Saving our sea lions

Led by Dr Rachael Gray, from the Sydney School of Veterinary Science, in the Faculty of Science, the research is investigating the effects of hookworm, environmental pollutants like heavy metals, and human-associated bacteria on mortality of sea lions in the first one-and-a-half years of their lives.

"Sea lion populations will continue to decline if we don’t do something to save these charismatic and iconic marine mammals," said Dr Rachael Gray.

"Losing sea lions is not just an unacceptable loss of another Australian mammal, but has wider consequences for the ecosystem, as sea lions are top-end predators, so their numbers effect the numbers of many other species of animals in the ecosystem."

Before we get into the specifics of the treatment trial, you may be wondering 'What are sea lions?' So here are some basics about sea lions:

What is the difference between a sea lion and a seal?

Both sea lions and seals are marine mammals in a group called pinnipeds, which also includes walruses. Some of the differences between sea lions and seals include:

How many species of sea lion are there?

There have been seven species of sea lion identified, however one of them – the Japanese sea lion – became extinct in the 1950s. The sea lion species are:

• Australian sea lion: Neophoca cinerea *
• New Zealand sea lion: Phocarctos hookeri *
• California sea lion: Zalophus californianus
• Galapagos sea lion: Zalophus wollebaeki*
• Steller sea lion: Eumetopias jubatus (near threatened status)
• South American sea lion: Otaria flavescens
• Japanese sea lion (extinct): Zalophus japonicas

* IUCN Red List Endangered status and decreasing population trend

Why are sea lions endangered?

Sea lions around the world are endangered, in part due to humans hunting them in the 19^th century, where whole colonies were wiped out. Sealing stopped in Australia in the 1920s, but population numbers of all pinnipeds have taken a long time to recover.  Current human threats are increasingly being recognised as likely to be contributing to population declines.

The Australian sea lion is listed as endangered by the International Union for Conservation of Nature (IUCN) and vulnerable by the Australian government’s Environment Protection and Biodiversity Conservation Act.

Australian sea lion numbers are estimated to be around 12,500 individuals – this small population makes the Australian sea lion one of the rarest pinniped in the world.

Our sea lion treatment trial

To work out why our Australian sea lion numbers are decreasing and what we can do to help them recover, Dr Rachael Gray and her team are setting up a world-first topical treatment trial treating and then monitoring sea lion pup health and mortality, starting in July 2019.

Hookworm infects the intestines of 100% of the Australian sea lion pups, so the team are using a novel and minimally invasive treatment for hookworm and monitoring what effect it has on pup mortality.

“Many Australian sea lion pups die from intestinal hookworm infection, so we want to see what effect treating the hookworm has, not just on the mortality directly from hookworm, but also death from other causes, such as accidental injury from adults and pollution,” explained Dr Rachael Gray.

“Our team has previously shown that an injectable form of hookworm treatment is effective, but we have recently piloted a topical treatment – which is easy to apply on the sea lion pup coat – and found that it is just as effective at treating hookworm.”

“We’re looking at how eliminating hookworm can increase survival from other factors that are also killing sea lion pups: a system weakened by hookworm, makes the sea lions more vulnerable to all sorts of other factors that can kill them.”

The team, including Dr Gray’s PhD students Mariel Fulham, Scott Lindsay and Shannon Taylor, are now at the exciting point of setting up the first large-scale topical treatment and long-term pinniped disease investigation anywhere in the world.

“We’re going to treat sea lion pups with a spot-on anti-parasite treatment in the Seal Bay colony on Kangaroo Island, South Australia, and monitor them for a year and a half to see how the treatment not only improves pup health, but also survival to breeding adult, and hopefully eventually leads to population recovery.”

Their innovative holistic investigation will simultaneously determine for the first time whether treating a naturally occurring parasite like hookworm alters the beneficial intestinal bacteria in sea lions, or reduces colonisation from human associated bacterial contaminants like Escherichia coli – commonly found in human sewerage.

The results of their experiment will be transformative in the wider context of preserving an endangered species by developing an effective disease and conservation management tool.

This project builds on nearly 14 years of strong, supportive and productive cooperation with the South Australian Department for Environment and Water (DEW), who manage the Seal Bay population of sea lions on Kangaroo Island, South Australia and is a collaboration with researchers at Macquarie University and the University of Adelaide.

Watch the experiment live!

Join Dr Rachael Gray, and her PhD students Shannon Taylor and Mariel Fulham, in the field on Kangaroo Island as they set up their big experiment and treat baby sea lions with an anti-parasitic:

• on Wednesday 24 July on the University of Sydney Instagram stories @sydney_uni
• on Thursday 25 July on the Faculty of Science Instagram stories @sydney_science