49
3.3 The Negative Impacts of Whale-Watching on Humpback
Whales
An increasing body of evidence suggests that whale-watching can negatively impact
individual cetaceans and populations (e.g. IWC 2004; Parsons 2012; Scarpaci and
Parsons 2014; Senigaglia et al. 2016), though most studies have only been able to
show short-term behavioural responses to observation by whale-watching vessels.
Understanding the long-term effects of these responses on individuals and populations, in terms of non-lethal or sub-lethal impacts, is essential to assess the longterm sustainability of whale-watching (Berrow 2003; Lusseau 2004, 2014; Parsons
et al. 2015).
However, cetaceans are long-lived and hard to study and thus only three studies
to date have been able to demonstrate long-term effects of whale-watching on cetacean vital rates, mainly a decrease in female reproductive success, and all on odontocetes (Bejder et al. 2006; Fortuna 2006; Lusseau et al. 2006). For mysticetes, the
long-term effects of whale-watching disturbance are still unknown (Christiansen
and Lusseau 2014). Weinrich and Corbelli (2009) looked at calving rate and survival of humpback whales exposed to whale-watching boats in New England and
found no long-term effects. Nonetheless, several studies have detected whalewatching induced alterations in the behaviour of humpback whales exposed to
observation. Responses include changes in respiration rate, direction of travel, time
spent on the surface and dive behaviour (Baker and Herman 1989; Corkeron 1995).
In their breeding grounds, humpback whales have been shown to react to the
approach of whale-watching boats by increasing speed significantly, reducing blows
per minute, moving more erratically, increasing breach frequency, decreasing resting behaviour and adopting a more direct path after the boat’s departure (Scheidat
et al. 2004; Morete et al. 2007; Avila et al. 2015). A study of the behavioural reactions of wintering humpback whales to biopsy sampling in Abrolhos, northeastern
Brazil, found that groups involved in social and resting activities usually change
these states to travel in response to disturbance from vessel approach (Cantor et al.
2010). Close vessel approach during biopsy sampling and whale-watching also
result in behavioural reactions such as ‘fluke slaps’ (personal observation) (Fig. 3.6).
A study in New Caledonia detected significant behavioural changes in over 80%
of humpback whales approached by boats at less than 335 m, mostly changes in
path predictability, and increased swim speed and dive time (Schaffar et al. 2013).
During migration, groups with calves in Hervey Bay, Australia, also had their
behaviour altered in the presence of vessels within 300 m of them, particularly a
reduction in surface behaviour and increased diving (Corkeron 1995). Stamation
et al. (2010) observed horizontal avoidance and longer dive times in the presence of
vessels, as well as a reduction on some surface behaviours. They also found pods
with calves to be more sensitive to the presence of vessels than non-calf pods.
In feeding grounds, behavioural responses of humpbacks to tour boats include
horizontal avoidance, higher frequencies of some surface activities and changes in
blow intervals, indicating possible shifts of behavioural patterns (from foraging to
3 An Integrated Framework to Assess the Carrying Capacity…
3.3 The Negative Impacts of Whale-Watching on Humpback
Whales
An increasing body of evidence suggests that whale-watching can negatively impact
individual cetaceans and populations (e.g. IWC 2004; Parsons 2012; Scarpaci and
Parsons 2014; Senigaglia et al. 2016), though most studies have only been able to
show short-term behavioural responses to observation by whale-watching vessels.
Understanding the long-term effects of these responses on individuals and populations, in terms of non-lethal or sub-lethal impacts, is essential to assess the longterm sustainability of whale-watching (Berrow 2003; Lusseau 2004, 2014; Parsons
et al. 2015).
However, cetaceans are long-lived and hard to study and thus only three studies
to date have been able to demonstrate long-term effects of whale-watching on cetacean vital rates, mainly a decrease in female reproductive success, and all on odontocetes (Bejder et al. 2006; Fortuna 2006; Lusseau et al. 2006). For mysticetes, the
long-term effects of whale-watching disturbance are still unknown (Christiansen
and Lusseau 2014). Weinrich and Corbelli (2009) looked at calving rate and survival of humpback whales exposed to whale-watching boats in New England and
found no long-term effects. Nonetheless, several studies have detected whalewatching induced alterations in the behaviour of humpback whales exposed to
observation. Responses include changes in respiration rate, direction of travel, time
spent on the surface and dive behaviour (Baker and Herman 1989; Corkeron 1995).
In their breeding grounds, humpback whales have been shown to react to the
approach of whale-watching boats by increasing speed significantly, reducing blows
per minute, moving more erratically, increasing breach frequency, decreasing resting behaviour and adopting a more direct path after the boat’s departure (Scheidat
et al. 2004; Morete et al. 2007; Avila et al. 2015). A study of the behavioural reactions of wintering humpback whales to biopsy sampling in Abrolhos, northeastern
Brazil, found that groups involved in social and resting activities usually change
these states to travel in response to disturbance from vessel approach (Cantor et al.
2010). Close vessel approach during biopsy sampling and whale-watching also
result in behavioural reactions such as ‘fluke slaps’ (personal observation) (Fig. 3.6).
A study in New Caledonia detected significant behavioural changes in over 80%
of humpback whales approached by boats at less than 335 m, mostly changes in
path predictability, and increased swim speed and dive time (Schaffar et al. 2013).
During migration, groups with calves in Hervey Bay, Australia, also had their
behaviour altered in the presence of vessels within 300 m of them, particularly a
reduction in surface behaviour and increased diving (Corkeron 1995). Stamation
et al. (2010) observed horizontal avoidance and longer dive times in the presence of
vessels, as well as a reduction on some surface behaviours. They also found pods
with calves to be more sensitive to the presence of vessels than non-calf pods.
In feeding grounds, behavioural responses of humpbacks to tour boats include
horizontal avoidance, higher frequencies of some surface activities and changes in
blow intervals, indicating possible shifts of behavioural patterns (from foraging to
3 An Integrated Framework to Assess the Carrying Capacity…