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ABSTRACT: The Venus’ fly trap (Dionaea muscipula Ellis) is a unique carnivorous plant listed as a
Species of Concern within the native range of southeastern North Carolina and northeastern South
Carolina. Although several large nature preserves support Venus’ fly trap populations, illegal harvest is
considered a factor in long-term population declines. Few data exist on the impacts of illegal harvest.
While monitoring Venus’ fly trap populations at Lewis Ocean Bay Heritage Preserve (LOBHP), South
Carolina, an illegal harvest occurred during summer, 2003. This allowed an assessment of harvest im-pacts. Most documented populations of Venus fly traps at LOBHP had less than 50 plants. I estimated that harvesters removed 136 plants from two populations. This harvest was roughly half of the plants in both populations and represented 5.5% of the documented adult Venus’ fly traps at LOBHP. Harvesters preferentially took plants with relatively larger petioles and/or relatively larger traps and overlooked smaller plants. The shift in size class distribution to smaller plants may affect future mortality and seed production. Because most human interactions with Venus’ fly traps growing in nature preserves are negative, the dual goals of conservation and public access may be difficult to achieve with a single management approach. Future management for Venus’ fly traps and other unique species might include high-use areas where human impacts (i.e., trampling, collecting, harvesting) are concentrated and remote low-use areas where populations are managed for long-term viability.
Index terms: carnivorous plant, Carolina Bay, collection, Dionaea, plant harvest, Venus’ fly trap Ocean Bay Heritage INTRODUCTION
ment, by modifying plant density that in turn affects plant growth, and by reducing Even when growing in protected areas, rare population size that leads to changes in genetic diversity (Freese 1997). However, it that contribute to long-term population de- is difficult to study effects of use in the con- clines (Bratton and White 1981). Of these text of field experiments or demographic threats, direct use by humans (e.g., collect- ing, digging, and harvesting) is perhaps of many rare species preclude controlled James O. Luken
least understood because it is clandestine removals. The human strategy of plant use activity varying in frequency, extent, and and thus the demographic impact are likely intensity. Research on commercially valu- determined by market forces, by population able wild plants such as American ginseng characteristics of the target species, and (Panax quinquefolium) and wild leek (Al- by the conservation status of the target lium tricoccum) suggests that even small species. Legal use of unprotected species levels of utilization may reduce populations can follow strict protocols for ensuring long-term population viability (Vance et al. et al. 1996, Van Der Voort et al. 2003). 2001). In contrast, illegal use of protected species may involve large-scale removals with little or no consideration of long-term plant populations are brought into closer inferred by broad field surveys (McGraw et al. 2003), by post-harvest assessment occurs, it should be studied in tandem with (Van Der Voort et al. 2003), by examining other factors that affect long-term popula- size class distributions of confiscated plants tion trends and should be considered as a (Nantel et al. 1996), or by estimating the Most carnivorous plants of the Southeast- ern Coastal Plain have been removed from forts to understand conservation threats to the wild by humans (Schnell 2002). These removals can generally be categorized as ing, analyses of life history stages, and the collections or harvests. Collections involve causes of variation in these stages. Plant use can potentially influence demography by removing adult plants that produce seed, Natural Areas Journal 25:295–299 by altering mortality rates, by creating soil do not repeat collection through time in the disturbances that allow seedling establish- same area, and as long as collectors do not Volume 25 (3), 2005
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focus their efforts on genetic variants, it is Venus’ fly trap generally occurs at the generally assumed that population impacts are minimal (Schnell 2002). In contrast, forest. It requires frequent fire to reduce petiole length. The Track Site included one harvest involves large-scale removals of the stature of the shrub canopy (Roberts of the largest Venus’ fly trap populations plants that are later placed on the market. at LOBHP. Prior to the harvest, this site Because of the large potential for negative was photographed in an effort to document change in population size and structure, The Venus’ fly trap is not federally pro- changes in coverage of Sphagnum mosses. harvest of carnivorous plants is generally tected but it is a Species of Concern in considered a serious conservation threat adjacent plots. Harvest at the