The value of by-catch data: how species-specific surveys can serve non-target species

Abstract

Camera trapping has a wide range of research application but, while research designs are often focused on the study of a single focal species, cameras can also record other non-target species. Occupancy modelling using bycatch data can be a valuable resource to gain information on these species maximizing the scientific effort and efficiency of wildlife surveys. In this study we used by-catch data from a European wildcat (Felis sylvestris sylvestris) survey in Southern Italy to assess the habitat covariates determinant for the occupancy of the crested porcupine (Hystrix cristata). We recorded 33 detections at 17 out of 51 cameras (naïve occupancy = 0.33). The best models fitted the data well and porcupine occupancy estimate was 0.58 (SE ± 0.09) with a detection probability of 0.11 (SE ± 0.03). Average model showed that woodlands and number of shrub patches increased porcupine occupancy, while the reverse was true for altitude. Our results have improved the insights on the habitat use and ecological needs of this understudied species and it is the first study that develops occupancy models for the porcupine using presence/absence data obtained from a camera trap survey. Our study is an example of how camera trap surveys are often an under-exploited source of valuable information on a wider spectrum of sympatric species beyond the focal species for which camera traps were deployed. Minimum requirements for a camera trap survey to provide robust occupancy estimates for non-target species are discussed.

Assumptions about fence permeability influence density estimates for brown hyaenas across South Africa

“…We utilised camera trap images of brown hyaenas collected by these camera traps (bycatch data) to model the population density of brown hyaenas. Analysing bycatch data is an efficient use of resources in conservation, provided species-specific methodological discrepancies are considered and accounted for 46,55,56 . Bycatch data on brown hyaenas from camera traps initially set up to survey leopards were used to successfully conduct occupancy analysis 46 .…”

Density responses of lesser-studied carnivores to habitat and management strategies in southern Tanzania’s Ruaha-Rungwa landscape

“…We used a photographic dataset from a research project targeting leopard. Considering the logistical and budget requirements of camera trapping, this study illustrates the value of by-catch data in terms of resource optimisation, provided that the survey design also complies with the ecology of the non-target species [66]. In this study, the conservative trap layout with an average distance between stations of around 2 km was compatible with the home ranges of the species we considered [67,68], and allowed individuals’ recapture at multiple camera trap stations [69].…”

Interspecific Aggressions between Crested Porcupines and Roe Deer

“…Therefore, interspecific interactions can be predicted, even with effects on rodent populations [56][57][58]. Up until now, most studies on rodent-ungulate interactions have been conducted on small rodents, with very few studies involving large ones [42,45]. Large-sized rodents would require a higher food amount with respect to small-sized ones, thus enhancing the potential for competition with other herbivores.…”

“…In this study, we reported, for the first time, some patterns of direct aggressive interactions between a large rodent and a cervid, i.e., the roe deer. Porcupines become particularly intolerant toward other species and conspecifics in cold months, i.e., at the peak of their reproductive period, both in feeding areas and in the surroundings of their burrows [42][43][44]. In cold months, harassments by crested porcupines (quill/crest erection) have been observed against wild boar, Sus scrofa, in feeding areas, and, in a few cases, wild boars have been wounded by porcupine quills (e.g., in Alta Val d'Elsa, A. Pieragnoli, personal communication 2020, [38]).…”

“…In cold months, harassments by crested porcupines (quill/crest erection) have been observed against wild boar, Sus scrofa, in feeding areas, and, in a few cases, wild boars have been wounded by porcupine quills (e.g., in Alta Val d'Elsa, A. Pieragnoli, personal communication 2020, [38]). Porcupines tend to avoid areas characterized by high densities of wild boar, particularly where rooting disturbance is high [42,45]. Furthermore, winter is the only period in which porcupines avoid den sharing with other species [43].…”