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Dogs on Leashes, Birds on Beaches

By Kiran Dhanjal-Adams

A bit of maths can help managers minimise the impact of dogs on migratory shorebirds.

Walking the dog on the beach is a great way to end a hot summer’s day. Yet little migratory shorebirds are also soaking up the late afternoon sunshine. These little creatures have made it all the way from their breeding grounds in eastern Russia and Alaska to spend the Australian summer feeding on the abundant sea life in the intertidal zone. They patiently wait until low tide to gorge on worms, shells and crabs, before retreating as the tide comes back in.

This feeding period is critical to these birds. Many will have flown non-stop all the way from Alaska to Australia, some 11,700 km in 6 days! Consequently, migratory shorebirds are hungry. They will have lost 50–80% of their body mass.

However, dogs have a tendency to chase birds. It’s no big deal if it happens only once, but these disturbances can be constant. Repeated disturbances can force birds to leave a good feeding area for less suitable feeding areas. And even if they move, dogs are likely to be wherever they move to.

Anything preventing birds from gaining enough weight can mean they will be unable to migrate and breed. Worse, it could mean they migrate and die of starvation before even getting to their breeding grounds.

This is a major problem. Many species of migratory shorebird are in rapid decline across Australia. Several species have been recently listed as threatened. In Moreton Bay, for example, some species have declined by 50–80% between 1995 and 2009.

The solution to this disturbance problem is simple – we should put our dogs on leashes. Unfortunately, not everyone is aware of the plight of shorebirds or the need to give them peace, and local shorebird managers are encouraged to carry out information campaigns.

This is where a little decision science can help. Given they must also manage commercial and recreational fisheries and tourism on top of shorebirds, there is a need to optimise where and when managers carry out information campaigns to avoid wasting precious time and funds.

Consider this: if you have ten sites that you could visit up to five times, there would be a total of 60,466,176 possible combinations of site visits. How would you figure out which of these possible combinations delivers the best outcome?

A few other numbers and a bit of maths can help. How many birds are at a site? How many disturbances? How much will it cost to manage that site? With this information it is possible to do a cost–benefit analysis to determine which combination of site visits delivers the best outcome within the specified budget.

However, the more you visit a site, the more you will start talking to the same people over and over again about shorebirds. There is therefore a trade-off between visiting a site too much and wasting your time talking to the same people, or visiting a site too little.

We attempted to explore this trade-off by expressing it as a mathematical formulation. We found that if management was effective (i.e. that almost everyone started putting their dog on a leash after talking to marine park officials), then it was best to manage a lot of sites a few times. However, if management was not very effective (i.e. only a handful of people started putting their dog on a leash), then it was best to find sites with lots of birds being disturbed, and repeatedly visit them. This ensures as many people as possible are persuaded to keep their dogs on a leash near shorebirds.

These methods extend well beyond shorebirds. Say, for instance, you are deciding which sites to visit to ensure as many rhinos as possible are protected from poaching, or where to patrol to ensure fish stocks are not depleted. All that is needed is information on target species (average number of rhino or fish), infractions (number of poachers or illegal fishers caught) and the cost of patrolling (number of staff).

Of course, enforcement is not the only tool available in the manager’s toolbox. For shorebirds, for example, better dog-walking facilities would reduce the number of people walking their dogs on the beach.

The underlying message is that everything is a balancing act, and successful conservation requires a mix of community involvement, government engagement and implementable management plans. Engaging communities and governments is a long and complex process, but devising cost-effective management plans need not be so with the right tools.

Kiran Dhanjal-Adams is an associate of the ARC Centre of Excellence for Environmental Decisions (CEED). This research was done while based at The University of Queensland.