Grand Teton National Research Articles

The effect of human activities and their associated noise on ungulate behavior.

BackgroundThe effect of anthropogenic noise on terrestrial wildlife is a relatively new area of study with broad ranging management implications. Noise has been identified as a disturbance that has the potential to induce behavioral responses in animals similar to those associated with predation risk. This study investigated potential impacts of a variety of human activities and their associated noise on the behavior of elk (Cervus elaphus) and pronghorn (Antilocapra americana) along a transportation corridor in Grand Teton National Park.Methodology/Principal FindingsWe conducted roadside scan surveys and focal observations of ungulate behavior while concurrently recording human activity and anthropogenic noise. Although we expected ungulates to be more responsive with greater human activity and noise, as predicted by the risk disturbance hypothesis, they were actually less responsive (less likely to perform vigilant, flight, traveling and defensive behaviors) with increasing levels of vehicle traffic, the human activity most closely associated with noise. Noise levels themselves had relatively little effect on ungulate behavior, although there was a weak negative relationship between noise and responsiveness in our scan samples. In contrast, ungulates did increase their responsiveness with other forms of anthropogenic disturbance; they reacted to the presence of pedestrians (in our scan samples) and to passing motorcycles (in our focal observations).ConclusionsThese findings suggest that ungulates did not consistently associate noise and human activity with an increase in predation risk or that they could not afford to maintain responsiveness to the most frequent human stimuli. Although reduced responsiveness to certain disturbances may allow for greater investment in fitness-enhancing activities, it may also decrease detections of predators and other environmental cues and increase conflict with humans.

Digenean trematode infections of native freshwater snails and invasive Potamopyrgus antipodarum in the Grand Teton National Park/John D. Rockefeller Memorial Parkway Area.

Outside its native range, the invasive New Zealand mud snail (NZMS), Potamopyrgus antipodarum, is rarely reported to harbor parasites. To test this observation, 7 sites along the Snake River and Polecat Creek in the Grand Teton National Park/John D Rockefeller Memorial Parkway area (Wyoming) were surveyed for native aquatic snails, NZMS, and associated digenean trematodes, in July 2005. At 6 sites, native snails harbored patent digenean infections; within 2 hr, < or =10% of lymnaeid snails shed furcocercariae or xiphidiocercariae, and < or =42% of physid snails released furcocercariae or echinostome cercariae. Partial 18S rDNA sequences were recovered from several furcocercariae. Potamopyrgus antipodarum was present at, and collected from, 5 sites. Polymerase chain reaction assays targeting digenean rDNA sequences in DNA extracted from pools of 150 NZMS snails did not detect parasites. The examination of 960 NZMS by overnight shedding yielded 1 occurrence of (surface-encysted) metacercariae of an unclassified notocotylid (based on 18S and 28S rDNA sequences). The dissection of 150 ethanol-fixed NZMS (30/site) revealed 2 types of digenean metacercariae encysted in tissues of 5 snails from Polecat Creek. Thus, invasive NZMS may serve as first and second intermediate host for digenean parasites.

Parasite Infection Status of Potamopyrgus Antipodarum

Outside its native range, the invasive species Potamopyrgus antipodarum (New Zealand Mud snail; NZMS) has seldom been reported to harbor parasites. To test this intriguing observation, 7 sites along the Snake River and Polecat Creek in the Grand Teton National Park/John D Rockefeller Memorial Parkway area (W yoming, USA) were surveyed for NZMS, native aquatic snails and parasites: digenean trematodes (specialist parasites of snails) and nematomorphs (horse hair worms, generalist parasites of aquatic invertebrates), in July 2005. Non-destructive examination of 96 native snails at each site revealed abundant presence of digeneans (parasites that specialize in snails) at 6 sites. Within 2 hours, up to 12.4% of lymnaeid snails shed furcocercous cercaria or xiphidiocercaria, and up to 50% of physid snails released furcocercous cercaria or echinostome cercaria. A total of ~900 NZMS (collected from 5 of the sites) were investigated for infection with digeneans by overnight shedding. One NZMS yielded amphistome­like metacercariae that had encysted in the observation tray. The dissection of 150 ethanol-fixed NZMS (30/site) revealed several types of internal metacercarial stages of digeneans in 5 snails (all from Polecat Creek). PCR-based assays targeting parasite rDNA sequences in DNA extracted from pools of 150 snails each also indicated associations between digenean parasites and NZMS. All parasites were detected in NZMS from Polecat Creek. NZMS were not observed to harbor nematomorph parasites with any of the techniques used. In conclusion, the sites tested contained multiple native snail-digenean parasite associations, and the capacity of invasive NZMS outside the native range to serve as first and second intermediate host for digenean parasites may have been underestimated previously.