Amphibian assemblages

Katherine Maxcy, B.Sc. (UBC 1997), M.Sc. 2001
e-mail: kmaxcy@interchg.ubc.ca

Thesis Title: Impacts of riparian harvesting on the demography and movement patterns of terrestrial amphibians.

Background
Amphibian declines

  • Apparent global decline of many amphibian species
  • Potential causes include: habitat destruction, introduction of predators and competitors, pathogens, increased UV-radiation, acid precipitation, pollution from pesticides, and global warming.
  • Habitat alteration due to forest harvesting principle threat to amphibians in PNW
  • Correlative studies report lower densities of amphibians species on clearcuts compared to mature forests but reasons for lower densities unknown. Potential importance of riparian areas
  • Lower temperatures and higher humidity compared to upslope areas may provide optimal habitat for amphibians
  • few studies have focused on the terrestrial component of riparian ecosystems and the potential impacts forest harvesting has on obligate or facultative terrestrial riparian users such as amphibians.
  • need to understand amphibian riparian habitat requirements and how forest harvesting influences population and community-level attributes.

    General questions

  • What is the proximate response of amphibian species, both behaviourally and demographically, to forest harvesting?
  • How effective are riparian buffer strips in mitigating the effects of forest harvesting on terrestrial amphibian species

    Location: Malcolm Knapp Research Forest

    Treatments: 2 each of control, 30 m buffer, and clearcut sites.

    Methods

  • 3 X 3 grid of pitfall arrays established at each site
  • Arrays consist of four pitfall traps a arranged such that one pitfall is oriented both downslope and upslope of the stream as well as in the downstream and upstream direction. The arrays are intersected by a total of 20 m of drift fencing arranged in an X. This X arrangement of the pitfall arrays was designed to determine the direction of movement of the amphibian species.
  • Additional single pitfall traps and cover boards were also added to the grid to increased the probability of capturing amphibians in the areas between the arrays.
  • animal captured are marked using a combination of elastomer dye colors and toe clips, or for the larger individuals, PIT tags.
  • Other measurements taken: array captured, trap captured, snout-vent length, total length, mass, sex (if possible), age (juvenile or adult), individual mark, and whether the animal is newly capture or a recapture.
  • Information is also being recorded on environmental conditions, which affect the activity levels of most amphibian species such air temperature, precipitation and soil moisture.

    Project update
    The final data collection will finish at the end of November 1999, which includes posttreatment data. A pretreatment data summary is in press. Abstract for this paper is given below.

    ABUNDANCE AND MOVEMENTS OF TERRESTRIAL SALAMANDERS IN SECOND-GROWTH FORESTS OF SOUTHWESTERN BC

    KATHERINE A. MAXCY and JOHN RICHARDSON, Department of Forest Sciences, 2424 Main Mall, University of British Columbia, Vancouver, BC V6T 1Z4

    ABSTRACT: There is a lack of quantitative work on amphibian communities located in second-growth forests in British Columbia. The relative abundance, variation in capture rates, and movement patterns of terrestrial salamanders were investigated in six second-growth sites located in UBC’s Malcolm Knapp Research Forest. These data indicate that while amphibian species richness is similar among sites, total abundance is highly variable both within and among species between sites, with coefficients of variation in capture rates ranging from 44.2% to 245%. This high natural variation in amphibian abundance between forested sites of similar age and structure emphasises the importance of collecting baseline data before drawing conclusions about the impacts of forest harvesting on amphibians. In addition, aquatic-breeding salamanders (Ambystoma gracile and Taricha granulosa) moved significantly greater distances and their direction of movement was generally parallel to the stream, while terrestrial-breeding salamanders (Plethodon vehiculum and Ensatina eschscholtzii) moved less and randomly with respect to stream location. These results suggest breeding biology (i.e., aquatic vs. terrestrial) may be a useful predictor of species’ responses to timber harvesting.

    SPECIES AND HABITATS AT RISK 00(0):000-000
    Key words: Ambystoma gracile, amphibians, British Columbia, Ensatina eschscholtzii, movement, Plethodon vehiculum, riparian, second-growth, Taricha granulosa