densities

History of deer colonization - Response of vegetation to deer - Response of animals to deer and squirrel - Deer biology

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Deer density and movement - Deer genetic and morphometric variations

Deer density and movement

Aim & scope - Where & when - How - Main results - Conclusion - Scientific Publications

Aim and scope

Deer density and distribution determine their impact over time on the vegetation. Deer presence, and deer density, in a given area, can vary with the time of the year, the type of habitat or the vegetation stage. Studying deer movement within the main islands or between islands can provide a better understanding of the basic traits in the biology of introduced deer population on Haida Gwaii.

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Where and when

Data on deer density and movements were collected along with vegetation studies in Laskeek Bay (in 1996 by Tanguy Daufresne and in 2000 by Steve Stockton) and cull operations (in 1997, 1998, 1999, 2006 and 2007). Data on Graham and Moresby Islands were collected in the course of a study of biomass availability (by Christian Engelstoft in 2001).

Deer movement was studied through the monitoring of 50 animals equipped with radio collars between 1998 and 2001 by Christian Engelstoft, Sean Sharpe and Todd Golumbia, in a range of habitats (recent cutblocks, free-to-grow blocks, old growth forest), under moderate (Graham Island) or low hunting pressure (Moresby and Louise Island).

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How

Deer density

Line transects

The first estimates of deer densities were made on Reef and East Limestone islands in 1996 using the line transect method.
The observer walked a fixed route of pre-defined length, watching on either side for animals.

When a deer was spotted, three measures were recorded:

distance from observer to animal (r)
angle between transect line and direction of animal (t)
shortest distance from animal to line of transect (x, calculated from r and t)

“x” provides an estimate of the distribution of sightings in relation to distance from the transect, and hence the effective transect width. The observer then calculates the effective area surveyed, and can deduce deer density.

Total count

The same year, a team of 10 observers equipped with walkie-talkies made a total deer count on East Limestone Island. The count was made possible by the relative small area of the island (48ha) and the tameness of the local deer.

Pellet count

In 2000, deer pellet group densities on seven islands in Laskeek Bay were estimated by counting the number of pellet groups along four 2 meters by 135 meters transects on each island. Deer densities were estimated by comparing the pellet group densities with the one on East Limestone Island, where deer density was known from a total count carried out in the same conditions as in 1996.

Deer density(deer/ha)=

Pellet group density(PG/ha) x Deer density on Limestone(deer/ha)

Pellet group density on Limestone (PG/ha)

In 2001, pellet group densities on study sites Graham and Moresby islands were estimated by counting the number of deer pellet groups along three parallel transects (1.66 meter wide, 100 meter long).

Pellet group estimates were converted to equivalent deer densities as following:

Deer density(deer/ha)=

Pellet group density(PG/ha)

Deterioration rate (day) x Defectation rate (PG.deer/day)

Cull operations

Deer densities were also inferred from initial kills on Reef and SGang Gwaay.

Deer movement

A total of 50 deer were equipped with radio collars in 1998 and 1999, most of them located from a helicopter and captured by netgun. They were then tracked from plane by radio telemetry on a monthly basis. When a radio collar was located, GPS coordinates were recorded, as well as the habitat type.

However the number of relocations remained low for many deer. Home ranges were calculated using a Geographic Information System.

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Main Results

Deer density

Reef and East Limestone – 1996 (before deer cull)

The sample sizes obtained from line transects were probably inadequate for accurate estimation of the numbers of deer, hence very low density estimates. The deer density estimated from the total count on east Limestone was three times higher than the one obtained by line transects. As no total count had been possible on Reef Island, it was assumed that the difference between the two methods would have been the same in order to provide a deer density estimate.

Reef: 32.4 deer/km²
East Limestone: 33.3 deer/km²

Laskeek Bay – 2000

South Low, Lost and Low Island had no trace of deer presence.
South Skedans: 29.8 deer/km²
West Skedans: 21.1 deer/km²
Haswell: 21.1 deer/km²
West Limestone: 36.8 deer/km²

Graham, Moresby and Louise – 2001

The average deer density estimated from pellet counts were:

Graham: 12.5 deer/km²
Moresby: 15.9 deer/km²
Louise: 11.9 deer/km²

Deer movement and repartition

Movements

Four different types of movements were suggested by the data:

large seasonal shift between summer and winter range
moving away from the original capture and marking location (displacement possibly caused by the stress due to capture)
occasional leaving of the core area in the fall or in the winter

Home range

At least 5 relocation points were necessary to establish a summer home range, and at least 9 for a winter home range. Home ranges were estimated around the relocation points.
There was no significant difference in the home ranges of male and female deer. Summer and winter ranges generally overlapped, and winter ranges were much larger than the summer ranges.

Habitat use

The deer seemed to move into the old-growth forest during the winter months, but also during the month of June. This may be indicative of increased hunting pressure as the hunting season is initiated.
They also tend to avoid South-East and North-West slopes in winter.

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Conclusion

This study was a preliminary study; more work is necessary.
However, it was found that:

deer distribution varies with season
some deer move considerable distances

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Scientific Publications

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