Visual encounters on line transect surveys under-detect carnivore species: Implications for assessing distribution and conservation status

Abstract

We compared the distribution and occurrence of 15 carnivore species with data collected monthly over three years by trained native trackers using both sign surveys and an encounter-based, visual-distance method in a well-preserved region of southern Guyana (Amazon / Guiana Shield). We found that a rigorously applied sign-based method was sufficient to describe the status of most carnivore species populations, including rare species such as jaguar and bush dog. We also found that even when accumulation curves for direct visual encounter data reached an asymptote, customarily an indication that sufficient sampling has occurred to describe populations, animal occurrence and distribution were grossly underestimated relative to the results of sign data. While other researchers have also found that sign are better than encounters or camera traps for large felids, our results are important in documenting the failure of even intensive levels of effort to raise encounter rates sufficiently to enable statistical analysis, and in describing the relationship between encounter and sign data for an entire community of carnivores including felids, canids, procyonids, and mustelids.

Mammal traits and soil biogeochemistry: Functional diversity relates to composition of soil organic matter

“…Furthermore, the C:N ratio of herbivore dung is similar to that of leaves, whereas that of carnivores is much lower and optimal for microbial growth (Benbow et al, 2019). Large mammal species are key components of the tropical forest fauna, including felid and canid predators, frugivorous primates and ungulates, folivores and herbivores, among others (Fragoso et al, 2016(Fragoso et al, , 2019. Collectively, the organic remains generated by these mammal assemblages alter carbon inputs to the soil and affect the molecular composition of SOM.…”

Completeness of rapid assessments of medium and large mammal diversity in the northwestern Amazon in Colombia

“…Shortterm surveys are necessary for environmental management in the Colombian Amazon and produce valuable information about biodiversity, but these data must be understood in the light of the representativeness of the sampling. More accurate estimates can be obtained using complementary methods to camera trapping, such as interviews with local inhabitants (Voss and Emmons 1996;López-Arévalo et al 2021), surveys of animal tracks or signs (Fragoso et al 2019), analysis of hunting records (Voss and Emmons 1996), and the prospection of remains of consumed animals that are usually available in indigenous and settler communities (Osorno et al 2014). It is also important to stress that, although useful, rapid assessments are not enough to assess long-term effects of environmental transformation and tendencies of biodiversity loss.…”

Roadkills as a Method to Monitor Raccoon Dog Populations

“…A variety of direct and indirect methods may be used to monitor the presence of large and medium-sized mammals and to evaluate their density indices, these including direct observations, trapping, hunting with known effort, transect counts, camera traps, the use of scent stations, field sign counts and hair traps. Some of these may be conducted by hunters or professional biologists, while others by citizen scientists [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 ].…”