preserve in 1998. From 1998 to 2004, over 1500 Karner blues were released into the oak savanna.

[FIGURE 1 OMITTED]

Of course, prescribed burning of occupied Karner blue habitat was not the first priority after reintroducing the butterfly, since it might actually jeopardize the only Karner blue population in Ohio, There appeared to be a trade-off between the short-term negative effects of burning butterfly habitat (i.e. potentially killing eggs) and the long-term benefits of maintaining early successional oak savanna and the butterfly's host-plant. Therefore, prescribed burning was initially used sparingly. This management strategy was likely a result of the lack of available information on how Karner blue individuals would respond to prescribed burning and how a relatively small population might be affected. However, the oak savanna continued to degrade into late successional habitat without burning and the further loss of wild blue lupine was likely inevitable. In 2001, an active fire program was reinitiated in Karner blue occupied habitat.

For these reasons, Dr. Karen Root and I initiated a study at Bowling Green State University to investigate the consequences of management on Karner blues in northwest Ohio. Our objective was to determine the effect of prescribed burning on Karner blues, and we used butterfly abundance surveys and oviposition rates as measures of habitat use. While methods such as performing surveys are difficult to interpret due to annual differences in abundance and small sample sizes, the behavior of an organism can rapidly provide insights into the perceived habitat quality of management treatments. The quantification of both butterfly abundance and reproductive rates within management treatments had the potential to determine the usefulness of these habitats.

Methods

A thorough review of our methodology and results can be found in Pickens and Root (2009); a brief overview follows. Four distinct Kitty Todd sites had Karner blues, and each site had approximately 1/3 of the host plants burned, 1/3 mowed, and 1/3 left unmanaged each year. For the past several years, each treatment had been rotated within each site; this also represented a chronological order of succession with burned areas (0 years since burn) and mowed areas (1-2 years since burn) being early successional while the unmanaged areas had been left unburned for [greater than or equal to] 4 years. This management strategy provided for four experimental sites to investigate and all sites included the three management treatments in the year of our study.

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[ILLUSTRATION OMITTED]

In 2005, one to three observers performed standardized butterfly survey transects within host-plant areas at Kitty Todd Preserve (Thomas 1983; Pollard & Yates 1993), and we recorded the number of Karner blues found within each management unit. Whenever we found a female Karner blue, we observed the butterfly for a 15-minute interval to quantify foraging rates, and most importantly, where the Karner blues oviposited their eggs. Ovipositions were characterized by a Karner blue crawling down a lupine stem, flexing its abdomen, and depositing an egg. By observing these behaviors, we hoped to have a clear picture of both the habitat use and behavior of the species in relation to burning and mowing. We also quantified canopy cover and lupine area to account for these differences within management units.

Results

Our survey results showed Karner blues were not consistently selecting for any of the treatments; essentially they were found randomly among treatments at each of the four sites. The only exception was the females in the second brood were more abundant in burned treatments compared to mowed treatments. Of course, these overall results actually meant the butterflies colonized the burned areas quite well because they were equally abundant in burned areas as in the other management treatments. The management treatments were within about 120 m of each other, therefore, the Karner blues did move substantially within each site. Incredibly, the oviposition rate in the unmanaged treatments was extremely low; only 5 of 127 eggs were oviposited in the unmanaged treatments. The pattern was statistically significant, and has important biological implications (Pickens & Root 2009). Meanwhile, there was no discernable pattern to foraging rates among management treatments.

Discussion

For the reintroduction of species and the management of small populations, there are likely to be trade-offs of short-term and long-term goals. Prescribed burning in an area occupied by an endangered insect is generally thought to have negative consequences, such as direct mortality (Swengel 1995), yet the consequences of burning are not fully understood. The results of our study showed that behavior can be a good indicator of management effects, since butterflies avoided ovipositing in unmanaged treatments. Reproduction primarily occurred in burned and mowed treatments, and both of these treatments represented the most recently burned savanna.