Track Site Of the various carnivorous plants of the habitat. Collection and sale of the species I estimated total harvest in the following Southeastern Coastal Plain, the Venus’ fly is regulated by a permit system in North ways. At the Shrub Site, number of plants trap (Dionaea muscipula; Dionaeaceae) has South Carolina is illegal, but is legal on plant was assigned to a size category based on petiole length, I was able to construct significant even though tissue culture meth- value, the Venus’ fly trap was listed as a size class distributions for plants removed ods allow mass propagation (Schnell 2002). and plants remaining. At the Track Site, There is anecdotal information regarding species with its snap traps is a botanical I counted gaps in the Sphagnum carpet historical rates of Venus’ fly trap harvest novelty and is universally in demand for However, little information is available one plant, two photographed areas within on the characteristics of harvest or on the The Setting
determine whether gap number was a reliable indicator of plant number. Plants This paper describes a single illegal har- remaining at the Track Site were counted vest of Venus’ fly traps from Lewis Ocean South Carolina is a 3640-ha tract of land that includes 22 Carolina bays in a matrix Carolina. Data collected prior to harvest teristics of these plants were compared to allowed me to address the following ques- plants in four reference populations not tions. How many plants were taken relative are important public areas for conserving the Venus’ fly trap and its associated spe- harvest selective in terms of plant size? And finally, how might human impacts to is located adjacent to the Grand Strand, a rare plants in nature preserves be better popular coastal tourist destination. Com- mercial and residential development pres- Venus’ fly traps at LOBHP, 75% are com- sures along the Grand Strand are intense prised of less than 50 plants. The Track Site LOBHP. Prescribed fire occurs in LOBHP, comprised of more than 150 plants. The sig- The Species
nificance of this illegal harvest event can be cast in several ways: effects on number of residential areas. Although visitation rates populations, effects on number of plants, or effects on size-class distribution of plants. to poor access, recent road improvements The number of populations was not affected cies deriving nutrition from the capture of and zoning changes will likely bring more because harvesters overlooked roughly half insects in leaves specialized as snap traps. of the plants at each site. However, at the Recent research suggests that this adapta- Data Collection
and this harvest reduced the known total native range is a relatively small area of southeastern North Carolina and northeast- During late July 2003, Venus’ fly traps ern South Carolina. Within this range, the were illegally harvested from two sites, Twenty plants were removed from plots at landscape is characterized by a mosaic of hereafter referred to as the Shrub Site and the Shrub Site; 25 plants were overlooked. the Track Site. Prior to harvest, small per- At the Track Site, there were 103 gaps in manent plots (0.25 m2) were established at 296 Natural Areas Journal
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the Sphagnum carpet. Examination of two photographs suggested that the number of gaps underestimated the number of plants by 11%. Thus, I estimated that 116 plants were taken from the Track Site; 111 plants were overlooked. Harvesters preferentially removed large plants from the Shrub Site, shifting the size class distribution of re-maining plants to the small size classes (Figure 1). A similar impact was noted at the Track Site where remaining plants had significantly (P<0.05, rank sum test) smaller traps than plants from reference populations (12.1 + 0.5 mm, n=111 for remaining plants vs. 16.0 + 0.3 mm, n=353 for reference plants, means + se). DISCUSSION
Potential Impacts of Harvest
This assessment of a single illegal har-vest of Venus’ fly traps from LOBHP indicated that the harvester(s) focused on larger plants and left behind mostly smaller plants. Impacts of this harvest must be understood in terms of critical life history stages of the species (Schem-ske et al. 1994). Carnivorous plants such as the Venus’ fly trap are adapted to low resource environments (Chapin et al. 1993, Brewer 2003) and have inherently slow rates of growth. It may take seedlings 3 yr. to reach the flowering stage (Roberts and Oosting 1958). Survivorship and flowering of Venus’ fly traps are closely linked to plants achieving a critical trap size that allows capture of larger insects such as grasshoppers (Schulze et al. 2001). Figure 1. Size class distribution of Venus’ fly trap plants measured at the Shrub Site, Lewis Ocean Bay
Heritage Preserve, S.C. Plants were either removed by harvesters or not removed. Size classes were based
Venus’ fly traps at LOBHP do not gener- on maximum petiole length. Size classes were as follows: 1 = 11-20 mm, 2 = 21-30 mm, 3 = 31-40 mm.
