Changing use of camera traps in mammalian field research: habitats, taxa and study types

Camera traps are automated cameras, triggered by movements, used to collect photographic evidence of the presence of animals in field research. I asked whether the use of camera traps in mammalian field research is distributed evenly and increasing equally in a range of habitats, taxa and study types. I aimed to understand where camera traps are used and for what purposes. I identified the population of papers published since 1994 in which camera trap methodology was used. I then explored the population for defined habitats, taxa and study types. I tested the derived data for growth and distribution. Over 96% of the population of camera trap papers identified were focused on mammalian species. Between 1994 and 2011, the use of camera traps for mammalian research increased: 73% of 414 studies were published after 2005. Over time, equipment has become more sophisticated, reliable, flexible, cost-effective and easy to deploy, and there have been other methodological advances. Growth in the number of mammal-related camera trap studies was matched by an expansion in the taxa studied and in study types. The most studied taxon is the order Carnivora; forests are the most studied habitat. No single study type dominates, although there are more population density studies than any other. Camera trap studies are focused on a limited number of habitats and taxa due to their particular strengths and the characteristics of the species that they are used to investigate. Developments such as infrared illumination and triggering, greater battery life, improved lenses, digital storage capacity, miniaturization, video and real-time links will enable camera traps to be used for an increasing range of habitats, taxa and study types and will reinforce their growing value in the areas in which they currently predominate.