COS 122-4 - Integrating three scales of analysis to compare Apalone spinifera (spiny softshell turtle) nesting habitat in dammed versus undammed rivers
Undergraduate research student Rocky Mountain College Billings, Montana, United States
Background/Question/Methods
Riverine turtles’ life cycles are highly adapted to the dynamic river systems in which they live. Apalone spinifera (spiny softshell, APSP), for example, rely on complex habitat produced through spring-flood pulse flows and minimal anthropogenic modifications for their life processes, particularly during the nesting period. The extent and quality of this sort of habitat appears to be increasingly limited by the effects of dams on river systems such as on the Bighorn River, located in south-eastern Montana. In comparison, the Yellowstone River is a relatively undammed river which experiences natural flood pulses. Little research has been done that focuses on how anthropogenic modifications, especially dams, affect spiny softshells’ habitats and population structure. Three scales of data were utilized (ground observations of turtle nesting sites; high-resolution (~2cm) unmanned aerial system (UAS) imagery; and medium resolution (10m) Sentinel-2A imagery, to generate a viable estimate of the amount of available spiny softshell nesting habitat in 32.2 km study areas along both the Yellowstone and Bighorn rivers in Montana. Since the collection of UAS imagery is a time consuming process, a 15-hectare polygon was flown on each river for the comparison between Sentinel-2A and UAS nesting habitat classification. Additionally, demographic data was collected.
Results/Conclusions
Using this smaller study area of 15-hectares within the full 32.2km study as a model for differences in nesting habitat availability between UAS imagery and Sentinel-2A imagery resulted in about 54% nesting habitat in common on the Yellowstone and almost 86% in common for the Bighorn. These percentages at the 15-hectare scale were used to create a corrected full study nesting habitat estimation for the entire 32.2km study area. When run, the Yellowstone River had almost nine times more APSP nesting habitat than that of the Bighorn. From an ecological and conservation perspective, this is important to consider. Demographic data for these two rivers revealed a limited number of recently recruited juvenile turtles within the sampled population in the Bighorn River (6.82%) compared to the Yellowstone (20.74%). These findings apply to river management and restoration in the consideration of persistence of APSP particularly within a dammed river.
