Parasites are the most significant threat to moose (Alces alces) across their North American range. Deer brainworm (Parelaphostrongylus tenuis) is the second leading cause of mortality of moose in New York. The nematode is found in adult form in the nervous system of white-tailed deer (Odocoileus virginianus), which are a dead-end host to the parasite. P. tenuis is excreted in deer feces, is consumed by gastropods, and the gastropods are subsequently ingested by moose while browsing. Prevalence of P. tenuis in gastropods may be associated with declines of moose populations in New York, yet there are no standard methods for assessing gastropod abundance. Our study evaluated alternative methods of gastropod sampling. We sampled four 100-m transects, spaced 50 m apart, in Mount Baker, NY. Each transect was checked every three days for two weeks. Four sampling methods at each transect were used: 1) visual tree searches every 10 m, 2) pitfall traps spaced 20 m, 3) moistened cardboard ground traps spaced 20 meters, and 4) water bottle traps placed in a tree in the same site as pitfall traps.
Results/Conclusions
Ground traps resulted in a greater number of gastropods captured than traps placed in trees. Cardboard ground traps captured three times more gastropods (n = 175) than pitfall traps (n = 57), and over nine times as many gastropods as the most effective tree trap, the tree search (n = 18). Tree searching resulted in three times more gastropods detected than the tree trap method (n = 5). It is possible that ground traps captured more gastropods because gastropods prefer moist environments and moisture is retained much longer on the ground than in trees after rain. There was no observable relationship between trap type and species of gastropod captured. We anticipate that the results of this study will be useful in further understanding how gastropods carrying P. tenuis affect moose populations as we provide information on sampling methodologies for gastropods, which can lead to improved estimates of abundance that may be linked to the health of the moose population in New York.