Kwinana Rockingham Mandurah Branch
The speaker for May was Dr. Tony Friend, Principal Research Scientist in the Fauna Conservation Program at DBCA. His topic was a summary of the history and developments in efforts to ensure the survival of Numbats in the wild.
Tony started the presentation with a discussion of numbat biology. The Numbat (Myrmecobius fasciatus) is the sole member of the family Myrmecobiidae, which is related to the carnivorous marsupials (Dasyurids). Their habitat is eucalypt woodlands and they’re adapted to eating termites, having a long tongue that is coated with sticky saliva that enables the animal to capture the termites and a number of hard ridges within its mouth that scrape the termites off the tongue. Numbat teeth are largely non functional, with prey being swallowed whole. They eat termite species in proportion to their occurrence (i.e. they aren’t fussy!) At Dryandra there are around 30 species of termites that make up their diet, each Numbat eating roughly 20,000 termites per day. Unlike most marsupials, Numbats are diurnal, foraging in the daytime during the period when termites are most active. In summer they feed early morning and late afternoon, taking a siesta in the middle of the day. In winter they feed from two hours after sunrise until just before dark. Numbats mate in early January and there is a two week gestation period. Female Numbats give birth in January or early February. The young spend five months attached to a nipple until early August when they are deposited in a burrow. In September the young emerge but stay very close to their mother. They are weaned in October and range widely during the day but still sleep with their mother. In November they disperse between 0.5 and 20 km from the natal burrow. Females mature in the first year and males in the second year.
In the 1800s Numbats were widespread across Australia. A dramatic range contraction corresponds to the introduction of the Red Fox (Vulpes vulpes). By 1985 only two populations remained: one at Dryandra, in Wandoo woodland, and one in Jarrah forest at Perup. Both of these populations had declined since the mid-1970s. Research has been carried out at Dryandra since 1980. Suggested causes for the decline include: food limitations; fire regimes (however, there was low incidence of fires at Dryandra); drought and feral predators. A fox control experiment was conducted at Dryandra between 1981 and 1984. Poison (1080) was used —native animals can tolerate 1080 but it kills introduced animals—and also shooting of foxes was employed. The results of the experiment were that there was an increase in the numbers of Numbats. To increase the number of populations, translocation of Numbats from Dryandra and Perup was conducted, with Boyagin Nature Reserve (1985), Karroun Hill NR (1986), Tutanning NR (1991), Batalling NR (1992) as well as Yookamura NR in South Australia receiving Numbats.
The timetable for Numbat recovery was: 1981 – 1984 fox control experiment; 1985 translocation program commenced; and 1989 monthly fox baiting commenced. As a result Numbat numbers at Dryandra rose but then fell again. Numbers peaked in 1992 with 11 sightings per 100km (sightings per 100km is the established metric based on the fact that Numbats have such large individual ranges that the best chance of seeing a Numbat is to drive slowly around the roads through Dryandra Woodland). By 2015 things looked bad for Numbats, with sightings dropping to as low as 0.5/100km. Monitoring of radio-collared Numbats in Dryandra showed unmistakable evidence of cat predation. A meso-predator study showed that as fox numbers declined cat numbers increased. Using DNA analysis of collar swabs the study showed that cats were responsible for 60 per cent of Woylie deaths. Cats were apparently favoured by fox removal—a result supported by studies in other areas (Shark Bay and the Gibson Desert). Predators of 14 radio-collared Numbats (between 2011 and 2013) were: cat 7; python 2; raptor 2; Chuditch 1; Fox 1; and 1 unknown. Cats are the most important predator of Numbats. Control methods for feral cats include: spotlighting/shooting (possible in farmland but difficult in woodland); trapping (has difficulties such as by-catch); baiting with special baits developed to target cats (Eradicat™ and Curiosity); and detector dogs/shooting (a program to train dogs is currently underway at Tutanning NR and there is optimism that this will be a successful approach to the problem.) Eradicat™ baits are smaller and softer than fox baits. They include flavour enhancers and the fat leaks out when thawed. However, they are more attractive to a range of native animals. Experimental investigations were conducted using non-lethal baits laced with bio-markers and results showed that species most at risk were the Mardo (Yellow-footed Antechinus) with 66 per cent showing the bio-marker present.
However, it has been shown that native marsupials do survive a dose of Eradicat™. To assist in the investigation of Eradicat™ baiting a total of five feral cats were trapped and radio-collared. Data from the collars show that cats are not always in the reserve, they spend considerable amount of time in surrounding farmland. Studies in Dryandra have shown a low uptake of baits by cats, possibly due to the length of time they spend in farmland. As a result there is an approach to collaborate with farmers to engage in spotlighting and shooting of cats on farmland. However, cats have taken no Numbats since cat baiting commenced.
An additional conservation measure has been the installation of a 1,000 ha fenced enclosure at Dryandra for Numbats and Woylies.
Future challenges include monitoring how the translocated populations are faring. The Boyagin NR is well monitored by DBCA and community members but other reserves need surveys to be conducted.
Colin Prickett