Ever since mist nets were first employed for bat capture, efforts to develop stacked, or canopy nets were attempted. This brought standard 2.6m-high nets into lofty realms exceeding 9m in altitude. Initial arrangements were borrowed from successful bird netting protocols in the 1960s (Kunz 1988). Early on, researchers reported that canopy nets greatly increased bat capture success. (Jones et al., 1996). Yet stacked canopy nets have been slow to catch on in the bat world, despite numerous allusions to their efficacy, including the following:

Lasiurus cinereus . . . is widely distributed across the United States; however, in Oklahoma only 19 specimens have been reported during the last 59 years. From May to August of 1985, 16 additional individuals were mist netted in southeastern Oklahoma. These are noteworthy in that they nearly double the number recorded in the state and add to our knowledge of the species’ ecology . . . It is not readily apparent why we were able to collect almost as many L. cinereus in one summer as have been collected in the past 59 years in Oklahoma. One explanation may be that the mist-netting technique we used was different that that used by previous collectors . . . we used a high mist net . . . three 9.1m long mist nets hoisted one above the other with a pulley system. When raised, the nets extended upward 7.6m and covered a 69.3 m2 area (Caire 1986).

Perhaps much of the resistance to canopy netting is attributed to the difficulties in transporting, erecting, and stabilizing the necessary equipment in the field to install 2 or more stacked mist nets and maintain proper tension across the entire set. Many of the initial canopy netting arrangements were custom made affairs based on years of personal trial and error, and involved complex rigging, with tarps, slingshots, sailboat masts and other unwieldy gear. Despite this, canopy nets at least 7m high have been required by the U.S. Fish and Wildlife Service sampling protocols for endangered Indiana myotis inventories (USFWS 2007) since the adoption of the Recovery Plan for the species.

Yet, with the exception of much of the Indiana myotis work in the northeastern and midwestern U.S., stacked canopy nets often remain an anomaly in bat research The perceived bias towards the complexity of canopy netting persists, and many of the most recent “species richness” and “relative abundance surveys” conducted, even in tropical locations where access to the canopy for sampling wildlife is known to produce impressive species diversity results, still rely upon standard, single-high, ground based mist nets (Flaquer 2007, Johnson 2008, Larsen 2007, and Weller 2007).

Today, with the first commercially available, triple-high mist net system from Bat Conservation and Management (BCM, Carlisle PA), excuses about the complexity of canopy netting can literally evaporate. The BCM system is eminently portable, genuinely easy to deploy, and impressively effective at capturing large numbers of bats easily and efficiently.

Since 2002, triple-high mist nets have been used at Bat Conservation International, Inc., (BCI) “Bat Conservation and Management Workshops” in Arizona, California, Kentucky, and Pennsylvania. During survey periods at these training courses, triple-high mist nets are often used side-by-side with traditional single-high net sets. Results of these efforts indicate that 3-8 times more bats (Figure 1.) and 2-3 times more species are caught in the larger nets. And this is despite the fact that triple-high nets must be lowered, and effectively removed from an active capture status, every time a bat is removed. Moreover, the BCM system is elegantly simple and has been deployed by first-time bat workers with little more than 20-minute of practical instruction

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Figure 1. Bat capture results from 2007 and 2008 BCI Bat Conservation and Management Workshops in AZ, KY, and PA where triple-high mist nets were deployed side-by-side with single-high mist nets at a single sampling area on a single night.

This said, it should be noted that certain species, especially those well suited for travel through cluttered environments, are often encountered more often in single-high mist nets. Therefore, triple-high mist nets are important components to help eliminate bias in any species richness or relative abundance survey. And, deployment alongside other capture methods including harp traps, ground-based mist nets, and acoustic recording devices is warranted to obtain the most comprehensive snapshot of bat species diversity and occurrence for any sampling period. The BCM triple-high set provides the most “bang for the buck” for increasing capture success and quickly becomes a treasured component in the bat research toolbox.

Work Cited

Caire, W., R.M. Hardist, and K.E. Lacy. 1986. Ecological Notes on Lasiurus cinereus (Chiroptera; Vespertilionidae) in Oklahoma. Proceedings of the Oklahoma Academy of Science. 66: 41-42.

Flaquer, C., I. Torre, and A. Arrizablaga. 2007. Comparison of sampling methods for inventory of bat communities. Journal of Mammalogy, 88(2): 526-533.

Johnson, J.B. and J.E. Gates. 2008. Bats of Assateague Island National Seashore, Maryland. American Midland Naturalist, 160: 160-170.

Jones C., W.J. McShea, M.J. Conroy and T.H. Kunz. 1996 “Capturing Mammals.” In: Wilson, D.E., F.R. Cole, J.D. Nichols, R. Rudran and M.S. Foster (Eds.) Measuring and Monitoring Biological Diversity Standard Methods for Mammals. Smithsonian Institution Press, Washington D.C., 409 pages.

Kunz, T.H. and A. Kurta. 1988. “Capture Methods and Holding Devices.” In: Kunz, T.H. (Ed.) Ecological and Behavioral Methods for the Study of Bats. Smithsonian Institution Press, Washington DC. 533 pages.

Larsen, R.J., K.A. Boegler, H.H. Genoways, W.P. Masefield, R.A. Kirsch, and S.C. Pedersen. 2007. Mist netting bias, species accumulation curves, and the rediscovery of two bats on Montserrat (Lesser Antilles). Acta Chiropterologica, 9(2): 423-435.

U.S. Fish and Wildlife Service (USFWS). 2007. Indiana Bat (Myotis sodalis) Draft Recovery Plan. First Revision. U.S. Fish and Wildlife Service, Fort Snelling MN, 258 pages.

Weller, T.J. and D.C. Lee. 2007. Mist net effort required to inventory a forest bat species assemblage. Journal of Wildlife Management, 71(1): 251-257.