Influence of camera-trap sampling design on mammal species capture rates and community structures in southeastern Brazil

Abstract

The distribution of species and population attributes are critical data for biodiversity conservation. As a tool for obtaining such data, camera traps have become increasingly common throughout the world. However, there are disagreements on how camera-trap records should be used due to imperfect species detectability and limitations regarding the use of capture rates as surrogates for abundance. We evaluated variations in the capture rates and community structures of mammals in camera-trap surveys using four different sampling designs. The camera traps were installed on internal roads (in the first and fourth years of the study), at 100-200 m from roads (internal edges; second year) and at 500 m from the nearest internal road (forest interior; third year). The mammal communities sampled in the internal edges and forest interior were similar to each other but differed significantly from those sampled on the roads. Furthermore, for most species, the number of records and the capture success varied widely among the four sampling designs. A further experiment showed that camera traps placed on the same tree trunk but facing in opposing directions also recorded few species in common. Our results demonstrated that presence or non-detection and capture rates vary among the different sampling designs. These differences resulted mostly from the habitat use and behavioral attributes of species in association with differences in sampling surveys, which resulted in differential detectability. We also recorded variations in the distribution of records per sampling point and at the same spot, evidencing the stochasticity associated with the camera-trap location and orientation. These findings reinforce that for species whose specimens cannot be individually identified, the capture rates should be best used as inputs for presence and detection analyses and for behavior inferences (regarding the preferential use of habitats and activity patterns, for example). Comparisons between capture rates or among relative abundance indices, even for the same species, should be made cautiously.

Buffer zone use by mammals in a Cerrado protected area

“…These results are very interesting, because they suggest that the buffer zone, although disturbed, can still provide favorable habitat and food resources for these large carnivores. Similarly, the generalist puma and maned wolf have been recorded outside of Emas National Park, another large Cerrado protected area (Silveira 2004;Vynne et al 2010;Vynne et al 2014). Our results support therefore the notion that buffer zones are potential usable area for these large carnivores, corroborating other authors (Massara et al 2012;Miotto et al 2012).…”

“…On the other hand, distance from the nearest road explained better the detection of wild cats. This result is expected since felids, in general, have been detected preferentially along unpaved roads, while species such as P. tajacu avoid roads and have been recorded with higher frequency in forest interiors (Trolle & Kéry 2005, Goulart et al 2009, Srbek-Araujo & Chiarello 2013). Moreover, although we did not assess the relative impact of poaching, the collared peccary is a traditional target in Brazil (Cullen et al 2000), and it might also be disturbed by domestic dogs (Canis familiaris), present in human settlements that are common outside protected areas.…”

First record of intestinal parasites in a wild population of jaguar in the Brazilian Atlantic Forest

“…In this scenario, the possibility of contact between jaguars and domestic dogs, culminating with the introduction of new parasites in the wild population, is a real threat for the conservation of this large cat. Indeed, the presence of domestic dogs has been recorded in the RNV through direct sightings, records of vocalizations and camera traps (SRBEK-ARAUJO; CHIARELLO, 2013). This situation is further aggravated by the extremely small size and isolation of this jaguar population in the Linhares/Sooretama block, with estimations of only approximately 20 animals (SRBEK-ARAUJO, 2013).…”

“…We identified the cat species by searching for guard hairs (hair ingested by specimens during self-cleaning and eliminated in the feces) and comparing them with a reference collection (futher details can be found in DEL DUQUE Jr., 2012). We also used genetic analysis to assist in the identification of cat species (fecal DNA extraction) (details of the methodology and results can be found in HAAG et al, 2009 andSRBEK-ARAUJO, 2013).…”

Ocupação de paisagens dentro e fora de unidades de conservação pelo veado-catingueiro (Mazama gouazoubira Fischer, 1814) no nordeste paulista

“…Este resultado também se relaciona a aspectos comportamentais da espécie, que utiliza estradas de terra para atravessá-las ("atravessadores") e não de forma a segui-las ("seguidores") em função da maior utilização destas como rotas de deslocamento por grandes felinos e por cachorros domésticos, potenciais predadores, além do maior fluxo de pessoas e máquinas agrícolas, como observado nas áreas de estudo do presente trabalho, aumentando assim os riscos à espécie. De fato, a maior probabilidade de detecção do veado-catingueiro fora de estradas de terra, bem como o padrão de movimentação nestes locais, foi observado em diferentes estudos (Harmsen et al 2010;Srbek-Araujo & Chiarello, 2013). Segundo estes autores, Mazama spp estão associadas aos cursos d'água e às bordas de florestas, o que corrobora a utilização de estradas de terra de forma oportunista, devido sua grande disponibilidade próxima ao seu hábitat.…”