29–30 October and 3 November 2009
Location: Carnac Island, Perth
Perth Zoo Field Workers: Paul Eden (Associate Veterinarian), Simone Vitali (Senior Veterinarian), Mikaylie Wilson (Acting Veterinary Nurse Supervisor), Kate O’Connell (Veterinary Nurse), Anna Le Souef (Resident Veterinarian), Karen Payne (Veterinarian)
Background
Australian Sea Lions (Neophoca cinerea) are large aquatic mammals that grow up to 2.5 m long and weigh up to 250 kg. Adult males (bulls) are approximately double the weight of females.
One of the sub-adult males on the beach at Carnac Island. Photo by Leighton DeBarros/DEC
Unlike other species that usually breed annually or seasonally, Australian Sea Lions have a 17-month breeding cycle, with the females coming into oestrus shortly after birthing. During the non-breeding period, the bulls congregate in bachelor groups, using islands such as Carnac Island as resting and foraging grounds.
In the 18th and 19th centuries, Australian Sea Lions were heavily hunted for their pelt and oil and today they are one of the rarest sea lion species in the world with only 10,000–12,000 remaining in the wild. While they now have little to fear from hunters, they often become entangled in fishing nets and crayfish pots, and are injured and sometimes killed by boats.
They are listed as Critically Endangered by the Australian Federal Government and as such are a protected species.
The veterinary team.
The Department of Environment and Conservation (DEC), the Department of Fisheries (DOF) and Perth Zoo undertook a collaborative project to place electronic tracking devices on the fur of male Australian Sea Lions at Carnac Island to determine the sea lions’ activities in the water. Blood and faecal samples and measurements were also collected to obtain information on the animals’ health.
This project is part of a larger investigation into the ecology of Australian Sea Lions, especially in relation to the impact of human activities such as fishing and boating, on their fragmented populations.
It is a first in Western Australia and is based on a similar project being conducted in South Australia.
Process
When we reached Carnac Island, the project team (which included Perth Zoo veterinarians and veterinary nurses and staff from DEC and DOF) selected a sea lion based on its size and estimated age.
Mikaylie Wilson and Paul Eden anaethetising a sea lion for attachment of the tracking device.
There were about 20 sea lions on the beach. Ideally we wanted an adult or subadult male that was close to his prime. Once chosen, the animal was sedated so that we could safely approach and then put him under a general anaesthetic.
We worked together quickly to achieve what we needed to get done. The Zoo staff did a health assessment which included taking body measurements and collecting blood and faecal samples.
Staff from DEC and DOF placed small tracking devices on the sea lion’s fur with non-toxic glue. The sea lions barely knew they were there.
Once the health check was completed and the tracking devices attached, the sea lion was recovered under the watchful eye of veterinary staff to ensure it didn’t injure itself or have any complications.
Results
Over a three day period, we were able to anaesthetise three sea lions for assessment and placement of the tracking devices. All three animals recovered smoothly after their procedure.
Initially, the tracking process was going well, until two sea lions lost their tracking devices – we suspect by rubbing against rocks in the ocean. The tracking devices use satellite navigation (like the Global Positioning Systems in some cars) to monitor the sea lions’ movement around the coastline and a depth gauge to show how deep they dive for their food.
Male sea lion after tagging. Photo by Leighton DeBarros/DEC
Every time the sea lion breached the surface of the water, a new position would be recorded and help plot where the sea lion had been.
Despite the loss, all of the tracking devices gave us interesting and useful information on the sea lions’ activities and use of the waters around Perth. Amazingly, one bull even managed a return trip to Bunbury.
This information has given us some preliminary understanding of how the sea lions use the waters off the coast of Perth and the potential for interaction with human activities. However, more tracking still needs to be undertaken to gain a better understanding of this and assess factors such as seasonal changes.
When we returned to the Zoo, we processed the blood and faecal samples from the health assessments and interpreted the results. We found that all three sea lions had a parasite similar to heartworm in dogs. This is probably a natural infection that won’t cause the sea lions any health problems but will be something for us to investigate in the future.
We can also use the results of these tests for reference in future tagging and information gathering projects, and for sick or injured sea lions that may be found off the coast.
Highlights
Male sea lion with tracking device attached to its fur. Photo by Leighton DeBarros/DEC
It was amazing to be able to participate in field work with such an iconic species and work that will benefit Australian Sea Lion conservation. Our participation in this project is an example of work undertaken in Conservation Medicine, a relatively new veterinary science field which focuses on understanding and managing the health of wild populations of animals. It is being recognised as a valuable tool in the preservation of animals and their habitats.
Being part of a collaborative project, with multiple Government departments working together, was also really valuable. The team worked well together and there was a lot of respect for the skills and knowledge each person brought to the project.
Challenges
Working with these animals was challenging. Complications can occur during the anaesthesia of sea lions, particularly during recovery. We spent a lot of time preparing for this field work so that we had procedures in place to minimise these complications and staff could respond appropriately if they occurred. I’m happy to say that everything ran very smoothly and this is due in large part to our preparedness.
The behaviour of wild sea lions is also less predictable compared to captive animals. They can be potentially dangerous, especially as bulls can weigh up to 250 kg and can charge if they feel threatened. However, they didn’t seem to mind our presence and we were able to work near the bulls without disturbing them. Some of them were quite inquisitive. Often there would be a couple of ‘on-lookers’ at the edge of the water, surveying what we were doing to one of their fellow bachelors.
