Northern Prairie Wildlife Research Center
Greg Marshall, National Geographic Television, 1145 17th Street NW, Washington DC 20036 USA
Crittercam is an animal-borne video and data-logging system designed for studying the at-sea behavior and ecology of large marine vertebrates. Over the past ten years, we have conducted exploratory Crittercam research on loggerhead, green and leatherback sea turtles; American alligators; nurse, lemon, bull, tiger, and great white sharks; harbor seals, fur seals, Hawaiian monk seals, elephant seals, bearded seals, Hooker's and Steller sea lions; sperm whales; and hippopotamus. In the case of harbor seals, monk seals, and sperm whales, we have moved from pilot to experimental phases of this work and have generated results that provide startling new insights to the hidden lives of these creatures.
In addition to data on dive profiles, stroke frequency, surface intervals and orientation, we have recorded behavior never seen before. We have documented visual and vocal territorial displays; intra- and interspecific aggression and defense; commensal foraging and selective feeding; dive-glide behavior; mother-calf/pup pairing and other unstudied aquatic behaviors.
By combining traditional data such as depth, temperature, and location with a visual and audio record, Crittercam provides a uniquely comprehensive perspective on factors that influence animal behavior and fitness, and that may impact the species and habitat as a whole.
Technology--Crittercam is an integrated video camcorder and data-logging system packaged in a small, streamlined housing. Harnessed to an animal, the system records images from the animal's perspective on Hi-8 or digital video tape. Housings are engineered to meet differing research needs. Aluminum systems have maximum operational depths of 600 m, while titanium units with integral image intensification capability can withstand 2000 m or more. Each of these fusiform systems is 8 to 10 cm in diameter, with a hydro-dynamically optimized nose with integral "headlights", and 20 to 50 cm long (systems with image intensifiers are longer). Other configurations are adapted according to specific study objectives.
The imaging and data-logging capability of these systems is controlled by an on-board, user-programmable micro-computer. Considerable latitude in control and data-logging capabilities is engineered into the system to meet the diverse needs of research under changing logistical, environmental, and biological conditions. Field reprogrammability of key elements is facilitated by personal computer. In particular, the following parameters can be used to control video and data-logging functions: time (real or relative), salt-water immersion, depth, temperature, light level, audio, and radio remote control. In turn, these can be used collectively to optimize and focus the data gathering period. Data and image sampling can be segregated so that data can be logged continuously while images are sampled periodically to focus on behavior of interest. Video tapes enable 3 hr of color recording.
While this system provides considerable flexibility and substantial data, we continue efforts to make the unit smaller, simpler, and more powerful and robust. Further developments in data acquisition also continue and can include velocity, accelerometry, compass orientation (for three dimensional tracking of animal movement), physiological parameters (EKG and stomach temperature), salinity, or other parameters of potential interest. These advances will make the system more user-friendly and improve its adaptability to varying research objectives, species and field conditions. We also continue to improve deployment techniques (whether harnessing, tagging, gluing or other) to ensure that Crittercam is used in the most benign possible way.
Conclusion--CRITTERCAM is a powerful tool for studying animal behavior and habitat use in applications where direct human observation is impossible and animal disturbance must be minimized. This benign and virtually unobtrusive system provides a means to investigate at-sea phenomena that were heretofore unapproachable... perhaps even unimagined.