Science shows that free-roaming cats often “go astray”—literally and figuratively. They capture wildlife (including native birds and rodents), are hit by cars, and contract and spread disease (Dabritz and Conrad 2010, Kays and DeWan 2004, Rochlitz 2003). There’s ongoing debate over the degree to which these activities pose a threat to wildlife, human and animal health, or the cats themselves. Regardless, many American cat owners allow their pets to wander outside. In fact, a recent study in Georgia revealed that 45 percent of cat owners in the study area allowed their pets to roam outdoors (Loyd and Hernandez, in press).
In 2010, a cat conflict was brewing in Athens, Georgia. Cat advocates suggested that cat predation is “natural” and insignificant, while conservation biologists cited the negative influence of cats on native species (Dauphiné and Cooper 2011). Inspired by the controversy — and concerned about the welfare of cats and wildlife — we decided to conduct research using small video cameras to monitor felines as they traveled through the great outdoors.
A Cat’s Eye View
Animal-borne video systems, called Crittercams, have been around for years, deployed to study habitat use, food habits, and general animal behavior in a variety of species including marine mammals, sea turtles, and even penguins (Marine Technology Society Journal 2007/2008). Those devices tend to be too large for cats, however, so we needed something smaller and lighter that cats would tolerate.
To that end, engineers from National Geographic Remote Imaging created what we call the KittyCam. The device is 7.5 cm by 5 cm by 2.5 cm and weighs about 90 grams — the smallest Crittercam to date. Its lithium-ion battery powers the camera for 10 to 12 hours at a time. It also contains a motion sensor that will stop the video recorder while cats are inactive or resting. The video data is stored on a 16-GB micro-SD card, allowing plenty of daily storage and easy down- loading and viewing. KittyCams also include a VHF transmitter so the camera may be located if a cat loses its collar outdoors. To ensure that the KittyCam is water resistant, the internal components are treated with spray-on silicone coating, and the openings around the lens and LEDs are filled with butyl rubber and further treated with silicone sealant.
Because of the controversial nature of the activities of free-roaming cats (especially with regard to inter- actions with native wildlife), we wanted to collect a fair amount of objective data using this new animal- borne video system. We determined that we would need a minimum of seven days of outdoor footage per participating cat in order to increase the probability of detecting a hunting event and identify the percentage of cats that were actually hunters.
To find study participants, we recruited volunteer cat owners through a human dimensions survey as well as through advertisements in two local newspapers. In all, we placed KittyCams on 60 free-roaming pet cats in suburban Athens, and monitored activities through all four seasons of the year. We relied on the cat owners to switch the camera on before placing it on their pets, charge the camera at the end of each recording day, and download video to a portable external hard drive. As incentive for participation, we offered a free total health screen for their cats including a physical exam, complete blood count, biochemical profile, and tests for Feline Immunodeficiency Virus, Feline Leukemia Virus, and heartworms.
What Happens in the Wild …
Over the course of our study, we collected more than 2,000 hours of video footage of free-roaming cat activities without disrupting cat movement, hunting, or resting. We found that on a daily basis, free-roaming pet cats spend an average of five to six hours outdoors. Some common activities involve crossing roads (potentially putting cats at risk of injury), interacting with other cats (a potential route of disease transmission or trauma from fights), climbing trees (a threat to nesting birds), and entering crawl spaces (potentially to hunt or rest).
While 44 percent of our project cats were witnessed stalking or chasing prey, only 30 percent successfully captured wildlife. Most captured just one or two prey animals during recording time, though a few captured four or five animals. Notably, reptiles topped the list of prey species in Athens and Clarke County, Georgia, including Carolina anoles, five-lined skinks, and small snakes. Reptiles were followed by mammals (such as voles and chipmunks), invertebrates (such as worms and butterflies), birds, and amphibians. Forty-nine percent of the cats’ prey was left at the capture site, 28 percent was eaten, and 23 percent was returned to the cats’ residences.
These findings are significant. Though we already knew that domestic cats were generalist predators that may exploit a wide range of prey, the frequency of predation has been unclear and a point of contention in public debates, specifically with regards to responsible cat ownership. Researchers have previously studied predation by collecting information from homeowners on the type and frequency of prey that pet cats deposit at residences (Baker et al. 2005, Lepczyk et al. 2004, Woods et al. 2003, van Heezik et al. 2010). That methodology, however, underestimates predation because cats do not bring all kills home. In fact, our study indicates that the majority of prey is eaten or abandoned at the capture site, suggesting that prey captures may be much more common than previously proposed.
Our video of cats climbing trees, entering the storm drain system, interacting with other cats, and preying on mammals, reptiles, birds, and insects was also enlightening. We saw numerous cats playing with their prey, with several bird captures lasting for over 20 minutes as cats released and recaptured the birds. One of the most surprising behaviors we witnessed was cats “cheating” on their owners: Four cats in our study entered other households for food and affection.
The KittyCam video system offers an effective option for studying the behavior of domestic cats, and for helping to educate researchers and the public about cat predation. We plan to use video footage and still images collected from our project, along with an informational brochure, as educational material for cat owners.
Similar animal-borne video systems may become useful for studying unowned stray cats. While truly feral cats may not be tame enough to handle for video work, many stray cats at subsidized outdoor colonies can be approached and handled. Video systems may also help researchers study species-specific predation and geographic distinctions in hunting activity and prey types, which are likely to differ by region and habitat. Scientists at the Smithsonian Institution in Washington, D.C., for example, are using cat-borne video technology to study predation of gray catbirds, and BBC news recently featured a cat-cam project being organized in England (BBC News 2011). Such data may yield useful insights into what free-roaming cats are up to all across the globe.
Kerrie Anne Loyd is a graduate student in Wildlife Ecology and Management at the University of Georgia’s Warnell School of Forestry and Natural Resources.
Sonia Hernandez, Ph.D., is an Assistant Professor of Wildlife Disease Ecology at the University of Georgia’s Warnell School of Forestry and Natural Resources.
Greg Marshall is Vice President of National Geographic’s Remote Imaging Department.
Kyler Abernathy is Director of Research for National Geographic’s Remote Imaging Department.
Barrett Foster is Director, Technical General Services of National Geographic’s Remote Imaging Department.