Department of Forest Sciences
3041-2424 Main Mall, UBC
Vancouver, B.C. V6T 1Z4
Position: M.Sc. Candidate
Study topics: The effects of fine, inorganic sediment and nutrients fluxes on larval development and over-summer survival of the Western Toad.
A number of studies have suggested a negative impact from sediment influxes from timber harvesting and road construction on stream-dwelling amphibians and fish populations (Corn and Bury 1989, Newcombe and Jensen1996), yet little is known about the effects sediment on pond-dwelling species. Due to slow moving and often turbid waters, ponds accumulate can large deposits of fine-sediment which interfere with primary productivity (Powers 1990, Ryan 1991) and thus grazer communities. Through the use of mesocosms experiments, I propose to study the effects of suspended sediments on tadpole survival and development in the western toad with respect to their algal resources and the carry-over effects to juvenile survival.
The western toad, Bufo boreas, is a pond-breeding species with herbivorous and highly gregarious larvae. Adults are primarily terrestrial, inhabiting up-land environments during the non-breeding season, but are explosive breeders producing between 12000-16500 eggs per clutch (Samollow 1980). Tadpoles mature and metamorphose in 5-7 weeks and emerging toadlets frequently form post-metaphoric mass aggregations in the thousands. It has been suggested that juvenile survival is the critical life-stage for population maintenance in the western toad (Vonesh and De la Cruz 2002). Thus, the effects of the larval environment on metamorph size or timing of emergence, which influence juvenile survival (Smith 1987), may be particularly important for toad populations. Currently the western toad is provincially Yellow-Listed and listed as a ‘Species of Special Concern’ by COSEWIC due to range contractions in the southern portion of their distribution.
The first part of my experiment will take place on UBC’s South Campus of UBC using cattle tank mesocosms to create artificial pond environments in which to raise tadpoles. Tadpoles will be subjected to manipulated levels of fine-inorganic sediment and nutrients, and the effects of the treatments on primary productivity, habitat variables and tadpole development will be monitored.
The second part of the study will take place at the Malcolm Knapp Research Forest. Over-summer survival of juveniles will be assessed by transferring recently metamorphosed toadlets of varying sizes and emergence dates to field enclosures and monitoring their growth and survival. Field enclosures are located in both mature forest stands and recent clear-cuts to allow us to investigate the impact of habitat type on survival.
Other Interests: I completed my Bachelors at Queen’s University in Kingston, Ontario in 2005. At Queen’s I undertook an undergraduate thesis project focusing on the reproductive trade-offs of re-nesting and maternal investment among clutches Barn Swallows at the Queens University Biology Station. Along with conservation and ecology I am keenly interested in issues of international development and resources management. Before and during my undergraduate degree I took part in two overseas volunteer projects in Sri Lanka and Bolivia working with local communities and on agricultural development projects. I enjoying travelling and outdoor activities, especially hiking and camping.
Corn, P.S. and R.B. Bury. 1989. Logging in western Oregon: responses of headwater habitats and stream amphibians. Forest Ecology and Management, 29: 39-57.
Newcombe, C.P. and J.O.T. Jensen. 1996. Channel suspended sediment and fisheries: a synthesis for quantitative assessment of risk. North American Journal of Fisheries and Management 16:693-727.
Power, M.E. 1990. Resource enhancement by indirect effects of grazers: armoured catfish algae and sediment. Ecology, 71(3): 897-904.
Ryan, P.A. 1991. Environmental-effects of sediment on New Zealand streams- a review. New Zealand Journal of Marine and Freshwater Research 25(2): 207-221
Samollow, P.B. 1980. Selective mortality and reproduction in a natural population of Bufo boreas. Evolution 34:18-19.
Smith, D.C 1987. Adult recruitment in chorus frogs- effects of size and date at metamorphosis. Ecology, 68(2): 344-350
Vonesh, J.R. and O. De la Cruz. 2002. Complex life cycles and density dependence: assessing the contribution of egg mortality to amphibian declines. Oecologia, 133:325-333