PROTECTING BEVERLY AND QAMANIRJUAQ CARIBOU
AND CARIBOU RANGE

C. Examples of Crossing Evaluations

(provided by Don Thomas)

Critical Crossings (3 examples)

(1) Thelon River between Beverly & Aberdeen Lakes

Alternative crossings: None in north-south direction for 35 km to west (west of Beverly Lake) and 85 km (east of Aberdeen Lake). These are caribou travel distances. The dangerous crossing in mid Aberdeen Lake is not a valid alternative. If caribou have to back track to the Thelon River west of Beverly Lake they must re-cross the Dubawnt River. The main crossing place is termed "box" (grave) crossing. It is located just below the second Island above Aberdeen Lake. A small proportion of Beverly caribou cross to that island and then to the north shore. Still fewer caribou cross using islands upstream.

Crossing width: Approximately 300 m at "box" crossing. Wider towards Aberdeen Lake.

Caribou sensitivity: Cows with young calves that cross in June and July are highly sensitive to disturbance.

Caribou condition: Cows are in poorest condition in late June and July because of milk production and from blood loss and fly harassment. Bulls generally are in good condition but can be weakened by fly parasitism.

Environmental stressors: Most extreme in late June and July from a combination of insect bites and harassment and high temperatures. The winter coat is not completely shed by breeding cows until late July. The new coat of others is black which absorbs heat on sunny days.

Regularity of use: Used by cows and calves in years when spring migration is delayed. Used by males and non-pregnant females every year.

Intensity of use: Used by most of the herd in years when migration is delayed. Used by a significant proportion of males and non-pregnant females in most years.

(2) Thelon River between Beverly Lake and Ursus Islands

Alternative crossings: The river can be crossed in either direction at any location along the 34 km section. A major crossing point from north to south is below the rapids where the river jogs 24 km above Beverly Lake and 10 km from sharp bend north of Ursus Islands. In late May-early June, when large numbers of caribou cross from south to north in spring migration, ice in the river is breaking up and the river is rising because of ice at Beverly Lake and below. Therefore, some parts of the river section may be unsuitable for crossing because of ice. Alternative locations may not be available in any given year. Options must be left open to the caribou to find suitable crossing locations.

Crossing width: Width varies from about 100 m at the rapids and just below it to about 250 m.

Caribou sensitivity: Crossings may occur from mid May until freeze-up in November. Sensitivity varies from very high to low.

Caribou condition: Physical condition varies from poor in July to good depending on the time of year and the age and sex of caribou crossing the river.

Environmental stressors: Stressors also vary from very high in July and early August to very low in the autumn.

Regularity of use: Caribou cross the river in that section every year and usually in both directions. There may be years when caribou cross it in both directions twice. At the end of August in 1981, caribou were moving north towards that section of the river.

Intensity of use: A minimum of 20,000 caribou likely cross the section every year.

(3) Dubawnt River between Marjorie Lake and the Thelon River

Alternative crossings: There are two identified crossing places: (i) above the rapids and (ii) below the rapids located about 10 km above the mouth in the island complex between Beverly and Aberdeen lakes. In 1957, when spring migration was late, up to 100 000 caribou crossed in a section 2-10 km above the rapids (crossing i). The alternative crossing (ii), between the rapids and the mouth was choked with ice. The section from the rapids to 2 km upstream had overhanging banks of ice and snow and was impassible for caribou.

Crossing width: i) 100-150 m; (ii) estimated 300-500 m.

Caribou sensitivity: Very high in June and July for groups with cow-calf pairs.

Caribou condition: Cows with calves have exhausted fat reserves by late June.

Environmental stressors: Fly season is advancing by late June and is severe in July and August.

Regularity of use: Used by cows and calves when spring migration is delayed. Used every year by males and non-pregnant females.

Intensity of use: Varies from most of the herd to a small proportion.

Lookout Point

Alternative crossings: Alternatives are wider and involve some backtracking. In 1958, a small proportion of the Beverly herd crossed at several locations up stream and few downstream.

Crossing width: Estimated to be 300 m at the main crossing with shallows extending out 50 m or so.

Caribou sensitivity: By late July, sensitivity high to moderate for groups with cow-calf pairs.

Caribou condition: Crossing is in late July-early August when cows with calves are still in poor condition.

Environmental stressors: Mosquitoes and black flies are intense in late July and warble flies are emerging.

Regularity of use: The crossing was used by large numbers of caribou in about 1 year in 10 (E. Kuyt, pers. comm.). It was used consistently in the late 1950s and early 1960s. In the 1970s and 1980s, caribou tended to travel west on the north side of the Thelon River and cross the Hanbury River to the west of the Thelon River. The pattern of movement may change again in the future.

Intensity of use: In some years, very large numbers cross in late July-early August from north to south.

See also Evaluating the Importance of Water Crossings

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