New publication: Spinner dolphins of Hawaii may be less resilient to disturbance than other cetaceans

Home / Hawaiian Spinner Dolphin Project / New publication: Spinner dolphins of Hawaii may be less resilient to disturbance than other cetaceans

We are pleased to announce the following publication by Dr Julian Tyne and co-authors in Royal Society Open Science.

Title: Temporally and spatially partitioned behaviours of spinner dolphins:implications for resilience to human disturbance
Authors: Julian A. TyneDavid W. Johnston, Fredrik Christiansen and Lars Bejder

Link to paper: http://rsos.royalsocietypublishing.org/lookup/doi/10.1098/rsos.160626

Abstract:

Selective forces shape the evolution of wildlife behavioural strategies and influence the spatial and temporal partitioning of behavioural activities to maximize individual fitness. Globally, wildlife is increasingly exposed to human activities which may affect their behavioural activities. The ability of wildlife to compensate for the effects of human activities may have implications for their resilience to disturbance. Resilience theory suggests that behavioural systems which are constrained in their repertoires are less resilient to disturbance than flexible systems. Using behavioural time-series data, we show that spinner dolphins (Stenella longirostris) spatially and temporally partition their behavioural activities on a daily basis. Specifically, spinner dolphins were never observed foraging during daytime, where resting was the predominant activity. Travelling and socialising probabilities were higher in early mornings and late afternoons when dolphins were returning from or preparing for nocturnal feeding trips, respectively. The constrained nature of spinner dolphin behaviours suggests they are less resilient to human disturbance than other cetaceans. These dolphins experience the highest exposure rates to human activities ever reported for any cetaceans. Over the last 30 years human activities have increased significantly in the Hawaii, but the spinner dolphins still inhabit these bays. Recent abundance estimates (2011 and 2012), however, are lower than all previous estimates (1979-1981, 1989-1992 and 2003), indicating a possible long-term impact. Quantification of the spatial and temporal partitioning of wildlife behavioural schedules provides critical insight for conservation measures that aim to mitigate the effects of human disturbance.

Spinner dolphins in a resting bay exposed to human activities. Picture taken under NOAA permit GA LOC 15409

Spinner dolphins exposed to human activities. Picture taken under NOAA permit GA LOC 15409

Background and context:

In the United States the National Marine Fisheries Service (NMFS) is mandated to protect the spinner dolphins of Hawaii under the Marine Mammal Protection Act (MMPA). Since the spinner dolphins of Hawaii are not listed as threated or endangered, the MMPA is the only major piece of federal legislation involved in protecting them. The fact that no exemption exists under the MMPA for viewing cetaceans, means there are no specific measures in place to manage human behaviour and their interactions with spinner dolphins in their resting bays at this time.

The number and frequency of the interactions has been of concern to managers and policymakers in the National Oceanic and Atmospheric Administration (NOAA) and specifically the NMFS for more than a decade. In 2005, the NMFS and NOAA announced its plan to implement new regulations to protect spinner dolphins and they suggested time-area closures as their proposed action. However, many stated that the effects of human-spinner dolphin interactions were not well understood and called for more research. This led to inception of the Spinner Dolphin Acoustics, Population Parameters and Human Impacts Research (SAPPHIRE) Project, a joint project between Murdoch University and Duke University. This project set out to quantify the possible effects of human interactions on spinner dolphins across multiple sites with variation in the levels of human and dolphin use and human-dolphin interactions. The SAPPHIRE project employed multiple methodologies in four spinner dolphin resting bays in Hawaii and included visual surveys, land-based and boat-based collection of time-series behavioural data and passive acoustic monitoring with the intent of providing sound scientific information to inform management action.

In August 2016, the NMFS and NOAA, proposed a no swim-with and 50-yard approach rule instead of time-area closures.

The ability of policymakers and managers to make informed decisions to effectively protect cetaceans from tourism and other activities relies on having sound scientific information on the population of interest. This scientific information should include the abundance and distribution, habitat use, the effects of the activity on the animals and their critical habitats, and the potential response of the animals to these activities.

