Chromogenic behaviors of the Humboldt squid (Dosidicus gigas) studied in situ with an animal-borne video package

Abstract

Dosidicus gigas (Humboldt or jumbo flying squid) is an economically and ecologically influential species, yet little is known about its natural behaviors because of difficulties in studying this active predator in its oceanic environment. By using an animal-borne video package, National Geographic's Crittercam, we were able to observe natural behaviors in free-swimming D. gigas in the Gulf of California with a focus on color-generating (chromogenic) behaviors. We documented two dynamic displays without artificial lighting at depths of up to 70 m. One dynamic pattern, termed 'flashing' is characterized by a global oscillation (2-4 Hz) of body color between white and red. Flashing was almost always observed when other squid were visible in the video frame, and this behavior presumably represents intraspecific signaling. Amplitude and frequency of flashing can be modulated, and the phase relationship with another squid can also be rapidly altered. Another dynamic display termed 'flickering' was observed whenever flashing was not occurring. This behavior is characterized by irregular wave-like activity in neighboring patches of chromatophores, and the resulting patterns mimic reflections of down-welled light in the water column, suggesting that this behavior may provide a dynamic type of camouflage. Rapid and global pauses in flickering, often before a flashing episode, indicate that flickering is under inhibitory neural control. Although flashing and flickering have not been described in other squid, functional similarities are evident with other species.

Dynamic Skin Patterns in Cephalopods

“…The species inhabits deep ocean areas from the eastern Pacific to the Chilean coast and the Sea of Cortez, where it performs vertical feeding migrations at dusk from the deep to shallower water (Markaida et al, 2005; Gilly et al, 2006; Zeidberg and Robison, 2007; Trueblood et al, 2015). The flashing patterns of D. gigas have been recorded and described on numerous occasions, including a recent deployment of the National Geographic “CritterCam” (Marshall et al, 2007; Rosen et al, 2015). Briefly, flashing patterns in this species involve the rapid opening and closing of chromatophores over the whole body in tight synchrony at a frequency of around 2–4 Hz (Figure 2a; Supplementary Video 3.1.1).…”

“…The pattern tends to occur when other D. gigas are nearby, suggesting an intraspecific communication function. The display probably plays a role in courtship as well as during agonistic interactions (Rosen et al, 2015), particularly given the high risk of cannibalization within the species (Markaida and Sosa-Nishizaki, 2003). Rosen et al (2015) also report a similar dynamic pattern in another large pelagic squid, Sthenoteuthis oualaniensis , but data supporting this is as yet unpublished.…”

“…The “CritterCam” study of Rosen et al (2015) recorded multiple instances of flicker patterns in the Humbolt squid, D. gigas . They describe the pattern as having a “ noisy wave-like appearance ” across the whole body and observed that it occurs as a “ basal level of chromatophore activity in the absence of flashing ” (Supplementary Information 3.2).…”

“…Rosen et al (2015) observed individuals of this species performing the display in the presence of other displaying conspecifics. Given that this species is known to be highly cannibalistic (Markaida et al, 2008), presumably one of the main functions of the display is as a warning or identification signal to conspecifics in the area.…”

Challenges and solutions for studying collective animal behaviour in the wild

“…accelerometers), and has been used extensively to understand foraging ecology of many species; it also has great potential for contributing to our understanding of collective behaviour. Cameras can map encounters or social interactions with conspecifics that occur out of sight of observers [111][112][113]. While technology is continuously improving, video cameras consume more power than many other sensors, analysis is often labour intensive, and it may be difficult to get a field of view that can capture all interactions of interest.…”