Counting bunnies

Guest bloggers
Published 07 Jul 2020 
by Sam Fischer – Bon Bon Field Officer 
about  Bon Bon Station Reserve  
<br/>A rabbit spotted through thermal imaging browsing on a small shrub.
A rabbit spotted through thermal imaging browsing on a small shrub.
<br/>Rabbit browsing on a young mulga (Acacia aneura). In extreme cases, rabbits can ringbark and kill small trees and shrubs by gnawing on bark.
Rabbit browsing on a young mulga (Acacia aneura). In extreme cases, rabbits can ringbark and kill small trees and shrubs by gnawing on bark.
<br/>Bon Bon Field Officer Sam Fischer mapping a very active rabbit warren.
Bon Bon Field Officer Sam Fischer mapping a very active rabbit warren.
The wide open landscape at Bon Bon. Photo Sara Petrov (Bon Bon Intern).<br/> The wide open landscape at Bon Bon. Photo Sara Petrov (Bon Bon Intern).
<br/>Using fixed monitoring points to monitor rabbit scat.
Using fixed monitoring points to monitor rabbit scat.

European Rabbits are considered to have a high impact on our conservation targets at Bush Heritage’s Bon Bon Station Reserve in South Australia.

They compete with native herbivores for resources, supress native vegetation through selective browsing, and provide a reliable food source for introduced predators such as foxes (Vulpes vulpes) and cats (Felis catus).

There are many ways to monitor rabbits such as using remote cameras, counting dung, looking for active warren entrances, track counts, and live counts. As a Field Officer, it's been my job to implement these methods, so we can begin to answer questions such as:

  • Where are rabbits within our management zones at Bon Bon?
  • How abundant are rabbits in these areas?
  • How effective is our management of rabbits?
Live counts, done by counting rabbits using a spotlight, is a widely used method for estimating rabbit abundance. Over several nights we drive a fixed length transect and count the number of rabbits seen.

A variation of this method is to use a thermal camera instead of a spotlight, which detects a difference in temperature in the environment – allowing us to spot warm-blooded animals without startling them with a spotlight. With this technology, not only have we seen rabbits, but roosting White-winged Fairy-wrens, Tawny Frogmouth, and even small rodents!

Another method for estimating abundance of herbivores is counting dung. This is done by setting up permanent monitoring sites where rabbit dung is collected, counted, and weighed from a fixed area (known as a quadrat) four times a year.

From this, we can get a rough abundance of rabbits browsing in an area. While it can sometimes be tedious searching for small rabbit scats, dung counts are especially useful when rabbits are not active at warrens and living above ground.

Track transects can also be very useful in estimating abundances and presence of rabbits over large areas. We are lucky at Bon Bon to have plenty of sandy roads that make excellent track transects for undertaking this monitoring method.

This is done by selecting transects to be surveyed along the road, dragging a tyre over them to remove old tracks, and revisiting in the morning to see what animals have crossed. By counting the number of times an animal crosses a track, we can get an idea of activity in that area.

A big advantage of track transects is that the monitoring is not just limited to rabbits. It can also tell us if small native mammals, wombats, or other introduced species are in the area, which can also be utilised in other monitoring programs on the reserve.

Monitoring rabbits at Bon Bon might seem like a large task, but it is an incredibly important part of our integrated pest management strategy.

Without monitoring programs like this one, we have no reliable way of measuring how effective we are at managing our pest species or the positive impacts we're having across our reserves.

<br/>A rabbit spotted through thermal imaging browsing on a small shrub.
A rabbit spotted through thermal imaging browsing on a small shrub.
<br/>Rabbit browsing on a young mulga (Acacia aneura). In extreme cases, rabbits can ringbark and kill small trees and shrubs by gnawing on bark.
Rabbit browsing on a young mulga (Acacia aneura). In extreme cases, rabbits can ringbark and kill small trees and shrubs by gnawing on bark.
<br/>Bon Bon Field Officer Sam Fischer mapping a very active rabbit warren.
Bon Bon Field Officer Sam Fischer mapping a very active rabbit warren.
The wide open landscape at Bon Bon. Photo Sara Petrov (Bon Bon Intern).<br/> The wide open landscape at Bon Bon. Photo Sara Petrov (Bon Bon Intern).
<br/>Using fixed monitoring points to monitor rabbit scat.
Using fixed monitoring points to monitor rabbit scat.