140 
Table 2 
Biomass” (grams) of collared lemmings on three grid areas 
near Prudhoe Bay during the summers of 1971 and 1972. 
June July Aug. mid-June early July late July mid-Aug 
Grid P 1971 1971 1971 1972 1972 1972 1972 
Biomass: ~ 
Male 194(5) 155(5) 32(1) 
Female 84(3) 95(2) 70(1) 
TOTAL 0 0 0 278 250 102 0 
Grid O 
Biomass: 
Male 31(1) 62(2) 108(3) 60(3) 
Female 36(1) 103(3) 100(3) 48(1) 
TOTAL 67 0 0 165 208 108 0 
Grid S 
Biomass: 
Male 0 15 32(1) 
Female 80(1) 62(1) 0 
TOTAL 0 0 Q 80 0 77 32 
*Live weight biomass of lemmings captured on the 0.25 ha grid area. 
+Numbers in parentheses are the number of lemmings for each biomass value. 
lemmings, this species was never seen or cap- 
tured in the present study. 
Maximal densities reported for lemmings in 
tundra habitats at Barrow have been 1-30 ha’! 
for Dicrostonyx groenlandicus (Batzli, in press) 
and 75-200 ha! for Lemmus sibericus (Schultz 
1969; Maher 1970). In contrast to the predomi- 
nance of Dicrostonyx found at Prudhoe Bay in 
1971-72, the numbers of Lemmus generally have 
exceeded those of Dicrostonyx at Barrow and 
the brown lemming is considered the only grazer 
of significance in the grass-sedge tundra of the 
Barrow region (Pitelka 1973). Pitelka (1973) has 
suggested that the higher densities of Djicro- 
stonyx may be reached only occasionally (every 
20 years) at some locations. 
Maximal densities of Dicrostonyx estimated 
at tundra sites in Canada range from 2-3 ha"! at 
Devon Island, N.W.T. (Speller 1972), to 25 ha"! 
at Baker Lake, N.W.T., (Krebs 1964) and south- 
ern Hudson Bay (Brooks 1970), to 35-40 ha'!, 
also in southern Hudson Bay (Shelford 1943). 
Factors which may limit lemming distribution 
and abundance 
Bee and Hall (1956) have suggested that on 
the Arctic Slope of Alaska fluctuation in the 
population of collared lemmings seems to occur 
less often and to be of lesser degree than in the 
brown lemming. The microtine rodent popula- 
tion levels found in 1971-72 at Prudhoe Bay 
may indicate that popuiations of these small 
herbivores have always been low (relative to 
Barrow). The possibility that the low numbers in 
1971-72 may reflect a trough (or fluctuation) in 
a lemming cycle cannot yet be eliminated. No 
systematic trapping for microtines was done in 
1973. However, live trapping efforts by D. 
Holleman over a 4-5 day period in mid-July 
1973 at Prudhoe Bay suggest that numbers were 
similar to or, in some areas, higher than those 
reported there for 1972 (D. Holleman, pers. 
comm.). In July 1973, although he captured no 
lemmings in the temporary live traplines near 
the BP camp, Holleman captured five Djicro- 
stonyx on grid area Q, using the outer perimeter 
of 40 traps (of original 100 traps). On grid area 
S, using 90 of the original 100 traps, he caught 
eight Dicrostonyx. Three of the eight were small 
juveniles, which indicated recent, active repro- 
duction. Comparison of these 1973 numbers on 
grid area S with those found in mid-July 1972 
(Table 1) suggests that, at least on grid area S, 
numbers of collared lemming were higher in 
1973. But this number does not exceed the 
highest found on grid areas P and QO in 1972 
(Table 1). Holleman found no brown lemmings 
at any of the trapping sites. 
