Effects of whale watching on the activity budgets of humpback whales,Megaptera novaeangliae(Borowski, 1781), on a feeding ground

Abstract

Whale watching can affect cetacean behaviour, and can in some cases lead to long‐term negative effects on survival and reproduction. The waters of Juneau (Alaska) represent a summer feeding ground for the Central North Pacific stock of humpback whales, Megaptera novaeangliae (Borowski, 1781). The recent dramatic expansion of the local whale‐watching industry has raised concerns over the potential negative impact of such activity on the whales. The aim of this study was to understand the impact of whale‐watching vessels on humpback whale behaviour in Juneau. From June to September 2015, land‐based observations were conducted to record whale behaviour in the presence and absence of vessels. Markov chains and model simulations showed that the presence of vessels was not associated with a reduction in the time spent feeding. Whales exhibited more surface‐active behaviour and travelled less in the presence of vessels. The lack of an overt response of feeding whales to whale‐watching disturbance could result from the importance of the Southeast Alaska study region as a feeding ground, which could make the whales less apt to interrupt feeding under disturbance; however, The high proportion of travelling observed may indicate that the study area represents a travelling corridor between other, localized feeding areas. The increase in surface‐active behaviour may represent a response to vessel presence that could potentially lead to energetic consequences. The large number of whale‐watching vessels operating could lead to the increased tolerance of whales towards whale‐watching activities. The lack of responses in this study may suggest that the reactions of whales are context specific, depending on their previous experience with vessels and their foraging behaviour, for example. Subtler negative effects could still occur, however, and a prolonged monitoring programme is required to assess less overt behavioural responses of whales over time.

Humpback Whale Movements and Behavior in Response to Whale-Watching Vessels in Juneau, AK

“…Humpback whale movement and behavioral data with respect to whale-watching vessel presence were collected using theodolite tracking methods described in Würsig et al (1991) and behavioral observation methods described in Di Clemente et al (2018). A "sighting" (i.e., observation period of behaviors for a humpback whale) began when an individual was spotted < 5 km from the field site.…”

“…Focal follow observations with all-occurrence sampling (Altmann, 1974) was used to record behavioral events ( Table 2) and continuous sampling was used to record behavioral state, heading, and number of vessels present within a 500 m radius of the whale at the time of the behavioral event. A 500 m threshold was used previously by Di Clemente et al (2018) as an intermediate distance between distance thresholds previously used in whale-watching studies on humpback whales [300 m (Corkeron, 1995;Morete et al, 2007) and 1000 m (Gulesserian et al, 2011;Schaffar et al, 2013)]. Vessels were considered present when within 500 m of the whale and observed approaching, departing, or tracking (i.e., following a whale in a straight line or in a parallel line according to the last heading observed of the whale).…”

“…This distance has been recommended for stations between 20 and 45 m above mean low sea level to reduce errors in precision from targets at greater distances (Würsig et al, 1991;Piwetz et al, 2018). This method was similarly used by Di Clemente et al (2018) to minimize the chance of sampling an individual that was different from the original focal animal.…”

“…There is mounting evidence that whale watching can lead to negative effects ranging from short-term behavioral changes that disrupt life functions (e.g., feeding) to long-term consequences such as declines in physical fitness and habitat alteration (Lusseau and Bejder, 2007). In the presence of whale-watching vessels, whales have exhibited short-term behavioral changes including alteration of swimming speed and direction (Scheidat et al, 2004), diving and foraging patterns (Stamation et al, 2010;Christiansen et al, 2013b), aerial behaviors (Stamation et al, 2010;Di Clemente et al, 2018), resting patterns (Lusseau, 2003;Lundquist et al, 2012;Steckenreuter et al, 2012), group size and cohesion (Steckenreuter et al, 2012), and acoustic communication (Sousa-Lima and Clark, 2008). If short-term avoidance behaviors by whales (e.g., traveling at higher speeds, frequent changes in direction, movement away from whalewatching vessels) negatively affects body maintenance behaviors such as foraging and resting, there could be long-term declines in vital rates (Lusseau and Bejder, 2007;Parsons, 2012).…”

“…To meet the demand of the rapid growth of tourism in Juneau, the whalewatching industry has tripled since 2000. Currently, there are approximately 65 vessels that offer dedicated whale-watching tours, in addition to fishing charter vessels which view whales opportunistically (Di Clemente et al, 2018). Due to this surge in vessel presence, it is unclear if the current Alaska whalewatching regulations, established in 2001 (Table 1), are sufficient to mitigate potential disturbance to humpback whales.…”