Chronic exposure of Hawaii Island spinner dolphins (Stenella longirostris) to human activities

Abstract

Habitat selection is strongly influenced by spatial variations in habitat quality and predation risk. Repeated exposure of wildlife to anthropogenic activities in important habitats may affect habitat selection, leading to negative biological consequences. We quantified the cumulative human exposure of a small, genetically isolated and behaviourally constrained spinner dolphin (Stenella longirostris) population, off Hawaii Island, and exposure effects on their daytime cumulative activity budget. Dolphins were exposed to human activities within 100 m for 82.7% of the daytime, with a median duration of 10 min between exposure events. Individual dolphins spent on average 61.7% (s.d. = 6.5) of their daytime resting. Of their total rest time, greater than 90% occurred inside sheltered bays. Despite high levels of human exposure, we did not observe an effect on dolphin resting behaviour. The short intervals between exposure events probably prevent dolphins from returning to a natural resting state before the next event. Consequently, ‘control’ observations may represent a resting behaviour of a more vigilant nature. Chronic levels of exposure to human activities could lead to rest deprivation, displacement from preferred resting habitats and ultimately negative population level effects. These results have implications for new proposed legislation aiming to reduce dolphin exposure to human activities.

Tour boats affect the activity patterns of bottlenose dolphins (Tursiops truncatus) in Bocas del Toro, Panama

“…It is often difficult to correlate short-term behavioral changes with long-term negative outcomes on the biology and ecology of targeted populations, however, there is growing evidence that repetitive short-term behavioral changes, induced by frequent disturbance, can influence life functions (i.e., feeding, predator response, migration and breeding) by imposing additional costs on the energetic budget of individuals (Christiansen, Rasmussen & Lusseau, 2013;Senigaglia et al, 2016;Noren et al, 2016). Tour boat disturbance has been linked to shifts in the activity budgets of numerous cetacean species (Williams, Lusseau & Hammond, 2006;Meissner et al, 2015;Pérez-Jorge et al, 2016;Tyne et al, 2018). These studies indicate that short-term avoidance tactics used by individuals can exert a cumulative effect on animals by altering activity budgets and potentially increasing energetic costs.…”

The Natural Environmental Factors Influencing the Spatial Distribution of Marathon Event: A Case Study from China

“…The common natural environments include water, atmosphere, sunlight, soils, and mountains [1]. The research subjects of natural environments mainly include the climate [2], weather [3], water resources [4], animals and plants [5], agroforestry [6], geomorphology [7], and landforms [8]. Researchers have explored the relationship between the natural environment and marathon running from different perspectives, such as the feasibility of marathon running in different natural environments, Chang et al found that the marathon can be held in combination with local environmental advantages.…”

Incidence of Odontocetes with Dorsal Fin Collapse in Maui Nui, Hawaii

“…Bent dorsal fins should be used in assessing the health of a population because, even at low rates, this condition could impact populations such as the endangered false killer whales, of which there are an estimated 150 to 200 in the Main Hawaiian Islands (Bradford et al, 2018), or spinner dolphins, which are facing increasing pressures from high levels of human activity (Tyne et al, 2018). Our observations of an individual surviving 16 years with a bent dorsal fin suggest these disfigurements are not necessarily fatal but could affect an animal's ability to swim, forage, and reproduce (Rommel et al, 1993;Baird & Gorgone, 2005), even when individuals can survive the initial injury.…”