Small Mammal Response to
Habitat Change Following Fire in
the Taiga of South-eastern Manitoba

Monica Reid-Wong

Taiga Biological Station, Department of Zoology,
University of Manitoba, Winnipeg, Manitoba R3T 2N2

 

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Reid-Wong, Monica. 2003. Small Mammal Responses to Habitat Changes Following Fire in the Taiga of Southeastern Manitoba. M.Sc. Thesis, University of Manitoba:384 pp.

 

Section I

Populations of small mammals were sampled annually by removal trapping in six different habitats over a twenty-five year period (1977-2001) near Wallace Lake, Manitoba. A total of 2,384 small mammals and 179 sciurids representing 14 species were captured in 43,800 trap-nights. The three most common species captured, in descending order of abundance, were Clethrionomys gapperi (red-backed vole), Sorex cinereus (masked shrew), and Peromyscus maniculatus (deer mouse). Changes in small mammal populations following fire were observed over time and the temporal patterns of short-term fluctuation and long-term synchrony were examined.

Deer mice increased within the first few years following the burn to populations above pre-fire levels; subsequent trapping sessions were unable to duplicate these early post-fire capture levels for Peromyscus. Red-backed voles also increased in abundance within three months after the fire on most sites, but they soon experienced a rapid decline in numbers until their short-term recovery during the mid-to late-1980s.

Similarities in the fluctuating abundance of red-backed voles were noted across several of the sampling plots, providing some evidence to suggest that extrinsic agents are affecting Clethrionomys populations through the synchronous occurrence of peak abundance years. Additionally, evidence of synchrony in small mammal biomass production was noted, with peak accumulations every 3 to 4 years.

Section II

The effects of secondary succession following forest fire on the structure of plant communities and the population attributes of small mammal communities were investigated in six different habitats surrounding Taiga Biological Station. Changes in small mammal community structure were assessed using several methods.

Peak periods of relative abundance and biomass for Peromyscus occurred during 1980-1985 (within 5 years of the fire). Clethrionomys experienced peak periods of relative abundance during 1986-1990, the 5- to 10- year post-fire period. The rank abundance curve of the small mammal fauna assumed a logarithmic shape, indicative of habitats that have a small number of abundant species, with a larger number of species of intermediate abundance but of few individuals. Changes in trophic contribution revealed that Peromyscus, the granivore-omnivore, rapidly exploited the recently-burned habitat. Clethrionomys, the grazer-omnivore, experienced brief initial increases shortly after the fire but overall required a more lengthy recovery period. Species richness and diversity of the small mammal community increased for a short period of time of several years across most sites following the 1980 burn.

The rates of vegetation recovery within the small mammal habitats at TBS were found to be site specific and dependent on the degree of fire damage.

Section III

The influence of biotic and abiotic features in small mammal habitat was examined to determine if certain factors affected species distribution and abundance. Individual microhabitat variables, including vegetation and structural characteristics of the microsite (a 4 m2 area surrounding each trap site) were found to be less reliable indicators of species presence than overall macrohabitat characteristics (e.g, blackspruce bog, mixed coniferous-deciduous forest, jackpine sandplain) of the small mammal nvironment.

The method of small mammal sampling can introduce bias into the collection and interpretation of data. Museum Special traps captured most of the small mammal fauna in this area while Schuyler traps proved more variable in terms of weight capture response. Highly productive small mammal plots (i.e., the number of individuals captured and degree of habitat heterogeneity) had more multiple species captures at trap stations than plots reporting fewer small mammal captures, with less vegetation heterogeneity.

Male animals of the different species were captured more frequently than females. Although fewer Clethrionomys were captured on fire-recovering Pinus banksiana plots, a higher proportion of these individuals were reproductive females. Actual red-backed vole captures were larger on mixed coniferous/deciduous plots, but consisted of fewer reproductive females.

 


 

This page created August 6, 2005.

 

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