Consumers 



Arthropods: The site visits to Pmdhoe Bay were made after the end of the main period of 

 emergence of adult insects. This occurred in mid-July 1970 at Barrow, with a rapid decline after 

 20 July. Samples of tundra sod from each of the study areas at Prudhoe were returned to Barrow 

 for extraction of insect larvae and other soil arthropods. As at Barrow, the major Prudhoe arthropods 

 were cranefly larvae (Diptera, Tipulidae). Two large larvae of Prionocera gracilistyla were found 

 in the samples from site 3, the polygon basin. Two larvae of Pedicia hannai were extracted from 

 the samples from site 4, the drained lake basin. Larvae of the former species are saprivorous, while 

 the smaller larvae of Pedicia hannai are carnivorous. 



The insect fauna at Prudhoe included many species, and even several families not found at 

 Barrow. Several species of large wolf spiders (Araneida, Lycosidae) were particularly abundant and 

 conspicuous. Although the number of samples taken was too small to support firm conclusions, the 

 number of insect larvae in the soil appeared to be equal to or less than the number found in similar 

 areas at Barrow. 



Microtine rodents: The tundra of northern Alaska is noted for the cyclic population fluctuations 

 of small rodents, particularly the brown lemming, Lemmus trimucronatus. At Barrow this species 

 undergoes population cycles of large amplitude. The collared lemming, Dicrostonyx groenlandicus, 

 is present at Barrow in smaller numbers and is not conspicuously cyclic. During July, August and 

 September, several separate sets of observations were made principally by MacLean and Whitney. 

 MacLean noted the following: 



In late July, a moderate amount of burrowing and cutting of vegetation, apparently dating from 

 the preceding spring, was evident; however, the microtine population was not large and no animals 

 were seen. Raised mounds and polygons were examined for cast pellets and nest scrapes of preda- 

 tory birds. The scarcity of these makes it doubtful that the microtine rodents ever reach high 

 populations of the magnitude seen near Barrow. Eleven raptor pellets [snowy owl (Nyctea scandiaca) 

 and pomaiine jaeger {Stercorarius pomarinus)] were collected and their contents were analyzed. 

 These contained remains of 19 Lemmus, 15 Dicrostonyx, 1 Microtus oeconomus (tundra vole), 

 1 Spermophilus undulatus (arctic ground squirrel), and 3 birds. Thus, at Prudhoe, the collared 

 lemming is far more abundant relative to the brown lemming than it is at Barrow, and two mammal 

 species occur there which are not found at Barrow. Careful trapping in the Prudhoe area may prove 

 to be particularly interesting. 



In early September, Whitney establislied two live trapping grids (Fig. 34, Location C) in the area 

 close to the plant observations and the revegetalion plots. One grid contained 100 traps at 5-m 

 intervals (10 x 10) and the other 65 traps at 5-m intervals. No microtines were captured during the 

 two days of trapping. The traps were left in place in locked-open positions, for future renms of the 

 trap grid. Sixty man-hours were spent on the tundra looking for fresh signs of animal activity. Signs 

 were nil, with no evidence of green cuttings, green fecal matter, or recently used runways. The 

 September observations indicate a decrease in the microtine population over that postulated from the 

 observed July and August signs. 



Large herbivores: At each of the study sites, and in the Pmdhoe Bay area in general, many 

 well traveled trails and piles of fresh feces evidenced the frequent passage of caribou Rungifer 

 tarandus through the area. This was particularly conspicuous at site 2, where the ground was 

 terraced by a series of parallel ganie trails, and at site 3, where the polygon was surrounded, but 

 not traversed, by recently used trails. The passage of large numbers of caribou, as was seen at 

 Prudhoe in mid-July, resulted in a heavy grazing pressure on the vegetation as well as severe 

 physical disturbance from tramping. Thus, unlike the immediate Barrow area, caribou are an import- 

 ant element in the tundra ecosystem near Prudhoe Bay. 



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