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Species distribution and conservation assessment of the black-headed night monkey (Aotus nigriceps): a species of Least Concern that faces widespread anthropogenic threats

Abstract

Deforestation rates in the Brazilian Amazon have been steadily increasing since 2007. Recent government policy, the projected growth of agriculture, and the expansion of the cattle industry are expected to further pressure primates within the Amazon basin. In this study, we examined the anthropogenic impact on the widely distributed black-headed night monkey, Aotus nigriceps, whose distribution and population status have yet to be assessed. We (1) modeled potential species distribution in A. nigriceps, (2) estimated the impact of habitat loss on population trends, and (3) highlight landscape-based conservation actions that maximize the potential for their long-term sustainability. We found the black-headed night monkey to be restricted by several biotic and environmental factors including forest cover, isothermality, precipitation, temperature, and elevation. Over the last two decades, over 132,908 km2 of tree cover (18%) has been lost within their currently recognized range based on satellite imagery. Based on a balance training omission, predicted area, and threshold values (BPTP), suitable habitat was only 67% (1,069,948 km2) of their hypothesized range, a loss of 16.5% from 2000, with just nearly a third of suitable habitat currently within protected areas. Over the last two decades, an estimated minimum 1.6 million individuals have been lost due to loss of suitable habitat. Projected deforestation rates equate to an additional loss of 94,458 km2 of suitable habitat over the next decade. Although classified as a species of Least Concern, we suggest that A. nigriceps may likely be more at risk than previously described. The future impact of the continued expansion of monoculture crops, cattle ranching, and wildfires is still unknown. However, we outline several steps to ensure the long-term viability of this nocturnal primate and other sympatric species throughout the Amazon Basin.

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Acknowledgements

Thank you to Hillary Fenrich, Sheridan Plummer, and Ben Sharaf who assisted in original model development. Thank you to Rob Wallace for sharing Wildlife Conservation Society occurrence data from Bolivia. We are indebted to the anonymous reviewers who provided constructive feedback.

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Study design, data collection, analysis, and writing: WDH; Modeling, analyses, and assistance with writing: JWV.

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Correspondence to William D. Helenbrook.

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Supplementary Information

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Supplementary file1 SUPPLEMENTARY S1: The predicted probabilities of Aotus nigriceps presence for each environmental variable in the optimal Maxent model. The curves represent a Maxent model created using only the corresponding variable, with the mean response of 15 replicate Maxent runs (red) and ± one standard deviation (blue) (PNG 162 kb)

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Supplementary file2 SUPPLEMENTARY S2: The predicted probabilities of Aotus nigriceps presence for each environmental variable in the optimal Maxent model. The curves represent a Maxent model created using the corresponding variable while keeping all other environmental variables at their average sample values. The mean response of 15 replicate Maxent runs are represented in red with ± one standard deviation in blue (PNG 138 kb)

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Supplementary file3 SUPPLEMENTARY S3: Jackknife tests for variable importance for regularized a) training gain, b) test gain, and c) AUC on test data averaged over 15 replicate bootstrap runs for predicting Aotus nigriceps distribution modeling (PNG 74 kb)

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Supplementary file4 SUPPLEMENTARY S4: Predicted suitability of Aotus nigriceps habitat within their range for a) 2018 and b) 2000. Greener areas represent areas with highest probability (PNG 311 kb)

Supplementary file5SUPPLEMENTARY TABLE 1: Data and source of information used in model development (XLSX 19 kb)

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Helenbrook, W.D., Valdez, J.W. Species distribution and conservation assessment of the black-headed night monkey (Aotus nigriceps): a species of Least Concern that faces widespread anthropogenic threats. Primates 62, 817–825 (2021). https://doi.org/10.1007/s10329-021-00922-w

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  • DOI: https://doi.org/10.1007/s10329-021-00922-w

Keywords

  • Amazon
  • Aotus nigriceps
  • Peru
  • Deforestation
  • Maxent
  • Primate
  • Red list
  • Rainforest