Progress Report for NIFR - Vole and Hare Monitoring

Here is the complete progress report: NIFR-Voles_and_Hares_Progress_Report.pdf

In general, for hares;

• Hares have not increased in abundance from last year. In contrast, hares have increased each year for the previous three years.
• Damage to seedlings is high since hares are preferentially feeding on the seedlings. Damage will not be limited to peak years but will be a chronic problem.
• Damage primarily happens in the summer and fall following planting - little damage occurs in subsequent years. Nursery fertilization has probably been diluted shortly after planting (3 to 5 months), making seedlings less desirable than freshly planted seedlings.
• Seedling mortality is actually very low on most sites with low to moderate densities of hares. Seedlings suffer a high rate of clipping of terminal shoots, but lateral shoots continue to growth, resulting in little mortality. For this reason, it is probably safe to plant sites with low to moderate levels of hare use.
• Hare abundance is strongly related to percent cover of shrubs and trees.
• Brushing reduces this cover and resulted in reduced stand use by hares and reduced substantially the clipping damage to seedlings. Brushing sites with a high abundance of hares or risk of damage may reduce the overall damage and mortality to seedlings on these problem sites.
• Overall, it appears to be safe to plant sites with a low abundance of hares (some damage will occur but seedlings will survive) and brushing those sites with a high abundance of hares (high cover) will reduce the abundance of hares, reduce damage to seedlings, and reduce competition between seedlings and shrubs.

In general, for voles;

• Meadow voles have not increased from last year and remain low (< 15 individuals/ha); currently, given the density of voles, damage to planted sites is very low.
• MPB-killed non-merchantable stands have become optimal habitat for meadow voles as vole densities on these sites have exceeded that on clear-cuts (typically preferred habitat in forested environments). Voles appear to be responding to the increased herbaceous layer developing in the MPB-killed non-merchantable stands.
• Voles typically reach irruptive densities every 3 to 5 years. We haven't seen a peak in the 4-year monitoring program. It is possible that we will see a peak (> 30 individuals/ha) in numbers in the next year or two.
• Sites planted just prior to the peak may be susceptible to high levels of damage. Sites planted after the peak should experience a low risk of damage.
• Controlling the herbaceous vegetation may help reduce the abundance of voles on these sites (should be tested/monitored). Diversionary food may help reduce this damage during the peak year (should be tested or monitored during the peak year).
• Overall, the current threat to seedlings from voles is low (this winter and next spring and summer) when their abundance is low. However, a peak in their abundance is anticipated in the next year or two (based on previous cycles), and the risk of damage to seedlings planted just prior to the peak will be high. Delaying plant to the spring following their peak would be the best damage-reduction technique.

Douglas B. Ransome, Ph.D., R.P.Bio.