Weather conditions:
The activity and emergence of rabbits from warrens varies with weather (temperature, wind, rain, snow), time of day (light intensity, phase of moon and activity phase of the rabbit) and the season (weather, vegetation condition, breeding activity).
Emergence times and behaviour vary on a local scale. If weather conditions are unseasonable such as strong winds, heavy rain, unusual or extreme temperatures, remember to record these changes.
Important points:
- Always use the same observer for each observation point.
- Always use the same approach route to the observation point
- Always arrive at the time relative to the start of your count.
- Always allow 30 minutes after arriving at the observation site to allow the rabbits to return to normal behaviour.
- Always record any disturbance to the site.
- Always notify the land manager at least one day prior to the counts to be aware of any potential disturbance to the site during the day of the count or before the count.
The Gibb and McLean Scales:
The Gibb and McLean methods can be used as indicators of relative rabbit abundance. Both these methods of estimating the presence of rabbits tend to be subjective and can have significant observer bias. These methods are usually done on foot.
Using Gibb and McLean:
The use of photographs to show graphically the levels on the Gibb scale and/or training days for both scales are recommended. The manner in which the scales will be interpreted should be agreed to if more than one person is conducting the surveys in your area.
How do use to the scales?
To use the scales: - have a copy of the scale(s) in a weatherproof plastic pocket, a clipboard or note pad, pen.
Then: -
- decide the scale to be used:-
- Gibb is a scale of sign (droppings/faeces)
- McLean is a scale of sign (rabbit numbers)
- define the area to be assessed
- set up a transect route across the site
- walk the route, at steady pace
- consistently use the same route/same observer
- simply walk the site
- record observations
- remember the fewer variables of route; observer; weather; and vegetation cover the more consistent the results.
The Gibb scale (1-10)
- Very few droppings, sometimes grouped, overlooked
- Very infrequent heaps; little if any scatter
- Frequent heaps; very light & patchy scatter
- Frequent heaps; light & patchy scatter
- Heaps occasionally within 5 paces of each other; moderate scatter almost over whole area
- Heaps often within five paces of each other; moderate scatter over whole area
- Usually two or three heaps within five paces of each other; dense scatter
- Usually two or three heaps within five paces of each other; dense scatter over whole area
- Some heaps almost merging; scatter very dense
- Some heaps merging; very dense overall
McLean scale (1-10)
- No rabbits seen but some sign noticeable
- Odd rabbits seen; sign and some dunghills showing
- Pockets of rabbits; sign fresh burrows very noticeable
- Infestation spreading out from heavy pockets
- Infestation over whole area and increasing
- Infestation heavy, rabbits moving in droves, pasture damage, numerous warrens
- Infestation at a high level throughout, severe pasture and vegetation change
- Infestation almost at peak
- Maximum level, rabbits must spread out over wide area or starve Both scales are from Coman (1994)
Integrated monitoring
Combine the monitoring methods, warren counts; Gibb; McLean; spotlight; and active entrance counts for a more accurate assessment of rabbit populations. Remember that rabbit monitoring is your responsibility.
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