Introduction
Coastal Tailed Frogs breed in cool and clear mountain streams. Due to disturbances in their habitat that result in the changes of the quality or quantity of the water or loss of riparian forest cover they are classified as a Blue listed species in British Columbia. There are two issues with the Coastal Tailed Frogs, one of them being the cold, continental climate and elevation that makes the population appear infrequent in the area, the second being the finite number of pathways that connect the eastern range of the frogs with the west where they originate from. Forest harvesting, road building, water intakes and run-of-river power projects as well as non-native fish all pose a threat to the Coastal Tailed Frog.
Background of the Research Project
It was the overall objective of the inventory and habitat assessment to keep the Coastal Tailed Frog populations in the Bridge-Seton area. This will be achieved by undertaking inventory, followed by assessments and restoration.
Methods, Materials and Study Area
The studies were conducted between Pemberton and Lillooet; the eastern range limit of the frog is located in this area. On the southwest, the border was defined by the divide into the Lillooet and Birkenhead Rivers and on the northwest by the southern Chilcotin Mountains. On the northeast the boundary was the Shulaps Range and on the southeast the Cayoosh Range. The area includes the watershed that is upstream of the Terzagi Dam on the Bridge River as well as upstream of the mouth of Seton Lake. This was called the Bridge-Seton study area. Samplings were done mostly south of the Bridge River with a few northern watersheds targeted too. Targets in the Seton system included basins the the Gates Pass area as well as both shores of the Seton and Anderson Lakes. A few research questions were used as guidance for the samplings, including the identification of possible dispersal corridors, assessment of microclimate effects and the evaluation of the morphometric variables of the basin on distribution. The samplings happened from July 1 to 18, 2009. During the search cobbles and small boulders were flipped, the underside of large boulders were swept and tadpoles were captured by raking through pebbles. Each survey site had habitat parameters that were measured including date, creek ID, weather, elevation, water temperature, data of the tailed frog and many more components.
Results of the Study
In the end 125 creeks and reaches were surveyed for Coastal Tailed Frogs. In only 8% of the streams was the species detected. A total of 58 tadpoles were observed during the whole survey. There were no tailed frogs found in the Tommy Creek watershed south of Carpenter Lake or in the Shulaps creek watershed west of the Yalakom River. Neither were they found north or east of Carpenter Lake. Through the survey it was discovered that the creeks where the species was found were warmer, less steep and had more boulders than the ones where no frogs were found. Restoration opportunities were not identified due to the low discovery of Coastal Tailed Frogs in the Bridge-Seton area.
Discussion
It was unexpected that the tailed frog was absent in most of the study area including historic locations at Shulaps Creek and Tommy Creek watersheds . Many streams in the Bridge-Seton area considered as suitable habitat surprisingly showed no frogs. The surveys show that the Coastal Tailed Frog has had a decrease in range and is now gone from two historic locations. The population has been low in the past and this information was known during this survey. The isolation from the coastal population might have contributed to the trends observed in the area. Due to lack of historic data it is hard to tell what the exact reason for the decrease in population is.
Suggested Action
There should be more surveys conducted in the future to confirm the findings of the past research. They should happen on a more regular basis to follow the tailed frog population distribution. It is recommended to initiate more projects for other at-risk species as well.
Conclusion of Research
To conclude,the surveys only discovered frog populations in 8% of the streams. It was unexpected to find such low numbers of population in the Bridge-Seton study area especially including the historic locations. More surveys should be done to monitor the population density of the Coastal Tailed Frog. More projects for other species at risk might be considered a higher priority due to the low density of the frogs and their closeness to the BC Hydro operations.
- Source Elke Wind. November 2009. FINAL REPORT Coastal Tailed Frog Inventory and Habitat Assessment BCRP project number: 09.W.BRG.01. Prepared by E. Wind Consulting, for BC Hydro Bridge Coastal Fish and Wildlife Restoration Program. Available at : https://a100.gov.bc.ca/pub/acat/documents/r40755/09_W_BRG_01_frogs_1389028246450_9014565261.pdf [Accessed 03/2021].