Thursday, September 10, 2009

Deer Repellent Trials

Deer aren't a headline browser in Tasmania, and yet within their range they can be a significant problem for plantation managers.

Fallow deer appear to be attracted to the seedling stockings used to control browsing damage from other species, often pulling them, and the seedlings they are meant to be protecting, out of the ground.

We're not sure whether the deer are just attracted to the stockings, or whether they are trying to eat the seedlings, although it is not uncommon to find seedling stockings in the guts of deer, indicating that they do at least eat some of the stockings.

The Alternatives to 1080 Program stumbled across a New Zealand Game Control company called Epro some months ago which has developed a deer repellent they use to stop deer eating 1080 baits, and the idea formed that if it is effective, maybe their repellent could be used on stockings to reduce the impact of deer.

Epro were contacted, and interested in the idea of trialing their product to protect seedlings from deer browsing, and so a couple of their staff came over to Tasmania in the first week of September to see the problem first hand and to see if their repellent might have some application.

With thanks to John Bennett of Gunns Limited, we visited some plantations south of Cressy to have a look at the problem, and to set up a small trial to see if we could actually apply the repellent to the seedlings and the stockings.

On a somewhat overcast day on the 2nd September, we mixed up a batch of their repellent (which is non toxic, as I can personally verify having tasted it) and we coated two areas of seedlings which both had evidence of signficant deer movement through them.

The main purpose of this little trial was to see if the repellent would actually "stick" to the seedlings and stocking material, and whether it could be painted or sprayed on, and the initial signs have been very positive.

We were able to both spray and paint the repellent onto seedlings in the field quite quickly and easily, though the cheapo sprayers we used did clog up eventually due to the sticky nature of the repellent.

What's even more positive is that after several days of quite heavy rain, a return to the site on the 8th of September showed that the repellent had survived the rain extremely well, and there was no browsing damage yet ... but then a walk around the larger plantation found no other browsing damage elsewhere either.

Other Species Effectiveness?

We already know that Epro's Deer Repellent doesn't repel brushtail possums as it was specifically designed this way (it's purpose r was to be used on 1080 bait aimed at killing brushtail possums), but we weren't so sure whether it might repel wallabies or not, so we decided to set up a short trial to see how wallabies would react to it.

To do this, we coated a pile of carrots in the repellent and put this pile in front of a camera in the wallaby pen at Prospect which is a population of wild bennett's and rufous wallabies. These wallabies are used to being fed carrot as a bit of a treat, so we fully expected the carrot pile to be gone the next day ... but when we came back it wasn't, in fact nearly 2 weeks after the initial carrot pile was put out, it remains largely untouched, and we expect most of the browsing is due to possums (which were recorded in the first few nights browsing the pile).

Video footage (of which some extracts are below) show typical responses of wallabies coming to the bait pile on the first night:

Somewhat intrigued by this unexpected result, we set up a second trial a week later in the same pen, but this time we put out two piles about 5 metres apart, each with 5 kgs of chopped up carrots, but one was again coated in the repellent, and the other was a control pile, just to make sure that other variables like alternative food availability weren't stopping the wallabies eating the green carrots.

As can be seen in the two videos below, the first wallaby was eating carrots off the uncontrolled pile within hours of it being put out, and well the second video just speaks for itself. Those wallabies like their carrots.

What is most interesting about this trial is that after 3 days, the control pile of carrots was all gone, but other than about 6 pieces of carrots which have been partially nibbled, the treated pile is pretty much untouched. This is a fascinating result, demonstrating the potential short term effectiveness of this repellent against wallabies.

I was in fact so intrigued by this outcome, and having been assured that the repellent is completely safe, I sampled one of the treated carrots that had been out for a week just to see if I could see what was repelling the animals. For me, there was no real smell or taste difference to a normal carrot, so one of my next thoughts is to just try a green dyed placebo to see if it has the same affect as the repellent.

So that's where we are at today. We will continue to monitor both our carrot piles and the seedlings out on the coupe to see how things are going, and if the results continue to look positive may further investigate this repellent with Epro in the coming months.

Some caveats on all this, include that (1) the repellent is fairly expensive and currently Epro do not sell or use second parties to distribute or use it, so there are some restrictions there, and (2) we still don't know it's effectiveness beyond a few weeks, where we need something that will work for at least a few months, however it's always good to get a trial like this off on the right foot like this one has.

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