Energetic Effects of Whale-Watching Boats on Humpback Whales on a Breeding Ground

Abstract

Interactions between whale-watching boats and cetaceans can lead to changes in their behavior. From a management perspective, it is important to understand how this type of disturbance can be translated into physiological effects, such as changes in their energetic metabolism. Humpback whales (Megaptera novaeangliae) typically do not feed while in breeding grounds, thus they depend on finite energy reserves. The effect of whale-watching boats on the energetic metabolism of humpback whales, in the breeding ground of northern Peru (4°10′35″S, 81°08′03″W) was evaluated. Groups of humpback whales were tracked from land, under the following scenarios: with, without, and before-during-after the presence of whale-watching boats. Mass-specific cost of transport (COT) was used as a proxy of energetic efficiency and calculated from swimming speed and breath frequency estimations. No differences were detected in breath frequency, swimming speed, and COT when comparing whales with and without boats. However, in the presence of boats, swim speed increased, and COT decreased as the number of boats increased. Exponential increment in breathing frequency at higher swimming speed was not detected. The absence of swimming speeds beyond the assumed optimal range suggested no shifts into metabolic inefficiency. Our results suggest optimal swimming speed between 2 and 4.05 m/s, representing COT values between 0.020 and 0.041 J × (kg × m)–1. In light of our results, we encourage the implementation of regulations of the activity, particularly limiting the number of boats interacting with the same group of humpback whales.

The Behavioural Impacts of Commercial Swimming With Whale Tours on Humpback Whales (Megaptera novaeangliae) in Hervey Bay, Australia

“…The results in Hervey Bay are different to previous studies for resting, travelling, and surface active behaviours, but still show an alteration in behaviour is occurring during swim-with-whale tours. Previous research has shown that behavioural changes can be energetically costly for whales (e.g., Lusseau and Bejder, 2007;Braithwaite et al, 2015;Villagra et al, 2021), therefore the observed high frequency of direction changes may mean that humpback whales in Hervey Bay are experiencing an increase in their energy expenditure in response to swim-with-whale tours. Further research is needed to quantify these energetic impacts and if long-term consequences are apparent.…”

Abundance and distribution patterns of cetaceans and their overlap with vessel traffic in the Humboldt Current Ecosystem, Chile

“…The detrimental effects of interactions between cetaceans and vessel-based activities are diverse and involve collisions, behavioral disruption, noise exposure, entanglement in fishing gear and prey depletion by fisheries [103][104][105][106][107] . Some of these negative impacts are being evaluated in the HCE, but studies are few and localized [34][35][36] . In the particular case of bycatch, information for Chilean waters is extremely scarce, sparse over time and in some cases not necessarily confirmed 33,105,108,109 .…”

Avistamiento de ballenas en el Perú: estado actual y recomendaciones para su buen control

“…Cabe resaltar que la presencia de una, dos o tres embarcaciones no lleva a las jorobadas a cambios significativos de comportamiento. Esto solo ocurre cuando este número se incrementa a más de tres y el tiempo de permanencia con ellas es elevado, ya que los niveles de ruido provocados por los motores podrían inducir a cambios en su comportamiento (Villagra et al, 2021;Sprogis et al, 2020).…”