Rabbit and hare damage
Cause and general information
Most damage to forest trees by rabbits and hares in Canada is caused by snowshoe hare (Lepus americanus [Erxleben]) and eastern cottontail (Sylvilagus floridanus [J.A. Allen]). Damage to broadleaf saplings via clipping of branches and gnawing of bark is most common in winter months when other food sources are scarce. Damage to conifer seedlings in newly reforested areas is more likely to take place in summer and autumn and in areas with nearby dense vegetation. Snowshoe hares have cyclical population peaks every 9 to 11 years, and damage is greatest in peak population years.
Distribution and species affected
Snowshoe hare inhabits in boreal and temperate forests in every province of Canada. Eastern cottontail inhabits open wooded areas of southern Manitoba, Ontario, and Quebec. Snowshoe hare has also been introduced and established in British Columbia, along with European rabbit (Oryctolagus cuniculus [L.]), which is found on Vancouver Island and the Okanagan in British Columbia.
Rabbits and hares eat buds, twigs, and bark from saplings of many species of conifers and broadleaf trees during winter months when other sources of food are scarce, but they prefer broadleaf trees such as aspen and other poplar species (Populus), and birch (Betula). In summer months, they will feed on young conifer seedlings, impeding reforestation of affected stands. Snowshoe hare populations are strongly cyclical in nature, and damage is greatest when their populations peak every 9 to 11 years. The population declines due to a corresponding increase in predator populations, especially the Canada lynx (Lynx canadensis [Kerr.]).
Tree parts affected
Sapling trunks, bark, shoots, and entire seedlings of conifers and broadleaf trees.
Symptoms and signs
Signs of rabbit and hare feeding are twigs and small branches that are neatly clipped at a 45° angle. Cut ends are clean, unlike the “fuzzy” appearance of shoots clipped by voles, or the ragged, flat ends of branches browsed by ungulates (deer and relatives). Gnawed stem bases of young trees have patches of stripped bark, with the exposed wood having a ragged appearance, covered in tooth grooves averaging 2 millimetres wide. Trunks of trees and saplings less than 6 centimetres in diameter are preferred.
Snowshoe hares often stand to clip shrubs up to 45 centimetres from the ground, and as the snow depth increases, they can clip higher and higher. In peak population years, snowshoe hares may kill saplings and shrubs by girdling main stems, removing bark in a complete ring around the base.
Other signs of snowshoe hare activity include their distinctive rear footprints, which on snow appear as four broadly spaced toes and when combined with the heel looks like a snowshoe in overall shape, measuring an average of 12.5 centimetres in length. Rabbit hindfoot tracks are shorter, averaging 10 centimetres long. Snowshoe hare and rabbit droppings consist of slightly flattened spheres measuring 10 millimetres in diameter.
Damage
Snowshoe hares will damage young conifers by feeding on them in years of peak populations when there is higher competition for other food sources. Seedling damage is most severe in replanted areas under forest management where there is overstory cover nearby, such as in adjacent young plantations 10 to 25 years old. Feeding damage greatly slows down natural regeneration and reforestation operations, requiring costly replanting and increasing the time required for the new stand to attain “free to grow” status.
Girdling of saplings by hares and rabbits can cause great damage to ornamental trees in urban settings and shelterbelt tree plantings.
Prevention and management
Damage to areas reforested with conifer seedlings can be reduced if planting can be planned for a year when the snowshoe hare population cycle is not at the start or end of a peak.
In the long term, snowshoe hare populations are reduced in young, pre-commercially thinned conifer stands compared with similar unthinned stands. The hare population density increases the first winter after thinning due to the fallen stems and branches but afterwards decreases as the more open landscape makes the habitat less attractive because of increased predation. Thinning has additional benefits of increasing the growth rate of remaining trees and decreasing forest fire risk, but it also reduces the dense cover the hares require for food and predator evasion.
Feeding damage to mature individual trees can be lowered or prevented by clearing vegetation around trees, constructing physical barriers and spraying chemical repellants. Rabbits and hares prefer dense vegetation to avoid predation, so mowing down plants around the trunks of desired trees and around seedlings reduces feeding activity in the cleared areas.
