A Comparison of Methods Used to Examine Snowshoe Hare Habitat Use

1. What they did

Researchers study where mammals spend their time either directly (watching, catching or radio-tracking them) or indirectly, from the signs they leave, such as browsing, tracks and droppings. Different methods are often assumed to tell the same story, but few studies had checked. The authors used three methods at the same time on snowshoe hares in Maine to see whether they gave similar answers about habitat use.

They worked in two study areas, Pierce Pond and Cherryfield, from September 1981 to May 1983. Earlier studies had shown that the density of the understory matters most to hares, so each method was compared against understory stem density (open, sparse, moderate and dense).

• Pellet counts. In two 49-hectare sampling areas per study area, they laid out seven 700-metre transects, each with fifteen 1-metre-radius plots 50 metres apart. Fifty more plots were added in each sampling area in the second year. Hare pellets were counted and removed in spring and late summer.
• Snow track counts. Hare tracks were counted on the 50-metre stretches between plots, within 40 hours of a snowstorm and after at least one full night without snow, so tracks could build up. Each stretch was assigned the understory type of the plot before it.
• Live trapping. Box traps baited with alfalfa were set every 100 metres along the transects, for 8 to 16 days in spring and autumn.

Because the true time hares spent in each understory type was unknown, the authors compared the patterns of the three indices, using only data from the leafless months.

2. What they found

• In both areas, all three indices were spread unevenly across the understory types, and pellets, tracks and captures all increased with understory density.
• All three methods showed hares using dense understory (20,000 or more stems per hectare) more than expected from how much of it was available.
• For open, sparse and moderate understory, the methods did not always agree on whether use was more, less or about the same as expected. Still, at least two of the three agreed in seven of the eight comparisons, according to the text.
• No method ever showed hares favouring an understory type while another showed them avoiding it.
• In early trials, more hares were caught with alfalfa bait than with apples, vanilla or no bait, but how far hares travelled to reach the bait was unknown.

3. What they concluded

• Pellet counts, track counts and live captures give similar information on how snowshoe hares use understory types, so biologists can choose a method to suit their other aims or their budget.
• Each index has weaknesses. Hare defecation rates might vary with activity or cover, as found in mule deer. Track counts measure distance travelled rather than time spent, so they may overestimate time in large, poor patches that hares cross to reach small feeding areas, where they move less. Bait may draw hares from unknown distances.
• Track counts are cheap over large areas but cannot show seasonal habitat use (they need snow).
• Live trapping is costly, labour intensive and usually limited to small areas, but it gives data for mark-recapture estimates of population size.
• Pellet counts are cheap over large areas and may show seasonal changes in habitat use and relative abundance.

4. How tracking was or was not used

Two of the three methods relied on tracks and signs: counting hare tracks in fresh snow along transect segments, and counting hare fecal pellets in fixed plots. No trailing was reported. The snow track counts were timed after snowfall, with at least one snow-free night, so that tracks of a known age could accumulate.

5. Tracker or observer certification

Not reported. The paper does not say who counted tracks and pellets or how hare tracks and pellets were identified; snowshoe hares were the only hares or rabbits in the study areas.