Importance of Observer Experience in Finding Desert Tortoises
Freilich JE and LaRue EL. 1998. Importance of Observer Experience in Finding Desert Tortoises. The Journal of Wildlife Management. 62(2):590-596
Because surveys for the desert tortoise (Gopherus agassizii) are usually conducted by experienced observers, we conducted 2 experiments in which observers of differing experience levels searched for desert tortoises and tortoise "sign" (burrows, scat) in replicated 1-ha plots. Each plot was seeded with a known number of tortoise scat, realistic-looking tortoise burrows, and 9 lifelike styrofoam tortoises of 3 size classes. When observers were divided into 2 groups, experienced and inexperienced, the groups did not differ (P ≥ 0.17) in their ability to find tortoises of several size classes, total tortoises, scat, or burrows. Additional analyses divided experience into novice, beginner, intermediate, and advanced levels based on previous survey experience. Again, tortoise-finding was unaffected by experience level (Ps > 0.15). Observers overestimated numbers of burrows, mistakenly counted holes made by other animals, and consistently found fewer tortoises and scat than were actually seeded in plots. Tortoise-finding skill is probably part inclination and part aptitude. We cannot say which factors may affect a person's ability to find tortoises, but previous experience, in these experiments, did not.
- Type
- Journal Article
- Authors
- Freilich, Jerome; LaRue, Edward
- Units
- JOTR , MOJA
- Keywords
- Desert Tortoise, desert tortoise council, Gopherus agassizii, Joshua Tree National Park (JOTR), Mojave Desert, Observer bias, observer experience, Reptiles (Reptilia), Sampling, survey design, Taxa Links To References, Vascular Plants (Plantae)