The loggerhead turtle is listed as an endangered species by both the Queensland and Commonwealth Government conservation legislation.

In the 1970s there were about 3,500 adult female loggerhead turtles breeding each year in eastern Australia. By the turn of the Century in 2000, there were only about 500 females per year still breeding in eastern Australia.
The principal problem had been the excessive drowning of our loggerhead turtles in prawn trawl nets in eastern and northern Australia. The prawn trawlers are now required (since 2001) to use turtle exclusion devices in their nets which allow turtles to escape without drowning.

As a result, our loggerhead turtle populations are no longer declining. We now have a very depleted population that is expected to take 50-100 years to recover to very robust populations levels. This is because loggerhead turtles take about 30yr to grow from a hatchling to age of first breeding.

 Mon Repos beach near Bundaberg is about 1.6km in length and supports approximately 50% of the total annual nesting population for loggerhead turtles (Caretta caretta) in the south Pacific Ocean.

Loggerhead turtles that breed in the south Pacific Ocean form one interbreeding genetic management unit. They breed only on the western side of the south pacific with the majority breeding in south east Queensland on the mainland coast from Bundaberg to Township of 1770 and on the coral islands of the southern Great Barrier Reef.
There are also a number of small nesting populations in New Caledonia which are part of this same genetic stock. There is no loggerhead turtle nesting in the central and eastern South Pacific.

The only other breeding by loggerhead turtles in the Pacific occurs in Japan and is part of a separate genetic management unit. Within the south Pacific loggerhead turtle population, there are only five major breeding concentrations: at Mon Repos and Wreck Rock beaches on the mainland of southeast Queensland and at Wreck Island, Tryon Island and Erskine Island in the southern Great Barrier Reef. Having said this, the reality is that the largest nesting concentration occurs at Mon Repos.

Marine turtles are characterised by temperature dependent sex determination – a process whereby the sex of the hatchling is determined by the temperature of the nest during mid incubation of the egg. Cool nests produce male hatchlings and warm nests produce female hatchlings.

The loggerhead turtles of eastern Australia have a pivotal temperature (the theoretical temperature that produces a 50:50 sex ratio) of 28.6oC. The brown siliceous sands of the mainland beaches from Bundaberg north to Agnes Water, including Mon Repos and Wreck Rock, are consistently above the pivotal temperature for most of the mid summer breeding season. Therefore the mainland beaches like Mon Repos produce predominantly female hatchlings (75% females or higher each year).

In contrast, the loggerhead nesting islands of the southern Great Barrier Reef are composed of white coralline sand that is very reflective and hence cooler by several degrees when compared to the mainland beaches. Nests on these island beaches are typically below the pivotal temperature for loggerheads and produce mostly male hatchlings.

Therefore Mon Repos is doubly important, it supports the major part of the nesting for loggerhead turtles for the entire south Pacific and the majority of the hatchlings produced from this beach are females.

The beach at Mon Repos has been protected by declaration of the Mon Repos Conservation Park under the control of Queensland Parks and Wildlife (QPW). The management of the beach has been effective in providing an undeveloped natural, dark environment that continues to attract nesting female to come ashore for nesting.

Predation of eggs by foxes and dogs is now a rare event on this beach because of the QPW management. The Park has a visitor information centre that is the focus of a major education project directed at tourists and school children. The associated tourist visitation is valued at in excess of A$1,000,000 annually to the district economy in terms of accommodation, meals, fuel and other purchases.

However, Mon Repos Conservation Park is quite narrow, being only about 100m in width along most of the beach. It does not include the coastal “creek” and swamp land that lies behind the frontal dunes of the Park.

During the 1970s, the swamp land behind what is now the Conservation Park was drained to increase the capacity for cane farming on this land. As a result of this draining of the swamp, the water table has been lowered behind and under the frontal dunes.
Since that time, there has been a general trend for reduction in hatchling emergence from nests on Mon Repos. The loggerhead hatchling emergence success was recorded at its lowest level during the 2005-2006 breeding season, when it was approximately 25% less than the high levels recorded prior to draining of the swamps (Figure 1).

The years with very poor incubation success coincide with the low rainfall years. While some of the long term decline in incubation success may be climate change related, the dropping of the water table has contributed to there being dryer and hotter sand on Mon Repos Beach in recent years (Figure 2).
Sand temperatures at nest depth within the turtle nesting habitat at Mon Repos since 1998 are now regularly exceeding the lethal level for successful incubation for increasing period of the later breeding season.

It is considered essential that the swampland behind the Mon Repos Conservation Park is rehabilitated if high loggerhead hatchling incubation and emergence success is to be maintained for this major breeding site.

Rehabilitation of the swampland will require the land being changed from its current usage for cane growing and the drainage lines being blocked to allow the water table to be restored back to its previous higher levels.

QPW staff within the Queensland EPA have been investigating the options for purchase of the swampland behind Mon Repos Conservation Park from the farming company that owns it and converting the land into a conservation tenure.