Here, our study is timely, as we show that spinner dolphins of Hawaii Island exhibit a constrained daily behavioural schedule. The spinner dolphins mainly rest between 10.00 and 16.00 upon their return to sheltered near shore habitats from their cooperative night-time foraging activities. Furthermore, the spinner dolphins socialize in the early morning between 07:00 and 09:00 and late afternoon between 16:00 and 18:00 within bays. Reinforcing social bonds and social cohesion between conspecifics may be important for the success of their cooperative night-time foraging activities. We are not aware of any other cetacean species that partitions its behavioural activities in such a temporally and spatially constrained manner on a 24-h basis. Following the theory of resilience of natural systems, such constraints may render spinner dolphins less able to compensate for disruptions to their behavioural schedule. Consequently, it is likely that they are more vulnerable to disturbance which, in turn, can lead to long-term population impacts. These spinner dolphins are exposed to human activities within 100 m for more than 82% of their time during the day with only a median time of 10 minutes between exposures. This doesn’t take into consideration the noise generated by humans in the spinner dolphin resting areas. Consequently, the exposure of the spinner dolphins to human activities could be more than the 82% when taking into account human generated noise.

The most recent abundance estimates from 2011 (631 (95% CI: 524-761)) and 2012 (668 (95% CI: 556-801)) are lower than all previous estimates from 1979-1981 (960), 1989-1992 (2,334) and 2003 (855-1,001) indicating a possible long-term impact. It is therefore essential to quantify the spatial and temporal partitioning of the spinner dolphins behavioural schedule, to provide critical insight for conservation measures that aim to mitigate the effects of human disturbance.

Funders and SAPPHIRE:

This research was conducted as part of the Spinner Dolphin Acoustics Population Parameters and Human Impacts Research Project, a joint project between Murdoch University and Duke University. The SAPPHIRE project was funded by NOAA, the Marine Mammal Commission, the State of Hawai‘i and Dolphin Quest.

Additional papers on the Hawaiian spinner dolphins that may be of interest include:

  • Tyne, J.A., Loneragan, N.R., Johnston, D.W., Pollock, K.H., Williams, R. and Bejder, L. 2016. Evaluating monitoring methods for cetaceans. Biological Conservation. 201:252-260 http://dx.doi.org/10.1016/j.biocon.2016.07.024
  • Tyne J.A., Johnston D.W., Rankin R., Loneragan N.R. and Bejder, L. 2015. The importance of spinner dolphin (Stenella longirostris) resting habitat: Implications for management. Journal of Applied Ecology 52: 612-630. doi: 10.1111/1365-2664.12434
  • Tyne J.A., Pollock K.H., Johnston D.W and Bejder L. 2014. Abundance and Survival Rates of the Hawai’i Island Associated Spinner Dolphin (Stenella longirostris) Stock. PLoS ONE 9(1): e86132. doi:10.1371/journal.pone.0086132. Included in the PLOS Marine Megafauna Collection: Marine Habitats and Conservation Biology
  • Tyne, J.A., Loneragan, N.R., and Bejder, L. 2014. The use of spatial-temporal closures as a tool to manage cetacean-watch tourism. In: Whale-Watching: Sustainable Tourism and Ecological Management (eds. Higham, J.E.S., Bejder, L. and Williams, R.). Cambridge University Press, Cambridge, UK, pp: 242-262. doi: 10.1017/CBO9781139018166.020
  • Heenehan, H.L., Van Parijs, S.M., Bejder, L., Tyne, J.A. and Johnston, D.W. 2017. Using acoustics to prioritize management decisions to protect coastal dolphins: A case study using Hawaiian spinner dolphins, Marine Policy, 75:84-90 doi: http://dx.doi.org/10.1016/j.marpol.2016.10.015.
  • Heenehan, H., Tyne, J.A., Bejder, L., Van Parijs, S.M. and Johnston, D.W. 2016. Passive acoustic monitoring of coastally associated Hawaiian spinner dolphins, Stenella longirostris, ground-truthed through visual surveys. Journal of the Acoustical Society of America : doi: 10.1121/1.4955094
  • Heenehan, H., Basurto, X., Bejder, L., Tyne, J.A., Higham, J. and Johnston, D.W. 2015. Using Ostrom’s common pool research theory to build and integrate ecosystem-based sustainable cetacean tourism systems in Hawaii. Journal of Sustainable Tourism 23: 536-556. doi: 10.1080/09669582.2014.986490
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