ally flower unless mean trap size exceeds 12 mm and only 30% of plants with mean trap size exceeding 12 mm produce flowers analysis was not done here due to absence (Luken, unpubl. data). Because of illegal of seedling recruitment data, populations comprised of smaller plants are likely to Illegal harvest of Venus’ fly traps may experience higher rates of mortality dur- modify population structure so that other size does not increase appreciably by the threats have greater impacts. For example, shrubs (Schulze et al. 2001). When fires next growing season, it was predicted that lack of frequent fire is considered the ma- do occur, populations of smaller plants will only six plants would flower in the sub- jor threat to long-term viability of Venus’ likely have lower rates of recruitment due fly trap populations. In the absence of to limited seed availability (Roberts and frequent fire, a dense canopy of shrubs flowered at the Track Site. However, this quickly forms and plants experience both another carnivorous species, Sarracenia is still a lower flowering percentage than light and insect limitation (Schulze et al. alata, indicated that large reproductive that observed in populations not affected individuals contribute more to population Volume 25 (3), 2005
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preserve such as LOBHP. Increased fines ACKNOWLEDGMENTS
varied fire regimens (Brewer 2001).
for plant removal might work, but this also increases the perception that Venus’ fly This project was supported by grants from the National Fish and Wildlife Foundation, People and Preserves
traps have high monetary value. Closure of areas where large populations of Venus’ may also indicate the locations of plants Coastal Carolina University. Jamie Dozier the Venus’ fly trap poses a dilemma for preserve managers. Heritage Preserves in facilitated many parts of the project. Scott South Carolina and most other states exist Considering the difficulties associated to protect natural features and to provide for with direct management of illegal Venus’ the “enjoyment” of people. Public access fly trap harvest, indirect methods warrant is maintained and interpretive information some consideration. For example, enlisting is made available. However, in the case of hunters in a program where violations are the Venus’ fly trap, almost any effort to immediately reported to a central location bring people in contact with the plant will is a sensible approach to wildlife poach- James Luken is Professor and Chair in the be detrimental. The soil where Venus’ fly ing. This program is well publicized and Department of Biology at Coastal Carolina traps grow has a high organic content and is is based on the idea that sound wildlife University. His research currently focuses often saturated. Foot traffic quickly creates on the ecology and management of wetland compacted areas. The plants are relatively to game laws. In the case of Venus’ fly communities in coastal South Carolina. obscure and are susceptible to accidental traps, users of LOBHP (i.e., bird watchers, trampling. When people encounter a Venus’ hunters, and hikers) could be enlisted in a fly trap in the wild, there is an irrepress- LITERATURE CITED
similar program where illegal plant harvest ible urge to trigger the trap. This activity Bratton, S.P., and P.S. White. 1981. Rare and 1948). Finally, collection and harvest are tive impacts of plant harvest, market values constant threats as long as people perceive potential threats and practical problems of Venus’ fly trap plants, and potential that Venus’ fly traps have high monetary fines if harvesting is discovered. Educa- 459-474 in H. Synge, ed., The Biological tional programs where Venus’ fly traps Aspects of Rare Plant Conservation. J. Wiley, are distributed free-of-charge to the public would also dispel the notion that Venus’ Brewer, J.S. 2001. A demographic analysis of and the policy forbidding plant removal is fly traps are valuable. Finally, preserve fire-stimulated seedling establishment of stated on a sign at the edge of the preserve. Sarracenia alata (Sarraceniaceae). Ameri- managers might consider two simultaneous visible from an access road. Thus, plant Brewer, J.S. 2003. Why don’t carnivorous servation of Venus fly traps. One strategy harvesters worked under threat of discov- pitcher plants compete with non-carnivorous ery, arrest, and fine. Furthermore, Venus’ plants for nutrients? Ecology 84:451-462.
