Only 16,516 sea lion pups remain in colonies along the southeastern coasts of Australia , a population that is declining for the first time in more than three decades. At least, these are the data from the most recent monitoring of the population, carried out in the period 2013-2014, and whose conclusions have been published in a study by the journal PLOS ONE .
The findings revealed that the population control of this animal species between the years 1970 and 2013 has indeed registered changes. The researchers compared the most recent count, collected in 2013-14, with an overall trend in the population since 1986 that has been broken.
Since a population monitoring of the sea lion (Arctocephalus pusillus doriferus ) was carried out, scientists were optimistic about the number of specimens, which was on an increasing trend. The number of cubs almost doubled between 1986 and 2002, reaching about 20,000 individuals. Then the population increased slightly between 2002 and 2007. But the 2013 census identified the first decline in the puppy population, estimated at 4.2% per year since 2007 , since the protection was implemented.
However, it is not all bad news. The study identified three new colonies in 2013 and, although the global number of offspring has decreased, the number increased by several colonies.
The researchers suggest that the number of cubs may be declining in many of the colonies as populations are approaching the maximum size that local environments can support.
They also noted that food availability had been unusually low in the 2013-2014 period.
But they also raised concerns that this could be the beginning of a sustained decline in the numbers of Australian sea lions. Unpublished data from the most recent census, which ended in February 2018, suggests that the number of cubs is not recovering.
Australian sea lion: a protected predator
In the marine environment, controlling the abundance and population trends of a top predator has a direct impact on the implementation of ecosystem health measures.
Sea lions are carnivorous mammals, similar to seals; but, unlike these, they have some characteristics of their own, such as differences in the fins, and a pair of appendages as ‘ears’ that protrude from their heads. It is a protected marine species that faces specific challenges related to fishing, ecotourism, and disasters such as oil spills. Also, despite being predators, they are a regular target of larger predators, such as sharks. This is why it is important to obtain accurate information about your population changes.
According to the authors: “As wildlife managers, it is important that we regularly review our species control programs to examine the reliability of the information we have collected, and also to identify improvements that may help better understand the population.” .
It should be noted that researchers currently use drone technology and Citizen Science programs in the Phillip Island Natural Parks to complete their work.
References: McIntosh RR, Kirkman SP, Thalmann S, Sutherland DR, Mitchell A, Arnould JPY, et al. (2018) Understanding meta-population trends of the Australian fur seal, with insights for adaptive monitoring. PLoS ONE 13 (9): e0200253. https://doi.org/10.1371/journal.pone.0200253
