Choosing the optimal conservation strategy for a rare butterfly based on movement behavior

Background/Question/Methods

Urban development can fragment landscapes, restricting the movement of rare species between remnant populations and placing them at a greater risk for extinction. Fragmentation creates distinct boundaries between habitat and non-habitat, and is particularly problematic for organisms that evolved in a continuous landscape. Thus, the behavior of these animals at habitat edges may provide a strong indication of how fragmentation affects movement between populations. We investigated the effects of urban fragmentation on the behaviors and population structure of Atrytonopsis new species 1, a newly identified butterfly endemic to a 30-mile stretch of barrier islands in North Carolina. The habitat of Atrytonopsis consists of sand dunes that are now fragmented by extensive development. We studied the behavior of Atrytonopsis individuals to determine how they respond to habitat edges. Stepping stones, small patches of habitat in between larger patches, would be an appropriate conservation strategy if Atrytonopsis readily moves through non-habitat. If the butterfly is reluctant to cross an edge into non-habitat, then linear strips of habitat connecting populations may be a more effective strategy. To determine the willingness of Atrytonopsis to enter non-habitat, we placed butterflies at the edge of sand dune habitat and three types of non-habitat: high intensity development, low intensity development, and shrubs. At each of these edges, we recorded the initial and final direction in which the butterfly moved.  

Results/Conclusions

Our results suggest that Atrytonopsis preferentially chooses sand dune habitat at a rate of about 75%, regardless of the type of edge. These results are consistent with genetic and mark-recapture studies that suggest that urban development is not a barrier to movement; rather, natural barriers such as oceans and maritime forest play a more important role in limiting butterfly movement. Given that Atrytonopsis does move through non-habitat, a stepping-stone approach would be suitable for maintaining connectivity of the butterfly throughout its range.