Statistical dependence for detecting whale-watching effects on humpback whales

Ana M. Garcia-Cegarra, Damian Villagra, Diego I. Gallardo, Aldo S. Pacheco

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


Whale-watching is one of the fastest growing ecotourism industries and involves the observation of endangered wild cetacean species. However, this growth has raised concerns because of the negative effects this activity may have on the behavior and survival of focal species. Hence, detecting the effects of this activity requires sensitive analytical methods allowing the implementation of regulations to protect cetacean welfare. We compared the performance of different hypothesis tests from classical and Bayesian approaches to detect whale-watching effects on humpback whale (Megaptera novaeangliae) behavior. From a cliff located 31 m above sea level in northern Peru, we measured breathing frequency, surface time, long dive duration, directness index (i.e., path linearity), and swimming speed of humpback whales before, during, and after encounters with whale-watching boats. During 167 hours of observation, we tracked 180 humpback whale groups; 43% of groups had calves and 57% did not. Inference by null-hypothesis testing indicated significant changes only in directness index after boat encounters in groups with a calf. Other methods of inference detected moderate behavior responses as increments in the number of adult breaths, swimming speed, and dive intervals for adults and calves. Whale-watching regulations must be implemented in Peru to regulate number of boats, distance to whales, approximate speed, and time observing humpback whales. Whale-watching of humpback whales with calves should be avoided.

Original languageEnglish
Pages (from-to)467-477
Number of pages11
JournalJournal of Wildlife Management
Issue number2
StatePublished - 1 Feb 2019

Bibliographical note

Funding Information:
We are especially grateful to A. H. Romero for the training in total station use. Thanks also to S. S. Buse for his help in spotting humpback whales in land-based observation point, B. A. Dulanto, S. G. Bruce, and the members of tour operator Pacifico Adventures for the logistic support during the field work. A. M. Alburquerque is also thanked for transporting us (A. M. Garcia and D. Villagra) every day to the land-based observation point. We thank T. Gerrodette and J. Carlisle for their friendly review and suggestions. Thanks to S. Livemore for her English grammar review. Finally, we thank Associate Editor and 2 anonymous reviewers for their comments, which helped to improve this manuscript. This study was funded by Rufford Foundation via Rufford Small Grants for Nature Conservation (RSG: 15903-1). A. M. Garcia is supported by a PhD Scholarship from the Chilean National Commission for Technology and Scientific Research (CONICYT/63140172-2014).

Publisher Copyright:
© The Wildlife Society, 2018


  • Bayesian inference
  • Megaptera novaeangliae
  • anthropogenic disturbance
  • ecotourism
  • management
  • null-hypothesis test
  • short-term response


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