Table 4.
Environmental variables of CT location that influence detection by CTs at different orders of detection
| Characteristica | Direction and magnitude of effect on detection probability per orderb | Mechanism | Studies needed | When to correct forc | References | |||||
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5 | 6 | |||||
| Attractant (bait or lure)d | + | ++/− | ++/− | Contact with CTs and retention time in front of CT | Design, season | (Diete, Meek, Dixon, Dickman and Leung, 2016; Satterfield et al., 2017; Suárez‐Tangil and Rodríguez, 2017) | ||||
| Background temperaturee | − | − | − | − − | Contact with CTs and PIR sensor functionality | Season, site | (Nagy‐Reis et al., 2017; Lesmeister et al., 2015; Pease, Nielsen and Holzmueller, 2016; Welbourne et al., 2016) | |||
| Denseness of the vegetation | − | − | − − | − − | − − | Contact with CTs, PIR sensor functionality, and identification of detected animals | Design, season, site | (Hofmeester et al., 2017a; Rich et al., 2016) | ||
| Distance of animal to the camera | − − | − − | PIR sensor functionality and identification of detected animals | Design, season, site | (Hofmeester et al., 2017a; Howe et al. 2017; Rowcliffe et al., 2011) | |||||
| Human disturbancef | +/− | +/− | +/− | (−) | (−) | Contact with CTs | Season, site | (Larrucea et al., 2007; Wearn et al., 2017) | ||
| Landscape features channeling animal movement (e.g., trails) | ++ | ++ | Contact with CTs | Design, season, site | (Cusack, Dickman, et al., 2015a; Harmsen et al., 2010; Kolowski and Forrester, 2017; Reilly, Tobler, Sonderegger and Beier, 2017; Srbek‐Araujo et al., 2013) | |||||
| Repulsive features in the landscapeg | − | − | − | Contact with CTs and retention time in front of CT | Design, season, site | (Khorozyan et al., 2014; Larrucea et al., 2007; Mann, O'Riain, & Parker, 2015; Nagy‐Reis et al., 2017; Rich et al., 2017) | ||||
| Resource availability | ++ | ++ | ++ | ++ | ++ | Contact with CTs and retention time in front of CT | Design, season, site | (Brassine & Parker, 2015; Lesmeister et al., 2015; Nagy‐Reis et al., 2017; Rich et al., 2017) | ||
| Time of day (day vs. night)h | +/− | Identification of detected animals | Season, site | (Cusack, Swanson et al., 2015b; Nagy‐Reis et al., 2017; Rowcliffe et al., 2014) | ||||||
| Weather | +/− | +/− | PIR sensor functionality and identification of detected animals | Season, site | (Lesmeister et al., 2015; Nagy‐Reis et al., 2017; Pease et al., 2016) | |||||
Characteristics are seen as continuous variables unless otherwise stated in the table or the footnotes, where the direction of the effect given is with an increase in the characteristic. For example, detection probability increases with an increase in resource availability.
Direction and magnitude of effect on detection probability given in a scale from ++ to − − with 0 if no effect was found, biases given between brackets are not based on literature but estimates from the authors. When multiple studies reported contrasting results, we give the reported range separated with a /.
Factor given needs to be corrected for if multiple of these are considered in a study (see main text). Design refers to studies using multiple study designs.
Attractants can have different effects on different species depending on the type of attractant and the species life history, for example, using meat as attractant will most likely attract carnivores but not necessarily ungulates or other herbivores.
Presented direction of bias is for endotherms, as for cold ectotherms, the relationship is reversed (they are better detected at higher background temperatures). The effect of temperature is both due to avoidance by animals of the hottest parts of the landscape (2nd‐4th order) and due to the influence of background temperature on the PIR sensor functionality (5th order)
Human disturbance can have a positive or negative bias depending on how well individuals in a population/of a given species are adapted to human disturbance. Furthermore, humans can damage or sabotage CTs which leads to a negative bias at the 5th and 6th order.
Repulsive features in the landscape are often human features, such as a highway, that reduce detection of certain species. There are however large differences between species in terms of being repulsed or attracted to the same landscape features (see cited references).
For most species, species and individuals can be better identified using color images (at day or with white flash) than using black and white images (infrared flash). Furthermore, the range of the flash decreases identification probability at night, while this is not the case with natural (day) light.