Introduction
Capture-mark-recapture (CMR) is a widely used technique to address fundamental questions in animal ecology, evolution, and biological conservation (Pradel, 1996; Lettink & Armstrong, 2003; Amstrup, McDonald, & Manly, 2010). It permits making powerful inferences about population size, survival rate, recruitment, dispersal, as well as predicting the effects of intrinsic (e.g. body size, age, disease) and extrinsic factors (e.g. temperature, precipitation, food) (Conn & Cooch, 2009; Martins et al., 2011; Hassall, Sherratt, Watts, & Thompson, 2015; Rose, Wylie, Casazza, & Halstead, 2018) on those parameters. While marking or tagging animals can be relatively easy, recapturing marked individuals is often a challenging process, even in systems where individuals do not disperse. These difficulties are enhanced for highly mobile animals such as mammals, birds, and insects (Dickinson, Lehmann, & Sane, 1999; Muijres, Johansson, Bowlin, Winter, & Hedenström, 2012).
Insect species can be good model organisms for CMR studies (Hagler & Jackson, 2001). Besides their smaller size which allows convenient capture, handling, and marking, they also have a short life cycle, conspicuous behavior, small home range size, and fixed adult size. Identifying a marked individual often requires immobilizing it, as small size and rapid speed means that marks are typically difficult to detect for an insect that is in motion. While repeated physical captures of individuals are one method that have often been used to accomplish identification of marked individuals (Hagler & Jackson, 2001), repeat captures of insects may alter their behavior and/or cause injuries, thereby affecting their survival (Morton, 1982; Cordero, Perez, & Andres, 2002). Telemetry is another possible solution, but it is still technologically challenging and costly to miniaturize transmitters to a size that is suitable for most insects (Daniel Kissling, Pattemore, & Hagen, 2014). Consequently, most CMR studies have been carried out with conventional direct observations of marks on insects, but theses often yield low recapture rates and, subsequently, produce unreliable demographic and/or dispersal estimates (Service, 1993). Such poor estimates can hinder conservation planning (Hammill & Clements, 2020).
One of the most frequent insect groups in CMR studies is odonates (dragonflies and damselflies) (Cordero-Rivera & Stoks, 2008). Usually, an alphanumeric code is written on the wing with a permanent marker. After marking, some species of odonates (belonging to Aeshnidae) are particularly challenging to resight, because they rarely perch, instead spending most of their time in flight, where they are too fast for the human eye (Corbet, 1999). The use of conventional visual observations leads to low resighting rates. To overcome this impediment, a tool that ideally does not require the physical capture of individuals to identify dragonflies in flight is needed. One such potential tool is high-speed video (HSV) cameras, which capture videos with a high enough frame rate that one can slow down the motion of the individual and wings (Li, Zheng, Pan, & Su, 2018), thereby allowing for identification of the mark. HSV has thus the potential to gather data that cannot be obtained with conventional visual observations.
HSV have been used in the study of animal behavior, particularly during the last few decades. Whether it is flying, running, swimming, feeding or drinking, high-speed videos have enabled scientists to examine diverse behaviors of various taxa meticulously (Altshuler, Dudley, & McGuire, 2004; Maie, Wilson, Schoenfuss, & Blob, 2009; Reis, Jung, Aristoff, & Stocker, 2010; Marras et al., 2015). The rapid recent uptake of this technology in ecology is due to the substantial decrease in the cost of such cameras, the decline in the camera’s size and weight making it suitable for field studies, and the improved video capabilities in duration and quality (Steen, 2014; Garbin, 2018; Lailvaux, 2018). Although HSVs have been used to study various aspects of animal behavior, thus far, HSV not been integrated into CMR studies of highly mobile animals.
Here we assess how HSV can contribute to the resighting of marked individuals and ask whether such a method can improve estimates of demographic parameters. Using populations at artificial ponds, we carried out CMR on two large North American dragonflies, Anax junius and Rhionaeschna multicolor(Paulson, 2009), and then used the Cormack-Jolly-Seber model to compare the resighting and survival rate of the capture history generated by the conventional visual method (CV: direct observation with the naked eye) to that generated by combining CV with high-speed video (CV+HSV). Further, we tested whether HSV improves our ability to estimate the effect sizes of covariates that might impact survival, such as body size and age.