area where Venus’ fly trap populations are fly traps are difficult to locate within the Chapin, F.S., III, K. Autumn, and F. Pugnaire. maintained and interpreted within a trail matrix of shrubs and herbs. Thus, it is not 1993. Evolution of suites of traits in response system. Here one assumes that Venus’ fly surprising that harvesters worked ineffi- to environmental stress. American Naturalist ciently. Previous efforts to harvest Venus’ due to trampling, collecting, and perhaps fly traps from nature preserves involved a Freese, C.H. (ed.) 1997. Harvesting Wild Spe- harvest. The other strategy would involve cies – implications for Biodiversity and variety of tactics to avoid arrest and fine maintaining existing populations or restor- (Stolzenburg 1993). The characteristics of ing new populations of Venus’ fly traps in illegal plant harvest will likely vary depend- remote and relatively inaccessible areas of Koopowitz, H., and H. Kaye. 1984. Plant Ex- ing on plant apparency and the perceived tinction: a Global Crisis. Stone Wall Press, risk associated with the illegal activity.
the number of populations and the number Lawler, J.J., S.P. Campbell, A.D. Guerry, Various strategies exist for managing illegal M.B. Kolozsvary, R J. O’Connor, and C.N. harvest of Venus’ fly traps. However, most Seward. 2002. The scope and treatment of two approaches are supportive in that the of these strategies are impractical and may threats in endangered species recovery plans. remote sites could eventually serve as a run counter to preserve goals. Obviously, source of replacement plants at the high-use Luken, J.O. 2003. Cultivating new populations area. The high-use area would garner posi- ers would lead to better plant protection. of Venus’ fly trap at Lewis Ocean Bay Heri- tive public opinion regarding management However, most state agencies cannot afford tage Preserve (South Carolina). Ecological activities (e.g., frequent fire) and off-site this, and it is logistically difficult in a large effects of management (e.g., smoke).
McGraw, J.B., S.M. Sanders, and M. Van der 298 Natural Areas Journal
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Voort. 2003. Distribution and abundance of Roberts, P.R., and H.J. Oosting. 1958. Respons- Stolzenburg, W. 1993. Busting plant poachers. Hydrastis canadensis L. (Ranunculaceae) es of venus fly trap (Dionaea muscipula) to and Panax quinquefolius L. (Araliaceae) factors involved in its endemism. Ecological Stuhlman, O. 1948. A physical analysis of the opening and closing movements of the lobes of Venus fly-trap. Bulletin of the Torrey elshaus, C. Goodwillie, I.M. Parker, and Nantel, P., D. Gagnon, and A. Nault. 1996. J.G. Bishop. 1994. Evaluating approaches Van Der Voort, M.E., B. Bailey, D.E. Samuel, Population viability analysis of American to the conservation of rare and endangered ginseng and wild leek harvested in stochas- goldenseal (Hydrastis canadensis L.) and Schnell, D.E. 2002. Carnivorous Plants of the American ginseng (Panax quinquefolius Robbins, S.C. 2000. Comparative analysis of Schulze, W., E.D. Schulze, I. Schulze, and R. Vance, N.C., M. Borsting, D. Pilz, and J. Freed. trade monitoring mechanisms for American Oren. 2001. Quantification of insect nitrogen 2001. Special forest products species in- ginseng and goldenseal. Conservation Biol- utilization by the venus fly trap Dionaea formation guide for the Pacific Northwest. muscipula catching prey with highly variable isotope signatures. Journal of Experimental U.S. Department of Agriculture Forest Ser- vice, Pacific Northwest Research Station, Portland, Ore.
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