Walt Klenner

Influence of Diversionary Food on Red Squirrel Populations and Damage to Crop Trees in Young Lodgepole Pine Forest

This study was designed to test the hypothesis that large-scale provision of diversionary food (sunflower seeds) would reduce red squirrel (Tamiasciurus hudsonicus) feeding damage to lodgepole pine (Pinus contorta) crop trees. Study areas with managed lodgepole pine stands were located near Vernon and Quesnel in south-central British Columbia, Canada. Large-scale applications of sunflower seeds were conducted on a manual basis in 1989, and by manual and aerial means in 1990, and an operational level by aerial means in 1991. Feeding damage to crop trees was assessed in control and treatment blocks. Populations of the red squirrel, northwestern chipmunk (Eutamias amoenus), and Columbian ground squirrel (Spermophilus columbianus) were sampled intensively by live-trapping on control and treatment blocks in 1990. Manual application of seed (clumped distribution) significantly reduced damage in the treatment block (11.3% of trees damaged) compared with the control (57.5% of trees damaged). Aerial application of seed (uniform distribution) also significantly reduced damage in replicated treatment vs. control blocks. Provision of diversionary food resulted in a temporary increase in the overall number of red squirrels caught on the treatment areas followed by a return to control levels within 6 wk. This increase was primarily the result of an increased number of transients in the trapped sample. The population density of resident (transients excluded) red squirrels did not increase when diversionary food was added. Similarly, we could not detect differences in reproduction, body masses, or survival of squirrels between control and food-supplemented areas. Northwestern chipmunks and Columbian ground squirrels also showed a temporary increase in density when food was added. Application of sunflower seed on an operational basis significantly reduced damage by squirrels in replicated study areas covering three different forest ecological zones. Provision of diversionary food is an effective strategy to protect intensively managed stands of lodgepole pine from red squirrel feeding damage.

Effects of Logging Pattern and Intensity on Squirrel Demography

Abstract We examined the effect of harvesting intensity and pattern on red squirrels (Tamiasciurus hudsonicus), northern flying squirrels (Glaucomys sabrinus), and yellow-pine chipmunks (Tamias amoenus) in mature inland Douglas-fir (Pseudotsuga menziesii glauca) forests in south-central British Columbia, Canada. We sampled squirrels 1 year before harvesting through 4 years after harvesting and estimated population parameters using open-population models. Relative to unharvested stands, each of the 3 species showed a strong response to tree removal. From 2 years to 4 years after logging, red squirrel density was 40% (SE = 7.1) lower in stands with 50% basal-area tree removal. From 1 year and up to 4 years after logging, northern flying squirrel density averaged 60% (SE = 5.2) lower in harvested treatments regardless of intensity or pattern of logging. In contrast, density of yellow-pine chipmunks increased markedly with increased logging intensity. Beginning 3 years after logging, yellow-pine chipmunk density was 734% (SE = 269) greater in stands with 50% basal-area tree removal. In the short term, harvesting intensity was a more important determinant of squirrel density than harvesting pattern. Retaining >10 m2 per ha of live residual stand structure in mature inland Douglas-fir forests maintained habitat for forest-dependent species such as red squirrels and northern flying squirrels, albeit at lower densities.

RESPONSE OF RED SQUIRRELS AND FEEDING DAMAGE TO VARIABLE STAND DENSITY IN YOUNG LODGEPOLE PINE FOREST

This study was designed to test the hypothesis that large-scale habitat al- teration by stand thinning would reduce red squirrel (Tamiasciurus hudsonicus) populations and feeding damage in young lodgepole pine (Pinus contorta) forest. An additional objective included integration of stand protection with an optimum thinning regime for growth rates of crop trees. Study areas were located near Penticton, Kamloops, and Prince George in south-central British Columbia, Canada. Each study area had three stands thinned to den- sities of -500 (low), 1000 (medium), and 2000 (high) stems/ha, with an unthinned, juvenile pine stand and old-growth pine stand for comparison. Squirrel populations were sampled intensively in the thinned stands from 1989 to 1991; feeding damage was assessed annually from 1989 to 1993. Five-year diameter and height increments of crop trees were measured in the thinned stands at Penticton and Prince George, and 4-yr increments in these stands at Kamloops. Red squirrel populations were significantly reduced in the low-density stand compared with either the medium- or high-density stands at Penticton and Prince George. Squirrels were less abundant in both the low- and medium-density stands at Kamloops. Squirrel populations in the unthinned and old-growth stands were similar or lower in abundance than those in the thinned stands. There were significantly higher numbers of red squirrel first captures in the medium- and high-density stands than in the low-density stand. There were no consistent significant differences between stands in proportion of squirrels breeding, recruitment, mean survival over summer and winter periods, or mean body mass. More trees per hectare were damaged in the high than in either low- or medium- density stands at all study areas. Mean diameter increments of trees in the low-density stands were significantly higher than those in the medium- and high-density stands at all study areas. Trees grew significantly faster in height in the high- than in the low-density stands at Penticton and Prince George; the converse was true at Kamloops. Manipulation of stand density on an operational basis in young lodgepole pine has clearly indicated that both stand protection from squirrel feeding damage and productivity of crop trees are enhanced by reducing the number of stems per hectare. This result has been achieved in replicated study areas covering three different forest ecological zones.

Response to Koford: Red Squirrels and Supplemental Feeding

Koford (1992) suggested that the increase in red squirrel ( Tamiasciurus hudsonicus ) populations in response to supplemental food may have reflected an increase or extension of movements of squirrels onto food-supplemented areas. However, deletion of transient squirrels (those captured only once or twice) from the analysis did not affect the 3–4 times greater number of squirrels on supplemented than control areas. Klenner (1991; unpublished) reported that behavioral observations indicated good agreement between capture frequency and territorial status of squirrels captured >2 times, and these animals were considered residents. Radiotelemetry measurements of territory size and behavior indicated that supplemental food decreased time spent away from territories by squirrels and increased movements through, and proportion of time spent defending territories. Average territory sizes in the presence of supplemental food, based on telemetry and direct observations, ranged from 0.15 to 0.29 ha, which were similar values to those calculated for Sullivans (1990) study by Koford (1992).