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Pilchards, an important prey species for the little penguin, have been found in the past to be able to transmit the disease once it gets into waterways.
Toxoplasmosis has also been observed in African penguins and New Zealand dolphins. Pregnant women are also advised not to handle cat faeces as the disease can be passed onto unborn babies with potentially serious health outcomes such as brain damage and blindness.
Scientists believe a parasite in some cat poo got into WA waterways, was transmitted to fish which were then eaten by penguins resulting in the latter’s death.Credit:International Journal for Parasitology: Parasites and Wildlife
Dr Cannell said the point of infection was still hard to determine as the penguins from the island travel as far south as Geographe Bay.
“But there’s also this question of why there was this real glut in 2011 to 2013 and not much since,” she said.
“We haven’t done any investigations on this but my thinking is ... 2011 was the year of the marine heatwave and we had a lot more tropical fish in the penguins’ diet in 2011 and into 2012.
“So whether they are feeding on species that are coming from more tropical areas and there are more cats in that area ... that’s the kind of thing we just can’t measure.”
Dr Cannell said the results from the study were just another factor to think about when it came to how cats impacted the environment.
“It certainly is something to consider that cats not only impact by killing birds and lizards on land. This is another impact they can have,” she said.
“It’s one of those silent and unseen impacts.”
Penguin numbers falling
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The WA little penguin population at Penguin and Garden Islands has been dwindling over the years.
Penguin numbers on Penguin Island which were previously more than 2000 have decreased to an estimated 300 after an 80 per cent drop between 2007 and 2020.
Half the chicks from the 2021 breeding season died as Perth sweltered through its hottest summer on record in another devastating blow.
A previous study by Dr Cannell in 2016 found 25 per cent of known penguin mortality in WA was from collisions with watercraft like boats.
Debate is also raging over a proposed replacement of the ageing Penguin Island Discovery Centre, which gets about 130,000 tourists every year, as some scientists say construction would be too disruptive while the Department of Biodiversity, Conservation and Attractions, which manages the reserve, wants it to go ahead.
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