Druscilla S. Sullivan

Use of predator odors as repellents to reduce feeding damage by herbivores. I: Snowshoe hares (Lepus americanus)

The effectiveness of predator odors (fecal, urine, and anal scent gland) in suppressing feeding damage by snowshoe hares was investigated in pen bioassays at the University of British Columbia Research Forest, Maple Ridge, British Columbia, Canada. A total of 28 bioassay trials tested the effects of these odors on hare consumption of willow browse and coniferous seedlings. Lynx and bobcat feces, weasel anal gland secretion, and lynx, bobcat, wolf, coyote, fox, and wolverine urines resulted in the most effective suppression of hare feeding damage. Novel odors of domestic dog urine and 2-methylbutyric acid did not reduce feeding. A field bioassay with lodgepole pine seedlings and weasel scent provided significant results comparable to the pen bioassays. The short-term (up to seven days) effectiveness of these treatments was more likely due to evaporative loss of the active repellent components of a given odor than habituation of hares to the stimulus. Predator odors as repellents have a biological basis compared with the anthropomorphic origins of commercial repellents. When encapsulated in weather-proof controlled-release devices, these odors could provide long-term protection for forestry plantations and agricultural crops which experience hare/rabbit feeding damage.

STAND STRUCTURE AND SMALL MAMMALS IN YOUNG LODGEPOLE PINE FOREST: 10‐YEAR RESULTS AFTER THINNING

Management of forested landscapes for biological diversity is a major objective across North America. Perhaps the greatest potential to diversify future forests lies in the vast areas of young second-growth stands which may be managed silviculturally to accelerate ecosystem development. This study was designed to test the hypotheses that large-scale precommercial thinning, at ages 17–27 yr, to various stand densities would, over the 10-yr period since treatment, enhance: (1) productivity of lodgepole pine (Pinus contorta) crop trees, (2) stand structure attributes, and (3) species richness and diversity of forest floor small-mammal communities. Study areas were located near Penticton, Kamloops, and Prince George in south-central British Columbia, Canada, in three forest ecological zones. Each study area had three stands thinned to densities of ∼500 (low), ∼1000 (medium), and ∼2000 (high) stems/ha, with an unthinned juvenile pine and old-growth pine stand for comparison. Understory vegetation was measured ...

Use of predator odors as repellents to reduce feeding damage by herbivores : III. Montane and meadow voles (Microtus montanus andMicrotus pennsylvanicus).

This study investigated the influence of the major anal-gland compounds from the stoat (Mustela erminea) and fecal and urine compounds from the red fox (Vulpes vulpes) in generating an avoidance response by montane voles (Microtus montanus), as well as suppressing feeding by montane and meadow (M. pennsylvanicus) voles on apple trees in orchards. In trap bioassays, a 1∶1 mixture of 2-propylthietane and 3-propyl-1,2-dithiolane significantly reduced vole captures. Other mixtures of stoat compounds reduced the number of new voles captured but not total individuals. 2,5-Dihydro-2,4,5-trimethylthiazoline, a component of fox feces, significantly reduced vole captures in one of two bioassays. Deer mice (Peromyscus maniculatus) did not show a negative response to any predator odor. In overwinter field bioassays, mixtures of 2-propylthietane and 3-propyl-1,2-dithiolane clearly reduced vole feeding on apple trees in four test blocks. 2,5-Dihydro-2,4,5-trimethylthiazoline and a synthetic fox urine mixture also significantly reduced vole attack in respective orchard blocks. Similarly, the intensity of vole feeding, in terms of amount of bark and vascular tissues removed from trees, was reduced by 60% to 97% in predator odor treatments compared with the control. Our study reports the first long-term (four to five months) use of synthetic semiochemicals as area repellents for crop protection from vole feeding damage.

Use of predator odors as repellents to reduce feeding damage by herbivores : II. Black-tailed deer (Odocoileus hemionus columbianus).

