Are camera traps really non invasive ?
Without engaging into a complicate debate regarding this question, we just want to expose several pictures of 20 different species that might question this assertion. Since we started ecological monitoring with camera traps in Mlele Beekeeping Zone in 2008 we captured images of 42 mammal species. Globally, all methods combined 53 species of mammals have been recorded so far (see Fischer et al., 2013, Hausser et al., 2014). The 20 species presented hereafter represent almost 50 % of all captured species during the camera trap surveys conducted on a yearly basis since 2008.
All the animals in the following selection of pictures definitely saw the camera – probably alerted by noise or light coming from the devices, and all of them were aware that there was something strange attached to a tree…
According to some research, different species have developed avoidance behaviours towards cameras (see Sequin et al., 2003 about coyotes, Canis latrans and Schipper, 2007 about kinkajous, Potos flavus). I’ve been told by some South African researchers that leopards (Panthera pardus) can develop such behaviours but our experience doesn’t confirm this for the leopard, with some individuals recaptured 9 times in the past 5 years. However, if we never explicitly observed avoidance behaviours, there are several species we’ve never managed to capture after 5 years of field surveys totalling several thousand camera trap days.
If the ecology of some species and the intensity of our sampling might explain these” false absences” – the species being frequently observed in the Beekeeping Zone by other methods (direct observations) such as the slender (Herpestes sanguinea) or dwarf (Helogale parvula) mongooses, and Kirks’ dik dik (Madoqua kirki), the non-detection of other species appears more difficult to explain. These species may remain undetected for several reasons, their home ranges are smaller or larger than the grid sampling unit we are using, their small size and limited body mass may induce poor detection by the Cuddeback capture model, surveys never targeted their prime habitat, such as termite holes and surrounding bushland – woodlands in the case of dwarf mongooses. The use of Reconyx and a more habitat oriented sampling strategy would permit to capture image of these species.
Among the recorded species, it seems surprising to never have captured images of the small bushbaby (probably Galago moholi) and rarely the Silver greater galago (Otolemur crassicaudatus). As suggested by literature, night active species, particularly arboreal ones, might be more sensitive to light than other species. The only question would remain how have they learnt to avoid traps if they never experienced it?
Carnivores seem particularly aware of the camera presence, because most of the species have been recorded looking directly to the camera, such as the pictured leopard, lion (Panthera. leo), wild dog (Lycaon pictus), hyena (Crocuta crocuta) or civet (Civettictis civetta).
Primates seem particularly aware of the cameras presence as well, with all species captured looking at the cameras. For one species, the vervet (Chlorocebus pygerythrus), some individuals really seem to not appreciate it!
Most ungulates species appear aware of the cameras’ presence. For some of them like the buffalo (Syncerus caffer), this awareness doesn’t induce behaviour change as the same individual can remain with the herd in front of the camera for hours, if the pasture is good and the threat limited. Similarly bushbuck (Tragelaphus scriptus) or common duiker (Sylvicapra grimmia) can be recaptured several times by cameras located strategically in their territory.
Fischer, C., R. Tagand and Y. Hausser (2013) Diversity and distribution of small carnivores in the miombo woodlands of Katavi region, Western Tanzania. Small Carnivores Conservation, Vol.48:60-66.
Hausser, Y., R. Tagand, E. Vimercati, S. Mermod and C. Fischer (2014) Revisiting conservation value of a community managed protected area in Western Tanzania with the use of camera traps.
Submitted to African Journal of Ecology, under review.
Schipper J. (2007) Camera traps avoidance by kinkajous (Potos flavus): rethinking the non invasive paradigm. Small Carnivores Conservation, Vol. 36:38-41.
Sequin, E. S., M. M. Jaeger, P. F. Brussard, R. H. Barrett (2003) Wariness of coyotes to camera traps relative to social status and territory boundaries. USDA National Wildlife Research Center, Staff Publication, Paper 233.