Effects of Population Size on Beetle Corridor Use Kaisha A. Pittser and Kristen A. Baum

1. Effects of Population Size on Beetle Corridor Use Kaisha A. Pittser and Kristen A. Baum Department of Zoology, Oklahoma State University, Stillwater, OK 4” 2.5” 5.5” Release Patch Corridor • Results • There was a significant difference in corridor choice in the trials containing 4, 8, and 16 beetles. No difference was observed for trials with one or two beetles. • One beetle: χ2=1.000, d.f.=3, p=0.8013 • Two beetles: χ2=3.308, d.f.=3, p=0.3466 • Four beetles: χ2=13.077, d.f.=3, p=0.0045 • Eight beetles: χ2=15.780, d.f.=3, p=0.0013 • Sixteen beetles: χ2=22.864, d.f.=3, p=0.0001 • Approximately 60-68% of beetles did not enter a target patch in each of the trials. Abstract A lot of research has focused on conservation corridors, but it is not clear if population size (or density) can affect corridor use by animals. My hypothesis is animals in small populations (or low densities) will use the corridors that are the least resistant to movement (i.e., easiest to walk on), but as the population sizes (or densities) increase, animals will start using the corridors that are more resistant to movement (i.e., harder to walk on). I found that beetles in trials with 4, 8, and 16 individuals showed a significant preference for corridor types that were the least resistant to their movement. This suggests that choice of corridor types depends on corridor resistance to movement. Conservationists should consider resistance to movement when designing corridors to increase movement between isolated habitat patches. Target Patch Corridor Target Patch 4” 3” Target Patch Corridor Discussion and Conclusions For the trials that showed a significant difference, the beetles always selected the poster board and duct tape corridors the most. Even though the population size increased, the beetles did not start using corridors of other types more often. This suggests that choice of corridor type is not dependent on population size. One possible explanation is that the poster board and duct tape are the least resistant to movement for the beetles or the most similar to substrates in their natural habitats. Another possible reason is that the beetles were choosing corridors based on other factors, such as orientation or some other unidentified factor. It is also possible that the range of population sizes used in this experiment were not large enough to detect a difference. These results suggest that conservationists do not need to consider population size when designing corridors. They also indicate that resistance to movement is an important consideration for corridor design. Introduction Conservation is a major issue, especially in fragmented areas. Corridors are a strategy used to increase the connectivity between fragmented patches of habitat. Corridors are linear features that are used to connect fragmented patches of an organism’s natural habitat. It has been found that corridor length affects if beetles find connected patches (Romero 2010). It has also been found that the matrix (the areas of non-habitat between habitat patches) is an important factor to consider when creating corridors between fragmented patches (Baum et al. 2004). The purpose of this research is to evaluate if darkling beetle population size will affect corridor use by beetles. My hypothesis is that at small population sizes (1, 2 or 4 individuals) the beetles will use the corridors that are the least resistant to movement (i.e., duct tape and poster board), and as population size increases (8 and 16 individuals) the beetles will begin using the more resistant corridors (i.e., the packing tape). Corridor Duct tape Poster board Packing tape Masking tape Target Patch Figure 1: Design of the artificial landscape. Future Directions Future research should evaluate if the beetles select corridors based on orientation, since this factor was not controlled for in this experiment. Additional population sizes could be tested, as well as additional surfaces, with different resistances to movement. • Materials & Methods • Landscapes were made from poster board with duct tape, masking tape, and packing tape (Figure 1). • Darkling beetles were kept at ambient conditions and tested once per week. • Before the start of each trial, a slice of potato was put inside each target patch to represent habitat (or an area with food resources). • A darkling beetle was placed in the center release patch under a 5cm diameter Petri dish for 15 second to allow it to acclimate. • The Petri dish was removed and the beetle was allowed to move around the poster board for 5 minutes. • The patch choice and time of patch choice was recorded. • The experiment was repeated for 1, 2, 4, 8, and 16 beetles at a time. • Each group was tested 20 times with different beetles each time. • I used a Chi-square test to evaluate if beetle preference for different corridor types differed within trials with different numbers of beetles. • Literature Cited • Baum, Kristen A, et al. "The Matrix Enhances The Effectiveness Of Corridors." Ecology 85.10 (2004): 2671-2676. • Morales, Juan M and Stephen P Ellner. "Scaling Up Animal Movements In Heterogeneous Landscapes:." Ecology 83.8 (2002): 2240-2247. • Romero, Susan A, et al. "Movement Behavior of Red Flour Beetle: Response to Habitat Cues." Environmental Entomology 39.3 (2010): 919-929. Figure 2: Number of beetles per patch.