The Christmas Island Pipistrelle (Pipistrellus murrayi)
at risk of extinction within six months!

Dr Lindy Lumsden.

Arthur Rylah Institute, Department of Sustainability and Environment, Heidelberg, Vic 3084.

E-mail: Lindy.lumsden@dse.vic.gov.au

The Christmas Island Pipistrelle Pipistrellus murrayi, at just 3 g is one of Australia’s smallest bats, and almost certainly, the rarest. It is endemic to Christmas Island, a tiny island in the Indian Ocean just 135 km² in size, and is the only species of microbat to occur there. Its distribution and abundance have declined dramatically in recent years, and as a result it was listed as ‘Critically Endangered’ under the Environment Protection and Biodiversity Conservation (EPBC) Act 1999 in 2006. Surveys undertaken in the mid-1980s found it to be common and widespread across the island (Tidemann 1985). However, by the mid-1990s there had been a marked reduction in abundance and a westward range contraction (Lumsden and Cherry 1997, Lumsden et al. 1999). This decline continued at a rapid rate and the species is now confined to the far west of the island, no longer occurring across most of its former range (James and Retallick 2007, Lumsden et al. 2007). Long-term monitoring using ultrasonic bat detectors indicates this species has undergone a 99% decline in relative abundance since 1994 (James and Retallick 2007, Lumsden et al. 2007, Parks Australia North Christmas Island unpublished data; Fig. 1).

A reassessment of the number of individuals remaining in January 2009 suggests there could be as few as 20 individuals left. The only known communal roost contains only four individuals. Three years ago there were 54 individuals in this colony and there were several other known, similar-sized colonies. The long-term monitoring data and the recent reassessment suggest that, if the current rate of decline continues, this species is likely to be extinct within the next 6 months!

The cause of this rapid decline remains unknown, despite the identification of a range of potential threatening processes (Schulz and Lumsden 2004, James 2005, James and Retallick 2007, Lumsden et al. 2007). Extensive areas of habitat are available, with 75% of the island covered by primary or secondary rainforest. The pipistrelle is a generalist aerial insectivore and as there appears to be an abundance of nocturnal flying insects, lack of food is unlikely to be the cause. Predation or disturbance at roost sites is considered one of the most likely threats to the survival of the species (Schulz and Lumsden 2004, Lumsden et al. 2007). Individuals roost in colonies under exfoliating bark on dead trees, many of which are heavily decayed and collapsing (James and Retallick 2007, Lumsden et al. 2007). A number of introduced species may be preying on, or disturbing bats from within their roosts, including Common Wolf Snake Lycodon aulicus capucinus, Black Rat Rattus rattus, Feral Cat Felis catus and Giant Centipede Scolapendra morsitans. Although not considered the primary cause of decline, the recent explosion of Yellow Crazy Ants Anoplolepis gracilipes is likely to have exacerbated the situation. It is also possible that some form of disease may be contributing to the decline, however, with the exception of individuals having low white blood cell counts, there is little evidence for this (Lumsden et al. 2007).

A range of management actions are currently being undertaken to monitor the population and control some threatening processes, including installing protective barriers around the base of known roost trees, extensive detector surveys to locate foraging areas and searches for potential roost sites. However, despite these efforts the population continues to plummet to a critically low level.

Figure 1: Christmas Island Pipistrelle decline. This is based on repeated sampling using bat detectors at set sites across the island up to 2006. Since 2006 the detector monitoring has focused just on the west of the island where the species still occurs. The 2007 and 2008 figures are based on the relationship between this data and that of 2006 at these same sites, to make this as comparable as possible. This suggest that the species has declined by 99% since 1994 and that the species could go extinct in 2008/09.

It is critical therefore that a captive breeding program is established immediately as insurance against further decline in numbers and as a source of individuals to re-establish wild populations once the cause of decline has been identified and controlled (James and Retallick 2007, Lumsden et al. 2007). An emergency rescue program has been proposed that will attempt to catch the remaining individuals to form the basis of a captive colony. It is essential this is undertaken within the next 3 months (i.e. by March 2009) – leaving it any longer than this there is a risk there will be so few animals left that it will not be possible to catch them. If sufficient animals can be caught and they acclimatise to captivity, a commitment will then need to be made to a long-term (10 year) breeding program to enable sufficient animals to be bred for a release program.

Immediate action and a significant commitment from the Australian government is required if the extinction of this species is to be prevented. We urgently need to bring the plight of this species to government’s attention with as many letters as possible.

Please write to Peter Garrett as Minister for the Environment and Bob Debus the Minister responsible for Territories, outlining the urgency of the situation and requesting their immediate action to:

a) fund an emergency rescue program aimed at catching the remaining few animals and establishing a captive colony;

b) if sufficient individuals are caught, fund a long-term captive breeding program by establishing a purpose-built facility on Christmas Island and employing experienced staff to run it; and

c) fund targeted research to determine the cause of the decline so that mitigation actions can be undertaken.

Without this urgent action it is inevitable that this species will go extinct in the very near future. Australia has the worst record of mammal extinctions in the world: we do not want to add another species to this list.

Contact details

The Honourable Peter Garrett

Minister for the Environment, Heritage and the Arts

PO Box 6022

Parliament House

Canberra ACT 2600

http://www.aph.gov.au/house/members/member.asp?id=HV4

The Honourable Bob Debus

Minister for Home Affairs

Parliament House

Canberra ACT 2600

http://www.aph.gov.au/house/members/member.asp?id=8IS

References

James, D.J. (2005). Christmas Island Pipistrelle Pipistrellus murrayi: An interim assessment of conservation status and threats. A report to Parks Australia North, Christmas Island.

James, D.J. and Retallick, K. (2007). Research into the conservation status and threats of the Christmas Island Pipistrelle Pipistrellus murrayi, 2004-2006. Parks Australia North Christmas Island Biodiversity Monitoring Programme: Report to Department of Finance & Administration and Department of the Environment and Water Resources, Canberra.

Lumsden, L. and Cherry, K. (1997). Report on a preliminary investigation of the Christmas Island Pipistrelle Pipistrellus murrayi, in June – July 1994. Arthur Rylah Institute for Environmental Research, Heidelberg, Victoria.

Lumsden, L., Silins, J. and Schulz, M. (1999). Population dynamics and ecology of the Christmas Island Pipistrelle Pipistrellus murrayi on Christmas Island. Report for Parks Australia North – Christmas Island. Arthur Rylah Institute for Environmental Research, Heidelberg, Victoria.

Lumsden, L., Schulz, M., Ashton, R. and Middleton, D. (2007). Investigation of threats to the Christmas Island Pipistrelle. A report to the Department of the Environment and Water Resources. Arthur Rylah Institute for Environmental Research, Department of Sustainability and Environment, Heidelberg, Victoria.

Schulz, M. and Lumsden, L.F. (2004). National Recovery Plan for the Christmas Island Pipistrelle Pipistrellus murrayi. Commonwealth of Australia, Canberra.

Tidemann, C. (1985). A study of the status, habitat requirements and management of the two species of bats on Christmas Island (Indian Ocean). Report to Australian National Parks and Wildlife Service, Canberra.