Anthropogenic influences on the distribution of a threatened apex-predator around sustainable-use reserves following hydropower dam installation

Raffo, Deborah C. Dávila; Norris, D. Ryan; Hartz, Sandra Maria; Michalski, Fernanda

doi:10.7717/peerj.14287

Cited by 1 publication

(1 citation statement)

References 43 publications

(63 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is therefore unlikely that the absence of diurnal observations was due to a temporal change in giant otter activity in the most disturbed river reaches. The most plausible explanations are that giant otters have either moved away from and/or been hunted out of areas more intensely used by humans ( Raffo et al, 2022 ). While our data provides a broad scale assessment, it is likely that giant otters with complex social interactions will also demonstrate population and individual level changes to human disturbances.…”

Section: Discussionmentioning

confidence: 99%

Human disturbances and the daytime activity of sympatric otters along equatorial Amazonian rivers

Norris

Michalski

2023

PeerJ

Self Cite

View full text Add to dashboard Cite

Background Previous studies suggest coexistence between sympatric neotropical (Lontra longicaudis) and giant otters (Pteronura brasiliensis) maybe facilitated by temporal and spatial differences in activity. Yet, to date there has been no systematic evaluation of activity of these species in sympatry. Here we use extensive multi-year field data to compare temporal and spatial patterns in the diurnal activity of sympatric giant and neotropical otters to answer three questions: Do temporal patterns in daytime river use change in relation to seasonal river levels (low, rising, high and declining river levels), do they change due to human disturbances (boats and fishing nets) and do patterns in neotropical otter activity change due to the presence of the larger sized giant otter? Methods Direct observations of both species were recorded using standardized boat surveys along 218 km of rivers over 53 months during nine years (2011–2013 and 2015–2020). Complementary techniques (Generalized Additive Models, Kernel density estimates and non-parametric tests,) were used to compare diurnal activity patterns along rivers subdivided into 41 river reaches. Results The presence of giant otters decreased threefold from 67% of the least disturbed reaches (few boats no fishing nets) to 18% of the most disturbed reaches with many boats and fishing nets. In contrast neotropical otter presence nearly doubled from 44% of the least disturbed to 73% of the most disturbed reaches with fewest giant otter detections. Both species were observed across all daytime hours but were observed rarely on the same day. There was no evidence to suggest simultaneous use of the same reach. When species were detected on the same day, they were separated spatially (median distance between species 12.5 km) and temporally (median time difference 3.0 hours). There was little change in activity of either species among seasons. Giant otters were less active in river reaches with fishing nets and boat use, whereas neotropical otter activity did not appear to be strongly affected by these activities. Conclusions Our findings support evidence that diurnal activity in both otter species is flexible, with daytime activity changing due to human disturbances in the case of giant otters.

show abstract

Section: Discussionmentioning

confidence: 99%