" Pitfall trapping is the standard method for collecting ground-dwelling arthropods and soil fauna in studies of ecological and agricultural entomology " ( Ruiz-Lupión et al. 2019).
In my current research assistant position I am working on analysis of macro-fauna in forests. We use pitfall traps to assess the abundance of macro-fauna in a given area. I'm curious to learn more about other methods used for this sort of analysis.
- What methods for pitfall trapping have you used, if any?
- What were the advantages/disadvantages and what would you have changed about the method you used.
Our methods are as follows:
In a study reviewing pitfall traps, Ruiz-Lupión et al. (2019) states the factors which should be considered by ecologists using pitfall traps. They state, "the capture rate of arthropods in pitfall traps is proportional to their activity, and the number of individuals that each trap catches may or may not reflect their true abundance, and instead just their activity. Thus, the rate of capture is proportional to the joint effects of abundance and activity, something that has very often been overlooked by ecologists for a long time... [Nonetheless,] activity estimates from pitfall trap catches can still be biased because of multiple factors such as the surrounding habitat structure or the environmental conditions such as temperature and water availability. Additional factors could be the vertical distribution of the soil and leaf litter layers, as well as the attraction or repulsion of preservative fluids, detergents, or baits, the effects of which vary according to the taxon, sex, season, and environment. Specifically, if a trap retains excessive amounts of water, it could act as an attractor for the fauna, especially during drought periods, therefore biasing the estimates of activity. "
References:
Dolores Ruiz-Lupión (2019). New Litter Trap Devices Outperform Pitfall Traps for Studying Arthropod Activity. Insects 2019, 10(5), 147; https://doi.org/10.3390/insects10050147
Hello Johanna; You may be interested in this reference;
Agosti, D, et al. 2000. Ants: Standard methods and monitoring biodiversity. Smithsonian Inst. Pr. 280 pp.
Chapter 10 discusses the relative merits of the various sampling methods. Pitfall traps are the least labor intensive sampling method for macroarthropods. The choices you make may depend on exactly what your study questions are. I've been sampling ants for 20 years. Early on I tried to compare several of the methods Winkler bags, Burlese funnels, baits, other kinds of traps. Pitfall traps actually detected all the species that any of the other methods did...in Mediterranean climates. If ground foraging arthropods are what you are interested in, that's what I'd go with.
Pitfalls don't sample subterranean species well nor are they particularly effective on arboreal species although some researchers have invented pitfalls that they can install high in trees.
A further precaution is that the use of abundance data amplifies the importance of the few commonest species and essentially ignores rare ones. If assessments of diversity are one of your goals, using incidence data avoids that problem.
One other problem is worth mentioning. Protracted monitoring of a site should yield a species list that is eventually complete. In one of my projects I sampled a single site for 10 years. The species accumulation curve NEVER drew to an asymptote! New rare species kept appearing now and then. Is that evidence of community turnover? A deficient sampling method? Who knows. Jack Longino has continuously sampled the ants at one site in Costa Rica for 30 years and continues to get new species. What this means is open to speculation.
Best regards, Jim Des Lauriers
Pitfall trapping is extremely common in field studies of herpetofauna. Check Fitzgerald 2012 "finding and capturing reptiles" and many other sources.
Hello Johanna; You may be interested in this reference;
Agosti, D, et al. 2000. Ants: Standard methods and monitoring biodiversity. Smithsonian Inst. Pr. 280 pp.
Chapter 10 discusses the relative merits of the various sampling methods. Pitfall traps are the least labor intensive sampling method for macroarthropods. The choices you make may depend on exactly what your study questions are. I've been sampling ants for 20 years. Early on I tried to compare several of the methods Winkler bags, Burlese funnels, baits, other kinds of traps. Pitfall traps actually detected all the species that any of the other methods did...in Mediterranean climates. If ground foraging arthropods are what you are interested in, that's what I'd go with.
Pitfalls don't sample subterranean species well nor are they particularly effective on arboreal species although some researchers have invented pitfalls that they can install high in trees.
A further precaution is that the use of abundance data amplifies the importance of the few commonest species and essentially ignores rare ones. If assessments of diversity are one of your goals, using incidence data avoids that problem.
One other problem is worth mentioning. Protracted monitoring of a site should yield a species list that is eventually complete. In one of my projects I sampled a single site for 10 years. The species accumulation curve NEVER drew to an asymptote! New rare species kept appearing now and then. Is that evidence of community turnover? A deficient sampling method? Who knows. Jack Longino has continuously sampled the ants at one site in Costa Rica for 30 years and continues to get new species. What this means is open to speculation.
Best regards, Jim Des Lauriers
Hello Johanna, These two recent references may also be helpful:
Privet, K. et al (2020) Relative Efficiency of Pitfall Trapping vs. Nocturnal Hand Collecting in Assessing Soil-Dwelling Spider Diversity along A Structural Gradient of Neotropical Habitats. Diversity 2020, 12, 81; doi:10.3390/d12020081.
Chaladze, G. (2020) Estimation of Ground Dwelling Arthropod Densities Using Pitfall Traps: Individual Based Simulations. Ecology and Evolutionary Biology 2020; 5: 1-5.
This is on RG now. Fitzgerald L.A. 2012. Finding And Capturing Reptiles. Pp.77-88. In R.W. McDiarmid, M. S. Foster, C. Guyer, J. W. Gibbons, and N. Chernoff (eds.), Measuring and Monitoring Biological Diversity: Standard Methods for Reptiles. University of California Press, Berkeley, California.
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