Provide diversionary feeding to reduce crop damage by mammals to reduce human-wildlife conflict

How is the evidence assessed?
  • Effectiveness
    50%
  • Certainty
    50%
  • Harms
    0%

Source countries

Key messages

  • Six studies evaluated the effects of providing diversionary feeding to reduce crop damage by mammals to reduce human-wildlife conflict. Three studies were in Canada and one was in each of France, Spain and Austria.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

BEHAVIOUR (0 STUDIES)

OTHER (6 STUDIES)

  • Human-wildlife conflict (6 studies): Three of six studies (including four controlled and one before-and-after study) in Canada, France, Spain and Austria found that diversionary feeding reduced damage by red squirrels to pine trees and European rabbits to grape vines, and resulted in fewer red deer using vulnerable forest stands. Two studies found that diversionary feeding did not reduce damage by voles to apple trees or wild boar to grape vines. One study found mixed results on damage by voles to crabapple trees depending on the food provided.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

  1. A randomized, controlled study in 1983–1984 at an orchard in British Columbia, Canada (Sullivan & Sullivan 1988) found that diversionary feeding with treated plywood sticks did not reduce damage by voles Microtus spp. to spartan apple Malus domestica trees. The percentage of apple trees damaged by voles did not differ significantly in orchard blocks with treated plywood sticks (32%) or those without sticks (36%). Trees with treated plywood sticks around them had more bark and tissues removed by voles (average 20–27 cm2/tree) than trees without sticks (5 cm2/tree), although the difference was not tested for statistical significance. In November 1983, three treatments (plywood sticks treated with sucrose, soybean oil or sorbitol) were randomly assigned to each of three orchard blocks of 100 spartan apple trees (15 and 30 years old). Three plywood sticks (5 x 37.5 cm, 9 mm thick kiln-dried Douglas fir Pseudotsuga menziesii) were placed in a triangle around each tree, 1–2 cm from the base. One control orchard block had no plywood sticks. The area of bark and vascular tissues removed by voles was measured on each of the 400 trees in March 1984.

    Study and other actions tested
  2. A randomized, controlled study in 1984–1985 at a newly planted orchard in British Columbia, Canada (Sullivan & Sullivan 1988) found that diversionary feeding with bark-mulch logs treated with soybean oil reduced damage by montane voles Microtus montanus to crabapple Malus spp. trees, but logs treated with apple or apple and soybean oil did not. Orchard blocks with logs treated with soybean oil had a lower percentage of trees damaged by voles (25%) and trees with stem or root girdling (4%) than those without logs (63% damaged; 25% girdling). The difference was not significant between orchards with logs treated with apple (46% damaged; 17% with girdling) or apple and soybean oil (58% damaged; 33% with girdling) and those without logs. In November 1984, logs made from sifted Douglas fir Pseudotsuga menziesii bark mulch mixed with wax and one of three treatments (soybean oil, apple powder or apple powder and soybean oil mixed together) were randomly assigned to each of three orchard blocks of 24 one year old crabapple trees. Three logs were placed around each tree, 8–10 cm from the base. Additional logs were added as required in December 1984–February 1985. One control orchard block had no logs. Numbers of trees with vole damage and stem or root girdling in each of the four orchard blocks were recorded in March 1985.

    Study and other actions tested
  3. A controlled study in 1989–1990 of managed forest in British Columbia, Canada (Sullivan & Klenner 1993) found that diversionary feeding reduced damage by red squirrels Tamiasciurus hudsonicus to lodgepole pine Pinus contorta crop trees. In each of three years, lodgepole pine blocks with diversionary feeding had a lower percentage of trees damaged by squirrels (average 5–11%) and fewer damage wounds (average 0.02–0.13 wounds/tree) than control blocks without diversionary feeding (average 26–61% of trees damaged; 0.5–2 wounds/tree). In May and June 1989, sunflower seeds were manually distributed in piles (45 kg/ha) within a 20-ha lodgepole pine block, and one 20-ha control block had no seeds. In 1990, two 15-ha blocks had seeds manually distributed in piles (22.7 kg/ha), two 20-ha blocks had seeds distributed by helicopter (22.7 kg/ha), and two 15-ha control blocks had no seeds. In 1991, seeds were distributed across three areas of 131–200 ha by helicopter (20 kg/ha), and three control areas had no seeds. Squirrel damage was recorded within 16–24 circular plots located every 50 or 100 m in a grid pattern within each treatment and control block or area in 1989, 1990 and 1991.

    Study and other actions tested
  4. A before-and-after study in 1990–1993 of 283 vineyards in Puechabon, France (Calenge et al. 2004) found that diversionary feeding did not reduce damage by wild boar Sus scrofa to grape vines. Average grape vine losses caused by wild boar did not differ significantly during two years before diversionary feeding (193 kg/ha) and one year with diversionary feeding (151 kg/ha). In July–September 1993, a total of 4.7 tons of grain maize (25 kg/day) was distributed along a 4.5 km trail through woodland located 500–1,000 m from 283 vineyards. The 50 owners of the vineyards were questioned on the estimated amount of damage to grape vines caused by wild boar in 1990–1992 (before diversionary feeding) and 1993 (with diversionary feeding).

    Study and other actions tested
  5. A controlled study in 2008 at three vineyards in Córdoba province, Spain (Barrio et al. 2010) found that diversionary feeding reduced damage by European rabbits Oryctolagus cuniculus to common grape vines Vitis vinifera. Grape vines within plots with diversionary feeding had a lower percentage of buds and shoots removed by rabbits (11%) than those without diversionary feeding (21%). However, grape vine yield did not differ between vineyard plots with or without diversionary feeding (both 4.7 kg/vine). At each of three vineyard sites, one plot had diversionary feeding (50 kg fresh alfalfa placed in strips along the edge of the plot each week during the growing season), and a second plot did not. All plots were unfenced. The proportion of buds and shoots removed by rabbits on 15–20 vines/plot was recorded throughout the growing season in 2008. Grape vine yields were estimated during harvest from the number and size of grape clusters on each vine.

    Study and other actions tested
  6. A study in 2009–2011 in a mixed timber forest in Austria (Arnold et al. 2018) found that diversionary feeding of red deer Cervus elaphus resulted in fewer deer using forest stands vulnerable to deer damage. Forest stands vulnerable to deer browsing and bark-stripping (young and mid-aged stands) were used less by red deer in areas 1.3–1.5 km from winter feeding stations compared to areas further away (data reported as statistical model results). Supplementary food (mainly apple pomace and hay) was provided during winter (October–May) at seven feeding stations (1 station/19 km2) within a 131-km2 area of mixed forest managed for production of Norway spruce Picea abies and European larch Larix decidua. In 2009–2011, eleven red deer (seven males, four females) were radio-tracked to a total of 29,799 locations within the forest. Deer damage was not directly measured.

    Study and other actions tested
Please cite as:

Littlewood, N.A., Rocha, R., Smith, R.K., Martin, P.A., Lockhart, S.L., Schoonover, R.F., Wilman, E., Bladon, A.J., Sainsbury, K.A., Pimm S. and Sutherland, W.J. (2020) Terrestrial Mammal Conservation: Global Evidence for the Effects of Interventions for terrestrial mammals excluding bats and primates. Synopses of Conservation Evidence Series. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

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Terrestrial Mammal Conservation

This Action forms part of the Action Synopsis:

Terrestrial Mammal Conservation
Terrestrial Mammal Conservation

Terrestrial Mammal Conservation - Published 2020

Terrestrial Mammal Conservation

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