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

5.7 Other studies - reactions of terrestrial mammals to human activities

Studies on terrestrial mammals show us that we can make broad generalisations from one species to another based on noise variability, the indication of danger posed by the noise due to past experience and other factors such as the reproductive or behavioural status of the animals. However, such studies also indicate to us that extrapolations within and among populations, habitats and species must be done with caution. Some animals or animal groups are more sensitive than others and may habituate to (or tolerate) human presence less. At the same time, there is variability among age/sex classes and individuals. This can lead to erroneous interpretations of response to human activity if, for example, a few animals have learned to tolerate much activity (perhaps to gain access to a food supply) while the majority of individuals of that population flee or hide from the same activity.

Terrestrial mammals can often be tracked and physiologically measured for long periods of time. New techniques of gaining behavioural and physiological data on cetaceans in nature are becoming ever more sophisticated and promise to provide better long-term impact studies in future. Especially important are measurements which allow comparisons between human activities and the animal's population and life history parameters: how does the activity affect reproduction, the immune system and the status of the health of the population or individual?

A number of basic generalisations can be made from research conducted on terrestrial mammals. Six generalisations follow, each of which is accompanied by examples:

1. Wild mammals often habituate to a variety of background human activities that are steady and predictable.

   a) Elk [Cervus elaphus] have adapted to present levels of human disturbance along normally and sometimes heavily used roads (Schultz & Bailey, 1978).

   b) The low reactivity of bighorn sheep [Ovis canadensis] to human disturbance confirms expectations for a population existing in a known and largely predictable environment (MacArthur et al, 1982).

2. Wild mammals are less likely to habituate to disturbance involving close approaches and pursuit, or to unusual, unpredictable events.

   a) Marmots [Marmota marmota] and bighorn sheep were less responsive to people on often- travelled roads than to the less common situation of encountering people off trails (MacArthur et al, 1982; lngold et al, 1993; Mainini et al, 1993).

   b) People leaving roads to approach elk caused animals to flee (Schultz and Bailey, 1978).

   c) The flight of caribou [Rangifer tarandus] in response to pursuing objects such as a snow machine or slow moving aircraft can be expected to be more prolonged since the threatening object can keep itself within a certain distance of the animal (Horejsi, 1981 ).

3. Several ungulate studies indicate that reactions to human activities may vary markedly with reproductive and nutritional status, habitat, or the experience of the animal.

   a) A mother moose [Alces alces] and her young calf will hide from disturbance since the calf is not yet a good runner and later will react to human intruders with very long flight distances; while a bull moose in velvet will hide, but in full rut will lose almost all caution with flight distance dwindling to near zero (Altmann, 1958).

   b) In some areas, deer [Odocoileus sp.] are attracted by chainsaw noise, which they may learn to associate with newly-felled browse (Richens and Lavigne, 1987).

   c) Individual mountain goats [Oreamnos americus] were noted to respond differently to varying intensifies of disturbance, possibly due to the degree of previous stressful encounters (Foster and Rahs, 1983).

4. Wild mammals may significantly change behavioural patterns in response to disturbances.

   a) Some deer were particularly sensitive to intrusion by man and vehicles and changed their home range to entirely different locations (Dorrance et al, 1975).

   b) Repeated aerial and ground surveys of mountain goats documented both temporary range abandonment and changing observability indices (habitat use and activity patterns) associated with areas of intense industrial exploration activities (Foster and Rahs, 1983).

5. Disturbance response patterns can be species-specific.

   a) Although some species reportedly habituate to many forms of noise and disturbance, the mountain goats under study (see 4b) did not. Disturbance functions are believed to be additive (=sensitisation) for mountain goats (Foster and Rahs, 1983).

6. Disturbance may have longer term stress-related impacts on wild mammals.

   a) Mule deer [Odocoileus hemionus] responded to experimental harassment by all-terrain vehicles with reproductive pauses in the following breeding season (Yarmoloy et al, 1988).

   b) In wild cougars [Felis concolor], repeated disturbance reduced the proclivity of the adrenals to release cortisol upon further disturbance and may have resulted in long-term changes in physiological adaptation (Harlow et al, 1992)

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