Experimental learning: fox baiting for malleefowl conservation

[This post is an expanded version of the article in the latest edition of ‘Around the Mounds‘, the newsletter of the National Malleefowl Recovery Team]

It is not every day that one adds a new megapode species to the life list! I’m spending a few days on Tetepare Island, a great conservation initiative to preserve the largest uninhabited island in the Solomons, and it has Melanesian megapodes (Megapodius eremita). Brownish, inconspicuous and rather small, they roam around the traditional palm leaf house that serves as lodge. The species resorts to external sources of heat to incubate the eggs, but unlike its cousin the malleefowl it tends to use piles of decomposing vegetation or volcanically-heated sandy soils.

Melanesian megapode

Clockwise from upper left: a) A shy Melanesian megapode (Megapodius eremita), a relative to the orange-footed scrubfowl (Megapodius reinwardt) that inhabits Australia. b) Mangrove monitor (Varanus indicus) digging eggs from a mound in Tetepare island. c) Megapode eggs on sale at Gizo market (S$7 = A$1). d) Man-made megapode hatcheries in volcanic soil on Simbo island, used to stimulate egg production for harvesting.

This morning, I found a monitor lizard digging megapode eggs from a mound. This reminded me of foxes and malleefowl, and I started reflecting on the progress that the Adaptive Management team has made over this year. Like the monitor lizard I was observing, we know for a fact that foxes prey on malleefowl. There is even very graphic evidence from camera traps of foxes digging eggs from mounds. From the conservation management point of view, however, the real question is whether such predation compromises the long term survival of malleefowl, and whether fox baiting – one of the main conservation actions currently undertaken – actually contributes to the recovery of the species. The evidence in the scientific literature regarding these questions is rather mixed.

Adaptive management is about using management actions to learn how we can improve future management decisions. In the case of foxes and malleefowl, a carefully planned “experiment” that compares malleefowl breeding activity at sites where baiting is carried out with similar sites where it isn’t, could help settle whether fox baiting is an effective way of protecting malleefowl. Indeed, the ideal way of conducting such an experiment would be to find pairs of sites where: a) one site can be baited and the other left unbaited as a reference; b) malleefowl mound activity (the ‘response’ of the species) is being monitored or monitoring can be started; and c) paired sites are close enough to share the same environmental variability (such as how much rain falls in a given year), but not so close that baiting can affect what happens at the non-baited site.

The adaptive management team set out to plan and organize such an experiment across the species’ range, with the help and support of Tim Burnard and Joe Benshemesh. Finding pairs of sites that fulfil these four conditions is a real challenge. Tim initially gathered information and contacts of potential malleefowl monitoring sites. They then both travelled across the country gathering support from land managers.

One of the keys to a successful statistical experiment is “replication”: if the same reaction to baiting is observed again and again at many experimental sites, we can draw conclusions with more confidence. So, how many pairs of sites are needed to be able to make some useful inference about fox baiting? The adaptive management team conducted a “power analysis” to help answer that question. This statistical procedure requires lengthy computer simulations and analyses, but the basic principle behind it is quite simple. If the increase in malleefowl breeding activity due to fox baiting is very large, then observing it at a few sites would be enough. At the other end of the spectrum, if the effect of baiting is very small, it would take many sites to detect it in a statistical analysis, but then again it wouldn’t matter because a small effect would mean that fox baiting would not be an efficient way of increasing malleefowl breeding activity. Our power analysis indicated that about 20 pairs of sites monitored for at least 5 years could be needed to have a reasonable chance to detect an effect of fox baiting that we believe would have a real impact at a population level.

The devil is in the details though, and conducting experiments with natural systems is often trickier that in a laboratory. Ecosystems are always messier and more nuanced than the simplified model used in our power analysis. We also know that we will never get pairs of treatment and reference sites that experience exactly the same environmental conditions over time. Furthermore baiting can be conducted at different regimes of intensity and timing, and the experimental sites will be located within a broader geographic landscape in which other landowners may conduct baiting. As we begin incorporating real sites into this plan, we can collect this more detailed information and account for at least some of it in our analysis.

Despite these challenges, the experiment approach we propose is still our best shot to obtain a robust answer to the question of fox baiting as a management tool for malleefowl conservation. A growing network of experimental sites will establish a solid base to provide the learning we need to improve management practices. And the methodology can be used more broadly, as it will serve as a blueprint to tackle other management uncertainties in malleefowl conservation, such as the effect of fire regimes on malleefowl populations.

It will take several years to gather enough data, so the sooner we start the better. In the adaptive management team, we are really excited to see the progress so far, with several potential sites in WA and SA already under consideration. Stayed tuned!

 

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2 Responses to Experimental learning: fox baiting for malleefowl conservation

  1. Pingback: Dbytes #176 (2 December 2014) | Dbytes

  2. Pingback: Fox baiting experiment workshops | José J. Lahoz-Monfort

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