The effectiveness of predator odors (fecal and urine) in suppressing feeding damage by black-tailed deer was investigated in pen bioassays at the University of British Columbia Research Forest, Maple Ridge, British Columbia, Canada. A total of eight bioassay trials tested the effects of these odors on deer consumption of salal leaves and coniferous seedlings. Cougar, coyote,and wolf feces as well as coyote, wolf, fox, wolverine, lynx, and bobcat urines provided the most effective suppression of deer feeding damage. Novel odors of ammonia and human urine did not reduce feeding. Predator fecal odor formulations in direct foliar application, adhesive application, and in plastic vials were all effective in suppressing deer feeding. Of all urines tested, coyote provided the most consistent suppression of deer browsing on salal. Deer consumed significantly more untreated Douglas fir and western red cedar seedlings than those protected by coyote urine odor. The active repellent components of predator odors which suppress deer feeding may be suitable for encapsulation in controlled-release devices which could provide long-term protection for forest and agricultural crops.

Use of predator odors as repellents to reduce feeding damage by herbivores. IV: Northern pocket gophers (Thomomys talpoides)

This study investigated the influence of the major anal-gland compounds from the stoat (Mustela erminea) and ferret (M. putorius) in generating an avoidance response by northern pocket gophers (Thomomys talpoides) in tree fruit orchards in the Okanagan Valley of British Columbia, Canada. A secondary objective assessed the impact of additional predator odors on gopher avoidance behavior in laboratory bioassays. In field bioassays, a 1: 1 mixture of 2-propylthietane and 3-propyl-1,2-dithiolane, as well as 3,3-dimethyl-1,2-dithiolane, placed in gopher burrows did not reduce the number of gophers colonizing treatment versus control grids in orchard blocks. However, these predator gophers did dramatically alter the distribution of gophers. Significantly more gophers were captured at perimeter than nonperimeter trap stations on treatment versus control grids in two of three orchards. In all orchards, significantly more gophers were captured at perimeter stations after the predator odors had been placed in burrows than prior to the start of the experiment. Gophers clearly avoided 2,5-dihydro-2,4,5-trimethylthiazoline, a component of fox (Vulpes vulpes) feces, but did not avoid 2,2-dimethylthietane from the mink (M. vison) or 3-methyl-3-butenyl methyl sulfide from fox urine in laboratory bioassays. Poor avoidance was also recorded for 3,3-dimethyl-1,2-dithiolane, although this may be due to the state of polymerization of this compound. An improved formulation is required to dispense these semiochemicals in controlled-release devices within orchards and other forest-agricultural areas.

SMALL MAMMALS AND STAND STRUCTURE IN YOUNG PINE, SEED-TREE, AND OLD-GROWTH FOREST, SOUTHWEST CANADA

Alternative silvicultural systems to clearcutting are receiving considerable attention in Pacific Northwest forests of North America. Understanding the implications of these harvesting systems on stand structure and biodiversity through time is a fundamental aspect of forest ecosystem management. This study was designed to test the hypothesis that diversity of stand-structure attributes and forest floor small-mammal communities will increase from young pine to seed tree to old-growth forest. The study area was within mixed Douglas-fir (Pseudotsuga menziesii)–lodgepole pine (Pinus contorta) forests within the Montane Spruce biogeoclimatic zone near Summerland in south-central British Columbia, Canada. This retrospective study had three replicate stands each of 17-yr-old “young pine” (clear-cut harvested), “seed tree” composed of young pine with Douglas-fir seed trees, and uncut “old-growth” composed primarily of Douglas-fir and lodgepole pine. Stand-structure attributes (coniferous tree layers and understo...

THE USE OF ALTERNATIVE FOODS TO REDUCE LODGEPOLE PINE SEED PREDATION BY SMALL MAMMALS

(1) Lodgepole pine seed predation by deer mice and related small mammals has been studied at three interior areas of British Columbia, Canada. (2) When the distribution and abundance of rodent seed predators was taken into account, the amount of seed damage was directly related to the relative density of animals. Deer mice and voles destroyed the majority (>85%) of pine seed within 3 weeks of application when the abundance of these rodents was >5 animals/ha. In areas with prolonged low densities (<3 animals/ha), lodgepole pine showed very good survival (60-70% after 3 weeks). (3) The use of sunflower seeds as an alternative food successfully reduced pine seed predation. A ratio of two sunflower seeds to one pine seed produced a range of 50-82% survival of pine seed after 3 weeks and 42-72% after 6 weeks compared with 12-15% and 8-10% survival of pine without sunflower. (4) This technique could be used for direct seeding cutover forest lands in areas suitable for growth of lodgepole pine in North America.

