Report of the Workshop on the Scientific Aspects of Managing Whale Watching

5.9 Causal links between measurable short-term impacts and possible long-term impacts

1. Monkey Mia, Australia

This is perhaps the clearest case where such a causal link has been demonstrated. in this area, whale watching is conducted from shore and includes the feeding of animals. The following problems were identified from MWW/95/40:

1. substantially altering natural behaviour, including foraging for food and migration

2. the loss of wariness of humans, placing the animals at increased risk of injury or death due to interactions with vessels, gear, or intentional harm by those who consider them as pests

3. inappropriate or contaminated food

4. increased injuries to humans due to the predictable increased aggressive behaviour of habituated animals

Short-term impact: change in foraging behaviour because the dolphins are being regularly hand fed by people from the shore.

Long-term impact: increased dolphin juvenile mortality.

Causal link: juvenile dolphins have not been trained to forage and so they are less able to forage independently. There is a reduced maternal investment in protecting juveniles from predators.

Conclusion: there is a strong indication of a causal link between feeding by humans and the juvenile mortality rate.

The short-term impact can be regarded as positive or at least neutral as the interaction is initiated by the dolphins. However, the long-term impact on the population is negative because recruitment is reduced.

It was noted that the juvenile mortality rate could be increased for a number of reasons linked to the feeding programme. For example, feeding male dolphins allowed them more time to harass the females which may have significantly inhibited the latter's ability to adequately take care of and train their young. Additionally, the greatly increased numbers of people drawn to the area caused environmental problems which had an impact on the dolphins, e.g., the sewage system overflowed causing a transference of pathogens to the dolphins.

2. Tangalooma, Australia

At Tangalooma there is also a dolphin feeding programme in place, but because of the Monkey Mia experience this is much more regulated and limited. It is too early yet to assess any short or long-term impacts.

3. Hervey Bay, Australia

This area is a resting area for migrating humpback whales (including mothers with calves).

Short-term impact: observed changes in habitat use. Fewer whales were observed in Hervey Bay in 1990 than in 1989 (survey data are only comparable for these two years) (MWW/95/38).

However, whale-watching operators believe that more whales were present in the Bay in 1994 (Franklin pers. comm.) and that the whales have become more friendly and remain near boats for extended periods of time.

Conclusion: it is not possible to assess if there has been any long-term impact because the origi nal survey methods were not maintained and surveys have now been discontinued.

4. Stellwagen Bank, New England

Stellwagen Bank is a feeding area for humpback whales and other species during the summer months.

Short-term impact: a significant change in distribution of humpback whales was observed between 1985 and 1986.The distribution returned to the previously observed levels in 1987 and 1988.

Long-term impact: by 1993 and 1994, a drastic drop in the number of humpbacks that were resident throughout the summer season was observed.

Causal link: it is difficult to demonstrate a causal link between short and long-term impacts due to whale watching because ancillary investigations of the prey species demonstrated a decline in sand lance beginning in 1985 and extending into the early 1990s. Whale watching effort remained relatively stable throughout this whole period.

Conclusion: a causal link between whale watching and the observed shift in distribution in humpback whales cannot be demonstrated.

5. Glacier Bay, Alaska

Humpback whales feeding in Glacier Bay appear to illustrate a similar situation in the short-term (MWW/95/40).

Short-term impact: significant changes have been reported in whale ventilation behaviour in response to vessel proximity, vessel speed and the presence of large ships. The greatest tendency to move away from vessels occurred as vessels reached their closest point of approach to the whales (MWW/95/40).

Long-term impact: there was a change in distribution of the whales with fewer animals reported in the fjords after 1970.

Conclusion: there is no clear link between the cruise ships using the whale watching area and the degre of use by humpback whales, because there is also evidence that the whales moved to an area of higher prey density.

6. Península Valdés, Argentina

This is a mating, calving and nursing area for southern right whales.

Short-term impact: right whales have changed their distribution:

i. from Golfo San José (no commercial whale watching) into the centre of an established whale watching area in Golfo Nuevo (Payne and Campagna pers. comm.).

ii. within Golfo Nuevo from an area where whale watching is concentrated to an area where limited whale watching has followed.

Long-term impact: none has been shown.

Conclusion: there is no evidence to suggest the causes for these observed changes in whale distribution. The whales have not moved from the Goifo Nuevo area despite a substantial increase in commercial vess and small boat traffic.

In these six case studies, the only clearly established causal link between short-term and long-term impacts due to whale watching appears to be the Monkey Mia situation.

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