To protect saplings, individual tree guards made of 10- or 20-millimetre square wire screen should be set 7.5 to 10 centimetres into the ground, with stakes to brace them away from the trees. Each tree guard should extend to 50 centimetres above the expected snowline to be effective.
Individual trees can also be protected by repellents. Various brands of rodent repellents formulated for domestic use can be purchased at hardware stores and garden centres, but most chemical repellents are not recommended for use on fruit-bearing trees. Thiram, a sulfur fungicide that is distasteful to rodents, is often used as a repellent and is sprayed on tree trunks with additives that prevent it from being washed away quickly.
Repellents are either painted or sprayed on the bottom 2 metres of tree trunks on a dry day in late autumn when daytime temperatures are above freezing.
In areas where rabbit and hare populations are high, trapping or poisoning are not effective measures to control populations because the treated areas are reinvaded in a matter of weeks. In many provinces it is illegal to poison rabbits or hares. Snowshoe hares are considered a keystone species in North American boreal forests because they are the main prey for important predators such as Canada lynx and great horned owl (Bubo virginianus [Gmelin]).
Pesticides (including animal repellent chemicals) registered for use against rabbits and hares under specific situations may change from year to year. Therefore, please search Health Canada’s Pesticide Product Information Database for currently registered pesticides and product information for use against rabbits and hares. The application of any registered product should be based on population size and applied only when necessary and against the approved life stage. It is also recommended to consult a local tree care professional. Pesticides may be toxic to humans, animals, birds, fish, and beneficial insects. Apply registered products only as necessary and follow all directions and precautions noted on the manufacturer’s label. In some jurisdictions and situations, only a licensed professional can apply pesticides. Consulting relevant local authorities to determine local regulations that are in place is recommended.
Selected references
Agriculture and Agri-food Canada. Protecting trees from animal damage. Available at: https://agriculture.canada.ca/en/agricultural-production/agricultural-pest-management/diseases-and-pests-agroforestry/protecting-trees-animal-damage [Accessed March 2024]
Ausband, D.E.; Baty, G.R. 2005. Effects of precommercial thinning on snowshoe hare habitat use during winter in low-elevation montane forests. Canadian Journal of Forest Research 35(1): 206–210. https://doi.org/10.1139/x04-152
Burleigh, J.T.; Ebata, T.; White, K.J.; Rusch, D.; Kope, H., editors. 2014. Field guide to forest damage in British Columbia (3rd edition). Crown Publications, Province of British Columbia. Victoria, British Columbia. Joint publication No.17. 368 p.
Canadian Wildlife Federation and Environment and Climate Change Canada. Hinterland Who’s Who: Snowshoe hare. Available at: https://www.hww.ca/en/wildlife/mammals/snowshoe-hare.html [Accessed March 2024]
Gill, R.M.A. 1992. A review of damage by mammals in north temperate forests: 2. Small mammals. Forestry 65(3): 281–308. https://doi.org/10.1093/forestry/65.3.281
Harestad, A.S.; Bunnell, F.L.; Sullivan, T.P.; Andrusiak, L. 1986. Key to injury of conifer trees by wildlife in British Columbia. British Columbia Ministry of Forests. Wildlife Habitat Research. Publication WHR-23. 38 p.
Internet Center for Wildlife Damage Management. 2024. Identifying wildlife damage to trees, shrubs, & bushes. Where is the damage occurring? Available at: https://icwdm.org/identification/inspection/outdoors/trees/ [Accessed March 2024]
Sullivan, T.P.; Sullivan, D.S. 1982. Barking damage by snowshoe hares and red squirrels in lodgepole pine stands in central British Columbia. Canadian Journal of Forest Research 12(2): 443–448. https://doi.org/10.1139/x82-068
Sullivan, T.P.; Sullivan, D.S. 1986. Impact of feeding damage by snowshoe hares on growth rates of juvenile lodgepole pine in central British Columbia. Canadian Journal of Forest Research 16(5): 1145–1149. https://doi.org/10.1139/x86-202
Sullivan, T.P.; Sullivan, D.S. 1988. Influence of stand thinning on snowshoe hare population dynamics and feeding damage in juvenile lodgepole pine. Journal of Applied Ecology 25(3): 791–805. https://doi.org/10.2307/2403746