François Potvin

The eradication of balsam fir stands by white-tailed deer on Anticosti Island, Québec: a 150-year process.

Abstract White-tailed deer (Odocoileus virginianus) were introduced 100 y ago on Anticosti, a 7,943-km2 island located in the Gulf of St. Lawrence, Québec. The forest of the island is typically boreal and, at the time of the introduction, was dominated by balsam fir (Abies balsamea), white spruce (Picea glauca), and black spruce (P. mariana). Since then, the vegetation has been modified as a result of high deer density (16 deer·km-2) and heavy browsing. The most important change is the progressive decline of balsam fir stands, formerly the prevalent forest type. We describe that process at three spatial and time scales. On the largest scale (whole island, 100 y), we examined the age and species composition of stands on recent forest maps as well as the age structure of 2,555 individual balsam fir and white spruce trees. Balsam fir was largely dominant before 1930, but was replaced by white spruce afterwards. We also estimated that fir stands, which now cover 20% of the island, occupied about 40% of the total area initially. On an intermediate scale (1,200 km2, 30 y), we examined the natural regeneration established after an insect outbreak that took place in 1971-1972 and massively killed predominantly balsam fir forests. In that area, white spruce regeneration now largely replaces that of balsam fir. On a finer scale (< 1 km2, 3 y), we monitored 1,800 balsam fir seedlings (2-5 cm high) individually tagged. Seedlings were browsed throughout the snow-free season, and the annual browsing incidence in forest was estimated at 26%. Considering the present age of remnant fir stands, we estimate that most of these will have been eradicated in 40-50 y.

From the Field: Testing 2 aerial survey techniques on deer in fenced enclosures—visual double‐counts and thermal infrared sensing

Abstract We evaluated the accuracy of 2 aerial survey techniques over 4 large enclosures (6.0–29.4 km2) where the deer (Odocoileus virginianus) population was reconstructed using hunting harvest and winter mortality data. We conducted surveys (n = 8) along equally spaced parallel lines. Six surveys using the double-count technique involved 2 independent observers located on the same side of a helicopter who simultaneously counted animals over narrow plots (60-m width). Four of these surveys yielded deer densities 64–83% of assumed densities (based on the reconstructed population). The 2 other surveys had accuracies of 37 and 46%, respectively, and were judged unreliable because the sighting probability of the front observer was <0.40. We conducted 2 surveys with a thermal infrared sensor. One survey had the highest accuracy (89%) among all surveys while the other gave poor results (54% accuracy). We concluded that when sighting probabilities of observers exceed 0.45 of deer groups, double-count surveys provided valid estimations of densities for management purposes, although 1 deer out of 4 was missed on average. Because of closed forest canopy, thermal infrared sensing of deer along systematic survey lines was not a reliable technique.

Importance of balsam fir as winter forage for white-tailed deer at the northeastern limit of their distribution range 1

ABSTRACT Interspersion of dense coniferous stands that offer cover and more open mixedwood stands providing food resources has been recommended for the management of white-tailed deer (Odocoileus virginianus) wintering yards in northeastern North America. On Anticosti Island, at the northeastern limit of this deers distribution range, previous studies have shown continuous decline of deciduous browse. As native balsam fir (Abies balsamea) stands progressively shift to white spruce (Picea glauca), the persistence of the deer population will increasingly depends on its capacity to use white spruce stands. To provide insights into deer responses to long-term changes in their habitat, we investigated resource use along a gradient of expected habitat quality for deer. Stand use increased with the proportion of balsam fir, reaching an asymptote when > 40% of the stands basal area was composed of fir. Stand use does not appear to be related to snow interception since sinking depth was lower in white spruce forests. Deer using white spruce stands mainly consumed balsam fir (72%), whereas spruce represented only 17% of their diet. The consumption of arboreal lichens increased from 6% in January to 21% in March. The observed patterns of habitat use and the composition of the winter diet confirm the dependence of deer on balsam fir in winter and give additional support to the hypothesis that litterfall from balsam fir provides an alternate food source sustaining high deer density in a boreal forest without predators. Nomenclature: Anonymous, 2005.

Aerial surveys for white-tailed deer with the double-count technique in Québec: two 5-year plans completed

Abstract Aerial surveys can provide direct density estimates for ungulates over large areas such as hunting zones, a prerequisite for intensive management. In 1991 Québec implemented double-count aerial surveys as part of its white-tailed deer (Odocoileus virginianus) management program, on a hunting-zone basis. This technique involves 2 independent observers located on the same side of an aircraft who simultaneously count animals in sample plots. Two 5-year survey plans have been successfully completed for the whole province. Deer densities for most zones could be estimated with a ±20% CI (P = 0.90), while the survey provided less precise evaluations for subunits or individual wintering areas. A typical survey for a hunting zone with 200 plots (5 km × 60 m) required approximately 30–40 helicopter hours and cost

How to test habitat selection at the home range scale: A resampling random windows technique

43,000 Canadian, including salaries and travel expenses. The technique offers great potential for a variety of landscapes as part of deer management programs.

Aerial Surveys Vs Hunting Statistics To Monitor Deer Density: The Example Of Anticosti Island, Québec, Canada

Abstract Habitat selection studies at the home range scale involve testing whether an animal selects a particular spatial arrangement of habitats within a landscape. We propose a technique based on comparing the landscape pattern indices (LPIs) of observed home ranges with those of a large sample of random windows. In order to determine the appropriate size of the windows, we examined how this variable influences LPIs in a 138-km2 boreal forest block where clearcuts were prevalent. Square random windows of three different sizes (289, 729, and 1156 ha) yielded similar habitat composition proportions but very different values for many of the other LPIs. When compared with values computed for the entire landscape as a single window, most LPIs except composition were very different in the random windows. An example of a comparison between marten (Martes americana Turton) home ranges (n = 11) and square random windows (n = 100) in our study area is given, showing a strong selection for mosaics containing more forest (> 30 years), fewer open regenerating stands, and a larger amount of core area in forest. We conclude that computing LPI values for the entire landscape as a single window is inappropriate for testing habitat selection at the home range scale, and that windows of similar size as the home ranges should be used instead.

Density‐related effects of deer browsing on the regeneration dynamics of boreal forests

Abstract Cervid densities have recently increased in many parts of North America and Europe. To design sustainable harvesting strategies, a good understanding of deer population dynamics and reliable estimates of population densities are required. This is especially true on Anticosti Island, Québec, Canada, where sport hunting is the main source of income, and where long-lasting impacts of white-tailed deer Odocoileus virginianus on the forest ecosystem have been reported due to high deer densities. We compared white-tailed deer densities estimated in 2001 on the basis of an extensive aerial survey of 512 plots, each 3.5 km long by 60 m wide, with indices based on hunting statistics in 24 hunting zones on the island. We found a positive correlation between the number of deer seen per hunter day and the density of deer estimated by the aerial survey, but this correlation was highly influenced by the four locations with the highest densities of deer. We detected no significant correlation between deer density estimated by the aerial survey within each hunting zone and the number of deer harvested per hunter day. Our results underline the need for comparative studies addressing the validity of density indices based on hunting statistics to monitor variations in cervid population numbers.