Effects of provisioning bottlenose dolphins in Cockburn Sound: injuries, entanglements, and changes to ranging and social behaviours

Brief description

Unpublished data and analyses from Rebecca Donaldson (1993-1997) and original data collected for the thesis (2000-2003) from Cockburn Sound were used to: 1) evaluate the link between high-risk behaviour by dolphins during provisioning interactions and rates of human-induced injury; 2) contrast the behaviour of known individuals before and after they engaged in provisioning interactions; and 3) examine the incidence of unregulated provisioning interactions within a population-level context in which the baseline demographic parameters were known.

Lineage

Maintenance and Update Frequency: notPlanned

Statement: - Behavioural surveys - Behavioural surveys and focal individual follows were used to collect ecological and behavioural data on the sub-population in Cockburn Sound. - Defining conditioned dolphins - Between 1993-2003 a sub-set of dolphins exhibited a series of behavioural events indicating that they were conditioned to human interaction by food reinforcement. Dolphins were classified as conditioned to human interaction by food reinforcement based on observations of the following set of behavioural events: 1) an active and directed approach towards a stationary boat; 2) maintenance of close proximity (within 2m) to the beam (side) or stern of stationary vessels for an extended period (>30 seconds) and 3) acceptance of food from humans (if offered). - High-risk behaviours during provisioning interactions - Samuals and Dejder (2004) described several components of human-dolphin interactions that they predicted would increase the risk of injury, illness, or death to humans or dolphins during provisioning interactions with humans in Cockburn Sound: 1) physical contact with (or close proximity to) humans; 2) maintenance of close proximity to vessels; 3) acceptance of food from humans; 4) acceptance of a foreign (non-fish) object from humans; 5) maintenance of close proximity to deployed fishing gear; and 6) participation in interactions in areas of poor water quality and high boat traffic. Instances of these behaviours were documented during observations of provisioned animals interacting with humans. - Case-study approach for behavioural changes - By inspection, the number of observations for provisioned individuals varied. To investigate behavioural changes associated with provisioning a case study approach was adopted and analysis of behavioural changes limited to five individuals for whom there were moderate to high number of post-provisioning observations. - Changes in ranging and association patterns - To investigate whether dolphins in Cockburn Sound changed their ranging patterns after becoming conditioned to human provisioning, the size and location of post-provisioning range of case study individuals were compared to their pre-provisioning range size and location. The methods used to determine ranging patterns of individuals were reviewed in Chapter 2 (Section 2.6 of thesis). - Male proximity to reproductive-age females - Changes in the frequency with which case study males were in close proximity to reproductive-age females post-provisioning were examined. - Observations of injury and mortality - Observations of injuries related to human interactions were compiled by the authors from direct observation or from personal communication. See section 5.2 for further detailed methodology

Notes

Credit
Donaldson, Rebecca

Purpose
To assist in the ecosystem-based conservation of dolphins within Cockburn Sound.