SHEDDING BEHAVIOUR LED LIGHT ON RAT BAIT STATIONS
Bait stations can seriously impede rat control unless they are designed and managed to interfere with natural rodent behaviour as little as possible, argue behaviour-led control specialists, Sharon Hughes and Grahame Turner of Sorex.
Responsible for the UK's foremost rodent control research and development programme, Sharon Hughes stresses that in addition to their pronounced neophobia, a well-developed survival instinct means rats show marked preferences for bait stations in specific locations, prefer to feed in family groups and do not like to enter enclosed spaces without immediately obvious exits.
"Regardless of their design, rats will always prefer some bait stations to others," she explains, "mainly because they feel safer and more secure in particular locations. If you put 20 bait boxes down you'll always find some used very much more than others. Bait from boxes that don't smell right or otherwise feel riskier to rats can remain uneaten even when supplies from preferred boxes are exhausted.
"As well as putting the onus on good siting, this means maximum bait capacity is a key criterion in bait box design. It minimises the risk of early bait depletion in the best-used boxes and allows sufficient bait to be provided in them to ‘double-up' effectively once significant takes occur. This prevents the under-feeding that is the most common reason for poor control and the best way of promoting resistance development.
"Capacity is also important in rat terms to enable several individuals to enter the bait station at the same time," notes Sharon Hughes. "We know this encourages longer stays at the bait and less likelihood of bait transfer. In this respect, height is as important as floor area, not least in allowing rats the room to eat more naturally alongside one another.
"More compact boxes have become very popular in recent years for their convenience, but from a rat control point of view bigger is invariably better. Quite simply, bigger boxes encourage more natural foraging behaviour while maximising bait capacity and the potential to ‘double-up'."
Sharon Hughes' third key to bait box design from a behavioural standpoint is to ensure rats can see an exit ahead of them as they enter the box. Once they are inside and eating, this appears to be less important. But lack of a visible exit can be a major deterrent to initial entry.
Bait station designer, Grahame Turner adds flexibility, stability and durability to the list of things to watch out for in bait box design and management in order to optimise control through rodenticide treatment while protecting people, pets and other non-target species.
"The security of boxes, the ability to stack them and the ease with which they can be opened, cleaned and fixed in place are things that tend to get emphasised in modern bait station marketing, but it is the things that make them more or less acceptable to rats that are actually the most important considerations," he points out.
"If they are to be permanently sited to minimise rat neophobia, for instance, bait stations must be highly durable. This requires boxes to withstand hot as well as cold conditions, so flexible locks and proper hinges are an advantage.
"At the same time they should be as flexible in their internal design as possible, allowing a variety of loose, block and liquid baits and traps to be sited within them. This enables baiting strategies to be adapted as required within the same familiar environment to minimise neophobia. It also facilitates final trapping-out to eliminate individuals that survive the baiting programme.
"Where bait blocks are involved, provision for vertical as well as horizontal mounting is very valuable too," Grahame Turner recommends. "After all, vertically mounted blocks are recognised as encouraging more natural feeding, as well as helping bait security in the box where there is a danger of wax blocks melting.
"Stability is also vital in baiting stations. They must be firmly anchored to the ground or walls to create the safest, most secure rat-feeding environment, while helping to prevent displacement of boxes and bait. At the same time, of course, the fixings need to be easily undone to enable the boxes to be routinely cleaned without difficulty."
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