State of the Greater Fundy Ecosystem

GREATER FUNDY ECOSYSTEM RESEARCH PROJECT

UNB Faculty of Forestry and Environmental Management

State of the Greater Fundy Ecosystem

Forestry and Small Mammals in the
Hayward Brook Watershed

Gerry Parker
Environment Canada - Canadian Wildlife Service
P.O. Box 1590, 17 Waterfowl Lane, Sackville, NB
E0A 3C0

Small mammals were intensively sampled in randomly selected one hectare subplots within each of the larger riparian buffer zone plots established for the Hayward Brook Watershed Study.

GOAL

The purpose of the small mammal sampling was to determine the impact of various cutting treatments on small mammal populations.

METHODS

Snap traps were placed in, or around, woody debris - often stumps or fallen logs - for 8 consecutive nights during the month of August for each sampling year. The traps were checked each morning and any captured mammals were catalogued, placed in plastic bags and frozen.

RESULTS

A total of 1489 small mammals were captured an removed from the 8 study plots during the first 4 years of the study. The most common species captured, in order of abundance, were Red-backed Vole, Deer Mouse, Masked Shrew, Woodland Jumping Mouse, and Short-tailed Shrew. Other species of occasional occurrence were the Meadow Jumping Mouse, Smoky Shrew, and Water Shrew. The abundances and distribution of the species collected were typical of small mammal populations found in most second growth mixed Acadian forests.

Red-backed vole (Photo: Fundy NP)

A noticeable decline in the overall number of animals collected during the last two years of the study was probably due to a natural cyclical population change in Red-backed Vole. The rather drastic decline in the numbers of this species may have been due to severe winter conditions rather than the effects of forestry operations. Small mammals tend to suffer during winters with little snowfall. Such conditions occurred in the study area during the winters of 1994-95 and 1995-96.

Changes in the numbers and distributions of small mammals were examined between treatment and control plots:

Control Plots (No Treatment):

The two plots which received no treatments, provided a measure of population change over the course of the study. The Red-backed Vole was the most common small mammal on the control plots, followed by the Deer Mouse and Masked Shrew (Figure 1). Overall, small mammals declined on the control plots through the first four years of the study. The overall decline of 45% was mostly due to the population drop in the number of Red-backed Vole. The Masked Shrew was the most abundant species during the last two years of sampling.

30 m Buffer Plots:

No sampling was done on these plots in 1995 due to ongoing timber harvest in late summer. During the first two years of small mammal sampling (1993-94) populations increased, due mostly to an increase in the number of Red-backed Vole. Two years later (1996), following timber harvest and retention of a 30 m buffer, overall populations declined. Again, the overall drop in the number of mammals captured was mostly due to a drop in the numbers of Red-backed Vole (Figure 2). Over this time, Deer Mouse and Masked Shrew remained the same or increased slightly. It is possible that the changes are due to natural population changes and not to the timber harvest operations conducted in 1995.

60 m Buffer Plots:

The 60 m buffer plots were sampled in 1994 (pre-treatment) and 1995-96 (post-treatment). A third post treatment survey will be carried out in 1997. Unlike the other plots, the Red-backed Vole was not the most abundant small mammal on these plots. The Masked Shrew was the most abundant small mammal in 1994 and 1996 and the Deer Mouse was the most abundant in 1995 (Figure 3). Population declines in the Red-backed Vole were again responsible for the overall drop in the number of small mammals collected.

Best Management Practice Plots:

The Best Management Practice (BMP) Plots were subject to some degree of selection removal of trees. The actual on-site treatments were developed by Dr. Helmut Krause of the University of New Brunswick as part of a larger province-wide demonstration program. The BMP plots were sampled in 1993-94 (pre-treatment) and 1996 (post-treatment). Forest harvesting on these plots occurred in 1995 and prevented sampling. In the pre-treatment period, populations were stable. The most abundant species was Red-backed Vole followed by Deer Mouse and Masked Shrew (Figure 4). The first year of post-treatment saw a large population decline in small mammals, again associated with a large drop in the numbers of Red-backed Vole. As expected, the opening of the canopy and the accumulation of slash resulted in an increase in the number of shrews. Shrews tend to respond favourably to changes that occur from forest harvesting. Cutting tends to provide immediate cover (slash) and available food (insects) for shrews.

IMPLICATIONS FOR MANGEMENT

Following the final year of sampling (1997) the small mammal data will be analyzed in greater detail to look for possible changes in spatial arrangement as well as differences among samples in terms of morphology, sex and age structure and reproduction.

Further reading:

Parker, G., J. Pomeroy, and A. Chaisson. 1996. The Hayward Brook Watershed Study (a research project of the Fundy Model Forest): Interim Report (1993-1995). Fundy Model Forest. Sussex, N.B.

Parker, G.R. 1989. Effects of reforestation upon small mammal communities in New Brunswick. Canadian Field-Naturalist 103: 509-519.

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