Population dynamics and regulation of the Douglas squirrel (Tamiasciurus douglasii) with supplemental food

SummaryIf food is in short supply, then provision of addition food should increase the density of Douglas squirrels. A squirrel population was supplied with extra food during the summers of 1977 and 1978 and winter of 1978–1979 in coastal coniferous forest at Maple Ridge, British Columbia. Food produced a 5-to 10-fold increase in squirrel density compared with control populations. Control densities generally varied from 3 to 10 squirrels per trapping area with the experimental population increasing to 65 animals during the winter feeding. This irruption was produced by immigration, more reproduction in females, and increased survival. After the food was withdrawn, the population declined to a level comparable with the controls. We conclude that Douglas squirrel populations fluctuate in accordance with the abundance of food. Territorial behavior may space individuals within populations of Tamiasciurus douglasii but to density levels determined by the available food supply.

Experimental studies of rainbow trout populations exposed to field applications of Roundup® herbicide

This paper reports the effects of Roundup®3 herbicide (MON 02139) on rainbow trout viability and behavior in several field experiments at the University of British Columbia Research Forest. Laboratory and field 96-hr LC50 values were similar: 54.8 and 52.0 mg/L. Avoidance-preference data indicated that fish would avoid lethal levels of Roundup. Operational application of Roundup at the recommended field dose of (2.2 kg a.e./ha), as well as 10× and 100× field dose resulted in no mortality to rainbow trout in field streams. Results indicate that operational spraying with this herbicide for weed control should not be detrimental to rainbow trout populations. Improper use or accidental spills of Roundup could be avoided by rainbow trout and should not be lethal if diluted in a moderately-flowing stream.

Influence of conventional and chemical thinning on stand structure and diversity of plant and mammal communities in young lodgepole pine forest

Abstract Silvicultural practices that provide a wide variety of vegetative composition and structure (habitats) in young stands should help manage for biological diversity across forested landscapes. This study was designed to test the hypotheses that: (i) abundance and diversity of stand structure attributes (species diversity and structural diversity of herb, shrub and tree layers) and forest floor small mammal communities, and (ii) relative habitat use by large herbivores, will increase from unthinned to conventionally thinned to chemically thinned stands of young lodgepole pine (Pinus contorta) forest. Replicate study areas were located near Summerland, Kelowna and Williams Lake in south-central British Columbia, Canada. Each study area had three treatments: a conventionally thinned, a chemically thinned and an unthinned stand. Pre-commercial thinning was conducted in 1993. Coniferous stand structure and understory vegetation were measured prior to thinning in 1993 and 5 years later in 1998. Small mammal populations were sampled intensively from 1993 to 1998. Relative habitat use by large herbivores was sampled in 1998. Our results indicate that chemical thinning of young lodgepole pine stands produced an aggregated pattern of crop trees compared with stands subjected to conventional thinning. Diameter growth of crop trees in the chemically thinned stands was similar to that in the conventionally thinned, but also to that in unthinned stands. Although horizontal stratification (aggregates of trees) was enhanced, vertical stratification (structural diversity of vegetation) was less in the chemically than conventionally thinned stands. Abundance and diversity of understory vegetation and small mammal communities were generally unaffected by stand thinning in these particular installations. Relative habitat use by mule deer (Odocoileus hemionus) occurred in a gradient from highest in the conventionally thinned stand to lowest in the unthinned stand. Habitat use by snowshoe hares (Lepus americanus) tended to have the opposite trend. Moose (Alces alces) exhibited no difference in habitat use among stands. Thus, although there were few differences among treatment stands, chemical thinning could be used to develop an aggregated pattern of crop trees in pre-commercially thinned stands to maintain habitat for herbivores such as snowshoe hares and mule deer. Understory plant and forest floor small mammal communities would be maintained in these stands as well.