Does survey effort influence sightability of mountain goats Oreamnos americanus during aerial surveys?
Kim G. Poole
Poole, K.G. 2007: Does survey effort influence sightability of mountain goats Oreamnos americanus during aerial surveys? - Wildl. Biol. 13: 113-119.
Practical techniques to estimate the sightability of mountain goats Oreamnos americanus during aerial surveys have not been developed or have been poorly tested. I evaluated sightability of 28 radio-collared goats in two study areas in southeastern British Columbia to assess whether sightability increased with increased helicopter survey effort, and to explore which factors might affect sightability. Three surveys at different survey efforts were conducted in each study area, during which attempts were made to locate collared goats 64 times. I detected no relationship between survey effort in the range tested (1.3-6.1 minutes/km2) and sightability (38-83%). Sightability averaged 63%. Only animal activity and larger group size influenced goat sightability. Sightability tended to decrease with increased vegetation cover. Survey efforts of . 2.0 minutes/km2 do not appear to result in higher sightability. For surveys of large areas not well-known to surveyors, a 60-65% sightability correction may be realistic, with a target of approximately 1.5 minutes/km2 effort.
Key words: aerial survey, census, mountain goats, Oreamnos americanus, sightability, survey effort
Received 29 November 2005, accepted 24 February 2006
Associate Editor: Marco Festa-Bianchet