Initially, we knew that other butterfly species were selective of hostplants due to scent (Feeny et al. 1989), host-plant nitrogen (Myers 1985; Ellis 2003; Prudic et al. 2005), size of hostplants (Ellis 2003), and the presence of ants (Pierce & Elgar 1985; Fraser et al. 2002). However, these types of studies are primarily performed as lab-based experiments, and few studies have shown host-plant selection in the field. We now have evidence that Karner blues avoid ovipositing in oak savanna that is unburned for [greater than or equal to] 4 years, and this is likely the result of successional processes in oak savanna. Of course, the initial recolonization of recently burned savanna is necessary to ensure butterflies have a chance to oviposit there. At Kitty Todd, the burned treatments were within about 120 m of unburned treatments. This is well within the dispersal distance of Karner blues (Knutson et al. 1999), and our survey results provided evidence that butterflies were able to quickly recolonize burned treatments. The overall management strategy allowed for a source of Karner blues to recolonize and provided butterflies with the opportunity to make behavioral decisions that could potentially maximize their reproduction. Importantly, the butterfly's lack of reproduction in units left unburned for [greater than or equal to]4 years probably makes these areas prime for burning the following winter.

The trade-off of managing for long-term habitat or short-term populations is not unique to insects and burning. For example, the wetlands of south Florida are home to the endangered snail kite [Rostrhamus sociabilis], where a perceived trade-off of providing potential short-term drought refugia by impounding water was given priority over the long-term benefits of water level variability in wetlands (Kitchens et al. 2002). Of course, the long-term dynamics and responses of species to management are difficult to understand, but studying behavior can provide important insights for a variety of species of concern. This is particularly true for reintroduced species because adaptive management must be conducted as soon as possible to allow small populations to persist. In conclusion, I recommend prescribed burning Karner blue habitat at approximately 3-4 year intervals based on their avoidance of reproduction in areas left unburned for longer periods.

Acknowledgements

The Ohio Department of Natural Resources, Division of Wildlife provided funding support for this project through a State Wildlife Grant; an additional grant was provided by the Ohio Biological Survey. We are thankful for the many people who were supportive of this project: G. Haase (The Nature Conservancy), P. Tolson and C. Ellsworth (Toledo Zoo) were especially helpful. We are grateful for the data collection efforts of E. Knurek, M. Ricci, and R. Kip. J. Bouzat, C. Pickens, H. Michaels, and K. Root of Bowling Green State University (BGSU) provided valuable insights throughout this project. Endangered species permits from the U.S. Fish and Wildlife Service were obtained through the Ohio Division of Wildlife. We are appreciative of the BGSU Geology Department and the BGSU Statistical Consulting Center for providing equipment and expertise.

Literature Cited

Davis, M. A., D. W. Peterson, P. B. Reich, M. Crozier, T. Query, E. Mitchell, J. Huntington and P. Bazakas. 2000. Restoring savanna using fire: Impact on the breeding bird community. Restoration Ecology, 8:30-40.

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Kitchens, W. M., R. E. Bennetts and D. L. DeAngelis. 2002. Linkages between the snail kite population and wetland dynamics in a highly fragmented south Florida hydroscape, p. 183-202. In J. W. Porter and K. G. Porter (eds.), The Everglades, Florida Bay, and coral reefs of the Florida Keys: an ecoystem sourcebook. CRC Press, Boca Raton, FL.

Knutson, R. L., J. R. Kwilosz and R. Grundel. 1999. Movement patterns and population characteristics of the Karner blue butterfly (Lycaeides melissa samuelis) at Indiana Dunes National Lakeshore. Natural Areas Journal, 19:109-120.

Myers, J. H. 1985. Effect of physiological condition of the host plant on the ovipositional choice of the cabbage white butterfly, Pieris rapae. The Journal of Animal Ecology, 54:193-204.

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Pickens, B. A. and K. V. Root. 2009. Behavior as a tool for assessing a managed landscape: a case study of the Karner blue butterfly. Landscape Ecology, 24:243-251.

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Prudic, K., J. Oliver, M. Bowers and O. Schmitz. 2005. Soil nutrient effects on oviposition preference, larval performance, and chemical defense of a specialist insect herbivore. Oecologia, 143:578-587.

Swengel, A. B. 1995. Observations of spring larvae of Lycaeides melissa samuelis (Lepidoptera: Lycaenidae) in central Wisconsin. The Great Lakes Entomologist, 28:155-170.

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U.S. Fish and Wildlife Service. 2003. Karner Blue Butterfly Recovery Plan (Lycaeides melissa samuelis). Department of the Interior, U.S. Fish and Wildlife Service, Great Lakes- Big Rivers Region (Region 3).

Bradley A. Pickens

School of Renewable Natural Resources, Louisiana State University AgCenter,

Baton Rouge, LA 70803

bpickens@lsu.edu
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Author:Pickens, Bradley A.
Publication:Endangered Species Update
Article Type:Report
Geographic Code:1USA
Date:Jan 1, 2009
Words:2524
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